Autocad 2000 manual

VISUAL LISP™ DEVELOPER’S GUIDE

00120-010000-5160

March 01, 1999

Copyright © 1999 Autodesk, Inc.
All Rights Reserved
AUTODESK, INC. MAKES NO WARRANTY, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY
IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, REGARDING THESE MATERIALS
AND MAKES SUCH MATERIALS AVAILABLE SOLELY ON AN “AS-IS” BASIS.
IN NO EVENT SHALL AUTODESK, INC. BE LIABLE TO ANYONE FOR SPECIAL, COLLATERAL, INCIDENTAL, OR
CONSEQUENTIAL DAMAGES IN CONNECTION WITH OR ARISING OUT OF PURCHASE OR USE OF THESE MATERIALS. THE
SOLE AND EXCLUSIVE LIABILITY TO AUTODESK, INC., REGARDLESS OF THE FORM OF ACTION, SHALL NOT EXCEED THE
PURCHASE PRICE OF THE MATERIALS DESCRIBED HEREIN.
Autodesk, Inc. reserves the right to revise and improve its products as it sees fit. This publication describes the state of this product
at the time of its publication, and may not reflect the product at all times in the future.

Autodesk Trademarks
The following are registered trademarks of Autodesk, Inc., in the USA and/or other countries: 3D Plan, 3D Props, 3D Studio, 3D
Studio MAX, 3D Studio VIZ, 3D Surfer, ADE, ADI, Advanced Modeling Extension, AEC Authority (logo), AEC-X, AME, Animator
Pro, Animator Studio, ATC, AUGI, AutoCAD, AutoCAD Data Extension, AutoCAD Development System, AutoCAD LT, AutoCAD
Map, Autodesk, Autodesk Animator, Autodesk (logo), Autodesk MapGuide, Autodesk University, Autodesk View, Autodesk
WalkThrough, Autodesk World, AutoLISP, AutoShade, AutoSketch, AutoSolid, AutoSurf, AutoVision, Biped, bringing information
down to earth, CAD Overlay, Character Studio, Design Companion, Drafix, Education by Design, Generic, Generic 3D Drafting,
Generic CADD, Generic Software, Geodyssey, Heidi, HOOPS, Hyperwire, Inside Track, Kinetix, MaterialSpec, Mechanical Desktop,
Multimedia Explorer, NAAUG, Office Series, Opus, PeopleTracker, Physique, Planix, Rastation, Softdesk, Softdesk (logo), Solution
3000, Tech Talk, Texture Universe, The AEC Authority, The Auto Architect, TinkerTech, WHIP!, WHIP! (logo), Woodbourne,
WorkCenter, and World-Creating Toolkit.
The following are trademarks of Autodesk, Inc., in the USA and/or other countries: 3D on the PC, ACAD, ActiveShapes, Actrix,
Advanced User Interface, AEC Office, AME Link, Animation Partner, Animation Player, Animation Pro Player, A Studio in Every
Computer, ATLAST, Auto-Architect, AutoCAD Architectural Desktop, AutoCAD Architectural Desktop Learning Assistance,
AutoCAD DesignCenter, Learning Assistance, AutoCAD LT Learning Assistance, AutoCAD Simulator, AutoCAD SQL Extension,
AutoCAD SQL Interface, AutoCDM, Autodesk Animator Clips, Autodesk Animator Theatre, Autodesk Device Interface, Autodesk
PhotoEDIT, Autodesk Software Developer’s Kit, Autodesk View DwgX, AutoEDM, AutoFlix, AutoLathe, AutoSnap, AutoTrack, Built
with ObjectARX (logo), ClearScale, Concept Studio, Content Explorer, cornerStone Toolkit, Dancing Baby (image), Design Your
World, Design Your World (logo), Designer’s Toolkit, DWG Linking, DWG Unplugged, DXF, Exegis, FLI, FLIC, GDX Driver, Generic
3D, Heads-up Design, Home Series, Kinetix (logo), MAX DWG, ObjectARX, ObjectDBX, Ooga-Chaka, Photo Landscape,
Photoscape, Plugs and Sockets, PolarSnap, Powered with Autodesk Technology, Powered with Autodesk Technology (logo),
ProConnect, ProjectPoint, Pro Landscape, QuickCAD, RadioRay, SchoolBox, SketchTools, Suddenly Everything Clicks,
Supportdesk, The Dancing Baby, Transforms Ideas Into Reality, Visual LISP, and Volo.

Third Party Trademarks
Élan License Manager is a trademark of Élan Computer Group, Inc.
Microsoft, Visual Basic, Visual C++, and Windows are registered trademarks and Visual FoxPro and the Microsoft Visual Basic
Technology logo are trademarks of Microsoft Corporation in the United States and other countries.
All other brand names, product names or trademarks belong to their respective holders.

Third Party Software Program Credits
ACIS® Copyright © 1994, 1997, 1999 Spatial Technology, Inc., Three-Space Ltd., and Applied Geometry Corp. All rights reserved.
Copyright © 1997 Microsoft Corporation. All rights reserved.
International CorrectSpell™ Spelling Correction System © 1995 by Lernout & Hauspie Speech Products, N.V. All rights reserved.
InstallShield™ 3.0. Copyright © 1997 InstallShield Software Corporation. All rights reserved.
Portions Copyright © 1991-1996 Arthur D. Applegate. All rights reserved.
Portions of this software are based on the work of the Independent JPEG Group.
Typefaces from the Bitstream® typeface library copyright 1992.
Typefaces from Payne Loving Trust © 1996. All rights reserved.
The license management portion of this product is based on Élan License Manager © 1989, 1990, 1998 Élan Computer Group,
Inc. All rights reserved.
Autodesk would like to acknowledge and thank Perceptual Multimedia, Inc., for the creative and technical design and the
development of the Visual LISP Garden Path tutorial.

GOVERNMENT USE
Use, duplication, or disclosure by the U. S. Government is subject to restrictions as set forth in FAR 12.212 (Commercial Computer
Software-Restricted Rights) and DFAR 227.7202 (Rights in Technical Data and Computer Software), as applicable.

1 2 3 4 5 6 7 8 9 10

Contents

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
AutoLISP and Visual LISP . . . . . . . . . . . . . . . . . .
What Visual LISP Offers . . . . . . . . . . . . . . .
Working with Visual LISP and AutoCAD .
Using Visual LISP Documentation . . . . . . . . . . .
Document Conventions . . . . . . . . . . . . . . . . . . .
Related Documents . . . . . . . . . . . . . . . . . . . . . . .

Part I
Chapter 1

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..2
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..3
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..7
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Using the Visual LISP Environment . . . . . . . . . . . . . . . . 9
Getting Started. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Starting Visual LISP . . . . . . . . . . . . . . . . . . . . . . .
Exploring the Visual LISP User Interface . . . . . .
Introducing the Visual LISP Text Editor . .
Other Visual LISP Windows. . . . . . . . . . . .
Touring the Visual LISP Menus. . . . . . . . . . . . . .
Variable Menu Contents . . . . . . . . . . . . . .
Visual LISP Menu Summary. . . . . . . . . . . .
Understanding the Console Window . . . . . . . . .
Understanding the Visual LISP Text Editor . . . .
Loading and Running AutoLISP Programs . . . . .
Running Selected Lines of Code . . . . . . . .
Using Extended AutoLISP Functions . . . . .
Exiting Visual LISP . . . . . . . . . . . . . . . . . . . . . . .

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. 12
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iii

Chapter 2

Developing Programs with Visual LISP. . . . . . . . . . . . . . . . . . . . . . 23
Getting Organized . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Using the Console Window . . . . . . . . . . . . . . . . . . . . . . . . . . .
Understanding Console Behavior . . . . . . . . . . . . . . . . . .
Using the Console Window with Multiple Drawings. . .
Using the Console Shortcut Menu . . . . . . . . . . . . . . . . .
Logging Console Window Activity . . . . . . . . . . . . . . . . .
Using the Text Editor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Editing a File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Using the Text Editor Shortcut Menu . . . . . . . . . . . . . . .
Using Keyboard Shortcuts in the Text Editor . . . . . . . . .
Moving and Copying Text . . . . . . . . . . . . . . . . . . . . . . .
Searching for Text . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Bookmarking Text . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Using Console and Editor Coding Aids . . . . . . . . . . . . . . . . . .
Understanding Visual LISP Color Coding. . . . . . . . . . . .
Using the Apropos Feature . . . . . . . . . . . . . . . . . . . . . . .
Letting Visual LISP Help You Complete Words . . . . . . .
Getting Help for AutoLISP Functions . . . . . . . . . . . . . . .
Formatting Code with Visual LISP . . . . . . . . . . . . . . . . . . . . . .
Understanding Visual LISP Formatting Styles . . . . . . . .
Applying Formatting Options . . . . . . . . . . . . . . . . . . . . .
Applying Visual LISP Comment Styles . . . . . . . . . . . . . .
Saving and Restoring Formatting Options . . . . . . . . . . .
Formatter Restrictions . . . . . . . . . . . . . . . . . . . . . . . . . . .
Formatting Shortcut Keys . . . . . . . . . . . . . . . . . . . . . . . .
Checking for Syntax Errors. . . . . . . . . . . . . . . . . . . . . . . . . . . .
Checking the Balance of Parentheses . . . . . . . . . . . . . . .
Using Color Coding to Detect Syntax Errors . . . . . . . . .
Using the Check Command to Look for Syntax Errors .

Chapter 3

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Contents

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24
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58
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61
61
63
64

Debugging Programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
Introducing Visual LISP Debugging Features . . . . .
Learning by Example . . . . . . . . . . . . . . . . . . . . . . .
Stepping through the Debugging Example. .
Using the Visual LISP Debugging Features. . . . . . .
Starting a Debugging Session . . . . . . . . . . . .
Understanding Break Loops . . . . . . . . . . . . .
Using Breakpoints . . . . . . . . . . . . . . . . . . . . .
Using Visual LISP Data Inspection Tools . . . . . . . .
Using the Watch Window. . . . . . . . . . . . . . .
Understanding the Trace Stack Window . . .
Using the Symbol Service Dialog Box . . . . . .
Using Inspect Windows . . . . . . . . . . . . . . . .

iv

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68
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69
75
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82
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85
92
95

Viewing AutoCAD Drawing Entities . . . . . . . . . . . . . . . . . . . . . . . . 104

Chapter 4

Building Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
Compiling and Linking Programs. . . . . . . . . . . . . . . . . . . . . . . .
Using the Compiler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Compiling a Program from a File . . . . . . . . . . . . . . . . . . .
Walking through a Compile Example . . . . . . . . . . . . . . . .
Loading and Running Compiled Programs . . . . . . . . . . . .
Linking Function Calls. . . . . . . . . . . . . . . . . . . . . . . . . . . .
Making Application Modules . . . . . . . . . . . . . . . . . . . . . . . . . . .
Creating a New Application. . . . . . . . . . . . . . . . . . . . . . . .
Loading and Running Visual LISP Applications . . . . . . . .
Changing Application Options . . . . . . . . . . . . . . . . . . . . .
Rebuilding an Application . . . . . . . . . . . . . . . . . . . . . . . . .
Updating an Application . . . . . . . . . . . . . . . . . . . . . . . . . .
Designing for a Multiple Document Environment. . . . . . . . . . .
Understanding Namespaces. . . . . . . . . . . . . . . . . . . . . . . .
Running an Application in Its Own Namespace . . . . . . . .
Sharing Data between Namespaces . . . . . . . . . . . . . . . . . .
Handling Errors in an MDI Environment . . . . . . . . . . . . .
Limitations on Using AutoLISP in an MDI Environment .

Chapter 5

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133
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136

Maintaining Visual LISP Applications . . . . . . . . . . . . . . . . . . . . . . 137
Managing Multiple LISP Files . . . . . . . . . . . . . . . . . . . . . . . .
Understanding Visual LISP Projects. . . . . . . . . . . . . . .
Defining a Project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Assigning Project Properties. . . . . . . . . . . . . . . . . . . . .
Using the Project Window to Work with Project Files
Working with Existing Projects. . . . . . . . . . . . . . . . . . . . . . .
Opening a Project . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Finding a String in Project Source Files . . . . . . . . . . . .
Including a Project in a Visual LISP Application . . . . .
Optimizing Application Code . . . . . . . . . . . . . . . . . . . . . . . .
Defining Build Options . . . . . . . . . . . . . . . . . . . . . . . .
Choosing a Compilation Mode . . . . . . . . . . . . . . . . . .
Choosing a Link Mode. . . . . . . . . . . . . . . . . . . . . . . . .
Understanding Safe Optimization . . . . . . . . . . . . . . . .

Chapter 6

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155
157
157

Working with ActiveX. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
Using ActiveX Objects with AutoLISP. . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
Understanding the AutoCAD Object Model. . . . . . . . . . . . . . . . . . . . . . . 162
Object Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164

Contents

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v

Object Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Collections of Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Accessing AutoCAD Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Using the Inspect Tool to View Object Properties . . . . . . . .
Moving Forward from the Application Object . . . . . . . . . . .
Summarizing the Process . . . . . . . . . . . . . . . . . . . . . . . . . . .
Performance Considerations . . . . . . . . . . . . . . . . . . . . . . . . .
Using Visual LISP Functions with ActiveX Methods . . . . . . . . . . .
Determining the Visual LISP Function You Need. . . . . . . . .
Determining How to Call a Function . . . . . . . . . . . . . . . . . .
Converting AutoLISP Data Types to ActiveX Data Types. . .
Viewing and Updating Object Properties . . . . . . . . . . . . . . .
Using ActiveX Methods That Return Values in Arguments .
Listing an Object’s Properties and Methods . . . . . . . . . . . . .
Working with Collection Objects . . . . . . . . . . . . . . . . . . . . .
Releasing Objects and Freeing Memory . . . . . . . . . . . . . . . .
Converting Object References. . . . . . . . . . . . . . . . . . . . . . . .
Handling Errors Returned by ActiveX Methods . . . . . . . . . .
Using ActiveX to Interact with Other Applications . . . . . . . . . . . .
Importing a Type Library . . . . . . . . . . . . . . . . . . . . . . . . . . .
Establishing a Connection to an Application . . . . . . . . . . . .
Coding a Sample Application . . . . . . . . . . . . . . . . . . . . . . . .
Using ActiveX without Importing a Type Library . . . . . . . .

Chapter 7

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198

Advanced Topics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
Attaching Reactors to AutoCAD Drawings. . . . . . . . . .
Understanding Reactor Types and Events . . . . .
Defining Callback Functions. . . . . . . . . . . . . . . .
Creating Reactors. . . . . . . . . . . . . . . . . . . . . . . . .
Working with Reactors in Multiple Namespaces
Querying, Modifying, and Removing Reactors. .
Transient versus Persistent Reactors . . . . . . . . . .
Reactor Use Guidelines . . . . . . . . . . . . . . . . . . . .

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215
216

Part II

Using the AutoLISP Language . . . . . . . . . . . . . . . . . . 219

Chapter 8

AutoLISP Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221
AutoLISP Expressions . . . . . . . . . .
AutoLISP Function Syntax .
AutoLISP Data Types. . . . . . . . . . .
Integers . . . . . . . . . . . . . . . .
Reals. . . . . . . . . . . . . . . . . . .

vi

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Contents

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Strings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Lists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Selection Sets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Entity Names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
VLA-objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
File Descriptors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Symbols and Variables . . . . . . . . . . . . . . . . . . . . . . . . .
AutoLISP Program Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Formatting AutoLISP Code . . . . . . . . . . . . . . . . . . . . .
Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Color Coding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
AutoLISP Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Displaying the Value of a Variable . . . . . . . . . . . . . . .
Nil Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Predefined Variables. . . . . . . . . . . . . . . . . . . . . . . . . . .
Number Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
String Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Basic Output Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Displaying Messages. . . . . . . . . . . . . . . . . . . . . . . . . . .
Control Characters in Strings . . . . . . . . . . . . . . . . . . .
Wild-Card Matching . . . . . . . . . . . . . . . . . . . . . . . . . .
Equality and Conditional . . . . . . . . . . . . . . . . . . . . . . . . . . .
List Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Point Lists. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Dotted Pairs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Symbol and Function Handling . . . . . . . . . . . . . . . . . . . . . .
Using defun to Define a Function . . . . . . . . . . . . . . . .
C:XXX Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Local Variables in Functions . . . . . . . . . . . . . . . . . . . .
Functions with Arguments . . . . . . . . . . . . . . . . . . . . .
Error Handling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Using the *error* Function. . . . . . . . . . . . . . . . . . . . . .
Catching Errors and Continuing Program Execution .

Chapter 9

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238
240
240
242
244
245
245
247
251
252
254
255
257

Using AutoLISP to Communicate with AutoCAD. . . . . . . . . . . . . 259
Query and Command Functions . . . . . . . . . . . .
Command Submission. . . . . . . . . . . . . . . .
System and Environment Variables. . . . . .
Configuration Control . . . . . . . . . . . . . . . .
Display Control . . . . . . . . . . . . . . . . . . . . . . . . . .
Controlling Menus. . . . . . . . . . . . . . . . . . .
Control of Graphics and Text Windows . .
Control of Low-Level Graphics . . . . . . . . .
Getting User Input . . . . . . . . . . . . . . . . . . . . . . .

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Contents

260
260
263
264
264
264
267
267
268

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vii

The getxxx Functions . . . . . . . . . . . . . . . . . .
Control of User-Input Function Conditions.
Geometric Utilities . . . . . . . . . . . . . . . . . . . . . . . . .
Object Snap . . . . . . . . . . . . . . . . . . . . . . . . . .
Text Extents. . . . . . . . . . . . . . . . . . . . . . . . . .
Conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
String Conversions . . . . . . . . . . . . . . . . . . . .
Angular Conversion . . . . . . . . . . . . . . . . . . .
ASCII Code Conversion. . . . . . . . . . . . . . . . .
Unit Conversion . . . . . . . . . . . . . . . . . . . . . .
Coordinate System Transformations . . . . . .
File Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
File Search . . . . . . . . . . . . . . . . . . . . . . . . . . .
Accessing Help Files. . . . . . . . . . . . . . . . . . . .
Device Access and Control . . . . . . . . . . . . . . . . . . .
Accessing User Input . . . . . . . . . . . . . . . . . . .
Calibrating Tablets . . . . . . . . . . . . . . . . . . . .

Chapter 10

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268
271
274
274
275
279
279
281
282
283
286
289
289
290
291
291
291

Using AutoLISP to Manipulate AutoCAD Objects . . . . . . . . . . . . 295
Selection Set Handling . . . . . . . . . . . . . . . . . . . . . . . . .
Selection Set Filter Lists . . . . . . . . . . . . . . . . . . . .
Passing Selection Sets between AutoLISP and
ObjectARX Applications. . . . . . . . .
Object Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Entity Name Functions . . . . . . . . . . . . . . . . . . . .
Entity Data Functions . . . . . . . . . . . . . . . . . . . . .
Entity Data Functions and the Graphics Screen .
Old-Style Polylines and Lightweight Polylines . .
Non-Graphic Object Handling . . . . . . . . . . . . . .
Extended Data—xdata . . . . . . . . . . . . . . . . . . . . . . . . .
Organization of Extended Data. . . . . . . . . . . . . .
Registration of an Application . . . . . . . . . . . . . .
Retrieval of Extended Data . . . . . . . . . . . . . . . . .
Attachment of Extended Data to an Entity . . . .
Management of Extended Data Memory Use . . .
Handles in Extended Data. . . . . . . . . . . . . . . . . .
Xrecord Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Symbol Table and Dictionary Access . . . . . . . . . . . . . .
Symbol Tables . . . . . . . . . . . . . . . . . . . . . . . . . . .
Dictionary Entries . . . . . . . . . . . . . . . . . . . . . . . .

viii

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Contents

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. . . . . . . . . . . . . . 298
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305
305
305
311
319
320
321
323
324
327
327
329
329
330
331
332
332
334

Part III

Working with Programmable Dialog Boxes. . . . . . . . 335

Chapter 11

Designing Dialog Boxes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337
Dialog Box Components . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Using DCL to Define Dialog Boxes . . . . . . . . . . . . . . . . . . . .
The base.dcl and acad.dcl Files . . . . . . . . . . . . . . . . . .
Referencing DCL Files . . . . . . . . . . . . . . . . . . . . . . . . .
DCL Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Displaying Dialog Boxes with Visual LISP . . . . . . . . . . . . . .
Preview Error Handling . . . . . . . . . . . . . . . . . . . . . . . .
Semantic Auditing of DCL Files. . . . . . . . . . . . . . . . . .
Adjusting the Layout of Dialog Boxes. . . . . . . . . . . . . . . . . .
Distributing Tiles in a Cluster . . . . . . . . . . . . . . . . . . .
Adjusting the Space between Tiles. . . . . . . . . . . . . . . .
Adjusting Space at the Right Side or Bottom. . . . . . . .
Fixing the Spacing Around a Boxed Row or Column .
Customizing Exit Button Text . . . . . . . . . . . . . . . . . . .
Design Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Aesthetics and Ergonomics . . . . . . . . . . . . . . . . . . . . .
Consistent Design and Clear Language . . . . . . . . . . . .
User Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Forgiving Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Providing Help . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Users with Disabilities . . . . . . . . . . . . . . . . . . . . . . . . .
Using Capitalization . . . . . . . . . . . . . . . . . . . . . . . . . .
Avoiding Abbreviations . . . . . . . . . . . . . . . . . . . . . . . .
Layout. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Size and Placement . . . . . . . . . . . . . . . . . . . . . . . . . . .
Disabling Tiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Nesting Dialog Boxes . . . . . . . . . . . . . . . . . . . . . . . . . .
Hiding Dialog Boxes. . . . . . . . . . . . . . . . . . . . . . . . . . .
Providing Defaults . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Handling Keyboard Input . . . . . . . . . . . . . . . . . . . . . .
International Language Considerations . . . . . . . . . . .
Guidelines for Predefined Tiles and Clusters. . . . . . . .
Error Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Chapter 12

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338
340
340
340
341
344
346
346
347
348
349
350
350
351
353
353
353
353
355
355
356
356
357
357
357
358
358
358
359
359
359
360
363

Managing Dialog Boxes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365
Controlling Dialog Boxes with AutoLISP Programs . . . .
Quick Overview . . . . . . . . . . . . . . . . . . . . . . . . . . .
Functions Restricted When a Dialog Box Is Open.
Action Expressions and Callbacks. . . . . . . . . . . . . . . . . .
Action Expressions . . . . . . . . . . . . . . . . . . . . . . . . .

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Contents

366
366
367
368
369

|

ix

Callback Reasons . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Handling Tiles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Initializing Modes and Values. . . . . . . . . . . . . . . . . .
Changing Modes and Values at Callback Time . . . .
Handling Radio Clusters . . . . . . . . . . . . . . . . . . . . . .
Handling Sliders . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Handling Edit Boxes . . . . . . . . . . . . . . . . . . . . . . . . .
Nesting Dialog Boxes . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Hiding Dialog Boxes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Requesting a Password . . . . . . . . . . . . . . . . . . . . . . .
List Boxes and Pop-Up Lists . . . . . . . . . . . . . . . . . . . . . . . .
List Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Processing List Elements . . . . . . . . . . . . . . . . . . . . . .
Image Tiles and Buttons . . . . . . . . . . . . . . . . . . . . . . . . . . .
Creating Images. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Handling Image Buttons . . . . . . . . . . . . . . . . . . . . . .
Application-Specific Data . . . . . . . . . . . . . . . . . . . . . . . . . .
DCL Error Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Setting the Auditing Level to Affect Error Messages .
Dialog Box Function Summary . . . . . . . . . . . . . . . . . . . . .
Function Sequence . . . . . . . . . . . . . . . . . . . . . . . . . .
The Sample Block Definition Dialog Box . . . . . . . . .

Chapter 13

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Contents

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372
372
373
374
375
376
376
377
379
380
380
382
383
383
385
386
386
387
388
388
389

Programmable Dialog Box Reference . . . . . . . . . . . . . . . . . . . . . 391
Tile Attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Attribute Types . . . . . . . . . . . . . . . . . . . . . . . . . .
Restricted Attributes . . . . . . . . . . . . . . . . . . . . . .
User-Defined Attributes. . . . . . . . . . . . . . . . . . . .
Synopsis of Predefined Attributes. . . . . . . . . . . . . . . . .
DCL Attribute Catalog . . . . . . . . . . . . . . . . . . . . . . . . .
Functional Synopsis of DCL Tiles. . . . . . . . . . . . . . . . .
Predefined Active Tiles . . . . . . . . . . . . . . . . . . . .
Tile Clusters. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Decorative and Informative Tiles . . . . . . . . . . . .
Text Clusters . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Dialog Box Exit Buttons and Error Tiles . . . . . . .
Restricted Tiles. . . . . . . . . . . . . . . . . . . . . . . . . . .
DCL Tile Catalog. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Programmable Dialog Box Function Synopsis . . . . . . .
Dialog Box Opening and Closing Functions . . .
Tile- and Attribute-Handling Functions . . . . . . .
List Box and Pop-Up List-Handling Functions . .
Image Tile-Handling Functions. . . . . . . . . . . . . .
Application-Specific Data-Handling Functions .

x

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392
392
393
393
394
397
408
408
408
409
409
410
410
410
427
427
428
428
429
429

Part IV

Appendixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 431

Appendix A AutoLISP Function Synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 433
Category Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Basic Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Application-Handling Functions . . . . . . . . . . . . . . . . .
Arithmetic Functions . . . . . . . . . . . . . . . . . . . . . . . . . .
Equality and Conditional Functions . . . . . . . . . . . . . .
Error-Handling Functions . . . . . . . . . . . . . . . . . . . . . .
Function-Handling Functions . . . . . . . . . . . . . . . . . . .
List Manipulation Functions . . . . . . . . . . . . . . . . . . . .
String-Handling Functions. . . . . . . . . . . . . . . . . . . . . .
Symbol-Handling Functions . . . . . . . . . . . . . . . . . . . .
Utility Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Conversion Functions . . . . . . . . . . . . . . . . . . . . . . . . .
Device Access Functions . . . . . . . . . . . . . . . . . . . . . . .
Display Control Functions. . . . . . . . . . . . . . . . . . . . . .
File-Handling Functions . . . . . . . . . . . . . . . . . . . . . . .
Geometric Functions . . . . . . . . . . . . . . . . . . . . . . . . . .
Query and Command Functions . . . . . . . . . . . . . . . . .
User Input Functions . . . . . . . . . . . . . . . . . . . . . . . . . .
Selection Set, Object, and Symbol Table Functions . . . . . . .
Extended Data-Handling Functions . . . . . . . . . . . . . .
Object-Handling Functions . . . . . . . . . . . . . . . . . . . . .
Selection Set Manipulation Functions. . . . . . . . . . . . .
Symbol Table and Dictionary-Handling Functions. . .
Memory Management Functions . . . . . . . . . . . . . . . . . . . . .
Visual LISP Extensions to AutoLISP . . . . . . . . . . . . . . . . . . .
ActiveX Collection Manipulation Functions. . . . . . . .
ActiveX Data Conversion Functions . . . . . . . . . . . . . .
ActiveX Method Invocation Functions . . . . . . . . . . . .
ActiveX Object-Handling Functions . . . . . . . . . . . . . .
ActiveX Property-Handling Functions. . . . . . . . . . . . .
Curve Measurement Functions . . . . . . . . . . . . . . . . . .
Dictionary Functions . . . . . . . . . . . . . . . . . . . . . . . . . .
Object-Handling Functions . . . . . . . . . . . . . . . . . . . . .
Reactor Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
VLX Namespace Functions . . . . . . . . . . . . . . . . . . . . . . . . . .
Namespace Communication Functions . . . . . . . . . . . . . . . .
Windows Registry Functions. . . . . . . . . . . . . . . . . . . . . . . . .

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434
436
436
437
439
440
441
442
444
445
446
446
447
448
449
450
451
452
453
453
453
455
455
457
457
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458
459
460
460
461
462
463
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467
468
469

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xi

Appendix B Visual LISP Environment and Formatting Options. . . . . . . . . . . . 471
Window Attributes . . . . . . . . . . . . . . . . . .
Syntax Coloring. . . . . . . . . . . . . . . .
Configure Current . . . . . . . . . . . . . .
Set Current Window to Prototype .
Set All Windows to Prototype . . . . .
Font . . . . . . . . . . . . . . . . . . . . . . . . .
Environment Options. . . . . . . . . . . . . . . .
General Options . . . . . . . . . . . . . . .
Visual LISP Format Options . . . . . .
Page Format Options . . . . . . . . . . . .
Save Settings . . . . . . . . . . . . . . . . . . . . . . .

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472
472
473
475
475
475
475
475
479
483
484

Appendix C AutoLISP Error Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 485
Error Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 486

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 491

xii

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Contents

Introduction

In This Chapter

For years, AutoLISP® has set the standard for
customizing AutoCAD ®. Now Visual LISP™ (VLISP)™rep-

s AutoLISP and Visual LISP
s Using Visual LISP Documentation
s Document Conventions

resents the next generation of LISP for AutoCAD, by

s Related Documents

adding significantly more capabilities. VLISP extends
the language to interface with objects via the Microsoft
ActiveX™ Automation interface, and enhances
AutoLISP’s ability to respond to events through the
implementation of reactor functions. As a development
tool, VLISP provides a complete, integrated development environment (IDE) that includes a compiler,
debugger, and other tools to increase productivity when
customizing AutoCAD.

1

AutoLISP and Visual LISP
AutoLISP is a programming language designed for extending and customizing AutoCAD functionality. It is based on the LISP programming language,
whose origins date back to the late 1950s. LISP was originally designed for use
in Artificial Intelligence (AI) applications, and is still the basis for many AI
applications.
AutoCAD introduced AutoLISP as an application programming interface
(API) in Release 2.1, in the mid-1980s. LISP was chosen as the initial
AutoCAD API because it was uniquely suited for the unstructured design
process of AutoCAD projects, which involved repeatedly trying different
solutions to design problems.
Visual LISP (VLISP) is a software tool designed to expedite AutoLISP program
development. The VLISP integrated development environment (IDE) provides features to help ease the tasks of source-code creation and modification,
program testing, and debugging. In addition, VLISP provides a vehicle for
delivering standalone applications written in AutoLISP.
In the past, developing AutoLISP programs for AutoCAD meant supplying
your own text editor for writing code, then loading the code into AutoCAD
and running it. Debugging your program meant adding statements to print
the contents of variables at strategic points in your program. You had to figure out where in your program to do this, and what variables you needed to
look at. If you discovered you still didn’t have enough information to determine the error, you had to go back and change the code again by adding
more debugging points. And finally, when you got the program to work correctly, you needed to either comment out or remove the debugging code you
added.

What Visual LISP Offers
During the development cycle of an AutoLISP application or routine, the
AutoLISP user performs a number of operations that are not available within
the AutoCAD software. Some of these operations—like text editing—are
available with other software tools. Others, such as full AutoLISP source-level
debugging, are introduced only with VLISP. In VLISP, you perform most of
the necessary operations inside a single environment. This permits text
editing, program debugging, and interaction with AutoCAD and other
applications.

2

|

Introduction

The following are components of the Visual LISP IDE:
s
s
s

s
s
s

s
s
s
s
s

Syntax Checker recognizes erroneous AutoLISP constructs and improper
arguments in calls to built-in functions.
File Compiler improves the execution speed and provides a secure and
efficient delivery platform.
Source Debugger, designed specifically for AutoLISP, supports stepping
through AutoLISP source code in one window while simultaneously displaying the results of code execution in an AutoCAD drawing window.
Text file editor uses AutoLISP and DCL color coding, as well as other
AutoLISP syntax support features.
AutoLISP Formatter restructures programs into an easily readable format.
Comprehensive Inspect and Watch features provide convenient access to
variable and expression values for data structure browsing and modification. These features may be used to explore AutoLISP data and AutoCAD
drawing entities.
Context-sensitive Help provides information for AutoLISP functions and
a powerful Apropos feature for symbol name search.
Project Management system makes it easy to maintain multiple-file applications.
Compiled AutoLISP files are packaged into a single module.
Desktop Save and Restore capabilities preserve and reuse the windowing
environment from any VLISP session.
Intelligent Console window introduces a new level of convenience and
efficiency for AutoLISP users. The basic functions of the Console correspond to the AutoCAD Text Screen functions and provide a number of
interactive features, such as history scrolling and full-input line editing.

Working with Visual LISP and AutoCAD
VLISP contains its own set of windows and menus that are distinct from the
rest of AutoCAD, but VLISP does not run independently of AutoCAD. Whenever you work in VLISP, AutoCAD must also be running. When you run
AutoLISP programs from the VLISP IDE, you will usually need to interact
with the AutoCAD graphics or Command windows to respond to program
prompts.
If AutoCAD is minimized when VLISP turns control over to it, you must manually restore and activate the AutoCAD window to continue. VLISP will not
restore the AutoCAD window for you. Instead, a Visual LISP symbol appears
in the VLISP window and remains there until you activate AutoCAD and
respond to the prompts at the AutoCAD Command prompt. The “Getting
Started” chapter shows an example of this; see “Loading and Running
AutoLISP Programs” on page 20.


|

3

Using Visual LISP Documentation
The Visual LISP Developer’s Guide explains how to use the VLISP IDE and how
to build and run AutoLISP applications. This guide also introduces the constructs of the AutoLISP language.
All users should check the AutoCAD Readme file for notices concerning
AutoLISP and Visual LISP. The Readme file is in the AutoCAD Help directory
and contains information that became available too late to be included in
this manual.
If you have developed AutoLISP applications in earlier releases of AutoCAD,
it is important that you refer to the Readme file for information on AutoLISP
changes that may affect your applications.
Additional AutoLISP and Visual LISP manuals are available online through
the Visual LISP and AutoCAD Help menus:
s

s

The AutoLISP Reference briefly describes and provides examples of every
AutoLISP function. Refer to the AutoLISP Reference when you need to look
up the syntax of a function, or determine what a function returns.
The Visual LISP Tutorial contains step-by-step instructions guiding you
toward building a working Visual LISP application.

This Visual LISP Developer’s Guide assumes you have some experience with
AutoCAD and have basic user-level skills with Microsoft Windows®. Prior
experience with AutoLISP is not required, but it will make your learning
curve much smoother.
The Visual LISP Developer’s Guide is divided into the following sections:
s
s
s
s

“Using the Visual LISP Environment” describes how to use VLISP to
develop and test AutoLISP programs.
“Using the AutoLISP Language” is a detailed guide describing the elements
and structures of the AutoLISP language.
“Working with Programmable Dialog Boxes” describes how to design and
implement dialog boxes in your AutoLISP applications.
“Appendixes” includes a function synopsis summarizing AutoLISP functions by category, information on AutoLISP error codes, and a summary
of the environment and program options available in Visual LISP.

If you are already familiar with AutoLISP, you may want to begin the Visual
LISP Tutorial after reading chapter 1. This is a matter of personal comfort: if
you feel you need to understand how everything works before using a tool,

4

|

Introduction

you might be better off reading some or all of chapters 2 through 7 of this
guide before trying the tutorial.
Following are some guidelines to help you get the most out of the Visual LISP
Developer’s Guide:
s

s

s

Begin by reading chapter 1, “Getting Started.” This chapter tells you how
to invoke VLISP from AutoCAD, identifies what you’ll see when VLISP
first starts, and describes how to load and run existing AutoLISP programs
from VLISP. Chapter 1 introduces and briefly describes the windows you
will be working with in the VLISP IDE. Use this chapter to orient yourself
to the VLISP environment.
If you do not already know AutoLISP, read all of chapter 8, “AutoLISP
Basics,” and at least browse chapters 9 and 10, “Using AutoLISP to Communicate with AutoCAD” and “Using AutoLISP to Manipulate AutoCAD
Objects,” respectively. After that, you can either work through the tutorial
or read more chapters in the Visual LISP Developer’s Guide.
To search for a function that meets a particular programming need, refer
to appendix A, “AutoLISP Function Synopsis,” in this guide.

The following table summarizes the organization of this manual:
Chapter organization
Chapter Title

Contents

1

Getting Started

Orientation to Visual LISP

2

Developing Programs with
Visual LISP

Shows you how to use the VLISP text
editor to enter AutoLISP program code,
format the code, and check the code for
AutoLISP syntax errors. Also shows you
how to run the code you’ve developed
from the VLISP editor window.

3

Debugging Programs

Shows you how to use VLISP to trace
program execution, watch the value of
variables change during program
execution, see the sequence in which
expressions are evaluated, and step
through program execution one
instruction at a time.

4

Building Applications

Introduces the VLISP file compiler and
shows how you can use the VLISP
Application Wizard to build standalone
applications.

Using Visual LISP Documentation

|

5

Chapter organization (continued)
Chapter Title
5

Describes how to define VLISP projects
and use them to simplify working with
multi-file applications. This chapter also
explains compiler optimization features,
and how to use them in a project.

Working with ActiveX

Describes how to use ActiveX objects
with VLISP, and how to access other
applications through ActiveX.

7

Advanced Topics

Describes how to attach reactors to
AutoCAD drawings and objects.

8

AutoLISP Basics

Introduces basic AutoLISP concepts,
such as how to use expressions and
variables, handle numbers and strings,
display output, build lists, and define
functions.

9

Using AutoLISP to Communicate
with AutoCAD

Describes AutoLISP functions that you
can use to issue AutoCAD commands
and to interact with users in the
AutoCAD environment.

10

Using AutoLISP to Manipulate
AutoCAD Objects

Describes AutoLISP functions you can
use to manipulate AutoCAD drawing
entities, selections sets, extended data,
and symbol tables.

11

Designing Dialog Boxes

Introduces the elements that make up
dialog boxes. Explains DCL file structure
and syntax, and presents AutoLISP and
DCL code that defines and displays a
sample dialog box.

12

Managing Dialog Boxes

Describes how to control dialog boxes
with AutoLISP programs.

13

|

Maintaining Visual LISP Applications

6

6

Contents

Programmable Dialog Box Reference Lists and describes all the DCL tiles and
their associated attributes, and
summarizes the AutoLISP functions
available tor work with programmable
dialog boxes.

Introduction

Document Conventions
This document follows a number of stylistic and naming conventions when
describing actions or defining terms. Often, distinct typefaces are used to distinguish items from the rest of the text. The following table lists some of the
conventions used in the Visual LISP Developer’s Guide.
Typographical conventions
Text element

Example

Program code examples are
displayed in 8 pt Courier font.

(defun initfunc ( )
(setq *GLOBAL-WARMING* 4.0))

Text you enter is shown
in boldface.

At the VLISP Console prompt, enter shape

File names and directory
names are shown in
italics when referred
to in a sentence.

Double-click the file name drawline.lsp.
The default install directory is
C:Program FilesAutoCADVLISP

In definitions that include
variable text, the variable is
in italics.

A FAS file named appname-init.fas, where
appname is the application module name

variable names are in
courier type.

Double-click on any occurrence of the variable
name origin-y
The *LAST-VALUE* system variable

AutoLISP function names are shown
in bold courier type.

Use the entget function...
Use vlax-import-type-library to import

Document Conventions

|

7

Related Documents
In addition to the AutoLISP Reference and the Visual LISP Tutorial, several
other AutoCAD publications may be required by users building applications
with Visual LISP:
s

s

s

s

AutoCAD ActiveX and VBA Reference contains information on accessing
ActiveX methods, properties, and objects. If you develop AutoLISP applications that use ActiveX automation to reference AutoCAD objects, you
will need to refer to this reference guide. It is available through the
AutoCAD and Visual LISP Help menus.
AutoCAD Customization Guide contains basic information on creating
customized AutoCAD applications. For example, it includes information
on creating customized menus, linetypes, and hatch patterns. The Customization Guide is available through the AutoCAD and Visual LISP Help
menus.
The DXF Reference describes drawing interchange format (DXF™ and the
)
DXF group codes that identify attributes of AutoCAD objects. You may
need to refer to the DXF Reference when working with association lists
describing entity data. The DXF Reference is available through the
AutoCAD and Visual LISP Help menus.
The ObjectARX Reference contains information on using ObjectARX™ to
develop customized AutoCAD applications. AutoCAD reactor functionality is implemented through ObjectARX. If you develop AutoLISP
applications that implement reactor functions, you may want to refer to
this manual.
The ObjectARX Reference is not included when you install AutoCAD. To
obtain the manual, download the ObjectARX SDK (Software Development
Kit) from the Autodesk World Wide Web site (http://www.autodesk.com).
Click on the Product Index link and look for ObjectARX under Development Tools.

8

|

Introduction

Part 1
Using the Visual LISP
Environment

9

Getting Started

1

In This Chapter

This chapter introduces you to the look and feel of the

s Starting Visual LISP

Visual LISP interactive development environment

s Exploring the Visual LISP User
Interface

(IDE), and shows you how to run AutoLISP programs in

s Touring the Visual LISP Menus

Visual LISP.

s Understanding the Console
Window
s Understanding the Visual LISP
Text Editor
s Loading and Running AutoLISP
Programs
s Exiting Visual LISP

11

Starting Visual LISP
The Visual LISP (VLISP) interactive development environment runs in a
separate set of windows from the rest of AutoCAD. You must explicitly start
VLISP to work in the interactive development environment.
To start Visual LISP
1 Start AutoCAD.
2 Choose Tools ® AutoLISP ® Visual LISP Editor from the AutoCAD menu, or
enter the following at the Command prompt:
vlisp

You can use either the menu or the vlisp command to return to the VLISP
IDE at any time.
Note that AutoCAD also recognizes the vlide command to start or return to
Visual LISP. This command name stands for “Visual LISP interactive development environment.” AutoCAD issues the vlide command to call VLISP, and
as a result you may sometimes see “VLIDE” displayed in the AutoCAD Command window.

12

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Chapter 1

Getting Started

Exploring the Visual LISP User Interface
When you first start VLISP, it displays the following screen:
menu
toolbars

console
window

status bar

The areas shown in the VLISP screen are as follows:
Menu

You can issue VLISP commands by choosing from the
various menu items. If you highlight an item on a menu,
VLISP displays a brief description of the command’s
function in the status bar at the bottom of the screen.

Toolbars

Click toolbar buttons to issue VLISP commands quickly.
There are five toolbars—Debug, Edit, Find, Inspect, and
Run—each representing a distinct functional group of
VLISP commands. (In the figure shown on this page, the
toolbars are adjacent to one another, each toolbar
beginning with an icon (
). You can execute many, but
not all, menu commands from the toolbars. If you move
your mouse pointer over a toolbar button and leave it
there for a couple of seconds, VLISP displays a tooltip
indicating the function of the button. A more descriptive
explanation appears in the status bar at the bottom of the
VLISP screen.

Exploring the Visual LISP User Interface

|

13

Console
Window

This is a separate, scrollable window within the main
VLISP window. In the Console window, you can type
AutoLISP commands, similar to the way you do in the
AutoCAD Command window. You can also issue many
Visual LISP commands from this window, instead of using
the menu or toolbars. See “Understanding the Console
Window” on page 18 for more information about the
Console window.

Status Bar

The information displayed in the status bar located at the
bottom of the screen varies according to what you are
doing in VLISP.

You may also see a minimized Trace window. During startup, this window
contains informational messages about the current release of VLISP, and may
contain additional information if VLISP encounters errors during startup.

Introducing the Visual LISP Text Editor
You will spend much of your time in VLISP creating or modifying AutoLISP
programs. VLISP comes with an integrated text editor for you to use with
AutoLISP code.
To see how the text editor window displays code, open a sample AutoLISP
program. Begin with the drawline.lsp file provided with VLISP.

NOTE The sample files are only included in your installation if you chose Full
install, or if you chose Custom install and selected the Samples item. If you
previously installed AutoCAD and did not install the samples, rerun the install,
choose Custom, and select only the Sample item.
To view a LISP program in the VLISP text editor
1 From the VLISP menu, choose File ® Open File.
2 In the Open File dialog box, select the SampleVisualLISP folder, which is in
your AutoCAD install directory.
3 Double-click the drawline.lsp file.
VLISP opens the file in a new window—the text editor window—and displays
the name of the file in the status bar. If you make a change to the text in the
editor window, or add new text, VLISP places an asterisk (*) next to the file
name in the status bar. The asterisk remains next to that file name until you
either save your changes or close the file.

14

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Chapter 1

Getting Started

You can work on more than one file at a time. Each time you open a file,
VLISP displays the file in a new text editor window.

Other Visual LISP Windows
VLISP displays some output in the Console window, but several VLISP functions create their own windows in which to display results. For example,
when you trace the sequence of events during a running AutoLISP program,
the Trace function opens a window and displays program events. You cannot
enter text in these output windows, but you can copy text from them and
paste the text into the editor or Console windows.

Touring the Visual LISP Menus
You can issue VLISP commands by choosing from the various menu items.
For example, from the File menu you can create a new AutoLISP program file,
select an existing program file to edit, and print the file you’re editing.

Variable Menu Contents
Menu contents may vary depending on which VLISP window (for example,
text editor, Console) is active. To activate a different window, click in the
window’s title bar, or in any empty area of that window.
As an example, click in the text editor window containing the drawline.lsp
file, then choose Edit from the VLISP menu. You’ll see the following list:

Note that the last items on the menu are Parentheses Matching and Extra
Commands.


|

15

Now click in the title bar of the VLISP Console window, then select the Edit
menu item again:

Notice that Extra Commands is no longer the last item on the menu. Parentheses Matching is followed by two new items, Console History Up and
Console History Down; these items apply only to a Console window.

Visual LISP Menu Summary
The following table summarizes the VLISP menu items.
Visual LISP menu items
Menu item Uses
File

Edit

Find and replace text strings, set bookmarks, and navigate among
bookmarked text. See “Using the Text Editor” on page 31 for information on
these topics.

View

|

Copy and paste text, undo the last change you made to text (or undo the
last command entered in the Console window), select text in the VLISP editor
or Console windows, match parentheses in expressions, and redisplay
previous commands entered in the Console window. See the chapter titled
“Developing Programs with Visual LISP” for more information on Edit
features.

Search

16

Create a new AutoLISP program file for editing, open an existing file, save
changes to program files, build Visual LISP application files, and print
program files.

Find and display the value of variables and symbols in your AutoLISP code.
For more information on this topic, see chapter 3, “Debugging Programs.”

Chapter 1

Getting Started

Visual LISP menu items (continued)
Menu item Uses
Project

Work with projects and compile programs. See “Managing Multiple LISP
Files” on page 138, and “Compiling and Linking Programs” on page 110 for
information on these topics.

Debug

Set and remove breakpoints in your program and step through program
execution one expression at a time. You can then check the state of variables
and the results of expressions. See chapter 3, “Debugging Programs,” for
more information on these features.

Tools

Set VLISP options for text formatting and various environment options, such
as the placement of windows and toolbars.

Window

Organize the windows currently displayed in your VLISP session, or activate
another VLISP or AutoCAD window.

Help

Display online help.


|

17

Understanding the Console Window
From the VLISP Console window, you can enter and run AutoLISP commands and see the results. This is similar to what you can do in the AutoCAD
Command window, but there are a few differences—some subtle—in how
you accomplish the same task in these two windows. For example, to display
the current value of an AutoLISP variable in VLISP, you simply type the variable name in the Console window and press ENTER . To view the value of a
variable in AutoCAD, you must precede the variable name with an exclamation point (!) when you type it in the Command window.
The Console window is also where VLISP displays AutoLISP diagnostic
messages and the results of many AutoLISP functions. For example, output
from the print and princ functions is displayed in the Console window. You
can scroll through the Console window to view previously entered text and
output.
For a description of VLISP Console window features, see “Using the Console
Window” on page 25. The following is a brief summary of these features:
s
s
s
s

s

s

s
s
s

18

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Chapter 1

Evaluating AutoLISP expressions and displaying the return values from
those expressions.
Entering AutoLISP expressions on multiple lines by pressing CTRL + ENTER
to continue on the next line.
Evaluating multiple expressions at one time.
Copying and transferring text between the Console and text editor
windows. Most text editor commands are also available in the Console
window.
Retrieving previous commands entered in the Console by pressing TAB .
You can press TAB repeatedly to retrieve earlier commands. Press
SHIFT + TAB to reverse the direction of command retrieval.
Performing an associative search through the input history by pressing
TAB . For example, if you begin an expression with (+ and then press TAB ,
VLISP retrieves the last command you entered that begins with (+. To
reverse the direction of the search, press SHIFT + TAB .
Pressing ESC clears any text following the Console prompt.
Pressing SHIFT + ESC leaves the text you entered at the Console prompt
without evaluating the text, and displays a new Console prompt.
Right-clicking or pressing SHIFT + F10 anywhere in the Console window
displays a menu of VLISP commands and options. For example, you can
use this feature to copy and paste text in the Console command line,
search for text, and initiate VLISP debugging features.

Getting Started

Note that if you type text at the Console prompt but switch to the AutoCAD
window before pressing ENTER , the text will no longer be at the prompt
when you return to the VLISP window.

Understanding the Visual LISP Text Editor
The VLISP text editor is much more than a writing tool, it’s a central
component of the VLISP programming environment. To appreciate the versatility and value of the VLISP text editor, you need to be familiar with the
AutoLISP language. If you are not yet familiar with AutoLISP, you can learn
the basics in chapter 8, “AutoLISP Basics,” and find additional information
in chapter 9, “Using AutoLISP to Communicate with AutoCAD,” and
chapter 10, “Using AutoLISP to Manipulate AutoCAD Objects.”
Here are some of the major features of the text editor:
Color Coding
of Files

The text editor identifies different parts of an AutoLISP
program and assigns distinct colors to them. This allows
you to find program components easily such as function
calls and variable names, and helps you find
typographical errors.

Formatting of
Text

The text editor can format AutoLISP code for you, making
the code easier to read. You can choose from a number of
different formatting styles.

Parenthesis
Matching

AutoLISP code contains many parentheses, and the editor
helps you detect missing parentheses by finding the close
parenthesis that goes with an open parenthesis.

Execution of
AutoLISP
Expressions

You can test expressions and lines of code without leaving
the text editor.

Multiple File
Searching

The text editor can search for a word or expression in
several files with a single command.

Syntax
Checking of
AutoLISP Code

The text editor can evaluate AutoLISP code and highlight
syntax errors.

Details on using the VLISP text editor begin with “Using the Text Editor” on
page 31.

Understanding the Visual LISP Text Editor

|

19

Loading and Running AutoLISP Programs
Once you have opened an AutoLISP program file in the VLISP text editor, you
can load and run it. Loading is the process by which functions in a program
file are made available to the VLISP command interpreter. You can try this
out with the drawline.lsp sample program.
To load and run a program in a Visual LISP text editor window
1 Make sure the text editor window containing the drawline.lsp program is
active. If you are not sure whether the window is active, click anywhere in
the window to activate it.
2 Choose the Load Active Edit Window button from the Run toolbar, or choose
Tools ® Load Text in Editor from the VLISP menu.
VLISP responds by displaying a message in the Console window indicating it
has loaded the program.
3 Run the drawline function from the Console prompt by entering the function name in parentheses, then pressing ENTER :
_$ (drawline)

The drawline function will ask you to specify two points, and will then draw
a straight line between those points. When drawline asks for user input,
VLISP turns control over to AutoCAD to prompt you for the points. What
you see next depends on whether or not the AutoCAD windows are currently
displayed on your desktop. If AutoCAD is already on your desktop, you’ll see
the AutoCAD windows. But if AutoCAD is currently minimized on your desktop, the windows won’t automatically be restored and displayed. Instead,
VLISP remains visible and your mouse pointer changes to a VLISP symbol:

This symbol indicates that the VLISP window is no longer active. If this is the
case, you must manually switch to the AutoCAD window. Click the
AutoCAD icon on the Windows task bar to activate AutoCAD.
The following figure shows AutoCAD prompting for the input requested by
drawline:

20

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Chapter 1

Getting Started

4 Respond to the prompts by specifying points in the graphics window or on
the Command line.
After you respond to the prompts, control returns to VLISP and you will once
again see the VLISP window.
When you enter commands in the VLISP Console window or run a program
loaded from the text editor, you may be frequently switching back and forth
between the VLISP and AutoCAD windows. Aside from using the standard
Windows methods of switching between windows, you can activate the
AutoCAD window by choosing Window ® Activate AutoCAD from the
VLISP menu, or by pressing the Activate AutoCAD button on the Run toolbar. If you are in AutoCAD and want to return to the VLISP environment, you
can enter vlisp at the Command prompt, or choose:
Tools ® AutoLISP ® Visual LISP Editor from the AutoCAD menu.

Running Selected Lines of Code
With VLISP, you can select lines of code in the text editor window and run
only the selected code, instead of the whole program.
To run selected lines of AutoLISP code in a Visual LISP editor window
1 Using the drawline.lsp program as an example, highlight the following lines
of code:
(setq pt1(getpoint "nEnter the start point for the line: ")
pt2(getpoint pt1 "nEnter the end point for the line: "))

2 Press the Load Selection button on the Run toolbar.
VLISP immediately runs the code and switches control to AutoCAD to
prompt you for input.

Loading and Running AutoLISP Programs

|

21

Using Extended AutoLISP Functions
VLISP provides some extensions to the AutoLISP language that are not
loaded automatically when you start AutoCAD. These functions have names
that begin with vla-, vlax-, and vlr. The vla- functions implement ActiveX support in AutoLISP (described in chapter 6, “Working with ActiveX”). The vlaxfunctions provide ActiveX utility and data conversion functions, dictionary
handling functions, and curve measurement functions. The vlr- functions
provide support for AutoCAD reactors. Before you can use any of these functions, you need to load the AutoLISP extensions with the following function
call:
(vl-load-com)

This function first checks whether or not the AutoLISP extensions are already
loaded; if so, the function does nothing, otherwise it loads the extensions.
If you’re using the VLISP interactive development environment to develop
code, chances are you’ll want to use the AutoLISP extensions at some point.
It’s a good practice to issue vl-load-com when you start VLISP, or to include
a call to the function in your acaddoc.lsp file, so that it loads automatically.
But if you write programs that use any of the extended AutoLISP functions,
you need to call vl-load-com in those programs to ensure that the functions
are available to other users running your code.

Exiting Visual LISP
When you are finished with your VLISP session, you can close the program
by either choosing Exit from the File menu or clicking the Windows Close
button. Note that AutoCAD does not completely unload VLISP but merely
closes all VLISP windows.
Upon exiting AutoCAD, if you have made any changes to the code in any
VLISP text editor window and have not saved those changes, you will be
asked if you want to save your changes. You can either save all the changes
you’ve made by choosing Yes, or save none of the changes by choosing No.
VLISP retains its state when you exit. The next time you start a VLISP session,
VLISP automatically opens whichever files and windows were open when
you last exited.

22

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Chapter 1

Getting Started

Developing Programs with
Visual LISP

2

In This Chapter

VLISP provides many tools and features that help you
develop AutoLISP programs. This chapter describes the

s Getting Organized
s Using the Console Window
s Using the Text Editor

features that help you during the coding phase of program development. These features format AutoLISP
code to improve readability and help you detect syntax

s Using Console and Editor Coding
Aids
s Formatting Code with Visual LISP
s Checking for Syntax Errors

errors in your code.

23

Getting Organized
To develop an AutoLISP program with VLISP you must perform the following
steps:
s
s
s
s
s
s

Think about which tasks you want to accomplish with your program, and
how to approach those tasks.
Design the program.
Write the code.
Format the code for readability.
Check for errors in the program.
Test and debug the program.

This chapter provides you with information to help you accomplish writing,
formatting, and checking tasks. The “Debugging Programs” chapter
describes the debugging features of VLISP. The “Building Applications” and
“Maintaining Visual LISP Applications” chapters describe how to package
your programs into applications that can be run by other users, and how to
organize application components to facilitate future updates.

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Chapter 2

Developing Programs with Visual LISP

Using the Console Window
Most programming in VLISP takes place within the confines of the VLISP text
editor, but the ability to program interactively with AutoLISP provides some
unique advantages to the development process. In the VLISP Console
window you can enter AutoLISP code and immediately see the results of
executing that code.
Enter text in the Console window following the Console prompt, which
looks like the following:
_$
VLISP saves the text you enter and any output from executing the text. You
can then scroll through the Console window and see what transpired. You
can copy any text in the window and paste it at the Console prompt or in
another Windows application.

Understanding Console Behavior
The VLISP Console window is similar in some respects to the AutoCAD Command window, but it provides many more features. Although the Console
window and the AutoCAD Command window provide similar capabilities,
you don’t always use the same process to accomplish identical tasks. For
example, to display the current value of an AutoLISP variable in VLISP, you
simply type the variable name in the Console window and press ENTER . To
view the value of a variable in AutoCAD, you must precede the variable name
with an exclamation point (!) when you enter it at the AutoCAD Command
prompt.
Unlike the AutoCAD Command window, where pressing SPACEBAR causes
expression evaluation, text input at the VLISP Console prompt is not processed until you press ENTER . This permits you to do the following in the
Console window:
s

s
s

Continue an AutoLISP expression on a new line. To continue entering an
expression on a new line, press CTRL + ENTER at the point you want to continue.
Input more than one expression before pressing ENTER . VLISP evaluates
each expression before returning a value to the Console window.
If you select text in the Console window (for example, the result of a previous command or a previously entered expression), then press ENTER .
VLISP copies the selected text at the Console prompt.


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25

The VLISP Console window and the AutoCAD Command window differ in
the way they process the SPACEBAR and TAB keys. In the VLISP Console window, a space plays no special role and serves only as a separator. In the
AutoCAD Command window, pressing the SPACEBAR outside an expression
causes AutoCAD to process the text immediately, as if you had pressed
ENTER .

Using the Console Window History
You can retrieve text you previously entered in the Console window by pressing TAB while at the Console prompt. Each time you press TAB , the
previously entered text replaces the text at the Console prompt. You can
repeatedly press TAB until you cycle through all the text entered at the Console prompt during your VLISP session. After you’ve scrolled to the first
entered line, VLISP starts again by retrieving the last command entered in the
Console window, and the cycle repeats. Press SHIFT + TAB to scroll the input
history in the opposite direction.
For example, assume you entered the following commands at the Console
prompt:
(setq origin (getpoint "nOrigin of inyn sign: "))
(setq radius (getdist "nRadius of inyn sign: " origin))
(setq half-r (/ radius 2))
(setq origin-x (car origin))
(command "_.CIRCLE" origin radius)

To retrieve commands entered in the Console window
1 Press TAB once. VLISP retrieves the last command entered and places it at the
Console prompt:
_$ (command "_.CIRCLE" origin radius)

2 Press TAB again. The following command displays at the Console prompt:
_$


3 Press TAB again. VLISP displays the following command:
_$


4 Now press SHIFT + TAB . VLISP reverses direction and retrieves the command
you entered after the previous command:
_$ (setq origin-x (car origin))

5 Press SHIFT + TAB again. VLISP displays the following command:

This was the last command you entered at the Console prompt.

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Chapter 2


6 Press SHIFT + TAB again. Because the previous command retrieved was the last
command you entered during this VLISP session, VLISP starts again by
retrieving the first command you entered in the Console window:
_$ (setq origin (getpoint "nOrigin of inyn sign: "))

Note that if you enter the same expression more than once, it appears only
once as you cycle through the Console window input history.
You can perform an associative search in the input history to retrieve a specific command that you previously entered.
To perform an associative search of the Console input history
1 Enter the text you want to locate. For example, enter (command at the Console
prompt:
_$ (command

2 Press TAB . VLISP searches for the last text you entered that began with
(command:

If VLISP does not find a match, it does nothing (except possibly emit a beep).
Press SHIFT + TAB to reverse the direction of the associative search and find
progressively less-recent inputs.

Interrupting Commands and Clearing the Console Input Area
To interrupt a command entered in the Console window, press SHIFT + ESC .
For example, if you enter an invalid function call like the following:
_$ ((setq origin-x (car origin)
((_>

Pressing SHIFT + ESC interrupts the command, and VLISP displays an “input
discarded” message like the following:
((_>
_$

; <input discarded>

(Note that in this example, you can also complete the command by entering
the missing close parentheses.)
If you type text at the Console prompt, but do not press ENTER , then pressing
ESC clears the text you typed. If you press SHIFT + ESC , VLISP leaves the text
you entered in the Console window but displays a new prompt without evaluating the text.
If you type part of a command at the Console prompt, but activate the
AutoCAD window before pressing ENTER , VLISP displays a new prompt when
you next activate the VLISP window. The text you typed is visible in the Console window history, so you can copy and paste it, but you cannot retrieve


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27

the text by pressing TAB , because it was not added to the Console history
buffer.

Using the Console Window with Multiple
Drawings
There is a single Console window for all open AutoCAD drawing documents.
When you scroll through the Console window, you see commands entered
in all document contexts. This differs from the AutoCAD Command window,
which shows only the commands issued against the current drawing. In
other words, each AutoCAD drawing has its own Command window, but all
drawings share the same VLISP Console prompt.
VLISP automatically switches context when you change the active drawing
document in AutoCAD. The active document in AutoCAD is always the
active document in VLISP. Commands entered in the VLISP Console window
always apply to the active document. The title bar of the VLISP window contains the name of the active drawing document. The following example
shows how the title bars of the AutoCAD and VLISP windows identify the
same drawing document downtown.dwg:

Using the Console Shortcut Menu
The most important functions needed when working with the VLISP Console
window are combined into a shortcut menu for fast access. Right-click anywhere in the Console window or press SHIFT + F10 to display the shortcut
menu.
Depending on whether there is text selected in the Console window and
depending on the cursor position, some commands may not be appropriate
at the moment and cannot be activated from the shortcut menu. The follow-

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Chapter 2


ing table summarizes the commands that may be available from the Console
window shortcut menu.
Console window shortcut menu commands
Command

Action

Cut

Removes the selected text from the Console window and
moves it to the Windows Clipboard

Copy

Copies the selected text to the Clipboard

Paste

Pastes the Clipboard contents to the cursor location

Clear Console window

Empties the Console window

Find

Finds specified text in the Console window

Inspect

Opens the Inspect dialog box

Add Watch

Opens the Watch window

Apropos window

Opens the Apropos window

Symbol Service

Opens the Symbol Service dialog box

Undo

Reverses the last operation

Redo

Reverses the effects of the previous Undo

AutoCAD Mode

Transfers all input to the AutoCAD command line for
evaluation

Toggle Console Log

Copies Console window output to the log file

Note also that you can cut and paste text between the VLISP Console window
and the AutoCAD Command window.

Logging Console Window Activity
You can keep a record of all Console window activity by logging the activity
in a file. Later, you can view the file and review the activity that occurred in
the Console window.


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29

To control Console logging activity
1 Create a log file by choosing File ® Toggle Console Log from the VLISP menu.
Note that the Console window must be active for the Toggle Console Log
option to be available.

2 Choose a directory for the log file and specify a file name for the log.
If the file already exists, VLISP prompts you with the following message:

If you reply Yes, VLISP appends future Console window information to the
current contents of the file. If you reply No, VLISP overwrites the file and its
original contents will be lost. Choose Cancel to terminate the operation and
specify a different file name.
3 To close the log file and quit the logging process, choose Toggle Console Log
from the File menu again.
The state of Console window logging is indicated in the Console window’s
title bar. If logging is in effect, VLISP displays the name of the log file in the
title bar. If logging is off, no file name appears in the title bar.
If you do not close the log file before exiting VLISP, it closes the log file automatically upon exit. After a log file is closed, you can view its contents with
any text editor, such as the VLISP text editor.

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Chapter 2


Using the Text Editor
If you just need to run a few simple AutoLISP expressions, entering the
expressions in the VLISP System Console may suffice. For anything more
than that, however, you will need to use the VLISP text editor and save your
AutoLISP code in a file.
The text editor is a basic component of VLISP. It is easy to use and, if you have
some experience using Windows, you can begin using it after a quick review
of this chapter.
The VLISP text editor has a number of features designed to support AutoLISP
programming, such as selecting of complete AutoLISP expressions, matching
of balanced parentheses, syntax coloring, and executing AutoLISP expressions without leaving the editor window. Most text editor commands can be
called from the menu bar, and some of the most frequently used commands
are also available from toolbar push buttons.

Editing a File
To open a new file in the VLISP text editor, choose File ® New File from the
menu bar. An empty editor window appears on the screen, and you can begin
entering text.
To start a new line, press ENTER . The text editor does not wrap your text
when it reaches the end of the visible text editor window, so everything you
type goes on the same line until you press ENTER .
You can indent lines of text manually, but VLISP automatically formats code
for you as you enter new lines of code. You can also copy text from another
file and have VLISP format the block of text you add. See “Formatting Code
with Visual LISP” on page 50 for details on using the VLISP code formatting
features.

Undoing Your Last Change
You can reverse your last edit action by choosing Edit ® Undo from the
VLISP menu bar. You can undo a virtually unlimited number of changes,
back to the point at which you last saved the file.
To reverse the effects of the Undo command, choose Edit ® Redo from the
menu. Redo only works if you issue it immediately after Undo.

Creating Automatic Backup Files
VLISP supports the automatic creation of backup copies of files loaded by the
text editor. The actual backup creation occurs when you save the file for the


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31

first time. Backup files have the same name as your original file, except the
file extension begins with an underscore (_) and is followed by the first
two characters of the original extension. For example, the backup file for
drawline.lsp would be drawline._ls.
Automatic creation of backup files is an option you can set by choosing
Tools ® Environment Options ® General Options. Choose the Editor option
labeled “Backup the File Edited on First Save” to turn on automatic backup.
By default, this option is already selected when you first install VLISP.

Restoring from a Backup File
If a backup file exists, you can restore the file you are editing to its original
content, reversing all the changes you made. From the File menu, choose
Revert to restore the file. If there is no backup file for the text in the editor
window, VLISP displays an error message.

Editing an Existing File
Choose File ® Open from the VLISP menu to open an existing file. VLISP
opens a new text editor window for the file you select. You can open any
number of files and work on them simultaneously. VLISP places each file in
its own editor window.

NOTE If you select text in any VLISP window before choosing File ® Open, the
selected text is placed in the File name field of the Open dialog box.
When you exit VLISP, it notes which files are open and saves this information
for your next VLISP session. The next time you start VLISP, it automatically
opens the files for you.

Using the Text Editor Shortcut Menu
Right-clicking your mouse in an active VLISP text editor window brings up a
shortcut menu for quick access to frequently used commands. Depending on
whether there is text highlighted in the editor window and depending on the
position of the cursor, some commands on the shortcut menu may be inactive. The following table summarizes the editor shortcut commands:

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Chapter 2


Text editor window shortcut menu commands
Command

Action

Cut

Moves the selected text to the Clipboard

Copy

Copies the selected text to the Clipboard

Paste

Pastes the Clipboard contents to the cursor position

Find

Finds the specified text in one or more editor windows

Go to Last Edited

Moves the cursor to the position you last edited

Toggle Breakpoint

Sets a breakpoint at the cursor position, or removes a
breakpoint if one is set currently at that position

Inspect

Opens the Inspect dialog box

Add Watch

Opens the Watch window

Apropos window

Opens the Apropos window

Symbol Service

Opens the Symbol Service dialog box

Undo

Reverses the last operation

Redo

Reverses the effects of the previous Undo

Using Keyboard Shortcuts in the Text Editor
The VLISP text editor provides numerous keyboard shortcuts you can use
instead of menu selections and mouse clicks.

Correcting Text
You can delete words or lines using the following shortcuts:
Text correction shortcut keys
To

Press

Erase a word to the left of the cursor

CTRL + BACKSPACE

Erase a word to the right of the cursor

SHIFT + BACKSPACE

Delete characters from the cursor position to the
end of the current line

CTRL +E, then press E


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33

You can also can use the overstrike mode to insert text. Overstrike mode is
toggled on and off by pressing INSERT. When in overstrike mode, each character you type replaces existing text. The cursor changes shape from vertical
to horizontal when in overstrike mode.

Selecting Text
The simplest method to select text is to double-click your left mouse button.
The amount of text selected depends on the location of your cursor.
s
s
s

If the cursor immediately precedes an open parenthesis, VLISP selects all
the following text up to the matching close parenthesis.
If the cursor immediately follows a close parenthesis, VLISP selects all preceding text up to the matching open parenthesis.
If the cursor immediately precedes or follows a word, or is within a word,
VLISP selects that word.

To select specific text, press and hold the SHIFT key while pressing the direction (arrow) keys on the keyboard. Other keyboard methods of text selection
are listed in the following table:
Text selection shortcut keys
To
Expand the selection to the next line

SHIFT + UP ARROW

Expand the selection to the end of the line

SHIFT + END

Expand the selection to the beginning of the line

SHIFT + HOME

Expand the selection down one window, or
abandon selection of the next window, if it is
currently selected

SHIFT + PAGEDOWN

Expand the selection up one window, or
abandon selection of the previous window,
if it is currently selected

SHIFT + PAGEUP

Expand the selection to the next word, or
abandon selection of the next word, if it is
currently selected

CTRL + SHIFT +RIGHT ARROW

Expand the selection to the previous word, or
abandon selection of the previous word, if it is
currently selected

|

SHIFT + DOWN ARROW

Expand the selection to the previous line

34

Press

CTRL + SHIFT +LEFT ARROW

Chapter 2


Text selection shortcut keys (continued)
To

Press

Expand the selection up to the matching left
parenthesis

CTRL + SHIFT +[

Expand the selection up to the matching right
parenthesis

CTRL + SHIFT +]

Move the cursor to the other side of the selection

ALT+ ENTER

Navigation Shortcuts
In addition to using the cursor arrow keys, you can use the following VLISP
editor shortcuts to navigate through your text:
Navigation shortcut keys
To move

Press

One word to the left

CTRL +LEFT ARROW

One word to the right

CTRL +RIGHT ARROW

To the end of a line

END

To the beginning of a line

HOME

Down one window

PAGEDOWN

Up one window

PAGEUP

To the end of a document

CTRL + END

To the start of a document

CTRL + HOME

To the matching left parenthesis

CTRL + [

To the matching right parenthesis

CTRL + ]

Indenting Shortcuts
Most indenting of program code is best handled by the VLISP automatic code
formatting and Smart Indent features, and by customizing the formatter’s
options (see “Formatting Code with Visual LISP”). But there are some things
you may want to do by yourself.


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35

To indent selected lines of code, press TAB or press CTRL + E, and then choose
Indent Block. VLISP inserts a TAB character at the beginning of each line you
selected. You can control the indent amount of the TAB character by choosing Tools ® Window Attributes ® Configure Current and setting the Tab
Width value. You can also use the following keyboard shortcuts to adjust the
indentation of text.

Code indentation shortcuts
To

Do

Adjust the indent of the current selection to the
preceding AutoLISP text.

Press SHIFT + TAB

Clear trailing SPACE and TAB characters, insert a Press SHIFT + ENTER
new line, and indent at the level of the previous
non-empty line.
Insert a new line without clearing trailing SPACE
and TAB characters of the current line.

Press CTRL + ENTER

Moving and Copying Text
In addition to using the standard Windows Cut, Copy, and Paste functions,
the VLISP text editor allows you to drag text from one location to another
within the edit window.

To move text by dragging
1 Select the text you want to move.
2 Point anywhere inside the selected area, and press and hold the left mouse
button.

3 Drag the text to the new location.
4 Release the mouse button.
To copy the text instead of moving it, follow the same steps, but press CTRL
before releasing the mouse button in step 4.
You can also take selected text and copy it into a new file. With the text
selected, press CTRL + E to display a list of options, and choose Save Block As.
VLISP replies by displaying a dialog box for you to specify where you want to
save the text.
VLISP uses the Windows Clipboard for all cut and copy operations. Therefore, you can exchange text with any other Windows application that

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Chapter 2


supports these functions. This also means you can copy and paste text
between the text editor and the VLISP Console window.
Remember that immediately after moving or copying text, you can change
your mind and reverse the action, using the Undo function.

Searching for Text
The VLISP text editor has extensive text-searching capabilities. From the
Search menu, choose Find to begin a search, or press the Find toolbar button.
VLISP displays the Find dialog box:

In the Find What data entry field, type the character string you want to
locate. If there is text selected when you enter the Find command, this text
is automatically placed in the Find What field.
Choose Find to start the search. When searching through a single file, press
F3 to search for the next occurrence of your search string. Choose Cancel to
end the search.
When searching through multiple files (see the next topic, “Choosing Search
Options”), VLISP displays the matches it found in an output window like the
following:


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37

Double-click on any highlighted lines in the Find Output window to open
the associated LISP file in a VLISP editor window.

Choosing Search Options
Under the Search heading, indicate the extent of the search you want VLISP
to conduct. You can choose one of the following:

Current
Selection

Searches only the text highlighted in the editor window.

Current File

Searches through the entire file in the active editor
window.

Find in Project

With this option selected, VLISP prompts you to specify
the name of the VLISP project you want to search. It will
search all the files in this project and display all matches
in a new output window. See “Finding a String in Project
Source Files” on page 150 for more information on this
option.

Find in Files

If you select this option, VLISP allows you to specify a
Windows directory (folder) to search for the text.
Optionally, you can instruct VLISP to search all
subdirectories of that directory as well. VLISP will search
through all the files and display all matches in a new
output window.

When searching for text within the current file, the Direction setting determines where VLISP looks next for the search text. Choose Down to search
forward (toward the end of the file) from the cursor position. Choose Up to
search backward (toward the beginning of the file) from the cursor position.
The Find dialog box also includes the following options:

Match Whole
Word Only

Match Case

38

|

If selected, VLISP will only match complete words. For
example, if the search term is ent and VLISP encounters
the word enter in the text, VLISP does not consider this a
match. However, if the Match Whole Word Only option
is not selected, VLISP considers the ent within enter to be
a match.
If selected, VLISP only matches text set in the same case.
In this instance, Ent and ent are not considered a match. If
Match Case is not selected, Ent and ent are considered a
match.

Chapter 2


Mark Instances

If you select this option, the position of the located text
will be added to the bookmark ring (see “Bookmarking
Text” on page 40). This lets you return quickly to this code
position later. Searches that find all occurrences of a string
add each position to the bookmark ring.

Repeating an Earlier Search
VLISP saves each search string you enter in a pull-down list on the toolbar.

To repeat a search you made earlier, click the pull-down arrow and select a
search term from the toolbar list. Press the Find Toolbar String button to conduct the search.

Replacing Text
The Search menu contains a Replace function that is used to replace the
search text with a text string that you specify.

The Replace dialog box is similar to the Find dialog box, but with fewer
options. It contains an additional Replace With entry field, in which you
specify the text you want VLISP to substitute for the search text. Specify the
search text in the Find What field.


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39

You can take the following actions from the Replace dialog box:
s
s

Press Find Next to find the next occurrence of the search string.
Press Replace to replace the found text with the replacement string.
If you don’t want to replace this occurrence of the text, press Find Next to
search for the next occurrence of the text, or Cancel to end the search.

Press Replace All to replace all occurrences of the search string with the
replacement string.
s Press Cancel to end the Replace function.
s

Bookmarking Text
The bookmark feature helps you navigate through VLISP text editor windows
by letting you mark up to 32 positions (bookmarks) in each window. Once
32 bookmarks are set, adding a new bookmark results in the oldest bookmark
being removed.
Each text editor window maintains its own set of bookmarks, and the bookmark navigation tools let you walk through the marks within each window
independently of the other windows. A set of bookmarks within a window is
known as a bookmark ring. You can step either forward or backward through
the ring, and eventually return to the starting point.
Whenever you step to a bookmark, VLISP automatically places a marker at
the location you are stepping from. In effect, the marker for the place you are
jumping to is moved to the place you jumped from. This makes it easy to
return to your original location just by stepping back in the opposite direction, or by cycling through all the bookmarks until you get back to the
starting point.

To add a bookmark
1 Move the cursor to the location you want to mark.
2 Press the Toggle Bookmark button on the toolbar, or press ALT + . ( ALT plus a
period).
Bookmarks may also be inserted automatically when using the Find command to search for text. See the discussion on search options in “Searching
for Text” on page 37 for more information on this feature.

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Chapter 2


To move the cursor from one bookmark to the next
1 Move the cursor to the previous bookmark in the ring by choosing
Search ® Bookmarks ® Previous Bookmark, or by pressing the
Previous Bookmark toolbar icon. You can also accomplish this by pressing
CTRL + , ( CTRL plus a comma).

2 Move the cursor to the next bookmark in the ring by choosing
Search ® Bookmarks ® Next Bookmark, or by pressing the Next Bookmark
toolbar icon. You can also accomplish this by pressing CTRL + . ( CTRL plus a
period).
In addition to jumping between bookmarks, you can also jump and select the
text between two bookmarks.

To move the cursor and select text between bookmarks
1 Press CTRL + SHIFT + , (comma) to select the text between the current location
and the next bookmark.

2 Press CTRL + SHIFT + . (period) to select the text between the current location
and the previous bookmark.
Removing a bookmark is similar to setting a bookmark.

To remove a bookmark
1 Move the cursor to the bookmarked location.
2 Press the Toggle Bookmark button, or press ALT + . ( ALT plus a period).
The Toggle Bookmark command works as an on/off switch. If you issue the
command when a bookmark is set, Toggle Bookmark turns it off. Issue the
same command when there is no bookmark set, and Toggle Bookmark inserts
a bookmark.

3 To remove all the bookmarks in the active window, press the Clear All Bookmarks button on the toolbar, or choose
Search ® Bookmarks ® Clear All Bookmarks from the VLISP menu.


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41

Using Console and Editor Coding Aids
Several VLISP coding aids are useful at both the Console and text editor windows. One highly visual aid is the assignment of colors to AutoLISP language
elements. Color coding helps you detect syntax errors in your code. VLISP
also contains several features to help you determine the names of variables
and functions that you need to refer to in your program, and shortcuts to
online help for AutoLISP functions.

Understanding Visual LISP Color Coding
As soon as you enter text in the VLISP Console or text editor windows, VLISP
attempts to determine if the entered word is a built-in AutoLISP function, a
number, a string, or some other language element. VLISP assigns every type
of element its own color. This helps you detect missing quotes or misspelled
function names. The default color scheme is shown in the following table .

Default color coding scheme for AutoLISP code
AutoLISP language element

Color

Built-in functions and protected symbols

Blue

Strings

Magenta

Integers

Green

Real numbers

Teal

Comments

Magenta, on gray background

Parentheses

Red

Unrecognized items (for example, user variables)

Black

You can change the default colors by choosing
Tools ® Window Attributes ® Configure Current from the VLISP menu. See
“Configure Current” on page 473 for more information on setting colors.
The VLISP text editor provides color coding for LISP files, DCL files, SQL files,
and C++ language source files (see “LISP, FAS, and Other File Types” on page
138 for a list of file types recognized by VLISP). VLISP uses the file name
extension to determine a file’s type, and then selects the color coding accordingly. You can change the color coding style associated with a file type by

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Chapter 2


choosing Tools ® Window Attributes ® Syntax Coloring from the VLISP
menu. All text entered in the Console window is treated as AutoLISP code.

Using the Apropos Feature
The Apropos feature is a tool that searches the VLISP symbol table. The symbol table contains every symbol read by the AutoLISP reader. This includes
symbols in user programs and symbols that implement the AutoLISP language.
You can define specific search criteria for Apropos to use in searching the
symbol table. For example, you can tell Apropos to search for all symbol
names that contain a specific character string, and you can further refine that
search to return only symbols that identify functions.
To invoke Apropos, choose View ® Apropos Window from the VLISP menu,
or press the Apropos button on the VLISP toolbar. If you select text prior to
invoking Apropos, VLISP immediately performs an Apropos search on the
selected text. If no text is selected, VLISP displays the Apropos options
dialog box:

In the input field of the Apropos options dialog box, enter the text you want
Apropos to search for. The dialog box contains the following options:

Match by
Prefix

If this option is turned on, Apropos searches for a match
starting only from the first character of the symbol name.
If the option is turned off, Apropos tries to match the text
you entered starting at any position of a symbol name.
For example, with Match by Prefix off, a search on the
word get returns symbol names including getint,
getpoint, ssget, and vla-getActive. With Match by
Prefix on, the same search does not return ssget and
vla-getActive, because get appears in the middle of those
symbol names, not at the beginning.


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43

Use
WCMATCH
(wild card
match)

If this option is turned on, Apropos treats asterisks as wildcard characters when searching. For example, if you
specify fun* as the symbol you want matched, Apropos
looks for all names that contain fun, no matter what
characters follow. In contrast, with Use WCMATCH
turned off, the asterisk is treated as a string and Apropos
only matches names that precisely contain fun*.

Downcase
Symbols

If turned on, any symbols you copy to the Clipboard with
the Apropos service are converted to lowercase characters.
If you paste the symbol name in another window, it
appears in lowercase.

Filter Flags

This option lets you choose symbols with matching flag
settings. VLISP displays a list of check boxes that
correspond to the symbol flags described in
“Understanding Symbol Flags” on page 94. If the flag filter
is on, only symbols set with the selected flags are
considered.

Filter Value

Opens the Filter Value dialog box, from which you can
select additional search criteria. You can choose one of the
following:

All No filter.
Null value

Only nil-valued symbols are considered for

matching.

Nonull value Only symbols that are not nil are
considered for matching.
Functions

All function types (user-defined, built-in, etc.)
are considered for m atching.

User function Only user-defined functions (USUBR) are
considered.

Built-in function Only built-in or compiled AutoLISP
functions (SUBR) are considered for matching.

Exrxsubr

Only external function names are matched.

If you specify a filter value or filter flag, the message area of the Apropos
options dialog box indicates your selections.
When you’ve specified the criteria you want Apropos to use in its search,
press OK to conduct the search.

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Chapter 2


To search for AutoLISP symbols that begin with set
1 Choose View ® Apropos Window from the VLISP menu.
2 Enter set in the text input field of the Apropos options dialog box.
3 Select the Match by Prefix option.
4 Clear all other options in the Apropos options dialog box.
5 Press OK to conduct the search.

Using the Results of an Apropos Search
Apropos displays the symbols matching your search criteria in the following
window:

The bottom of the Apropos results window contains a message area with
information about the results of the search. In the current example, the message indicates the number of symbols Apropos found in its search.
If the Apropos results window is not large enough to show all the symbols
found, the window is displayed as scrollable. If the search returns over a
thousand matches, Apropos will not be able to list all the symbols, even in a
scrollable window. The message area in the results window warns you when
this occurs, as in the following example from a search on the prefix VL:


|

45

If your search results in too many symbols for Apropos to display in the
results window, you can use the Copy to Trace/Log feature to view the complete list of symbols in the VLISP Trace window.
To return to the Apropos options window and refine your search, press the
Apropos options button in the Apropos results window toolbar. The toolbar
also contains the following buttons:

Copy to
Trace/log

Copies the results of the Apropos search to the VLISP Trace
window. Data in the Trace window can be copied using
the Windows copy command. If Trace logging is active,
the contents are also copied to the log file (see “Using
Visual LISP Data Inspection Tools” on page 82 for
information on Trace logging).

Help

Invokes online help for the selected symbol. The symbol
name is used as the Help index search value.

You can also use the Apropos results window’s shortcut menu on selected
symbols. For example, you can select a symbol from the list and insert it into
the VLISP Console or text editor window.

To insert a symbol from the Apropos results window
1 Select a symbol from the list.
2 Right-click to display the shortcut menu, and choose Copy to Clipboard
from the list of options.

3 Click in the VLISP window at the point you want to insert the symbol name.
4 Right-click and select Paste from the context menu, or press CTRL + V to paste
the text.
The other options on the shortcut menu are:

Inspect

Print

|

Print the symbol name in the Console window. If you
select a symbol name displayed in the Console window
and press ENTER , VLISP copies the symbol name to the
Console prompt.

Symbol

46

Invoke the VLISP Inspect feature for the selected symbol.
See “Using Inspect Windows” on page 95 for information
on using this feature.

Invoke the VLISP Symbol Service feature for the selected
symbol. See “Using the Symbol Service Dialog Box” on
page 92 for information on using this feature.

Chapter 2


Copy

Copy the selected symbol name to the *OBJ* system
variable.

Add to Watch

Add the selected symbol to the Watch window. See “Using
the Watch Window” on page 83 for information on using
this feature.

Help

Invoke online help for the selected symbol.

Letting Visual LISP Help You Complete Words
Two VLISP features, Complete Word by Match and Complete Word by Apropos, allow you to type part of a word and get help in completing the rest.

Completing a Word by Matching
Using Complete Word by Match, VLISP completes a partially entered word
by matching the part you have typed with another word in the same window. For example, suppose the following shows the history of your VLISP
Console window:
_$
_$
_$
_$
_$


In other words, these are the last five commands that you entered from the
Console.

To complete a word by matching
1 Type the following at the Console prompt:
_$ (c

2 Press CTRL + SPACEBAR to invoke Complete Word by Match. VLISP finds the
last word you entered that began with the letter “c,” and completes the word
you started to type:
_$ (command

3 If that is not the word you are looking for, press CTRL + SPACEBAR again.
VLISP searches back through the Console history for the previous occurrence
of a word beginning with the letter “c”:
_$ (car

VLISP will keep searching for matching words each time you press
CTRL + SPACEBAR . If you keep pressing CTRL + SPACEBAR after VLISP finds the
last matching word, VLISP repeats the retrieval sequence. (Note that you can


|

47

also choose Search ® Complete Word by Match from the VLISP menu instead
of pressing CTRL + SPACEBAR to invoke the Match feature.)
If VLISP does not find any matching words, it does nothing.
You can use Complete Word by Match in either the Console window or the
text editor window. When you invoke the feature from the Console window,
VLISP only searches the Console for a match; when invoked from a text editor window, VLISP only searches that editor window for a match.
The Complete Word by Match feature is not case-sensitive. In the previous
example, you would have achieved the same result had you entered a capital
C instead of a lowercase c.

Completing a Word by Apropos
With the Complete Word by Apropos feature, VLISP completes a partially
entered word with a matching symbol name from the VLISP symbol table. To
demonstrate this feature, assume you have entered the following commands
shown in your VLISP Console window:
_$
_$
_$
_$
_$


To use the Complete Word by Apropos feature
1 At the Console prompt, type the following:
_$ (ha

2 Press CTRL + SHIFT + SPACE to invoke Complete Word by Apropos on the partially entered word. VLISP lists all symbol table entries that begin with “ha”:

VLISP found two matching words in the symbol table. The half-r symbol is
a variable you defined in the Console window, and the handent symbol represents an AutoLISP function.

3 Select the symbol you want to complete your typing. If you do not want to
select a symbol, press ESC .

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Chapter 2


Note that you can also choose Search ® Complete Word by Apropos from the
VLISP menu instead of pressing CTRL + SHIFT + SPACE to invoke the feature.
If no symbols match the text you’ve entered, VLISP displays the Apropos
options dialog box:

The message area of the Apropos options dialog box shows the value that
Apropos could not match. See “Using the Apropos Feature” on page 43 for
information on setting Apropos options and renewing your search.
If VLISP finds more than 15 matching names in the symbol table, it displays
the Apropos results dialog box. For example, type get at the Console prompt,
then press CTRL + SHIFT + SPACEBAR to invoke the Apropos feature. VLISP displays the following dialog box:

You can select a symbol from the results window and copy it into your code
using a shortcut menu. If you need additional help with copying the symbol
to your program code, or using other features of the Apropos results window,
see “Using the Results of an Apropos Search” on page 45.


|

49

Getting Help for AutoLISP Functions
If you select a function name anywhere in a text editor or Console window,
and then press the Help button on the Tools toolbar, VLISP displays help for
the function. This feature works for any function recognized by VLISP. You
can also press CTRL + F1 to view Help for the selected function.

Formatting Code with Visual LISP
The VLISP code formatter arranges the text of AutoLISP expressions in a style
that improves text appearance and readability. The code formatter includes
a Smart Indent feature to arrange the indentation of program code automatically. The code formatter works automatically as you enter code in a VLISP
text editor window. You can also explicitly invoke the formatter to rearrange
selected blocks of text or all text in a VLISP editor window. This is useful for
formatting text you copy from other editors, or for reformatting your code in
a different style.

To format text in an active editor window
1 To format all the code in the window, choose Tools ® Format code in Editor
from the VLISP menu, or click the Format Edit window button on the Tools
toolbar.

2 To format only part of the code in the editor window, select a fragment of
code text and choose Format Code In Selection from the Tools menu, or click
the Format Selection button on the Tools toolbar.
If you select text to be formatted, the selection must contain valid AutoLISP
expressions or the formatter will issue an error message.
If the formatter finds unbalanced parentheses in your code, it issues the following message:

Choose Yes to have VLISP add parentheses where it thinks they belong;
choose No if you want to fix the parentheses on your own.

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Chapter 2


NOTE The VLISP formatter can balance the number of parentheses but usually
does not insert the additional parentheses in the right places. See “Checking the
Balance of Parentheses” on page 61 for more information on detecting and correcting unmatched parentheses.
The VLISP Smart Indent feature works in the background as you type in the
text editor. The indent is evaluated up to the current AutoLISP parenthesis
nesting level. If the current expression is preceded by only a sequence of
completed top-level AutoLISP expressions, the indentation will be zero. You
can affect the amount of indentation by specifying Visual LISP format
options; see the next two topics.

Understanding Visual LISP Formatting Styles
The VLISP formatter chooses the appropriate formatting style according to
rules that are explained in this section. You can influence the choice of VLISP
styles through the options you set in the Format Options dialog box. To display the Format Options dialog box, choose
Tools ® Environment Options ® Visual LISP Format Options from the
VLISP menu:

Initially, VLISP displays only a subset of the formatting options you can specify. Press the More Options button in the Format Options dialog box to
expand the window with additional formatting options.


|

51

The following are two main formatting style sets:
s
s

A single-line formatting style—Plane
Multiple-line formatting styles—Wide, Narrow, Column

The sample text below demonstrates the different formatting styles.
Sample text initial appearance:
(autoload "appload"
'("appload"))

For a general function call expression, the formatter applies one of the styles
in the following sections:

Plane Style
In the Plane style, all arguments are placed in the same line, separated by a
single space:
(autoload "appload" '("appload"))

The Plane style is applied to an expression when all the following conditions
are met:
The expression’s last character position does not exceed the value of the
Right Text Margin environment option.
s The expression’s printing length is less than the value of the Approximate
Line Length environment option (that is, last character position minus
starting indentation position is less than this value).
s

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Chapter 2


s

The expression does not contain embedded comments with Newline characters.

Wide Style
In the Wide style, the first argument is placed in the same line as the function
name, and other arguments are aligned in a column below the first
argument.
(autoload "appload"
'("appload")
)

The Wide style applies to an expression when the following conditions
are met:
s
s

The Plane style cannot be applied.
The first element is a symbol, and the first element’s length is less than the
Maximum Wide Style Car Length environment option.

Narrow Style
In the Narrow style, the first argument is placed on the next line after the
function name, and other arguments are aligned in a column below the first
argument. The displacement of the first argument’s starting position relative
to the expression starting position is controlled by the value of the
Narrow Style Indentation environment option (in the following example,
this value is equal to 2):
(autoload
"appload"
'("appload")
)

The Narrow formatting style applies for progn expressions, and for those
instances when the Plane and Wide formatting styles cannot be applied.

Column Style
In the Column style, all elements are positioned in a column. This style is
appropriate for displaying quoted lists and COND-expression clauses. For
example, the following text:
'((10 "{insertion}")
(7 "{style}"))

(1 "{string}")

would be displayed as:
'((10 "{insertion}")
(1 "{string}")
(7 "{style}")
)


|

53

Applying Formatting Options
In addition to affecting the basic formatting styles, you can choose from a
number of Visual LISP format options.

Close Parenthesis Style
This style controls the position of the close parenthesis for multiple-line formatting styles. You can select one of the following options:

Parenthesis Position Options (continued)
Close parenthesis on the last line of each formatting
Close at the
expression.
Same Line
Close at the
New Line with
Inner
Indentation

Close parenthesis on the next line following the last line
of each formatting expression with the inner indent.

Close at the
New Line with
Outer
Indentation

Close parenthesis on the next line following the last line
of each formatting expression with the outer indent.

Examples:
The initial expression is written as:
(cond
((/= (logand mask flg) 0)
(list (list txton)))
)

Formatting result when Close at the Same Line option is selected:
(cond ((/= (logand mask flg) 0)
(list (list txton))))

Formatting result when Close at the New Line with Inner Indentation option
is selected:
(list (list txton))
)
)

Formatting result when Close at the New Line with Outer Indentation is
selected:
(list (list txton))
)
)

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Chapter 2


Insert Form-Closing Comment
If you select this option, VLISP adds a comment following the close of an
expression. However, the option takes effect only if the Close Parenthesis
Style format setting is either Close at the New Line with Inner Indentation or
Close at the New Line with Outer Indentation.
When the Insert Form-Closing Comment option is on, the VLISP formatter
inserts a comment of the form
;_ end of <function name>

after each multiple-line function. This comment does not appear if an inlinecomment, single-semicolon comment, or pasted-comment exists after the
function call. You can change the comment text by entering a different comment in the Form-Closing Comment prefix field of the Format Options
dialog box.

Example
Initial text:
(autoarxload "image"
'("gifin" "pcxin" "riaspect" "ribackg" "riedge"
"rigamut" "rigrey" "rithresh" "tiffin"))

Formatted text:
(autoarxload "image"
'("gifin"
"pcxin"
"ribackg"
"riedge"
"rigrey"
"rithresh"
)
) ;_ end of autoarxload

"riaspect"
"rigamut"
"tiffin"

Note the _ end of autoarxload comment in the last line of code.

Preserve Existing Line Breaks
When the Preserve Existing Line Breaks option is on, the VLISP formatter
inserts new lines whenever a new line is detected in the text it is formatting.
When the option is off, the formatter can squeeze a multiple-line expression
to the Plane style, if it fits within the right margin.
The following example shows how the Preserve Existing Line Breaks option
works.


|

55

Initial text:
(if (/= s "Function canceled")
"nError: "
s)) ;single semicolon cmt
)

(princ (strcat

Formatting result if the option is on (default):
(princ (strcat
"nError: "
s
)
)
)

;single semicolon cmt

Formatting result when the option is off:
(princ (strcat "nError: " s))
)

;single semicolon cmt

Note that multiple-line princ and strcat expressions are compressed to a
single line.

Split Comments
When the Split Comments option is on, the formatter splits long comments
that extend past the right margin.
For the previous example, if the Right Text Margin setting is 60, and SingleSemicolon comment indentation is 40, the formatter will split the comment
as follows:
(princ (strcat "nError: " s))

;single
;semicolon cmt

)

Long List Format Style
Long lists are lists of formal arguments in defun, lambda, or quoted lists containing more than five elements. The Long List format style applies to lists
that do not fit on a single line (within the Right Text Margin).
If the Long List format style options do not appear in your Format Options
dialog box, press the More Options button to display additional formatting
options. The available modes for Long List format are listed below and illustrated with an example based on the following list elements, and with Right
Text Margin set to 45:
'("entdel" "entmake" "entmod" "entnext"
"entsel" "entupd")

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Chapter 2


Single-Column formatting:
'("entdel"
"entmake"
"entmod"
"entnext"
"entsel"
"entupd"
)

Two-Column formatting:
'("entdel"
"entmod"
"entnext"
)

"entmake"
"entsel"
"entupd"

Multi-Column formatting:
'("entdel"
"entsel"
)

"entmake"
"entnext"

"entmod"
"entupd"

Fill-the-String formatting (places as many quoted strings on one line as possible, up to the right margin):
'("entdel" "entmake" "entmod" "entsel" "entnext" "entupd"
)

The Preserve Existing Line Breaks option, if selected, may supercede the formatting indicated by Long List format style.

Setting Case for Symbols
By default, the VLISP formatter does not change the case of AutoLISP symbols. You can set the formatter to change the case of symbols according to
the VLISP protection state for symbols.
The Protected options subgroup controls the case conversion of protected
symbols (built-in symbols or symbols with the ASSIGN-PROTECT flag set). The
Unprotected options subgroup controls case conversion of unprotected
(user) AutoLISP symbols.

Case settings for symbols
Setting

Effect

None

Does not change the case

downcase

Forces all characters in a symbol's name to lowercase

UPCASE

Forces all characters in a symbol's name to uppercase


|

57

Applying Visual LISP Comment Styles
The VLISP formatter recognizes five types of AutoLISP comments, and positions each comment according to its type.

Visual LISP comment formatting
Comment

Formatted appearance

;| Inline |;

The single-line comment appears after
formatting as any other expression; the
multiple-line comment appears starting at a new
line.

; Single-Semicolon

Starts at the comment-column position, as
defined by the “Single-Semicolon comment
indentation” format option.

;; Current-Column

The comment appears starting on a new line,
indented at the same level as the last line of
program code.

;;; Heading or 0-Column

Appears on a new line, without indentation.

;_ Function-Closing

Appears just after the previous expression.

The following example demonstrates each comment style.
Initial text:
(defun foo (x)
;|inline comment |;
(list 1 2 3) ;comment-column comment
;;current-column comment
;;; heading or 0-column comment
)
;_ function-closing comment

Formatted text:
(defun foo (x) ;|inline comment |;
(list 1 2 3)
;;current-column comment
;;; heading or 0-column comment
) ;_ function-closing comment

;comment-column comment

Saving and Restoring Formatting Options
To save your formatting options so that they carry over to subsequent VLISP
sessions, choose Tools ® Save Settings from the VLISP menu. Alternatively,
you can save the current settings specifically for the program in the active

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Chapter 2


text editor window. VLISP saves formatter settings in a program when the
Save Formatting Options in Source File option is selected. To select or cancel
this option, choose Environment Options ® Visual LISP Format Options
from the Tools menu. If the option is in effect, VLISP adds formatting information as comments at the end of the program, when you run the formatter.
Each formatter invocation checks for formatting options settings at the bottom of the selected text. If found, these settings override the session settings
listed in Tools ® Environment Options ® Visual LISP Format Options.

Formatter Restrictions
The following restrictions apply to the VLISP code formatter:
The formatter relies on a fixed window font and a particular tab size. To
change font settings, choose Window Attributes ® Font; to change tab
settings, choose Window Attributes ® Configure Current.
s The formatter is available only within VLISP text editor windows.
s Existing SPACE and TAB characters placed outside of inline comments and
strings will not influence the formatting result.
s

Formatting Shortcut Keys
Press CTRL + E while in an active VLISP text editor window to display a list
containing the following editor options.

Text editor code formatting commands
Option

Effect

Indent Block

Indents the selected block of text by adding a tab to the
beginning of each line.

Unindent

Unindents the selected block of text by removing a tab.

Indent to Current
Level

Indents the current line to the same level as the previous line of
program code.

Prefix With

Adds a text string to the beginning of the current line, or to
each line in a block of selected lines, after prompting you for
the string.

Append With

Appends a text string to selected lines of text, after prompting
you for the string.

Comment Block

Converts a block of code to comments.


|

59

Text editor code formatting commands (continued)
Option
Uncomment Block

Copies selected text to a new file.

Upcase

Converts the selected text to all uppercase.

Downcase

Converts the selected text to all lowercase.

Capitalize

Capitalizes the first letter of each word in the selected text.

Insert date

Inserts the current date (default format is MM/DD/YY).

Insert time

Inserts the current time (default format is HH:MM:SS).

Format Date/Time

Changes the date and time format.

Sort Block

Sorts the selected block of code in alphabetical order.

Insert File

Inserts the contents of a text file into the current editor window
at the cursor position.

Delete to EOL

Erases everything from the cursor position to the end of the
current line.

Delete Blanks

|

Changes a block of comments to active text.

Save Block As

60

Effect

Deletes all blank spaces from the cursor position to the first
non-blank character in the line.

Chapter 2


Checking for Syntax Errors
One main attraction of using VLISP is the extensive debugging tools it provides. These tools allow you to watch what your program is doing while it is
executing, and to take a “snapshot” of your program at any point. However,
VLISP also provides a number of features designed to detect program errors
before you run the program.

Checking the Balance of Parentheses
AutoLISP uses parentheses more frequently than most other computer languages. One of the most frequent syntax errors in AutoLISP is an unequal
number of open and close parentheses. VLISP includes a number of tools to
help you detect unbalanced or unmatched parentheses.
As noted earlier in this chapter (“To format text in an active editor window”
on page 50), the VLISP code formatter searches for unbalanced parentheses
when it formats your code. If you allow it to, the formatter will add parentheses where it thinks they are missing. Typically, though, the VLISP
formatter adds parentheses at the end of a program, not to where you really
need them. If you let VLISP add the parentheses, you will probably have to
remove them later.

NOTE If you do not allow the formatter to add the balancing parentheses, it
won’t format your code either!
In any event, you must check the structure of your program to determine
where the parentheses are really missing. You can use these Parentheses
Matching items from the Edit menu to help you find unbalanced
parentheses:

Parenthesis Matching Commands
Moves the insertion point (marked by the cursor) just past
Match
the close parenthesis that matches an open parenthesis.
Forward
( CTRL +])

If the current cursor position is just before an open
parenthesis, VLISP matches that parenthesis with its
closing parenthesis. If the cursor position is in the middle
of an expression, VLISP matches the current expression’s
open parenthesis with its closing parenthesis.


|

61

Match
Backward
( CTRL +[)

Moves the insertion point to just before the open
parenthesis that matches a close parenthesis.

Select Forward
( CTRL +
SHIFT +]

Moves the insertion point as the Match Forward
command does, but also selects all text between the start
and end positions.

If the current cursor position is just after a close
parenthesis, VLISP matches that parenthesis with its
opening parenthesis. If the cursor position is in the
middle of an expression, VLISP matches the current
expression’s close parenthesis with its open parenthesis.

With the cursor positioned right before an open
parenthesis, double-clicking also selects all text up to the
matching close parenthesis, but does not move the
insertion point.

Select
Backward
( CTRL +
SHIFT +[)

Moves the insertion point as the Match Backward
command does, but also selects all text between the start
and end positions.
With the cursor positioned right after a close parenthesis,
double-clicking also selects all text up to the matching
open parenthesis, but does not move the insertion point.

For example, look at the following code:
1 (defun yinyang (/ origin radius i-radius half-r origin-x origin-y)
2 (setq half-r (/ radius 2))
3 (setq origin-x (car origin))
4 (setq origin-y (cadr origin))
5 (command "_.CIRCLE"
6
origin
7
radius
8
(command "_.ARC"
9
"_C"
10
(list origin-x (+ origin-y half-r))
11
(list origin-x (+ origin-y radius))
12
origin
13
)
14
(command "_.ARC"
15
"_C"
16
(list origin-x (- origin-y half-r))
17
(list origin-x (- origin-y radius))
18
origin
19
)
20 )

(The line numbers are not part of the text; they are used to help explain the
example.)

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Chapter 2


Here is what happens if you load this code in VLISP and continually issue the
Match Forward command, starting with the insertion point at the beginning
of line 1.
s
s
s
s
s
s

VLISP does not find a matching close parenthesis, so the cursor does not
move.
Move the cursor to the beginning of line 2.
Cursor moves to the end of line 2.
Cursor jumps to the last right parenthesis in the program! (20)

In other words, the close parenthesis that matches the open parenthesis on
line 5 is the last parenthesis in the program. You know this is an error because
the last close parenthesis in an AutoLISP program should match the open
parenthesis of the program’s defun. Notice also that all the statements after
line 5 are indented in a manner unlike in the preceding program code. These
two clues indicate something is amiss at this point in the program. In fact,
the close parenthesis to the command that begins on line 5 is missing.

Using Color Coding to Detect Syntax Errors
The AutoCAD SampleVisualLISP directory contains a file named
drawline-with-errors.lsp. It is similar to the drawline.lsp program file introduced
earlier in this manual, but it contains a couple of errors. Open the file in
VLISP, so that you can see how color is used in the file:
(defun drawline(/ pt1 pt2) ; Local variables declared
;; get two points from the user
(setq pt1 (getpoint "nEnter the start point for the line: "))
(setq pt2 (getpoint pt1 "nEnter the end point for the line: "))
;; check to see that the two points exist
(iff (and pt1 pt2)
(command "_.line" pt1 pt2 "")
(princ "nInvalid or missing points!")
(princ)
;; exit quietly
)
)

(This example also uses different fonts to represent different colors, so you
can differentiate between the fonts on a black and white printed page.)
If you use the standard VLISP syntactic colorations, systems functions such
as setq, defun, getdist, getpoint, and / are displayed in blue. The items
VLISP does not recognize, such as user-defined variables, are printed in black.
In this example, if you look at the unrecognized elements in the program, the
word iff might easily catch your eye. Change it to the correct spelling, if, and
the color immediately changes to blue.


|

63

Using the Check Command to Look for Syntax
Errors
You can perform additional syntax checking with the VLISP Check command. The Check command can detect the following errors:
Incorrect number of arguments supplied to a known function
Invalid variable name passed to a function (for example, a quoted symbol
where a variable is required)
s Incorrect syntax in special form function calls (for example, lambda, setq,
and foreach)
s
s

Some syntax errors can only be determined at runtime and Check cannot
detect these errors. For example, if you call a function that expects an integer
argument and you supply a string, AutoLISP does not detect this until runtime. As a result, this error will not be detected until you run your program.

To run the Check command on text in an editor window
1 Switch to the editor window containing the code you want to check.
2 To check the entire file, choose Tools ® Check Text in Editor from the VLISP
menu.

3 To syntax-check a selected piece of code instead of the whole program,
choose Tools ® Check Selection.
VLISP displays error messages in a new Build Output window, if it detects
errors. For example, if you change the iff in drawline-with-errors.lsp to if and
run Check, the following error message results:

The message indicates that an if function call contains too many arguments.

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Finding the Location of the Syntax Error in Your Program
If you double-click on the error message in the Build Output window, VLISP
activates the editor window, places the cursor at the beginning of the statement that caused the error, and highlights the entire expression, as follows:

This error results from the last princ statement following the if. The if statement only allows two arguments: the statement to execute if the expression
is true, and the statement to execute if the expression is false. The last princ
statement, which is used in this program to cause a quiet exit, belongs after
the close parenthesis that currently follows it. (See “Exiting Quietly” on page
236 for an explanation of a quiet exit.) If you move the statement to the correct location and run Check again, the code should pass as error-free.


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Debugging Programs

3

In This Chapter

Programs do not always behave in the way they were

s Introducing Visual LISP Debugging
Features

intended. When the results you get appear to be wrong,

s Learning by Example

or cause the program to crash, it can be difficult to

s Using the Visual LISP Debugging
Features

determine what is going wrong. VLISP provides many

s Using Visual LISP Data Inspection
Tools

features that help you with the debugging process—
finding and resolving program problems.

67

Introducing Visual LISP Debugging Features
Debugging is usually the most time-consuming stage in the development of
any program. For this reason, VLISP includes a powerful debugger that provides the following features:
s
s
s
s
s
s
s

Tracing of program execution
Tracing of variable values during program execution
Viewing the sequence in which various expressions are evaluated
Inspecting the values of parameters used within function calls
Interrupting program execution
Stepping through program execution one instruction at a time
Inspecting the stack

VLISP provides the following facilities to implement these features:

Break Loop
Mode

Inspect

Watches the values of variables during program
execution. The content of the Watch window is updated
automatically. This means that if the value of a variable
placed in the Watch window is changed, this change will
automatically be reflected in the Watch window.

Trace Stack
Facility

|

Provides detailed information on an object in an Inspect
dialog window. If the object being inspected is composed
of nested objects (a list, for example), the Inspect feature
allows you to inspect all the components, each one listed
on its own line within the window. You can also
recursively inspect any nested object until an atomic
object (such as a number or a symbol) is reached.

Watch
Window

68

Halts program execution at specified points, allowing you
to look at and modify the value of objects during the
break. Examples of AutoLISP objects are variables,
symbols, functions, and expressions.

Views the function call stack. The call stack is a
mechanism by which VLISP records the sequence of
functions as they are executed by your program. You can
view the stack during a debugging session (when the
program is in a suspended state, such as stepping through
after a breakpoint), or after your program has crashed. If

Chapter 3

Debugging Programs

viewed after your program crashes, the function call stack
shows what VLISP was doing at the moment the
application failed.

Trace Facility

A standard LISP facility, logs the calls and returns values of
traced functions into the special Trace window.

Learning by Example
This section takes you through a VLISP sample program and demonstrates
some VLISP debugging facilities along the way. You can find the sample program, yinyang.lsp, in the SampleVisualLISP directory under the AutoCAD
install directory path. Open the file in VLISP so that you can try the examples
in this section.

Stepping through the Debugging Example
First, load the file and run the yinyang function to see what it does. The
function draws the yin-yang symbol, which is used symbolically by many
religions and philosophies, including Confucianism and Taoism:

When you run the program, VLISP passes control to AutoCAD and you need
to respond to the prompts in the AutoCAD Command window.
VLISP evaluates AutoLISP programs by evaluating the expressions contained
in parentheses. These parenthetical expressions are similar to operators in
other programming languages such as C++ and Visual Basic ®. The VLISP
debugger uses an expression-based approach, unlike the line-by-line
debuggers of languages such as C. In this approach, the debugger can suspend program execution immediately before or after the evaluation of any
expression.
Debugging options are controlled from several different places within VLISP,
including the text editor, the System Console, and various menus.

Learning by Example

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69

Setting a Breakpoint to Interrupt Program Execution
Begin by entering some debugging information in the text editor window
containing the yinyang.lsp program.

To set a breakpoint that interrupts program execution
1 Move the cursor in front of the open parenthesis in the line of code that
reads:

The following screen snapshot indicates the position of this statement
within the program:

breakpoint

2 Click the Toggle Breakpoint button in the Debug toolbar, or choose
Debug ® Toggle Breakpoint from the VLISP menu. Toggle Breakpoint
switches breakpoints on and off. When no breakpoint exists, Toggle Breakpoint adds a break; if a breakpoint already exists at the cursor position, Toggle
Breakpoint removes it.

3 Load the yinyang function, if you have not done so already, then run it from
the VLISP Console prompt by entering the following command:
(yinyang)

After you reply to the prompts the program displays at the AutoCAD command line, VLISP halts yinyang execution at the breakpoint you set and
displays the code in the text editor window:

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Note how the statement following the cursor is highlighted.

Stepping through the Program
The Step commands allow you to move through a program by executing one
or more expressions at a time.

To step through a program from a breakpoint
1 Click the Step Into button, or choose Debug ® Step Into from the VLISP
menu. You can also press F8 to issue the Step Into command.
Execution begins and halts before evaluation of the inner parenthetical
expression, that is, before the specified division occurs. The expression is
highlighted, as shown in the following figure:

Now look at the Step Indicator button on the Debug toolbar; it is the last
button on that toolbar.

Learning by Example

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71

The Step Indicator button is active when you are stepping through a program. It indicates where you are in relation to the expression at the
breakpoint. The current symbol indicates that you are stopped just before an
open parenthesis.

2 Click the Step Into button again. The cursor moves to a position directly after
the evaluated expression , and the Step Indicator button indicates this.
3 Click the Step Into button again. The cursor moves to the end of the entire
statement (the expression and all nested expressions).

4 Click the Step Into button again and the cursor moves to a position just
before the beginning of the statement on the next line:

5 Now take a bigger step . Click the Step Over button, or choose
Debug ® Step Over from the menu, or press SHIFT + F8 to issue this
command:

With the Step Over command, VLISP evaluates an entire expression (and all
nested expressions), then stops at the end of the overall expression . The cursor moves to the end of the evaluated expression.

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Monitoring the Evaluation Results of an Expression
As you step through a program, you may want to monitor the values resulting from the evaluation of individual expressions.

To monitor variables during program execution
1 From the Debug menu, choose Watch Last Evaluation.

VLISP displays the Watch window, which shows the value of the
*LAST-VALUE* system variable. VLISP always stores the value of the last evaluated expression in the *LAST-VALUE* variable.

2 In the text editor window containing yinyang.lsp , double-click on any occurrence of the variable name origin-y.

3 Click the Add Watch button in the Watch window. VLISP passes the
origin-y variable name to the Watch window and displays the current value

of the variable in the window:

If the Watch window is not already open and you want to view a variable’s
value, you can open the window by choosing View ® Watch Window from
the VLISP menu.
If you click the Watch window’s Add Watch button without double-clicking
on a variable name first, the following window appears:

In this window, you can enter the name of the variable you want to view.
VLISP may anticipate your choice by copying the name of the variable near-

Learning by Example

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73

est the cursor into the window. If this is not the one you want to view, simply
type over the name.
VLISP updates the variables in the Watch window after each execution step.

4 Click the Step Over button (or press SHIFT + F8 ) twice .
In the Watch window, note how the value of ORIGIN-Y changes. It was nil
at first, but after execution it took on the value corresponding to the point
you clicked in the AutoCAD window.

Continuing Program Execution
To continue running your program to the next breakpoint, or to the end, if
there are no more breakpoints, press the Continue button on the Debug toolbar, or choose Debug ® Continue from the VLISP menu.

Running in Animate Mode
Another debugging feature, animation, allows you to watch as VLISP steps
through your program code and evaluates each expression. In Animate
mode, it’s as if VLISP repeatedly enters a Step Into command for you. Text
editor windows highlight expressions being evaluated, and the Watch window continuously updates its data.

To see how Animate mode works
1 Turn on Animate mode by choosing Debug ® Animate from the VLISP
menu.

2 Enter (yinyang) at the Console prompt to begin executing the program.
You’ll see each function highlighted as VLISP evaluates the function. You’ll
be prompted for input, as usual. Notice how the Watch window is updated
whenever a watched variable changes. Because you previously set a breakpoint in the program, execution will halt at that breakpoint.

3 After you stop at the breakpoint, press the Continue button to resume execution; VLISP resumes executing in Animate mode.
You can also interrupt animation by pressing BREAK (it’s the key next to
SCROLL—LOCK on most keyboards). Once animation is paused you can add
Watch values, set variables to new values, and add breakpoints.

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To adjust the rate of animation, choose Tools ® Environment
Options ® General Options, and select the Diagnostic tab. The Animation
Delay setting defines the pause between program steps, in milliseconds.
To turn off Animate mode, choose Debug ® Animate from the VLISP menu
again.

Using the Visual LISP Debugging Features
In addition to setting breakpoints and running in Animate mode, as
described in the “Learning by Example” section of this chapter, VLISP provides a number of other options for controlling program execution. For
example:

Break on Error

Causes VLISP to break unconditionally when it evaluates
the very first LISP expression encountered. You turn on
this mode of operation by choosing Debug ® Break on
Error from the VLISP menu.

Stop Once

Automatically activates the interactive break loop
whenever your program encounters a runtime error. You
turn on this mode of operation by choosing
Debug ® Stop Once from the VLISP menu.
Note that if this option is selected, some errors that result
from function calls entered at the AutoCAD Command
prompt will cause VLISP to get focus. That is, the active
window may switch from AutoCAD to the VLISP Console
window, where you will be in a break loop.

Break on
Function Entry

Sets the Debug-on-Entry flag for a function’s name
symbol, causing a break to occur every time you invoke
that function. At the break, the source code for the
function will be shown in a special window. You can set or
clear the Debug-on-Entry flag interactively with the
Symbol Service dialog box. See “Using the Symbol Service
Dialog Box” on page 92 for information on setting this
flag.

Top-Level
Debugging
Mode

Controls the loading of a program from a file or an editor
window. If the option is set, breaks occur before
evaluating every top-level expression (such as defun). The
Top-Level debugging mode is turned on by switching off
the Do Not Debug Top Level option. To find the check box


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75

for this option, choose Tools ® Environment
Options ® General Options from the VLISP menu, then
click the Diagnostic tab.
If Top-Level debugging and Stop Once mode are turned on, VLISP will enter
the debugging mode every time you load a file. This is due to the fact that
VLISP is debugging defun, setq, and other functions defined within the file
as they are loaded. This is usually not a helpful debugging technique and
should only be required in rare instances.

Starting a Debugging Session
The easiest way to start debugging is to choose Debug ® Stop Once from the
VLISP menu. When this item is selected, the evaluation of the first LISP
expression will be interrupted. After that you can resume program execution
using various Debugger commands. Another way to enter into the debugger
mode is to set a breakpoint, as shown in “Setting a Breakpoint to Interrupt
Program Execution” on page 70.
When a break occurs, the corresponding VLISP text editor window will show
the current LISP expression at the point which the break took place. A break
loop marker will appear in the Console window. Using the Console window,
you can access and manipulate the program environment in which the break
occurred. You can also examine variables using the Watch window.

Understanding Break Loops
Expressions are the basic structural units of AutoLISP, and VLISP works by
repeatedly reading, evaluating, and printing expressions. In LISP terminology, this is a read-eval-print loop.
When you are running an AutoLISP program without any debugging intervention by VLISP, you are running in the Top-Level read-eval-print loop.
When you evaluate an expression within the VLISP Console window, and the
normal prompt is displayed, you are also working at the Top Level.
When a program’s evaluation is interrupted or suspended in the middle of
execution, VLISP passes control to the Console and you enter a break loop.
This break loop is a separate read-eval-print loop, and is nested underneath
the original read-eval-print loop. It is possible to interrupt a break loop and
start yet another read-eval-print loop beneath it. The nesting level of a break
loop with respect to the Top Level is called the break level.
When you enter a break loop, VLISP prefixes the Console prompt with a
number indicating the level where you are located. For example, when you

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first enter a break loop in a program, the prompt indicates this with the
number 1:
_1_$

While you are in a break loop, you cannot switch control to the AutoCAD
window.
On exiting from a break loop (for example, after issuing the Quit command),
the current read-eval-print loop is terminated and the previous level loop is
resumed. If you change the value of a variable in the break loop, this value
will be used when the program resumes execution.

Continuable Break Loops
There are continuable and noncontinuable break loops in VLISP. You can
enter the continuable break loop at the very first break in program execution
by any of the following methods:
s

s
s
s
s

Turning on the Stop Once mode and reaching an expression with debugging information (that is, an expression that is loaded from source code,
as opposed to from a compiled .exe file)
Reaching a function marked for Debug on Entry
Reaching a breakpoint you set in the program
Entering a break loop by pressing the Pause button
Proceeding with a Step Over, Step Into, or Step Out command from the
previous break loop state

When the program is interrupted, you enter the break loop. This is apparent
if the VLISP Console window is active, because the prompt is changed to
reflect the current level of the break loop. In this suspended state, you have
read-write access to all variables in the environment in which the break
occurred. For example, if the break occurred within a function containing
several local variable declarations, those variables are accessible and you can
change their values by issuing setq assignments at the Console prompt.
When stopped at a breakpoint, you can control subsequent program execution by choosing one of the following items from the Debug menu, or by
pressing the equivalent toolbar button:

Reset to Top Level terminates all currently active break loops and returns
to the Console top-level (the top read-eval-print loop).
s Quit Current Level terminates the current break loop and returns to a
break loop one level up. This may be another break loop or the top-level
read-eval-print loop.
s Continue resumes normal program execution from the breakpoint.
s


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The Step commands evaluate portions of program code before resuming suspended mode:

Step Over looks for the close parenthesis matching the open parenthesis
where the program is currently paused, and evaluates the expressions in
between.
s Step Into jumps into a nested expression, if any. If there are no nested
expressions, it jumps to the next expression in sequence.
s Step Out searches for the end of the function where the program is currently paused, and evaluates all the expressions up to that point.
s

After exiting the break loop to the Console top-level, the Console prompt
returns to its original form (without a number prefix).

Non-Continuable Break Loops
A non-continuable break loop is activated when an error causes program
interruption and the Break on Error option is set. In a non-continuable break
loop, you can access all variables in the error environment, but you cannot
continue program execution or execute any of the Step commands. To distinguish between continuable and non-continuable break loops, check to see
if the Step and Continue toolbar buttons are active.
To leave a non-continuable break loop step, use either the Reset to Top-Level
command to jump to the Console top-level loop, or Quit Current Level to
return to the previous break loop level.

NOTE If you activate AutoCAD while in the midst of a non-continuable break
loop, you will not be able to enter anything in the command window; in fact,
the window will not contain a Command prompt. However, if you accidentally
try typing anything in the AutoCAD command window, your keyboard input will
be queued until AutoCAD regains control (that is, after you exit the break loop
and activate the AutoCAD window). At that point, anything you typed is evaluated by AutoCAD as if you had just entered it at the Command prompt.

Using Breakpoints
Breakpoints allow you to mark a position in a program at which program
execution should be interrupted. You can set breaks to occur before or after
parenthetical expressions. Breakpoints can only be set from a VLISP text editor window.

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To set a breakpoint
1 Move the cursor to the position at which you want to halt execution. For
example, to halt execution just before the open parenthesis of an expression,
place the cursor just to the left of that open parenthesis.

2 Press the Toggle Breakpoint toolbar button or press F9 to set the breakpoint.
(For variety, you can set a breakpoint by choosing Debug ® Toggle Breakpoint from the VLISP menu, or by right-clicking the mouse and selecting
Toggle Breakpoint from the resulting shortcut menu.)
If you move the cursor to an ambiguous position, such as in the middle of an
expression, VLISP will move the cursor to the nearest parenthesis and display
the following message asking whether you agree with the breakpoint
placement:

3 Click Yes to accept the breakpoint location, or No if that is not where you
want to set the break.

To remove a breakpoint
1 Position your cursor at the breakpoint you want to remove.
2 Press the Toggle Breakpoint toolbar button, or press F9 .
The Toggle Breakpoint works as an on/off switch. When no breakpoint exists,
Toggle Breakpoint adds a break; if a breakpoint already exists at the cursor
position, Toggle Breakpoint removes it. You can also use the Breakpoint Service dialog to remove breakpoints; see “Listing and Viewing the Breakpoints
in Your Program” on page 80 for information on this procedure.

3 To remove all the breakpoints you have set, choose Debug ® Clear
All Breakpoints from the VLISP menu.

Changing Breakpoint Highlight Colors
VLISP marks each breakpoint position with a colored rectangle, so you can
easily locate the breakpoints in your program. By default, active breakpoints
are marked in red. You can change this color by setting the :BPT-ACTIVE
option in Tools ® Window Attributes ® Configure Current. See “Configure
Current” on page 473 for more information on changing colors in VLISP
windows.


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Disabling Breakpoints Temporarily
When using multiple breakpoints within a source file, it may be useful to disable one or more breakpoints temporarily, but leave the breakpoint position
defined for possible later use. This saves time over deleting and restoring the
breakpoint.

To disable a breakpoint
1 Place the cursor at the breakpoint marker and press the right mouse button.
2 From the resulting menu, choose Breakpoint Service. VLISP displays the following dialog box:

3 Click the Disable button in the Breakpoint Service dialog box to disable the
breakpoint temporarily.
VLISP changes the color of the breakpoint marker when it disables the breakpoint. By default, it marks disabled breakpoints in blue. You can change this
color by resetting the :BPT-DISABLE option.

Listing and Viewing the Breakpoints in Your Program
From the View menu, choose the Breakpoints window to see a list of all
breakpoints currently defined to VLISP:

The Breakpoints window lists the breakpoints in all programs you are editing
in VLISP, not just the program in the active editor window. In the example
above, only one program (yinyang) contains breakpoints. But you could have
breakpoints set in any number of files.

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Each entry in the Breakpoints window shows the name of the source file containing the breakpoint, and the location of the breakpoint in the source. A
leading + or - sign differentiates between active and disabled breakpoints.
The dialog box allows you to delete all breakpoints at once or to edit (or display) one breakpoint at a time. Press Show to display the source position of
the breakpoint. The Edit button opens the Breakpoint Service dialog, from
which you can disable the breakpoint.

Life Cycle of a Breakpoint
You can set breakpoints in a program either before or after you load the program. However, if you change the text in a program after loading the
program, and then add a breakpoint, the breakpoint only takes effect after
you reload the code.
Breakpoints remain in effect during the VLISP editing session and will survive between sessions if you choose Save Settings from the Tools menu.
In addition to removing breakpoints using the methods previously described
in this chapter, program breakpoints are automatically lost when you do any
of the following:
Delete the code fragment containing the breakpoint
Modify the file outside the VLISP editor (for example, edit and save it with
Notepad)
s Apply VLISP formatting commands to code fragments containing breakpoints
s
s

Note also that if you modify a program’s code and run it without reloading
it (with the Load Active Edit Window command), the program will be interrupted when a breakpoint is reached, but the exact source position will not
be shown. The following dialog box indicates this situation has occurred:

To enable the proper display of a source position, you must reload the code
and restart the program.


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Using Visual LISP Data Inspection Tools
VLISP gives you almost unlimited access to symbols, values, and functions at
any stage of program execution. The VLISP data inspection tools are implemented as modeless windows (except for the Symbol Service dialog box),
meaning they stay on the screen as long as you need them, no matter what
your program does.
The Watch window displays the current value of any set of variables.
The Trace Stack window displays the most current call hierarchy. At any
level of the stack you can view the corresponding code, the calling code,
the local variables, and more.
s The Symbol Service dialog box displays the current value of a symbol as
well as its current flags. You can modify both the value and the flags from
here.
s Inspect windows display any LISP object (from a string to an AutoCAD
block definition) to any level of detail needed.
s Frame Binding windows display the values of all local variables for their
particular stack frame (that is, the specific function invocation in the call
sequence).
s
s

VLISP provides a logging feature that, when active, allows you to copy the
contents of a Data Inspection window to a log file.

To turn trace logging on and off
1 Activate the Trace window.
2 Specify a log file by choosing File ® Toggle Trace Log from the VLISP menu.
Note that if the Trace window is not active, the Toggle Trace Log option will
not be available.

3 Press Save to select the file you specified. If the file already exists, VLISP
prompts you with the following message:

If you reply Yes, VLISP appends new data to the current contents of the file.
If you reply No, VLISP overwrites the file and its original contents will be lost.
Choose Cancel to terminate the operation and specify a different file name.

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4 To close the log file and quit the logging process, choose Toggle Trace Log
from the File menu again.
When Trace logging is turned on, any information displayed in the Trace
window is also written to the log file. Most VLISP data inspection tools provide a toolbar button for copying data to the Trace window.
The state of Trace logging is indicated in the Trace window’s title bar. If
logging is in effect, VLISP displays the name of the log file in the title bar. If
logging is off, no file name appears in the title bar.
If you do not close the log file before exiting VLISP, it closes the file automatically upon exit. After a log file is closed, you can view its contents with any
text editor, such as the VLISP text editor.

Using the Watch Window
The Watch window monitors the values of AutoLISP variables during program execution. Each Watch window element line displays the name of a
variable and its current value, as illustrated in the following figure:

The Watch window is updated at each step of a VLISP interactive session and
always shows the current environment state. In debugger mode, the Watch
window is refreshed automatically at the end of every expression evaluation.

To add variables to the Watch window
1 Highlight the variable name in any VLISP context (that is, in a text editor
window, the Console window, etc.).

2 Press the Add Watch button, or choose Add Watch from the Debug menu.
You can also select Add Watch from a shortcut menu by right-clicking the
mouse while the cursor is on a variable name.

3 If the Watch window is already active, you can add variables to the watch list
by clicking the Add Watch button on the toolbar in the Watch window.
If VLISP cannot determine which variable you are interested in based on the
cursor position or the text you’ve selected, it displays the Add Watch
window:


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Specify the name of the variable to be watched in this window, then click OK.
The Watch window retains its variables during a VLISP session. This means
that if you invoke Watch, add variables to the Watch window, and then close
the Watch window, the variables you added will appear in the Watch window, if you invoke Watch again during the current session.
The introductory section of this chapter includes an example of using the
Watch window (See “Monitoring the Evaluation Results of an Expression” on
page 73.)

Using the Watch Toolbar
The toolbar on the Watch window contains the following buttons:

Add Watch

Invokes the Add Watch command to add a new variable
to the Watch window. This variable can be selected from
any active text window or typed in the Add Watch dialog
box.

Clear Window

Removes all variables from the Watch window.

Sort
Expressions

Sorts the variables in the Watch window alphabetically by
name.

Copy to
Trace/Log

Copies the contents of the Watch window to the Trace
window. If logging is active, the contents of the Watch
window are also copied to the trace log.

Using the Watch Item Shortcut Menu
To display the Watch Item shortcut menu, select an item in the watch list and
right-click.
The following items appear on the Watch Item menu:

Inspect Value
Copy Value

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Invokes the Inspect feature for the selected value. (See
“Using Inspect Windows” on page 95.)
Copies the value of the selected variable into system
variable *obj*.

Chapter 3

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Print Value

Prints the selected variable value in the Console window,
prefixed with a single quote (').

Symbol

Calls the Symbol Service dialog box for the selected
variable. (See “Using the Symbol Service Dialog Box” on
page 92.)

Apropos

Calls the Apropos dialog box using the selected symbol’s
name as the Apropos argument.

Remove from
Watch

Removes the selected variable from the Watch window.

Understanding the Trace Stack Window
VLISP has a special debugging tool called a trace stack which is a historical
record of the execution of functions within your program. (The term stack is
derived from a computer programming structure of the same name.) The following figure illustrates adding and removing items from a stack. You can see
why a stack structure is often referred to as LIFO—Last In, First Out:

The trace stack is used by VLISP to “remember its way out” of a nested series
of expressions. By viewing the stack, you can see what is happening within
your program as it is executing (within a suspended break mode) or immediately after it has crashed.


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Before you invoke a function at the Console window or from AutoCAD, the
trace stack is empty. The action of invoking a function causes a record, or element, to be placed on the stack. As that function calls additional nested
functions to perform the work of your program, additional elements may be
added to the stack. VLISP only needs to place elements on the stack when it
needs to remember its way out of nested functions.
There are two conditions where it is useful to examine trace stacks. The first
is when your program is in a suspended state, such as during a breakpoint
pause. The second is after an error occurs, causing your program to fail.

Stack Element Lists
A stack element is an individual record or line-item history within a trace
stack. There are five kinds of elements that may appear within a stack:
s

Function call frames show one individual function invocation. Each function call frame appears in the following format:
level (function-name {argument1}...)

Arguments within this listing are displayed not by their local parameter
name, but by the values that were actually passed to the function.
s

Keyword frames are displayed at the very top and bottom of a trace stack.
They are displayed in the following form:
level :keyword – {optional-data}
The keyword indicates the type of the frame. The optional-data displays
additional information relating to the state of the program.

s

Top forms indicate an action that was initiated by typing an expression at
the top-level Console window, or from the invocation of a function that
was triggered during the loading of a file or selection within a VLISP editor
window.

s

Lambda forms are placed within a stack whenever a lambda function is
encountered within your program.

s

Special forms display the invocation of the foreach and repeat functions.
The arguments for these functions are not displayed. They appear as:
level (function-form ...)

Function call frames and keyword frames are discussed in more detail in the
following sections. These sections use the following code to demonstrate the
trace stack. If you wish, you can copy this code into a VLISP editor window,
set a breakpoint as indicated in the code comments, and run this sample:

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(defun stack-tracing (indexVal maxVal)
(princ "At the top of the stack-tracing function, indexVal = ")
(princ indexVal)
(if (< indexVal maxVal)
(stack-tracing (1+ indexVal) maxVal)
(princ "Reached the maximum depth.") ; place a breakpoint
; at the beginning of
; this line
)
)
(defun c:trace-10-deep ()
(terpri)
(stack-tracing 1 10)
)

Viewing the Current Trace Stack
To see the state of a function call stack while your program is suspended at a
breakpoint, choose View ® Trace Stack from the VLISP menu, or click the
Trace toolbar button. VLISP displays the Trace Stack window:

The Trace Stack window displayed above shows a function call frame for the
stack-tracing function. The second element, or frame, in the trace stack is

highlighted:
[2] (STACK-TRACING 10 10)

The number [2] simply identifies it as the second element in the stack. The
numbers following the stack-tracing function name (10 10) indicate the
actual values that were passed to the function.

Displaying Information on a Trace Stack Element
To obtain more information about an element in the trace stack, select the
element and right-click to display a shortcut menu.


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Active items available on the shortcut menu depend on the type of stack element you selected before right-clicking. Possible menu commands include
the following:

Inspect

Calls the Inspect feature for the selected stack element.

Print

Prints the stack element to the Console window.

Function
Symbol

Calls the Symbol Service feature for the function call in
the stack frame, if the function is called by the symbol.

Copy

Copies the selected trace stack element to system variable
*obj*.

Local Variables

Displays the Frame Bindings dialog box to allow browsing
of local variable values at the time the function was called;
see “Using the Frame Binding Window” on page 88.

Source Position

Checks whether or not the source text is available for the
function called at the selected stack frame. If the source
code is available, the text window with the source code is
displayed, with the current position inside the function
highlighted.

Call Point
Source

Shows the position of the caller expression, similar to
Source Position.

Using the Frame Binding Window
Choose the local variables item from the Trace Stack shortcut menu to display the Frame Binding window:

The Frame Binding window displays information about the local variables in
the frame. In the example shown above, it lists the parameter names
(INDEXVAL, MAXVAL), along with the values assigned to these parameters.
These values were passed to the function. The parameters are listed in the
order they are defined within the function.
If you right-click on an entry in the Frame Binding window, VLISP displays a
shortcut menu containing the following items:

Inspect
Print

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Calls the Inspect feature for the selected value.
Displays the selected value in the Console window.

Chapter 3

Debugging Programs

Symbol

Calls the Symbol Service dialog box for the selected
symbol.

Copy

Copies the selected value into the system variable *obj*.

Add to Watch

Adds the selected symbol to a Watch window.

Understanding Keyword Frames
A keyword frame indicates a specific type of operation that occurs within the
VLISP environment. The keyword indicates the type of operation. Keyword
frames will appear in only two locations: at the very top of the stack, or at
the very bottom of the stack.
The following types of keyword frames will appear only at the bottom of a
stack:

Keyword frames (bottom)
Frame type

Operation that occurred

:ACAD-REQUEST

A call to the function shown in the frame immediately above
the :ACAD-REQUEST keyword frame was invoked from the
AutoCAD command prompt.

:DCL-ACTION

Execution of a DCL tile or dialog action was requested from
AutoCAD. The keyword :DCL-ACTION is followed by two
strings: the DCL dialog name and the value of the $KEY
variable in the DCL action body. If a number appears, it is
the value of the $REASON variable in the DCL action body.
The frame immediately above the keyword describes the
function call built from the action string.

:INSPECT-EVAL

Evaluation of an Inspect command.

:INSPECT-VERBOSE

Entrance into a drawing Inspect hook function.

:TOP-COMMAND

The VLISP IDE requested the action resulting in the first
element placed within the stack. This situation occurs, for
example, when a function is invoked directly from loading a
selection or a file.

:USER-INPUT

The character string shown in the frame was entered from
the VLISP Console window. The frame immediately above
the keyword describes the expression as it was translated
from the user input. If the input string is too long, right-click
to open a context menu, and choose Show Message to view
the entire text. You can also choose the Inspect command
to inspect the entered string.

:WATCH-EVAL

Evaluation of a watch expression.


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The following types of keyword frames may appear at the top of a stack:

Keyword frames (top)
Frame type
:ACMD-CALLBACK

Indicates that your program is interrupted in a debugging
break mode, and the Step Into or Step Over command just
stepped out of an expression.

:ARQ-SUBR-CALLBACK

Indicates a normal call from AutoCAD to a VLISP-defined
function.

:AXVLO-IO-CALLBACK
:DWF
:DWG

Saves or restores a VL object in a DWG.

:BEFORE-EXP

Debugger break upon entering the function. This message
will appear whenever you are stepping through using Step
Into or Step Over, and the step is entering an expression (as
opposed to just leaving an expression, which is indicated by
the :AFTER-EXP keyword).

:BREAK-POINT

User-specified breakpoint.

:ENTRY-NAMESPACE

A call in the context of a separate-namespace VLX.

:ERROR-BREAK

General runtime error. The Show Message right-click
context menu selection allows you to view more specific
error messages.

:FUNCTION-ENTRY

Debugger break upon entering the function. The stack
element following this message contains the call frame for
the function in which the break occurred.

:KBD-BREAK

The PAUSE key was pressed, placing the program on hold.

:PROTECT-ASSIGN

Assignment of a value to a protected symbol. From the
right-click shortcut menu, you can choose Show Message to
view the variable name, the current value, and the new
value that was attempted to be assigned to the variable. You
can also choose the Inspect command to view the list
containing the symbol, and the new value indicated
following :PROTECT-ASSIGN.

:REACTOR-CALLBACK

|

Registered AutoCAD command call.

:AFTER-EXP

90


Reactor call.

Chapter 3

Debugging Programs

Keyword frames (top) (continued)
Frame type


:READ-ERROR

Error during a read operation. The Show Message right-click
context menu selection provides additional information
about the error.

:SYNTAX-ERROR

VLISP encountered incorrect AutoLISP program syntax.

Understanding Special Function Call Frames
There are two special function call frames.
The FOREACH frame indicates a call to the foreach function. From the shortcut menu, choose the Local Variables option to display the name and current
value of the user-supplied variable and list variables bound by the foreach
function. For example, if the following expression were evaluated
(foreach n '(a b c) (print n))

then selecting the Local Variables option displays a Frame Binding window
like the following:

This Frame Binding window identifies the user-supplied variable (N), the current value of that variable (A), and the items remaining to be processed in the
list supplied to foreach ( B C).
The REPEAT frame indicates a call to the repeat function. From the shortcut
menu, the Local Variables command displays the special name counter and
the current value of the repeat internal counter. The internal counter value
is initially set to the integer value passed to repeat, indicating the number
of iterations desired. The counter decreases by one at each loop iteration. It
shows the number of iterations remaining, minus one.
Note that each repeat expression possesses its own counter, but only one
such counter can be added to the Watch window.
AutoLISP functions such as if, cond, and, and setq do not appear on the
stack. They are not necessary because their call position may be viewed
within the source file in the VLISP text editor window.


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Viewing an Error Trace Stack
If your program terminates due to an error, choose Error Trace from the View
menu to see the state of function invocations up to the time your program
crashed:

The error trace is a copy of the trace stack as it appeared at the time the error
occurred. If the Break on Error debugging option is selected, the error trace
and the trace stack are identical immediately after an error occurs. You can
see this by selecting Break on Error from the Debug menu, intentionally causing an error (for example, issuing a function call that divides by zero), and
opening the two trace windows.
The toolbar on the Trace Stack window contains two buttons:

Trace Stack T
oolbar (continued)
Refreshes contents of Trace Stack window.
Refresh

Copy to
Trace/Log

Copies the window contents to the Trace Stack window or
open log file.

When you issue a Reset command to exit a break loop (for example, Reset to
Top Level), pressing the Refresh button in the Trace Stack window replaces
that window’s contents with the latest trace stack data. In contrast, refreshing the Error Trace window does not change the window’s contents, unless a
subsequent error has occurred.

Using the Symbol Service Dialog Box
The Symbol Service feature is designed to simplify access to the different
debugger features provided for symbols. Most facilities available for symbols
are also available through this feature.

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To open a Symbol Service dialog box and update a symbol
1 Highlight the name of any symbol in your program’s source code or in the
Console window.

2 Choose View ® Symbol Service from the VLISP menu, or press the Symbol
Service button on the Debug toolbar.

The Symbol Service dialog box contains the following components:
A toolbar
A Name field, where you can enter or change the symbol to work on
s A Value field that displays the symbol’s value or its initial substring
s A series of check boxes for symbol flags described in “Understanding
Symbol Flags” on page 94
s
s

3 To update the value of the displayed symbol, enter an expression in the Value
field. When you press OK, VLISP evaluates the expression and assigns its
value to the symbol.
If the symbol you specified is a protected symbol, the Value field will be readonly. To remove protection, clear the Protect Assign check box. See
“Understanding Symbol Flags” for more information on Protect Assign.
Use the OK and Cancel buttons to close the dialog box and to continue working in VLISP.


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Using the Symbol Service Toolbar
The Symbol Service toolbar contains the following buttons:

Symbol Service Toolbar Buttons (continued)
Adds the symbol to the Watch window.
Watch

Inspect

Opens the Inspect window to show the value of the
symbol.

Show
Definition

If the symbol names a user-defined function, this
command opens the text editor window containing the
function definition and highlights the function.

Help

Displays information from the VLISP Help file, if the
symbol refers to a built-in function.

Understanding Symbol Flags
The Symbol Service dialog box provides direct access to symbol flags and
properties of functional objects that may be associated with them. The following symbol flag options are available:

Trace (Tr)

The Trace flag activates the tracing of any user-defined
function (shown as a symbol within the Symbol Service
window). Tracing will only occur when the symbol is a
function, and the expression being evaluated uses the
symbol name as a function (not as a local variable name,
for example).

Protect Assign
(Pa)

This flag intercepts attempts to assign values to protected
symbols. For instance, the symbol pi is a protected
symbol. All symbols that are the names of built-in
AutoLISP functions are assignment-protected by default.
See “Protected Symbols” on page 228 for more
information on symbol protection.
Note that symbol protection works only for explicit setq,
set, or defun invocations. Binding a protected symbol in
an argument list of a user-defined function is not
intercepted.

Debug on
Entry (De)

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If this flag is set, a breakpoint occurs at each function
invocation, regardless of whether the function was loaded
with debugging information. The De flag is tested at each
function invocation, not during load or defun execution.

Debugging Programs

Note that VLISP ignores the Debug-on-Entry flag for all
SUBR and EXRXSUBR symbols.

Export to
ACAD (Ea)

If the Ea flag is set, the function associated with this
symbol is defined as an external subroutine. This makes
the function available to ObjectARX applications.

Using Inspect Windows
The Inspect feature is the component of VLISP that provides you with the
ability to browse, examine, and modify AutoLISP and AutoCAD objects. You
can use Inspect to view the following items:
Any AutoLISP objects such as lists, numbers, strings, and variables
AutoCAD drawing entities
s AutoCAD selection sets
s
s

Using Inspect, you can also browse through complex data structures.
The Inspect tool creates a separate window for each object you inspect.

To open an Inspect window
1 Select an AutoLISP object name (for example, a variable).
2 Choose View ® Inspect from the VLISP menu, or press the Inspect button on
the Debug toolbar.
The Inspect command is also available from a number of shortcut menus and
from the windows displayed by the Apropos and Symbol Service features.

3 If you invoke the Inspect command without selecting an object name, VLISP
prompts you to specify the object you want to inspect, displaying the following dialog box:

Enter the object or expression you want to inspect, then press OK to open the
Inspect window or press Cancel to cancel the action.
VLISP saves the last 15 items you enter in the Inspect prompt box. You can
choose a previously specified object for inspection by selecting it from the
drop-down list.


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For example, to inspect the definition of the yinyang function, select the
name in the text editor window containing the yinyang.lsp, then press the
Inspect button to view the Inspect window:
caption (title bar)
object line
element line

Using the Inspect Window
All Inspect windows have a similar appearance and contain a caption, an
object line, and an object element list (which may be empty). The window
elements contain the following content:
The caption of an Inspect dialog box shows the type of object being
inspected.
s The object line shows a printed representation of the inspected object.
s The element list displays the components of the inspected object.
s

The element list may vary in size and content for different object type. Each
element list is shown as a pair: name and content. The name is enclosed in
brackets. Square brackets ( [ ]) denote that you can modify the item by issuing a Modify command from the shortcut menu associated with the item,
and curly brackets ( { }) indicate that you cannot modify the item.
Both the object line and the element list lines have their own associated
shortcut menus. These menus are described in “Common Inspect Commands” on page 102.
VLISP will display up to 50 element lines in an Inspect window. If there are
more than 50 elements to be shown, Inspect displays the elements in a series
of pages. When you scroll to the bottom of the Inspect window and there are
more entries remaining to be displayed, the bottom of the list contains a
">>> [Next page]" element line. To navigate among the pages, use the following procedures:
To page down, double-click on the " >>> [Next page]" element line, or
select that line and press ALT + E .
s For Inspect windows showing AutoLISP lists and selection sets, you can
page up by double-clicking the "<<< [Previous page]" element line,
which appears at the top of the list. (Or select that line and press ALT + E .)
s For AutoLISP lists and selection sets, when you reach the last page of element lines, you can return to the first page by double-clicking on the
"<<< [First page]" element line, or by selecting that line and pressing
ALT + E .
s

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VLISP expands an item in the element list if you double-click on it. For example, the {Auxiliary} component in the sample Inspect window is itself a list.
Double-click on the {Auxiliary} item to open another Inspect window showing the elements in the list:

Understanding Object Element List Formats
The contents of an Inspect element list vary, depending on the data type of
the object being inspected. The following table identifies the list contents for
each data type.

Inspect element lists
Data type

Contents of element list

INT (integer)

The various representations of integers.

REAL (floating point
number)

Empty.

STRING

The sequence of characters in the string, which may in turn
be inspected as integers.

SYMBOL

Three elements: value, print name, and flags.

LIST (for proper lists)

Items of the inspected list.

LIST (for improper lists) Two elements: the car and cdr fields. It serves for all cases
that are not proper LISP lists, that is, where the last cdr is
not nil.
FILE

The name of the corresponding file and the file’s opening
attributes.

SUBR, EXRXSUBR, and The name of the function (the name that was specified in
USUBR
defun or at load time). SUBR refers to internal and
compiled functions, EXRXSUBR refers to external ARX
functions, and USUBR identifies user-defined functions.
ENAME (drawing
entity)

The fields in this element list correspond to the AutoCAD
DXF object list, as returned by the AutoLISP built-in
function.


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Inspect element lists (continued)
Data type

Contents of element list

PICKSET (selection set) List of selected AutoCAD objects.
VARIANT

The data type and value of the variant.

SAFEARRAY

The data type, number of dimensions, and value of the
safearray.

Sample Inspect windows for each data type follow.

INT

The INT (integer) Inspect window shows the number
represented in binary, octal, decimal, hexadecimal, and
character formats. Character format means the ASCII
character that corresponds to the number (for large
numbers it takes the last byte).

The INT Inspect window does not have an element list.

REAL

The REAL Inspect window does not have an element list.

STRING

Shows the string as a list of characters represented as
numbers:

Double-click on a listed character to see its number
representation.

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SYMBOL

Contains the symbol name, the symbol value, and the
flags that represent symbol attributes. Flags may be one of
the following:

Pa Protect Assign
Tr Trace
De Debug on entry
Ea Export to ACAD

To change a symbol’s value or flag settings, use the object
line menu command Symbol Service, which shows the
Symbol Service window.
Note that the information supplied by the SYMBOL
Inspect window is available more conveniently through
the Symbol Service feature.

LIST
(proper list)

Shows the elements of a proper list:

LIST
(improper list)

Shows the car and cdr of an improper list. For example, a
list constructed by (cons 4 '(5 . 0)) is represented as
follows:


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FILE

File Inspect fields include the following:

File name is the name string used in the open function.
Mode indicates whether the file is open for input, output,
append, or whether the file is closed.

ID shows the internal file identifier.
Position shows the current position in the file.
EOF indicates whether or not the end of the file has been
reached. This field does not appear if a file is open for
output.

SUBR

The SUBR data type represents functions that cannot be
debugged with the VLISP debugging tools (for example,
you cannot set breakpoints). These are internal AutoLISP
functions, or functions loaded from FAS or VLX files.
The SUBR Inspect window shows a string containing the
name of the symbol, as in the following example:

USUBR

The USUBR data type represents functions that can be
debugged with the VLISP debugging tools (for example,
you can set breakpoints and view the values of program
variables). These functions are loaded from LISP source
code.
The USUBR Inspect window shows the name of the
symbol, a list of function parameters (arguments), and a
list of local variables declared in the function (listed after
the “/” in the defun argument list). The following
example shows an Inspect window for a function that
accepts no arguments and declares several local variables:

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EXRXSUBR

The EXRXSUBR data type represents functions loaded
from external ARX applications. The EXRXSUBR Inspect
window shows a string containing the function name, as
in the following example:

ENAME

The contents of the ENAME Inspect window depend on
the properties of the entity being inspected. The following
example shows an Inspect window for a circle:

PICKSET

The PICKSET Inspect window lists the elements in a
selection set:

VARIANT

The VARIANT Inspect window shows the data type and
value of the variant. The following example shows an
Inspect window for a variant that contains an array of
doubles:


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SAFEARRAY

The SAFEARRAY Inspect window shows the data type,
number of dimensions, and value of the safearray. The
following example shows a Safearray Inspect window for
a single dimension array of doubles:

You can also use the Inspect feature to examine ActiveX objects. See “Using
the Inspect Tool to View Object Properties” on page 166 for an example of
this.

Common Inspect Commands
The Inspect windows provide shortcut menus containing commands relevant to the data being inspected.
To display the object line shortcut menu, press ALT + O , or right-click the
object line. The following commands may be present in an object line shortcut menu:

Symbol Service

Invokes the Symbol Service feature.

Print (ALT + P )

Prints the object in the Console window.

Pretty Print

Formats and prints the object in the Console window.

Copy

Copies the object to the *obj* variable.

Log

Copies the current contents of the Inspect dialog box to
the Trace window. If logging is active, the contents are
also copied to the trace log.

Update
(ALT + U )

Updates the Inspect dialog box to show the most recent
status of the inspected object.

The element line shortcut menu appears after highlighting the element line
and right-clicking. The following commands may appear on the element line
shortcut menu:

Inspect
(ALT + I)
Descend
(ALT + D)

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Calls Inspect and passes it the element value as an
argument.
Calls Inspect, passes it the element value as an argument,
and closes the current Inspect window.

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Copy

Copies the value of the inspected element to the
*obj* variable.

View Source

Activates a text editor window containing the selected
text. If the text was loaded from the Console window or
from a list representation, this command activates a new
text editor window.

The default command for an element line, invoked by pressing ENTER , is the
Inspect command.

Copying Inspect Objects to the *obj* System Variable
Sometimes it is useful to access some part of an object from your program or
from the VLISP Console window. You may also want to copy the value of one
object’s item into another item and so on. To perform all these tasks, the
Inspect feature manages a reserved system variable named *obj*. This variable can be used as a temporary storage area while browsing through data
structures. From inside an Inspect dialog box, you can assign a value to this
variable and replace the value of the current item with the value of *obj*.
To assign the value of an inspected object to the *obj* variable, right-click
the item in the Inspect window and choose Copy.

Handling Errors in the Inspect Command
In text editor windows it is not possible to inspect selected expressions longer
than 256 characters. If you select a string longer than 256 characters, you will
be prompted to enter an object name.
If you specify an object or expression that VLISP cannot evaluate, VLISP
issues a standard AutoLISP error message. Once the error message appears,
you can correct the expression in the dialog box and try to evaluate it once
more.
Errors arising from evaluation of the object you entered cannot be investigated from a nested break loop, because all breaks are disabled during such
evaluation. If you wish to examine the error, choose View ® Error Trace from
the VLISP menu, or copy the expression to the Console prompt and press
ENTER .

Closing All Inspect Windows
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Viewing AutoCAD Drawing Entities
VLISP provides facilities to walk through the AutoCAD drawing database and
inspect the raw data for each drawing entity reported by AutoCAD. You
access drawing entities through the VLISP Browse Database feature. Browse
Database displays entity information in Inspect windows. You can set a diagnostic option telling VLISP how much information to supply about entities.

To control the amount of Inspect information displayed for drawing objects
1 Choose Tools ® Environment Options ® General Options.
2 Click the Diagnostic tab in the General Options window.
3 Select Inspect Drawing Objects Verbosely to view detailed entity information. Clear the option check box to minimize the amount of information
supplied by Inspect.

Viewing Entities in the Drawing Database
To Open an Inspect window for the collection of entities in the current drawing database, choose View ® Browse Drawing Database ® Browse All Entities
from the VLISP menu. VLISP displays a window listing the entities in the
database:

Note that VERTEX and ATTRIB entity types are not included in this list. You
access these entity types through their parent entities, which are available
when you inspect POLYLINE and INSERT entities.
The shortcut menu commands available for the object line in the ACAD Entities Inspect window are Log and Update.
To open an Inspect window for a specific entity, double-click on the entity
name, or select the entity, then right-click, and choose Inspect:

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The title bar of this window identifies the drawing entity type. The object
line of the window displays the entity name.
<Entity name: 1cdf190>

The shortcut menu for the object line contains the common Inspect commands Print, Copy, Log, and Update, plus some new item s.

Modify

If available, this command opens the standard AutoCAD
DDMODIFY dialog for the inspected entity.

Inspect Raw
Data

Displays an Inspect window containing the list resulting
from an entget function call for the entity.

Inspect Next
Entity

Displays an Inspect window for the next entity in the
entities list.

Inquire
Extended Data

Displays a list of applications currently registered by
regapp. If you select an item from the list, any extended
data related to the chosen application is included in the
Inspect entget list. See “Viewing Extended Data” on page
107 for more information.

Viewing Symbol Tables in the Drawing Database
Choosing View ® Browse Drawing Database ® Browse Tables from the VLISP
menu opens an Inspect window for the collection of symbol tables in your
drawing:


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105

You can inspect each table as a collection of named attributes. Double-click
on a name to view its attributes, or select the name, right-click, and choose
Inspect:

To view a table entry for a selected attribute, double-click on the attribute
name, or select the attribute, right-click, and choose Inspect:

Viewing Blocks in the Drawing Database
Choose View ® Browse Drawing Database ® Browse Blocks from the VLISP
menu to open an Inspect window for the blocks in your drawing:

Double-click on the block name you are interested in to open an Inspect window for the block, or select the block, right-click, and choose Inspect.

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The raw-data element shows the symbol table entries for the inspected block.
Double-click on the parts item to open an Inspect window listing the collection of entities residing within the block.
The raw-data and parts element lines occur in all block Inspect windows.
Other element lines, such as {name}, appear only if the Inspect Drawing
Objects Verbosely Diagnostic option is selected. See “Diagnostic Options” on
page 477 for information on setting VLISP diagnostic options.

Viewing Selected Objects in a Drawing
Choose View ® Browse Drawing Database ® Browse Selection from the
VLISP menu to select the drawing objects you want to view. VLISP invokes
the ssget function to prompt you to define a selection set in the AutoCAD
drawing window. When you complete the selection, VLISP opens the Inspect
window for your selection:

.

Double-click on an entity name to open an Inspect window for the entity, or
select an entity, right-click, and choose Inspect.

Viewing Extended Data
Choose View ® Browse Drawing Database ® Inquire Extended Data from the
VLISP menu to see a list of the applications currently registered (through
regapp) as containing extended data. If you select an application from this
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To view extended data associated with an AutoCAD object
1 Choose View ® Browse Drawing Database ® Inquire Extended Data from the
VLISP menu.

2 Select the application whose data you are interested in viewing.
3 In the AutoCAD window, select the drawing objects whose extended data
you want to view.

4 From the VLISP menu, choose View ® Browse Drawing Database ® Browse
Selection. VLISP displays an Inspect window listing the AutoCAD objects you
selected:

5 In the Inspect window element list, double-click on an object whose
extended data you want to view. VLISP displays an Inspect window for the
object.

6 Select the object line in the Inspect window and right-click to view a shortcut
menu.

7 Choose Inspect Raw Data from the shortcut menu. VLISP displays an Inspect
window like the following:

Extended data is identified by the -3 DXF group code. The last line in the
entity list shows the extended data for the selected object. You can doubleclick on this line to open a separate Inspect window containing just the
extended data.

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4

In This Chapter

This chapter describes how to build applications with
VLISP.
VLISP allows you to compile your program files and cre-

s Compiling and Linking Programs
s Making Application Modules
s Designing for a Multiple
Document Environment

ate a single executable module that you can distribute to
users. The first part of this chapter provides basic knowledge about the VLISP compiler and may be sufficient for
building macros and small programs that work in a single document. The rest of the chapter helps you build
more complex applications. These remaining sections
discuss design considerations for an environment where
several AutoCAD drawings may be open at the same
time, and provide information on fine-tuning the performance of compiled code.

109

Compiling and Linking Programs
Each time you load AutoLISP source code, the code is translated into instructions the computer understands (executable code). The advantage of having
source code translated each time you load it is that you can make a change
and immediately try it out. This is useful for quickly testing new code, and
for debugging that code.
Once you are sure your program is working correctly, translating AutoLISP
source code each time it loads is time-consuming. VLISP provides a compiler
that generates executable machine code files from your source files. These
executable files are known as FAS files. Because the executable files contain
only machine-readable code, the source code you spent weeks or months
developing remains hidden even if you distribute your program to thousands
of users. Even strings and symbol names are encrypted by the VLISP file compiler.
VLISP also provides features for packaging more complex AutoLISP applications into VLISP executable (VLX) files. VLX files can include additional
resources files, such as VBA and DCL files, and compiled AutoLISP code. See
“Making Application Modules” on page 117 for instructions on building VLX
files.
Using VLX files, you can further control your application’s operating environment by exposing only those functions you choose to expose, and by
maintaining a wall between your program’s variables and the variables users
can interact with in AutoCAD. For more information on controlling the
operating environment of a VLX, see “Designing for a Multiple Document
Environment” on page 126.

Using the Compiler
VLISP provides several ways to access and use the file compiler. To compile a
single AutoLISP file you can use the vlisp-compile function. To compile
many AutoLISP files into a single VLX file, you can use the Make Application
wizard. The vlisp-compile function and the Make Application wizard are
described in this chapter.
If your application consists of a set of AutoLISP files loaded in parallel, it is
recommended that you use the VLISP integrated project management facilities to compile your files. The project manager automatically recompiles files
that have changed, allows you to find code segments without knowing
which files contain them, and optimizes the use of function calls and local

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variables in the compiled files. These features are explained in detail in “Managing Multiple LISP Files” on page 138.

Compiling a Program from a File
To compile a single AutoLISP file, call the vlisp-compile function. The function syntax is
(vlisp-compile 'mode “filename” [out-filename])

For this function
s
s
s

mode is a symbol identifying the compiler mode
filename is a string naming the source file
out-filename is a string naming the compiled output file

Choosing a Compiler Mode
The mode parameter indicates the compilation mode, which can be one of
the following:
st

Standard build mode

lsm

Optimize and link indirectly

lsa

Optimize and link directly

The standard mode produces the smallest output file and is suitable for programs consisting of a single file.
The optimization options result in more efficient compiled files, which
becomes important as your programs grow in size and complexity. The basic
functions of optimization are as follows:
Link function calls to create direct references to the compiled function in
the compiled code, instead of to the function symbol. This feature
improves the performance of the compiled code and protects the code
against function redefinition at runtime.
s Drop function names to make the compiled code more secure and to
decrease program size and load time.
s Drop the names of all local variables and directly link their references.
This also makes the compiled code more secure and decreases program
size and load time.
s

The VLISP project management feature allows you to tailor the optimization
options to the specific needs of your application. See “Choosing a Compilation Mode” on page 155 to learn more about choosing optimization options.


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Identifying the Input File
If your source file is in the AutoCAD Support File Search Path, you do not
have to include the path name when specifying the file name. The search
path is set by choosing Tools ® Options from the AutoCAD menu, then clicking the Files tab and selecting Support File Search Path:

For example, if you are compiling the yinyang.lsp program file that is in the
AutoCAD SampleVisualLISP directory, and Support File Search Path is set as
indicated in the previous figure, you can issue the following command to
compile the program:
(vlisp-compile 'st "yinyang.lsp")

If the AutoCAD SampleVisualLISP directory is not in the Support File Search
Path, you must include the entire path name when specifying the source file.
For example:
(vlisp-compile
'st "c:/program files/autocad T/Sample/VisualLISP/yinyang.lsp")

If you omit the file extension from a file name, VLISP assumes the .lsp
extension.
When specifying the file path name, replace the backslash symbol () you
normally use for file names with either a forward slash or a double backslash,
following the usual AutoCAD convention.

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Naming an Output File
The compiler produces code in the fast-load AutoLISP format (FAS). By
default, the output file containing this code has the same name as the input
file, but with an extension of .fas. You can override the default name by specifying an output file name. For example, to compile yinyang.lsp and produce
an output file named GoodKarma.fas, issue the following command:
(vlisp-compile 'st "yinyang.lsp" "GoodKarma.fas")

NOTE If you specify an output file name but do not specify a path name for
either the input or the output file, VLISP places the output file in the AutoCAD
install directory! This is probably not what you want.
In most instances, you’ll want to specify the full path name of the output file.
For example:
(vlisp-compile 'st "yinyang.lsp"
"c:/program files/.../Sample/VisualLISP/GoodKarma")

This ensures that the output file is placed in the directory you want it to be.

Walking through a Compile Example
You can use the yinyang.lsp file in the AutoCAD SampleVisualLISP directory
to exercise the vlisp-compile function.

To compile the yinyang.lsp sample program
1 At the Console prompt, enter the following:
(vlisp-compile
'st "c:/program files/acad2000/Sample/VisualLISP/yinyang.lsp")

This command requests a standard mode compile of the yinyang.lsp file. No
output file name is specified, so the compiled result will be saved in a file
named yinyang.fas and will be placed in the same directory as the input file
(c:Program FilesACAD2000SampleVisualLISP).


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2 Look at the Build Output window displayed after the command executes. If
necessary, scroll up in the window to see all the compiler messages. If the
compile completed successfully, the window contains messages like the following:

During compilation, the compiler prints function names and various messages about each stage of compilation. The first stage is syntax and lexical
checking of the source code. If the compiler encounters errors, it issues messages and halts the compilation process. The compiler issues warnings if it
encounters expressions it considers dangerous, such as redefining existing
AutoLISP functions or assigning new values to protected symbols. If the compiler displays warning or error messages, you can view and edit the source
code that caused these messages by double-clicking on the message in the
Build Output window.
If compilation is successful, as in the example above, the Build Output window displays the name of the compiled output file.

Loading and Running Compiled Programs
Compiled AutoLISP programs can be loaded and run from either the VLISP
Console window or the AutoCAD Command prompt, or by choosing
Tools ® Load Application from the AutoCAD menu. This is true of both .fas
files and . vlx files, which may contain multiple compiled programs. (See
“Making Application Modules” on page 117 for information on creating .vlx
files.)

To run a compiled program from the Visual LISP Console window
1 Load the program by invoking the load function from the Console prompt.
For example, to load the compiled yinyang program created in “Walking
through a Compile Example” on page 113, enter the following command:
(load "c:/program files/ACAD2000/sample/VisualLISP/yinyang.fas")

If you do not specify a file extension, load first looks for a file with the name
you specified (for example, yinyang), and an extension of .vlx . So if you have
previously built an application named yinyang.vlx , load uses that file instead

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of the .fas file you just compiled. If no . vlx file is found, load searches next
for a .fas file, and finally, if no . fas file is found, load searches for a .lsp file.
If you prefer less typing and more clicking, choose File ® Load File from the
VLISP menu, and use the Load Lisp File dialog box to select the file you want
to load. Remember to use the Files of Type pull-down list in this dialog box
to specify the type of file you want to load, otherwise VLISP lists only . lsp files
in the dialog box. You can select from the following types:
Lisp Source Files (.lsp files)
Compiled AutoLISP Files (.fas files)
s VL Packed Application (.vlx files)
s All files (lists all files in the specified directory)
s
s

Press Open to load the selected files.

2 At the VLISP Console prompt, enter the name of the function you want to
run, enclosing the name in parentheses. For example:
(yinyang)

VLISP transfers control to AutoCAD to display program prompts and accept
user input.
Once you load a program, you can run it from either the AutoCAD Command prompt or the VLISP Console window prompt. Note that if the name
of the function you are running begins with c:, you can invoke it from the
AutoCAD Command prompt as if it were an AutoCAD command, that is,
without enclosing the name in parentheses. See “C:XXX Functions” on page
247 for more information on this feature.
Refer to the AutoLISP Reference for more information on the load function.

Loading Extended AutoLISP Functions
VLISP provides some extensions to the AutoLISP language that are not
loaded automatically when you start AutoCAD. These functions have names
that begin with vla-, vlax-, and vlr-. The vla- functions implement AutoLISP
ActiveX support. The vlaxfunctions provide ActiveX utility and data conversion functions, dictionary handling functions, and curve measurement
functions. The vlr- functions provide support for AutoCAD reactors. Before
you can use any of these functions, you must load the AutoLISP extensions
with the following function call:
(vl-load-com)

This function first checks if the AutoLISP extensions are already loaded; if so,
the function does nothing, otherwise it loads the extensions.


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AutoLISP code that includes calls to vla-, vlax-, or vlr- functions should always
begin with a call to vl-load-com to ensure that the code will run; it should
not be left up to the user to load the extensions. If your application does not
call vl-load-com, the application m ay fail.

Linking Function Calls
The process of compiling function calls results in VLISP creating a loadable
module containing in-line copies of some AutoLISP built-in functions. Inline compilation of built-in functions increases the efficiency of the resulting
code, but may change the behavior of some tricky AutoLISP programs.
For example, if your program contains an in-line copy of a built-in function,
and that function is subsequently redefined, your program does not use the
new function definition. A copy of the old definition is part of the program’s
load module, and that version is called directly. You must recompile your
program to pick up the new function definition.
If you include both direct and indirect calls to the same function, your program could end up using different versions for different function calls. This
is one reason why combining direct and indirect calls within a single program is not recommended.
When using multiple-file applications in conjunction with direct linking, it
is highly recommended that you use the VLISP built-in project management
system along with its functions to optimize code automatically. The project
management system provides a greater degree of control over compilation
and linking of program files than does the vlisp-compile function. See
“Managing Multiple LISP Files” on page 138 for details.

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Making Application Modules
VLISP provides you with the ability to create a single, standalone executable
module for your application. This module incorporates all your application’s
compiled files, and can include DCL, DVB, and other files that your application may need. Executable VLISP modules are known as VLX files, and are
stored in files named with a .vlx extension.
A Make Application wizard guides you through the application building process in VLISP. The result of this process is a Make file, which is often referred
to by its file extension, .prv. The Make file contains all the instructions VLISP
needs to build the application executable.

Creating a New Application
It is recommended you build your application only after you have fully
debugged it. Compiler errors during the Make process may prevent the application wizard from completing successfully.
There are two modes of the Make Application wizard: simple and expert. In
the simple mode, you need only identify the files in your application and
name the files you want to create. The expert mode allows for many additional options.

To build an executable file with the Make Application wizard
1 Choose File ® Make Application ® New Application Wizard from the VLISP
menu to start the Make Application wizard. VLISP displays a Wizard Mode
dialog box asking you to choose the mode you want:

Select Expert mode, so you can see all the possible Make options; then press
the Next button.


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2 VLISP displays the following Application Directory dialog box, where you
name your application and specify where you want the application files built
by Make Application to reside:

The Application Directory dialog box appears in both the Simple and Expert
Wizard modes.
You can enter the full path name in the Application Location field, or press
the Browse button and identify the output directory (folder) using a standard
Windows dialog box.
The Make Application wizard uses the Application Name when it creates the
application executable (.vlx) file and the Make (.prv) file. For example, if you
specify an application nam e of myapp, the Make Application wizard creates
files myapp.vlx and myapp.prv.
If you need to go back to a previous Make Application wizard step and
change something, press the Back button. Otherwise, press Next to continue.

3 The Application Options dialog box is displayed when you run the Make
Application wizard in Expert mode. In this dialog box, you choose whether
you want your application to run in its own namespace or in the namespace
of the document from which the VLX is loaded. See “Designing for a Multiple Document Environment” on page 126 for a discussion of namespaces
and separate-namespace VLX behavior.
The ActiveX Support option is available if you choose to run your application
in a separate namespace. Selecting this option results in automatic loading of
AutoLISP ActiveX support functions when the VLX is loaded.

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Press Next to continue building the application.

4 VLISP displays a dialog box in which you specify the LISP files to be loaded
when your application loads.

pull-down list to select
type of program file

The LISP Files to Include dialog box appears in both the Simple and Expert
Wizard modes.


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You can specify AutoLISP source code files, compiled AutoLISP (FAS) files, or
a VLISP project file. Click the pull-down button to choose the type of file you
want to include, then press the Add button to display the following dialog
box for selecting the files:

You can select multiple files using the standard Windows file selection
methods. After selecting file names, press Open to add the files to your application. To add more files of a different type, choose the file type from the
pull-down list and press Add again.
If you specify AutoLISP source files, VLISP compiles those program files when
it builds the application. If you specify a project file, all the project’s files are
compiled and included in the output module. See “Managing Multiple LISP
Files” on page 138 for information on creating and using project files.
To remove files from the application, select the files you no longer want and
press the Remove button. You can also select one or more files, right-click,
and choose Remove from the shortcut menu.
VLISP loads the application’s files in the order they are listed in the List Files
to Include dialog box. You may need to reorder the file list. For example, if
you call a function at load time, the function must be defined before it is
used. In this case, you want to place the file defining that function first. The
List Files to Include dialog box contains buttons you can use to move files
around in the list. Select a file name, then choose from among the following
buttons:
s
s
s
s

Top Move to the top of the list.
Up Move ahead of the file just above in the list.
Dn Move behind the file just below in the list.
Btm Move to the bottom of the list.

You can also right-click and choose these actions from a shortcut menu.

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Note that the load order of project files is specified when you define the
project. (See “Changing the Order in Which Visual LISP Loads Files” on page
144 of the “Maintaining Visual LISP Applications” chapter.)
When you have finished specifying your application’s AutoLISP files, press
Next to continue to the next step in the Make Application wizard.

5 The Resource Files to Include dialog box is displayed when you run the Make
Application wizard in Expert mode. If your application includes additional
files, such as dialog control language (DCL) files, you can include them in
your application’s VLX module by selecting them in the dialog box.

You can specify the following types of resource files:
s
s
s
s
s
s

AutoLISP source files
Compiled LISP files
Visual LISP project files
DCL files
DVB files
Text files

All program files can be loaded by the VLX. If you choose a Visual LISP
project file, all files defined in the project files are compiled and included in
the VLX.
Click the pull-down button to choose the type of files you want to include,
then press the Add button to display the dialog box for selecting the files. In
the file selection dialog box, you can select multiple files using the standard
Windows file selection methods. After selecting file names, press Open to add
the files to your application.
To add more files of a different type, choose the file type from the pull-down
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To remove resource files from your application, select the files you no longer
want and press the Remove button. You can also select one or more files,
right-click, and choose Remove from the shortcut menu.
After selecting resource files for your application, press Next to continue the
Make Application process.

6 The Application Compilation Options dialog box is displayed only in Expert
mode. You can select the compilation and linkage options for your application in the dialog box.

Refer to “Choosing a Compiler Mode” on page 111 for information on these
options.
After selecting your compilation options, press Next to continue to the final
step of the Make Application process.

7 For the final step in the Make Application wizard, you can tell VLISP to build
your application. The Review Selections/Build Application dialog box
appears in both Simple and Expert modes.

VLISP saves all your application options in a Make (.prv) file. The Make file
also includes all the instructions that VLISP needs to build the application. If

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you do not elect to build the application now, VLISP can use the Make file to
build the application later.
Press Finish to conclude the Make Application process.

Understanding the Output from Make Application
VLISP executes instructions in a Make file to build an application. Output
messages from this process appear in two VLISP windows: the Build Output
window and the Console window. The Build Output window contains messages relating to any compilation of AutoLISP source code into .fas files. In a
successful compile, the output looks like the following:

The compiler messages identify the following items:
s
s

The name and directory path of the source files being compiled.
The functions defined in the source file.
In the above example, four functions are identified: GP:GETPOINTINPUT,
GP:GETDIALOGINPUT, GP:DRAWOUTLINE, and C:GPATH.

s

The name and path of the output .fas files.

The VLISP Console window displays messages relating to the creation of the
application executable, the . vlx file. If the Make Application process succeeds,
the Console window displays the path and file name of the . vlx, as in the following example:


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Loading and Running Visual LISP Applications
To execute the functions in a VLX application, you must first load the VLX
file using any of the following methods:
Call the AutoLISP load function.
Choose File ® Load File from the VLISP menu.
s Choose Tools ® Load Application from the AutoCAD menu.
s
s

See “Loading and Running Compiled Programs” on page 114 for specific
instructions on loading and running application functions.

Changing Application Options
VLISP allows you to change the way your application is designed. For example, you can change compilation options, or add or remove AutoLISP files
from the application.

To change an application’s definition
1 Choose File ® Make Application ® Existing Application Properties. VLISP
displays a dialog box for you to specify your application’s Make (.prv) file,
which is where VLISP stores the application’s properties.

2 Specify the name of your application’s Make file, then press Open. VLISP displays the Application Properties dialog box.

3 Click the tab of the property you want to change. The tab options are:
Load/Compile
Options

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Compile AutoLISP source files using the Standard compile
option, or Optimize and Link the files.


Tune
Directories

Identify LISP Object directory and Target directory. The
Object directory is where VLISP places . fas and temporary
files created by the compiler. Target directory is another
name for “Application directory,” which is where Make
Application stores the VLX file. If a field identifying a
directory is blank, VLISP uses the .prv directory.

Application
Options

Create a separate-namespace VLX and include ActiveX
support. If ActiveX Support is selected along with Separate
Namespace, loading the VLX will automatically result in
the loading of AutoLISP ActiveX support functions.

Load Files

AutoLISP source files included in the application.

Resource Files

Additional resource files included in the application.

4 After changing a property, press Apply to save the change, or press OK to save
the change and exit the Application Properties dialog box.

Rebuilding an Application
After changing application options or modifying source code, you need to
rebuild your application for the changes to take effect.

To rebuild an application
1 Choose File ® Make Application ® Rebuild Application from the VLISP
menu.

2 Specify the location of your application’s Make file.
3 Press Open to rebuild the application.
In rebuilding the application, VLISP recompiles all .lsp source files, applying
the specified compilation options, and packages your application files into a
new .vlx file. If your application contains many AutoLISP files, and you have
only changed the source code in one or two files, the Make Application
option can rebuild your application more efficiently. See the following section for information on using this option.

Updating an Application
If you change just a small piece of your application’s AutoLISP source code,
you can have VLISP rebuild your application VLX while compiling only
those files you’ve updated. To effect this type of update, choose
File ® Make Application ® Make Application from the VLISP menu, and
select your application’s Make file. VLISP rebuilds the application based on


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the information contained in the Make file, and automatically compiles any
application source files for which either of the following are true:
s
s

There is no compiled (.fas) version of the file.
There is a compiled version of the file, but the source file has been modified since that compile (that is, the date of the source file is more current
than the date of the .fas file).

Note that if you change application options (for example, from Standard
compile mode to Optimize and Link), you must use the Rebuild Application
menu option to create a new VLX with the changes you specified. The
Make Application command only checks for changes to AutoLISP source
code files, not to application options.

Designing for a Multiple Document
Environment
AutoCAD 2000 introduced the ability to open many drawing documents in
a single AutoCAD session. This feature, known as multiple document interface (MDI), provides many benefits to AutoCAD users, such as allowing you
to copy objects between drawings and to display several drawings side by side
in a single AutoCAD session. When you design an AutoCAD application, you
need to understand how open drawing documents relate to one another.

Understanding Namespaces
To prevent applications running in one drawing window from unintentionally affecting applications running in other windows, the concept of
namespaces was introduced in AutoCAD 2000. A namespace is a LISP environment containing a set of symbols (for example, variables and functions).
Each open AutoCAD drawing document has its own namespace. Variables
and functions defined in one document namespace are isolated from variables and functions defined in other namespaces.

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Relationship of Namespace to Dynamic Memory
Dynamic Memory
Document 1
Namespace
foo
blit

Document 2
Namespace
foo
blit
c:drawline
var1

foo
"A string"
foo
34.5
c:drawline
45

(Doc 1)

(Doc 2)

You can see how this works by trying a simple example.

To see the effect of multiple namespaces
1 Open two new drawings in AutoCAD.
2 Choose Window ® Tile Vertically from the AutoCAD menu. You should see
two open document windows side by side within the main AutoCAD
window:

The document’s title bar indicates which window is currently active. In the
preceding example, Drawing1.dwg is the current document.

Designing for a Multiple Document Environment

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3 Enter the following at the Command prompt:
(setq draw1foo "I am drawing 1")

This sets the draw1foo variable to a string.

4 Activate Drawing2.dwg (click in the window’s title bar).
5 See if draw1foo contains the value you just set for it:
Command: !draw1foo
nil

The variable is nil because it has not been set in this document’s namespace;
you set it in the namespace belonging to Drawing1.dwg .

6 Enter the following at the Command prompt:
(setq draw2foo "I too am a drawing, but number 2")

This sets the draw2foo variable to a string.

7 Activate Drawing1.dwg .
8 Test the values of variables draw1foo and draw2foo:
Command: !draw1foo
"I am drawing 1"
Command: !draw2foo
nil

The draw1foo variable contains the value you set for it, but draw2foo is nil
because you did not set it to a value in the current namespace; you set a different variable of the same name in Drawing2.dwg’s namespace.
VLISP provides ways for you to share variables between namespaces, but you
must take explicit action to do so. (See “Sharing Data between Namespaces”
on page 133.)
Like variables, functions defined in an AutoLISP file are known only to the
document that was active when the file was loaded. The functions in the file
are loaded in the current document’s namespace and are known only to that
document.

To see how functions are affected by multiple namespaces
1 Load a LISP file from either the AutoCAD Command prompt or the VLISP
Console prompt. For example:
(load "yinyang.lsp")

2 Invoke the function.
3 Open a second drawing window.
4 With the second drawing window active, try invoking the function again.
The response will be an error message saying the function is not defined.

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You can use the vl-load-all function to load the contents of an AutoLISP
file into all AutoCAD drawing documents. For example, the following command causes the contents of the yinyang.lsp file to be loaded into all open
documents, and into any documents opened later in the AutoCAD session:
(vl-load-all "yinyang.lsp")

The vl-load-all function is useful for testing new functions in multiple documents, but in general you should use acaddoc.lsp to load files that are
needed in every AutoCAD document.

Running an Application in Its Own Namespace
You can define a namespace for a VLX application in VLISP. A VLX application defined in this manner is referred to as a separate-namespace VLX.
When you load a separate-namespace VLX, it runs in its own namespace, not
the namespace of the document from where you loaded the VLX. The option
to define a VLX application with its own namespace is part of the Make
Application procedure (see “Making Application Modules” on page 117).
If you try to load a separate-namespace VLX that is already loaded, you’ll
receive an error indicating this. Use the vl-unload-vlx function to unload
the application. The function’s syntax is
(vl-unload-vlx “appname”)

For appname, specify the file name of the VLX, without the path or the . vlx
extension.
Variables and functions defined in a VLX application’s namespace are known
only to the application, not to the drawing document that was active when
the application was loaded. This allows you to protect your variables from
accidentally—or intentionally—being overwritten by other applications
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A VLX application can export function names to a document namespace to
enable those functions to be accessed within the context of that document.
The following diagram illustrates how this works:
Relationship of Namespaces to VLX Namespaces

Document 1
Namespace

Dynamic Memory

foo
blit
bar

Document 2
Namespace
"Hangman" VLX
bar
dooley

foo
blit

(Doc 1)
foo
"A string"
bar [Hangman]
foo
34.5

(Doc 2)

(Hangman)
bar
"some value"

The diagram shows an AutoCAD session containing two open drawing documents. A VLX application named “hangman” is loaded with respect to
Document1 (for example, a user opened Document1 and then loaded the VLX
application from the AutoCAD Command prompt). The hangman application established its own namespace and declared the bar function and the
dooley variable in that namespace. The VLX exported the bar function to
Document1’s namespace. When a user invokes bar from Document1, bar runs
in the application’s namespace. The bar function is unknown to Document2,
and neither document has access to the dooley variable (because the VLX did
not export it). You can load another instance of the hangman VLX into
Document2, but this instance will have its own namespace and its own copies
of bar and dooley.

NOTE When you load a VLX file that has not been defined as having its own
namespace, the environment is similar to that of a loaded file. All functions and
variables defined in the VLX are loaded in the document’s namespace.

Making Functions Available to Documents
By default, functions defined in a separate-namespace VLX are not exposed
to the document namespace from which the VLX is loaded. You must use the
vl-doc-export function to expose functions to document namespaces.
When issued from a VLX that runs in its own namespace, vl-doc-export
exposes the specified function to any document namespace that loads the
VLX. The vl-doc-export function accepts a single argument, a symbol identifying the function name. For example, look at the following code:

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(vl-doc-export 'kertrats)
(defun kertrats ()
(princ "This function goes nowhere")
)

This examples defines the kertrats function, which simply prints a message.
The defun for the function is preceded by a vl-doc-export call that causes
the function to be exported to the document namespace.

To see how vl-doc-export works in a separate-namespace VLX
1 In a VLISP text editor window, copy the following code into a file:
(defun kertrats ()
(princ "This function goes nowhere")
)

Note that this code does not contain a call to vl-doc-export.

2 Save the file you just created.
3 Use the VLISP Make Application wizard to build a VLX from your program
file. Specify the following wizard options:
Wizard mode: Expert
Application name: doctest
s Application options: Separate-namespace
s Compilation options: Optimize
s
s

4 From either the AutoCAD Command prompt or the VLISP Console window
prompt, load the doctest VLX file.
5 Try running the kertrats function.
You should receive an error message indicating the function is not defined.

6 Add the following line of code to the beginning of your program file:
(vl-doc-export 'kertrats)

7 Save the file, then rebuild the application.
8 Use vl-unload-vlx to unload the VLX, then load and run the VLX again.
This time, kertrats should run successfully.
You can issue a vl-doc-export call outside the context of a separatenamespace VLX application, but it has no effect.
The vl-list-loaded-vlx function returns a list of all separate-namespace
applications associated with the current document. For example:
_$ (vl-list-loaded-vlx)
(DOCTEST)

To determine what functions have been exported from a separate-namespace
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When calling this function, you must pass it a string naming the application
you are checking. For example, the following command returns a list of the
functions exported by the doctest application:
_$ (vl-list-exported-functions "doctest")
("KERTRATS")

The results show that a single function, kertrats, was exported from doctest
to the current document’s namespace.

NOTE Currently, if separate namespace VLX A associated with document A
loads separate namespace VLX B, then all of VLX B’s exported functions are automatically defined in document A. This behavior will not be supported in future
releases of AutoCAD. Note also that VLX B’s exported functions are not defined
in VLX A until VLX A issues an explicit import (see the next topic).

Making Separate-Namespace Functions Available to Other
VLX Applications
Functions defined in one separate-namespace VLX are not exposed to any
other separate-namespace VLX applications. If a function has been exported
through vl-doc-export, you can use the vl-doc-import function to make
the function available to another separate-namespace VLX.

Referencing Variables in Document Namespaces
Variables defined in a separate-namespace VLX are not known to the document namespace associated with the VLX. However, a separate-namespace
VLX can access variables defined in a document namespace using the
vl-doc-ref and vl-doc-set functions.
The vl-doc-ref function copies the value of a variable from a document
namespace. The function requires a single argument, a symbol identifying
the variable to be copied. For example, the following function call copies the
value of a variable named aruhu:
(vl-doc-ref 'aruhu)

If executed within a document namespace, vl-doc-ref is equivalent to the
eval function.
The vl-doc-set function sets the value of a variable in a document
namespace. The function requires two arguments: a symbol identifying the
variable to be set, and the value to set for the variable. For example, the following function call sets the value of a variable named ulus:
(vl-doc-set 'ulus "Go boldly to noone")

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If executed within a document namespace, vl-doc-set is equivalent to the
setq function.
To set the value of a variable in all open document namespaces, use the
vl-propagate function. For example, the following function calls set a variable named fooyall in all open document namespaces:
(setq fooyall "Go boldly and carry a soft stick")
(vl-propagate 'fooyall)

This command not only copies the value of fooyall into all currently open
document namespaces, but also causes fooyall to automatically be copied to
the namespace of any new drawings opened during the current AutoCAD
session.

Sharing Data between Namespaces
VLISP provides a blackboard namespace for communicating the values of
variables between namespaces. The blackboard is a namespace that is not
attached to any document or VLX application. You can set and reference
variables in the blackboard from any document or VLX. Use the vl-bb-set
function to set a variable, and use vl-bb-ref to retrieve a variable’s value.
For example, the following command sets the foobar blackboard variable to
a string:
Command: (vl-bb-set 'foobar "Root toot toot")
"Root toot toot"

The vl-bb-ref function returns the specified string. The following example
uses vl-bb-ref to retrieve the value of foobar from the blackboard:
Command: (vl-bb-ref 'foobar)
"Root toot toot"

Note that these functions require you to pass a symbol naming the variable
you are referencing ( 'var-name), not the variable name (var-name).
Setting or retrieving variable values in the blackboard namespace has no
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To demonstrate that document variables are unaffected by blackboard
variables
1 From the VLISP Console window (or the AutoCAD Command prompt), use
vl-bb-set to set the *example* blackboard variable.
_$ (vl-bb-set '*example* 0)
0

The *example* variable is set to 0 in the blackboard namespace.

2 Use vl-bb-ref to verify the value of the variable you set in the previous step.
_$ (vl-bb-ref '*example*)
0

3 See what value *example* has in the current AutoCAD document.
_$ *example*
nil

The *example* variable is nil because it has not been set in the document
namespace.

4 Set *example* in the current document.
_$ (setq *example* -1)
-1

The *example* variable is set to -1 in the document namespace.

5 Check the current value of *example* in the blackboard.
_$ (vl-bb-ref '*example*)
0

The blackboard variable named *example* is still set to the value assigned in
step 1; setting the document variable of the same name in step 4 had no
effect on the blackboard.
VLISP also provides the vl-doc-set and vl-doc-ref functions to set and
retrieve document namespace variables from a separate-namespace VLX, and
vl-propagate to set the value of a variable in all open document namespaces.
These functions are described in “Referencing Variables in Document
Namespaces” on page 132.

Handling Errors in an MDI Environment
By default, each document namespace is provided with its own *error*
function, which is defined as follows:
(defun *error* (msg)
(princ "error: ")
(princ msg)
(princ)
)

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A VLX application running within a document namespace shares the default
error-handler function. You may want to add error-handling logic to your
application.

Handling Errors in a VLX Application Running in Its Own
Namespace
For VLX applications executing within their own namespace, you can either
use the default error function or you can define an error handler specifically
for the application.
If you define an error handler for a VLX running in its own namespace, you
can call the vl-exit-with-error function to pass control from the VLX error
handler to the document namespace’s *error* function. The following
example uses vl-exit-with-error to pass a string to the document’s *error*
function:
... ; processing in VLX namespace/execution context
(vl-exit-with-error (strcat "My application bombed! " msg)))

A VLX *error* handler can use the vl-exit-with-value function to return
a value to the document namespace from which the VLX was invoked. The
following example uses vl-exit-with-value to return the integer value 3 to
the program that called the VLX from the document namespace:
... ; processing in VLX-T namespace/execution context
(vl-exit-with-value 3))
(vl-doc-export 'foo)
(defun foo (x)
(bar x)
(print 3))
(defun bar (x) (list (/ 2 x) x))

Any instructions pending at the time the error occurred are flushed.
If your VLX namespace error handler does not use either
vl-exit-with-error or vl-exit-with-value, then control returns to the
command prompt after execution of the error handler. You can only call
vl-exit-with-error and vl-exit-with-value in the context of a VLX application’s error handler; it is an error to invoke these functions in any other
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Limitations on Using AutoLISP in an MDI
Environment
When using native AutoLISP in an MDI environment, you can only work
with one drawing document at a time. Although AutoLISP provides support
for exchanging variables and exposing functions to multiple namespaces,
you cannot, for example, run a function in one document namespace and
issue entmake to create an entity in another document namespace. AutoLISP
does not support accessing information across multiple drawings.
You can access multiple document namespaces using ActiveX automation,
and AutoLISP provides access to ActiveX methods (see chapter 6, “Working
with ActiveX”). However, accessing multiple documents with ActiveX is an
unsupported feature of AutoLISP. For example, an AutoLISP program running
in the context of document A can change the active document to document
B by calling vla-put-activedocument. Changing the active document,
though, immediately suspends execution of the program. The program may
resume execution if the user activates the window containing document A
but the system will be in an unstable state and likely to crash.

WARNING! If you do use ActiveX to work in MDI, be aware that if you close
all AutoCAD drawings you lose access to AutoLISP and will cause an exception.

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Maintaining Visual LISP
Applications

5

In This Chapter

This chapter describes how you can maintain large
applications containing multiple files by defining the

s Managing Multiple LISP Files
s Defining a Project
s Working with Existing Projects

application as a VLISP project. Aside from defining the

s Optimizing Application Code

components in your application, you can use VLISP
projects to define compiler options for the application.
This chapter describes the various compiler options and
the consequences of each, and tells you how to override
these options for individual files in a project.

137

Managing Multiple LISP Files
Many program examples you have seen in this document have been small,
standalone AutoLISP files. Typical AutoLISP applications, however, consist of
larger files with many lines of code. An application may include many source
code files. After compiling the programs in such an application, you also
have a number of FAS files to track.
As the number of application files grows, it becomes more difficult to maintain an application. Determining when you need to recompile files after
source code changes can be a challenge. VLISP provides functions that
greatly simplify the process of managing multiple-file applications.

Understanding Visual LISP Projects
To aid you in the process of maintaining multiple-file applications, VLISP
provides a construct called a project. A VLISP project contains a list of
AutoLISP source files, and a set of rules on how to compile the files. Using the
project definition, VLISP can do the following:
Check which .lsp files in your application have changed, and automatically recompile only the modified files. This procedure is known as a Make
procedure.
s Simplify access to source files by listing all source files associated with a
project, making them accessible with a single-click.
s Help you find code fragments by searching for strings when you do not
know which source files contain the text you’re looking for. VLISP limits
the search to files included in your project.
s Optimize compiled code by directly linking the corresponding parts of
multiple source files.
s

Before discussing how to define and use VLISP projects, it may help to introduce file types used in VLISP.

LISP FAS, and Other File Types
,
The basic file type in VLISP is the AutoLISP source file. Typically, AutoLISP
source files are named with an .lsp file extension. You have seen .lsp files used
frequently in previous chapters.
The FAS (.fas) file type was introduced in the previous chapter, “Building
Applications.” FAS files are compiled AutoLISP files. These files load faster
than AutoLISP source files and are more secure because their contents are not
intelligible to users.

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Here is a brief summary of the types of files used by the VLISP project management feature:

Visual LISP project file types
File ext.

Type of file

Function

fas

Compiled AutoLISP code

Compiled AutoLISP programs. May be loaded
and run, or compiled into VLX modules.

lsp

AutoLISP source code

Program source files.

ob

Object code

Used internally by VLISP, these files contain
compiled AutoLISP code used in building FAS
files.

pdb

Project database

Used internally by VLISP, these files contain
symbol information used by the compiler.

prj

Project definition

Contains the location and names of all source
files that build the project, as well as certain
parameters and rules on how to create the final
FAS files.

In addition to the files recognized by the project manager, VLISP either
creates, processes, or recognizes a number of additional types of files, as
summarized below:

Additional Visual LISP file types
File ext.

Type of file

Function

dsk

Desktop save

Contains VLISP environment and window
settings. (Note: Do not edit this file unless you
are certain you know what you are doing.)

_xx

Backup files

Backup copies of edited files, maintained by the
VLISP editor. Backup files contain the same
name as the original, except that the file
extension begins with the underline character
(_) and is followed by the first two characters of
the original file’s extension. For example, the
backup file of an .LSP file has an ._LS extension;
the backup of a DCL file has a ._DC extension.

vlx

Standalone applications

Standalone AutoCAD applications, which can be
created using the VLISP Make Application
wizard.

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Additional Visual LISP file types (continued)
File ext.

Type of file

Function

c, cpp,
cch, hpp,
hh

Language source files

Contain program source code. The VLISP editor
recognizes the syntax of these files and colorcodes reserved words, strings, and numbers.

dcl

Dialog control language

Contains definitions of AutoCAD dialog boxes.
VLISP can preview these files, and you can
include them in Visual LISP executable (VLX)
files.

prv

Make application

Defines the files and options used to build a VLX
application with the VLISP Make Application
wizard.

sql

Structured query language

Contains SQL statements. The VLISP text editor
recognizes this file type and color-codes the text
according to SQL syntax rules.

Defining a Project
To demonstrate the use of projects in VLISP, you can use the sample programs supplied with the VLISP Tutorial. This code is available on the
AutoCAD installation CD, but the tutorial files are only included in your
installation if you choose a Full install, or if you choose Custom install and
select the Samples item. If you have already installed AutoCAD and did not
install the samples, you can rerun the install, choose Custom, and select only
the Sample item.
The sample files used in this chapter are in the TutorialVisualLISPLesson5
folder of the AutoCAD install directory. The files are:
s
s
s
s

Gpmain.lsp
Gpdraw.lsp
Gp-io.lsp
Utils.lsp

To create a VLISP project, choose Project ® New Project from the VLISP
menu:

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VLISP displays a standard Windows dialog box for you to specify a file path
and name. For the example in this chapter, the project name is Tutorial.
VLISP assigns a . prj extension to the project file name.

Assigning Project Properties
The Project Properties dialog box displays after you specify a project file
name:

project home
directory
click to change
Source
directory

list of selected files displays
in this window

list of .lsp files in
the Source
directory

Selecting the Files to Include in a Project
There are two tabs in the Project Properties dialog box. Choosing the Project
Files tab displays the window shown above. In this window, you specify the
AutoLISP source files for the project.

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The project’s home directory is identified just below the tabs. This is where
the project file ( tutorial.prj) resides. In this example, the home directory is
c:My DocumentsVisualLISPExamples. That’s not the directory containing
the tutorial sample files, though. To identify the source directory, press the
button:

Use the Browse for Folder window to identify the location of the project
source files. If you select the Lesson5 directory, the Project Properties dialog
box looks like the following:

VLISP lists all files in the directory having an .lsp extension (but does not display the extension in the list). The window is designed so that, by default,
you can select multiple file names by just choosing each name. You do not

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have to press and hold CTRL to select more than one file. To clear a selected
name, just choose it again.
To include all the listed files in your project, press the button labeled
“(Un)Select all,” then choose the right arrow button. VLISP moves the file
names to the window on the right:

To remove a file from the project, select the file’s name in the right window
and click the left arrow button.

Identifying the Path Name of Project Files
The list of included files does not identify the path name of each file (nor
does the Look In field; this just identifies the path of the files listed in the left
window). Because you can include files from multiple directories in your
project, you need to be able to identify the path name of each file. You can
do this by highlighting one or more file names and right-clicking to display
a shortcut menu:

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To display the full path nam e and the size (in bytes) of source files in the
project, choose Log Filenames and Size from the shortcut menu. The information appears in a small, scrollable window near the bottom of the Project
Properties dialog box:

If a file is in the Home directory shown in the Project Properties dialog box,
VLISP does not spell out its path name. Use the scroll bar to see information
about all the files in the project.
Note that you cannot include two files of the same name in a project, even
if they are in different directory paths.

Changing the Order in Which Visual LISP Loads Files
The shortcut menu for the list of included files also provides commands to
move files up and down in the list, and to sort the list by file name or by full
path name. VLISP loads the project’s files in the order in which they are
listed. Sometimes the load order is important. For example, you might have
an initialization file that defines global variables needed by all the other program files, and thus must be loaded first. You could select that file name and
choose Move to Top to place it first in the project’s file list.
You can also use buttons in the Project Properties dialog box to move files
around in the list: Top (move to top), Up (move up), Dn (move down), and
Btm (move to bottom).
For the tutorial project, the gpmain.lsp file should be loaded last. It contains
the following instructions at the end of the file:
(princ "nType GPATH to draw a garden path.")
(princ)

This results in a prompt telling users how to invoke the application. If VLISP
loads gpmain.lsp last, these instructions will display at the AutoCAD Command prompt.
After you move any needed files, press the Apply button.

Choosing Compiler Build Options
The Build Options tab displays a dialog box in which you can specify compiler options to VLISP. This topic is covered in the “Choosing a Compilation
Mode” section later in this chapter. For now, choose OK to close the Project
Properties dialog box.

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Using the Project Window to Work with Project
Files
When you open a VLISP project, VLISP displays a window listing the files in
the project:

By default, VLISP lists the project members in the order in which they will be
loaded (as defined in the Project Properties dialog box). You can change this
order by choosing Arrange Files from the shortcut menu for this window (see
below).
The project name appears in the window title bar. Below the title bar are five
icons. Each icon is a button that performs a function. The buttons and their
functions are as follows:

Project
Properties

Displays the Project Properties dialog box for the project.
This allows you to view the full path name of each file in
the project, add, remove, and reorder project files, and
view and change project compiler options.

Load Project
FAS

Loads all compiled (.fas) files for the project.

Load Source
Files

Loads all the project source files, making them available to
be run.

Build Project
FAS

Compiles all project source files that have been modified
since their last compile.

Rebuild Project
FAS

Recompiles all project source files, whether or not they
have changed since their last compile.

If you right-click within the file list of the Project Properties dialog box,
VLISP displays a shortcut menu. Many of the functions available from the
project shortcut menu can also be accomplished in other ways. For example,
you’ve already seen how to add files to projects and remove files from
projects. Choosing Remove File from the shortcut menu is a quick way of
removing a file from a project, while choosing Add File merely brings you to
the Project Properties dialog box.

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The following summarizes the commands on the shortcut menu:

Edit

Edits the source code of the selected project members.

Add File

Opens the Project Properties dialog box to add files to the
project.

Remove File

Removes the selected members from the project.

Load

Loads the FAS file for the selected project members. If no
FAS file exists for a member, load the AutoLISP source file.

Load Source

Loads the .lsp file for the selected project members.

Check Syntax

Checks AutoLISP syntax of the source code for the
selected members.

Touch

Indicates that the selected source files have been updated,
but make no change to the files. This causes VLISP to
recompile these programs the next time you ask to
compile all changed project files.

Arrange Files

Sorts the project member list, according to one of the
available suboptions (load order, name, type, or date).

Multiple
Selection

Tells VLISP whether or not to allow selection of multiple
members from the list in the Project Properties dialog box.
If this option is selected, multiple selection is allowed.

[Un]Select All

Selects all members of the project list, if none are currently
selected. If any members are currently selected, this
command cancels their selection.

Close Project

Closes the project.

Save Project As

Saves the project.

Selecting Multiple Project Members
The Multiple Selector menu item is available only from the Project Properties
dialog box shortcut menu. Choosing this option allows you to select multiple members from the list in the Project window. If the option is selected, a
check mark appears next to the Multiple Selector item on the menu. Click on
the menu item to toggle it on and off.
If Multiple Selector is in effect, clicking a member name in the Project Properties dialog box acts as a toggle to select or deselect the member. For
example, none of the members listed in the following window is selected:

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If you click on the name GP-IO, then click on the name GPDRAW, both are
selected.

This is unlike the default Windows behavior, where selecting the second list
item cancels the first item’s selection, unless you press CTRL while selecting
the item.
You can also use the Project Properties dialog box shortcut menu to select all
members of the project or cancel selection of all members. If no members are
currently selected, right-click and choose [Un]Select All to select all the members. If any or all members are already selected, [Un]Select All cancels all
selections.

Loading Project Files
To load the project’s compiled program files, click the Load Project FAS button. This allows you to run the application. If VLISP detects that some of the
source files do not exist in compiled format, it displays a message and asks if
you want to compile those files:

If you choose Yes, VLISP attempts to compile all .lsp files that do not have a
corresponding .fas file. If you choose No, VLISP loads all FAS files it finds for
the project, and loads the AutoLISP source for the remaining project files.
Press Cancel to abort the load operation.
To load all project source files, instead of their compiled versions, click the
Load Source Files button. Remember that debugging breakpoints may be
saved within source code files but are removed from the compiled version of

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the code. You might want to load source files to debug changes you’ve made
to your programs.
Using the Project Properties dialog box shortcut menu, you can choose to
load just selected files. Select the files you want to load, then right-click and
choose Load to load the FAS files, or choose Load Source to load the source
code. Note that if you choose Load and a FAS file does not exist for a selected
file, VLISP loads the AutoLISP source file instead.

NOTE The Lesson5 example from the VLISP Tutorial requires a DCL file to run
successfully. The DCL file is included in the Lesson5 folder, but you cannot define
a DCL file as part of a VLISP project. To run this example successfully you must
copy the DCL file to a directory in the AutoCAD Support File Search Path. You
can also define the DCL file as an application component, using the VLISP Make
Application wizard. Using this method, the file does not have to be in the
AutoCAD search path. “Including a Project in a Visual LISP Application” on page
151 demonstrates how to define an application composed of a VLISP project and
supporting files, such as DCL.

Compiling and Recompiling Project Files
One key advantage in defining VLISP projects for your applications is that it
provides an efficient method of updating compiled code. You can elect to
have VLISP recompile all source files that have changed since the last time
they were compiled. By choosing this option, you ensure all FAS files in your
application correspond to the latest versions of the program source code. At
the same time, you save time by avoiding unnecessary compiles. To invoke
this feature, click the Build Project FAS button in the Project Properties dialog
box.
You can also choose to recompile all the programs in your project, whether
or not they have changed. Click the Rebuild Project FAS button to enable
this feature.

Editing Project Files
To edit the source file of a project member, select the member from the list
in the Project window, then right-click and choose Edit. If the Multiple Selector option is on, you can select multiple members, and VLISP will open a text
editor window for each.

NOTE If the Multiple Selector option is not turned on, you can simply doubleclick a member name to edit it.

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Saving and Closing the Project
To save the project properties you defined or modified, right-click in the
Project window and choose Save Project As from the shortcut menu. VLISP
displays a list of project files. You can either select the name of the current
project file to update its contents, or enter a new file name to save the
changes as a new project.
When you are finished working with a project, right-click in the Project window and choose Close Project. Note that this only closes the .prj file; any
project files that are open in VLISP editor windows remain open.

NOTE If you close the Project Properties dialog box by clicking the Close button, this does not close the project itself. The Project is still open, and you can
reopen a Project window for it by choosing it from the Project menu, as
described in the next section,“Opening a Project.”

Working with Existing Projects
Some VLISP features described in previous chapters have special application
with VLISP projects. The features described in this section are the text editor
search functions and the Make Application wizard.

Opening a Project
To open an existing project, choose Project ® Open Project from the VLISP
menu:

If the project file you want to open is in the current directory, you can simply
enter the project name here. If the project file is not in the current directory,
or if you don’t know what the current directory is, press the Browse button
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Note that you can have more than one project open at a time. You can view
a list of all open projects by choosing the Project menu and looking at the
bottom of the menu displayed:

At any time, only one of the projects is active. The check mark in front of the
project name indicates the active project. The commands in the Project
menu, such as Load and Build, apply to the active project. These commands
work the same when selected from a Project window, as described earlier in
this chapter.
If you attempt to open a project that has the same name as the active project
(that is, the project file has the same name, but is in a different directory than
the current active project), VLISP displays a message box asking you if you
want to “relocate the project definition.” If you choose “Yes,” VLISP loads the
new project file and replaces the active project. If you choose “No,” VLISP
does not load the new project file, leaving the current active project in place.

Finding a String in Project Source Files
The VLISP text search function, described in “Searching for Text” on page 37,
provides you with the ability to search all of a project’s source files for a string
of text.
For example, suppose in reviewing gpmain.lsp you see calls to a function
called gp:getPointInput, and you cannot remember in which source file this
function is defined. To search for it, choose Search ® Find from the VLISP
menu. In the Find dialog box, select Project in the list of Search options:

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A Project selection field now appears at the bottom of the Find dialog box. If
the name of the project you want to search is not already displayed in this
field, choose it from the pull-down list. Choose the Find button to perform
the search. VLISP displays the results in a Find Output window like the following:

The output shows that four files were searched (there are four source files in
the project), and four occurrences of gp:getPointInput were found. The
occurrences were found in two files; the defun for the function is in gp-io.lsp.
You can open an editor window for the file by double-clicking anywhere
within the highlighted text in the Find Output window. You can also press
SHIFT + F11 to display the first source location at which the text string was
found, and then repeatedly press F11 to view subsequent occurrences in the
source files.

Including a Project in a Visual LISP Application
After you’ve made changes to an application’s source files, you’ll want to
incorporate those changes in the application’s executable file. “Making
Application Modules” on page 117 showed you how to keep individual application files synchronized, so that the application executable contained the
latest versions of all its source files. Defining the application files as members
of a single project simplifies this process further. Instead of listing every
source file in your application’s Make file, you can point to the VLISP project
file and use the project file to identify your source files.


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To define an application that includes a Visual LISP project
1 Choose File ® Make Application ® New Application Wizard from the VLISP
menu to start the Make Application wizard.

2 Select Expert mode, then press Next.
3 Identify the directory path in which you want VLISP to save your application
files, and enter a name for the application.
Press Next to continue.

4 Press Next to accept the default application options.
5 In the LISP Files to Include dialog box, click the pull-down menu to the right
of the Add button and choose Visual LISP project file as the type of file to
include.
Press the Add button to display the Add Visual LISP Project Files dialog box.

6 Specify the .prj file you created for the Lesson5 tutorial example, then press
Open to add the file to your application. All the project’s files will be included
in the application.
Press Next to continue to the next step in the Make Application wizard.

7 In the Resource Files to Include dialog box, click on the pull-down to the
right of the Add button and choose DCL files, then press the Add button to
display the dialog box for selecting the DCL files.
Select the DCL file in the TutorialVisualLISPLesson5 directory, then press
Open to add the file to your application.
Press Next to continue the Make Application wizard.

8 Accept the default options in the remaining steps and complete the Make
Application process.
If you add files to the VLISP project you included in your application, the
new files are automatically included the next time you build the application.

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Optimizing Application Code
The optimization features of VLISP can produce more efficient compiled
files, and are useful as your programs grow in size and complexity. With the
VLISP project management feature, you can tailor the optimization options
to the specific needs of your application.

Defining Build Options
VLISP provides a number of options for compiling and linking a project’s
source code that affect the efficiency of the compiled code. For example, you
can specify whether to create a separate FAS file for each source file or merge
all compiled files into a single FAS file. You can choose to have the compiler
remove the names of all local symbols from your compiled files. You specify
these options in the Project Properties dialog box.

To specify project build options
1 Open the project file (choose Project ® Open Project from the VLISP menu).
2 Press the Project Properties button in the Project window toolbar.
3 Select the Build Options tab in the Project Properties dialog box. VLISP displays the Build Options dialog box:


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Some of the build options require extensive background information, which
is provided in the following sections of this chapter. The build options are:

Compilation
Mode

Choose between standard and optimized compilation.
Optimized compilation creates smaller and faster
programs but is not suited for every project. See
“Choosing a Compilation Mode” on page 155 for more
information on this topic.

Merge Files
Mode

Tell the compiler whether to create a separate FAS file for
each source file, or to merge all compiled files into a single
FAS file.
A single FAS file is faster to load and is required for certain
types of optimization. Sometimes, however, you will
prefer to load your code one file at a time. This is
important if you have not completed the debugging or
modification of the application’s code. FAS files do not
allow source code debugging, so it is recommended that
you compile your code only after the initial debugging is
done.

Edit Global
Declarations

FAS Directory

|

Specify the directory for compiled files. If you indicate a
relative path, VLISP applies it in relation to the project’s
home directory. If you leave the field blank, VLISP places
compiled files in the same directory as the project
definition (.prj) file.

Tmp Directory

154

Create or edit a global declarations file for the project.

Specify the directory for project-related temporary files. A
relative path is applied in relation to the project’s home
directory.

Chapter 5

This feature is provided for compatibility with the Preview
version of VLISP. The functionality provided by the
Global Declarations file will be provided by other features
in future releases of VLISP.


Link Mode

Specify how function calls are to be optimized. This
option is only available if optimized compilation is
selected. Choose from the following:
s

Do not link: This results in indirect linking of functions.

The compiler stores the address of the symbol naming
the function.
s Link: If selected, the compiler directly addresses
function definitions and all calls where the functions
are referenced.
s Internal: This directly links function calls and removes
(drops) the function names from the resulting FAS
files.
See “Choosing a Link Mode” on page 157 for further
information on these options.

Localize
Variables

If selected, the compiler removes (drops) the names of all
local symbols from compiled files and directly links their
references, wherever possible. This means the program
code points to the address where a variable is stored, not
to a symbol used to find the address of the variable.

Safe Optimize

If selected, this option directs the compiler to refuse some
types of optimization, if there is a chance they will result
in incorrect code. For more information on optimization,
see “Choosing a Compilation Mode,” below.

Message Mode

Select the level of detail you want VLISP to produce in its
compilation reports. You can choose to receive a report
showing only fatal errors (those causing compilation
failure), a report showing errors and warning messages, or
a full report showing errors, warnings, and compiler
statistics.

Choosing a Compilation Mode
Combining compiled code from multiple files to a single binary file allows
the compiler to add a high level of optimization. It also means that there are
more choices to make.
When producing standard, non-optimized binary code, the VLISP compiler
preserves the symbol names associated with functions and global variables,
because these symbols may be referenced from other files. When the symbol
is referenced, VLISP looks in a table to determine what area in memory is
assigned to the symbol.


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When optimizing code, the VLISP compiler assumes all files in a project work
together to form a complete application. This allows the compiler to discard
the symbol names and, when executing the code, jump directly to the memory location containing the value associated with the symbol.

Analyzing for Optimization Correctness
Optimizing code may introduce bugs to software that runs perfectly when
non-optimized. Also, the level of performance gain depends highly on the
internal structure of the source code. LISP is a language in which you can easily write programs that create or modify functions at runtime. This use of the
language by definition contradicts compile-time optimization.
The VLISP compiler analyzes the code it compiles and links, then it creates a
report pointing you to all source code segments that may cause problems
when optimized. If you do not receive any optimization warning messages,
you can assume optim ization did not introduce new problems to your code.
The compiler is able to detect most problematic situations in AutoLISP code.
However, there are situations in which it is impossible to detect code that
may become incorrect during the optimization. If your program uses one of
the following constructs, the compiler will not be able to prove correctness
of the optimized code definitively:
s
s
s
s
s

Interaction with external ObjectARX applications that set or retrieve
AutoLISP variables
Dynamic calls to functions defined by other ObjectARX applications
Evaluation of dynamically built code using eval, apply, mapcar, or load
Use of set to set dynamically supplied variables
Dynamic (program evaluated) action strings in action_tile and
new_dialog

Remember that any optimization will change program semantics. The compiler intends to preserve the behavior of project components relative to one
another. The compiler cannot guarantee unchanged behavior between your
project and external procedures. Typical effects of optimization include the
following:
Outer applications and the VLISP Console window lose access to program
functions and symbols.
s Functions available from the Console window in interpreter mode are
unknown in compiled mode.
s Functions are available from the Console window, but redefining them
does not change the program’s behavior.
s

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Choosing a Link Mode
If you instruct the VLISP compiler to link functions in your project directly,
the compiler tries to resolve all explicit function calls by referencing the
function’s definition in memory. In contrast, when you indirectly link your
functions, the compiler creates references to symbols that VLISP later uses to
look up the actual memory location of the function. Direct linking improves
the performance of the compiled code and protects the code against function
redefinition. However, if your application needs to redefine a function, you
cannot directly link that function.
Once function calls are directly linked, the compiler can optimize one level
further by dropping the function name completely so that the function
becomes invisible to users. To select this feature, choose the Internal Link
mode option. Note that symbols exported to ACAD (for example, function
names starting with C:) are never dropped.

Understanding Safe Optimization
Choosing the Safe Optimize option reduces the amount of compiler
optimization but protects your code against compiler-induced errors. Safe
optimizing prevents runtime uncertainty that could cause an optimized program to fail, even though the source code seems to be correct. For example,
imagine the following situation:
The function symbol fishlips is defined by defun and used somewhere
in your code. This is a typical candidate for link optimization.
s In another segment of your code, a variable named fishlips is assigned
using (setq fishlips expression).
s

Now there are two possible conditions. If the value assigned through setq is
intended to alter the definition of the function fishlips, direct linking will
prevent this from happening. The first definition will be referenced directly
and cannot be changed by the setq function. On the other hand, if the identical names are handled independently, fishlips can be linked without
creating incorrect code.
If safe optimizing is on, the compiler will always stay on the safe side, even
if you explicitly request that fishlips be directly linked. This may result in
less efficient code, but it ensures code correctness. If safe optimizing is off,
you can override the compiler’s recommendation to link fishlips indirectly.
You are responsible for the link option.
The Safe Optimize mode is on by default. Be sure you fully understand the
consequences before you turn it off.


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Optimization Conditions Bypassed by Safe Optimization
When Safe Optimization is in effect, the VLISP compiler ignores an optimization option if it determines that adhering to the option may induce an
error condition. The following list identifies the conditions under which an
option is ignored:

Link

If the compiler encounters the following situations while
Safe Optimize is on, it ignores any related Link directive:
A symbol is bound as a parameter anywhere in the
project.
s A symbol is bound as an auxiliary variable and
referenced by value anywhere in the project.
s A symbol is explicitly assigned somewhere (by setq).
s

Drop

If the compiler encounters a symbol referenced by value,
it ignores any Drop directive for the symbol.

Localize

If the compiler encounters the following situations while
safe optimize is on, it ignores the Localize directive or the
corresponding variable:
A variable has a non-local reference or assignment to it
within the project.
s A variable is called by name.
s

Safe Optimization Warning Messages
If optimized compilation is on and the compiler finds a condition that forbids a certain level of optimization, it issues a warning message. For example,
if the function fishlips cannot be linked because the compiler found two
definitions for the function, you’ll see:
;*** WARNING: Cannot LINK fishlips;
Two DEFUNs found.
See Another DEFUN

Right-click on a warning message to open a shortcut menu. In addition to
displaying symbol commands, the menu allows you to view the source code
associated with the message. Double-click on the highlighted message to
show the source code. To browse all source files related to the compiler messages, press F11 repeatedly, or press SHIFT + F11 to return to the first message.

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Each line of the previous warning message guides you to a different code segment. For example:
; *** WARNING: Cannot LINK fishlips

shows the function call that could not be linked.
; Two DEFUNs found

shows the first defun found for function fishlips.
; See Another DEFUN

shows the second defun found for function fishlips.
When the compiler works in Safe Optimization mode and finds a problem
condition, the warning starts with:
; *** WARNING: Safe: Cannot …

If Safe Optimization is off, but message mode is set to Full report, the same
warnings are prefixed by:
; *** WARNING: Dangerous …

If you disable Safe Optimize mode, these problematic conditions result in
compiler warnings.

Compiler Checking of Optimizing Conditions
The compiler always checks for optimizing consistency. If you specify an
optimization option that contradicts certain security rules, the compiler will
issue warning messages. The security rules are:

Link

The compiler directly links AutoLISP function calls only if
the following conditions are met:
The function is defined only once, or is predefined by
AutoLISP and no user defun redefines it.
s The function name does not appear in the parameter
list of another function.
s The function is not assigned anywhere in the project.
s


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Drop

The compiler tries to drop a function symbol only if all
corresponding function calls are directly linked to the
function definition. The compiler does not drop the
symbol for a function definition if the program calls the
function by its symbol name. A function is called by
symbol in the following cases:
The symbol appears in a vl-acad-defun declaration.
The function was called from an ACTION_TILE action
string.
s The function symbol is a quoted argument for apply,
mapcar, or eval somewhere in the project.
s
s

Note that for functions called from top-level expressions,
the Drop declaration will be ignored without warning
messages.

Localize

The compiler does not localize a variable in bound lists of
defun, lambda, and foreach expressions if any of the
following conditions are true:
The variable has a non-local reference (or assignment)
to it within the outer top-level expression.
s The variable is called as a function by name.
s The variable symbol appears as a function call
somewhere in the top-level read-eval loop.
s

Other than these conditions, which always cancel the
optimization and result in warning messages, there are
other conditions that may or may not result in incorrect
code. Choose the Safe Optimize option for the project to
disallow these conditions as well. Disabling Safe
Optimization results in compiler warnings if these
conditions are met. See “Understanding Safe
Optimization” on page 157 for more information on this
topic.

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6

In This Chapter

VLISP not only makes program development easier and

s Using ActiveX Objects with
AutoLISP

faster, it also provides new functionality to AutoLISP

s Understanding the AutoCAD
Object Model

applications. For example, you can use VLISP to access

s Accessing AutoCAD Objects
ActiveX objects from AutoLISP code. You can also use
ActiveX to interact with other Windows applications
that support ActiveX methodology.

s Using Visual LISP Functions with
ActiveX Methods
s Using ActiveX to Interact with
Other Applications

161

Using ActiveX Objects with AutoLISP
ActiveX Automation is a new way to work programmatically with the contents of an AutoCAD drawing. In many instances, ActiveX works faster than
traditional AutoLISP functions in manipulating AutoCAD drawing objects.
The ActiveX programming interface is usable from a number of languages
and environments, such as C++, Visual Basic™ and Delphi™ When you work
,
.
with ActiveX objects in AutoLISP, you work with the same object model,
properties, and methods that can be manipulated from other programming
environments.
Objects are the main building blocks of an ActiveX application. In some
ways, you are already familiar with this notion. For example, AutoCAD drawing items such as lines, arcs, polylines, and circles have long been referred to
as objects. But in the ActiveX schema, the following AutoCAD components
are also represented as objects:
Style settings, such as linetypes and dimension styles
Organizational structures, such as layers, groups, and blocks
s The drawing display, such as the view and viewport
s The drawing’s model space and paper space
s
s

Even the drawing and the AutoCAD application itself are considered objects.
ActiveX includes much of the functionality provided by standard AutoLISP
functions such as entget, entmod, and setvar. Compared to these functions,
ActiveX runs faster and provides easier access to object properties. For example, to access the radius of a circle with standard AutoLISP functions, you
must use entget to obtain a list of entities and assoc to find the property you
want. You must also know the code number (DXF key value) associated with
that property to obtain it with assoc, as shown in the following example:
(setq radius (cdr (assoc 40 (entget circle-entity))))

With an ActiveX function, you simply ask for the radius of a circle as follows:
(setq radius (vla-get-radius circle-object))

Understanding the AutoCAD Object Model
AutoCAD objects are structured in a hierarchical fashion, with the Application object at the root. The view of this hierarchical structure is referred to as

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the object model. It shows you which object provides access to the next level
of objects. The AutoCAD object model is described in the following figure:
AutoCAD Application
Preferences
Documents
3DFace

Document

3DPoly
Blocks

Blo9ck
3DSolid
Database
Arc
ModelSpace
Attribute
PaperSpace

AttributeRef
PViewport

Dictionaries

BlockRef

Dictionary

DimStyles

Circle

XRecord

Dim3PointAngular
DimAligned

DimStyle

DimAngular
Groups

Group

Layers

Layer

Layouts

Layout

Linetypes

Linetype

PlotConfigurations

PlotConfiguration

DimDiametric
DimOrdinate
Hyperlinks
DimRadial
DimRotated

RegisteredApps

RegisteredApplication

SelectionSets

Hyperlink

Ellipse
ExternalReference

SelectionSet

Hatch
Leader
TextStyles

TextStyle

UCSs

UCS

Line

Views

View

MInsertBlock

Viewports

Viewport

LightweightPolyline

MLine
MText

DatabasePreferences

Point
Plot
PolyfaceMesh
Utility
Polyline
MenuBar

PolygonMesh
PopupMenu

Raster
Ray

MenuGroups

Region

MenuGroup

Shape
PopupMenus
Solid
PopupMenu
Spline
PopupMenuItem
Text
Toolbars

Tolerance

Toolbar

Trace

ToolbarItem

XLine

Understanding the AutoCAD Object Model

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Using ActiveX is not always a matter of choice. For example, you must use
ActiveX to access drawing objects from reactor callback functions. You’ll
learn more about this in “Attaching Reactors to AutoCAD Drawings” on page
202.

Object Properties
All objects in the AutoCAD object model have one or more properties. For
example, a circle object can be described by properties such as radius, area, or
linetype. An ellipse object also has area and linetype properties, but it cannot
be described in terms of its radius. Rather, you describe it in terms of its major
to minor axis ratio, a property named RadiusRatio. Property names are necessary when accessing AutoCAD data through ActiveX functions.

Object Methods
ActiveX objects also contain methods, which are simply the actions available
for a particular kind of object. Some methods can be applied to most
AutoCAD drawing objects. For example, the Mirror method (creating a mirror image copy of an object around a mirror axis), and the Move method
(moving a drawing object along a specified vector), can be applied to most
drawing objects. By contrast, the Offset method, which creates a new object
at a specified distance from an existing object, applies only to a few classes of
AutoCAD objects such as Arc, Circle, Ellipse, and Line.
In VLISP, ActiveX methods are implemented as AutoLISP functions. You’ll see
many references to ActiveX functions in VLISP documentation, but keep in
mind that in ActiveX terminology, they are always known as methods.
To determine which methods and properties apply to a specific type of
AutoCAD object, refer to the ActiveX and VBA Reference. This reference is
available from the VLISP and AutoCAD Help menus, or by opening the
acadauto.hlp file in the AutoCAD Help directory.
You will probably want to have the ActiveX and VBA Reference open at all
times when you are developing VLISP programs that use ActiveX. If you open
the acadauto.hlp file from the AutoCAD Help directory, you can keep the reference open when you use VLISP online help. If you open the reference by
selecting it from the AutoCAD Help menu, it closes when you choose an item
from the VLISP Help menu.

Collections of Objects
All objects in the AutoCAD object model are grouped in collections. For
example, the Blocks collection is made up of all blocks in an AutoCAD draw-

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ing, and the ModelSpace collection comprises all graphical objects (circles,
lines, polylines, and so on) in the drawing’s model space. Collections are
labeled in the object model diagram.

Accessing AutoCAD Objects
The Application object is the root object for the AutoCAD object model.
From the Application object, you can access any of the other objects, or the
properties or methods assigned to objects.
Before you can use ActiveX functions with AutoLISP, you need to load the
supporting code that enables these functions. Issue the following function
call to load ActiveX support:
(vl-load-com)

This function first checks if ActiveX support is already loaded; if so, the function does nothing. If ActiveX support is not already loaded, vl-load-com
loads ActiveX and other Visual LISP extensions to the AutoLISP language.

NOTE All applications that use ActiveX should begin by calling vl-load-com.
If your application does not call vl-load-com, the application will fail, unless the
user has already loaded ActiveX support.
After loading the ActiveX support functions, the first step in accessing
AutoCAD objects is to establish a connection to the AutoCAD Application
object. Use the vlax-get-acad-object function to establish this connection,
as in the following example:
(setq acadObject (vlax-get-acad-object))

The vlax-get-acad-object function returns a pointer to the AutoCAD
Application object. In the example above, the pointer is stored in the
acadObject variable. This return value exists as a unique VLISP data type
called VLA-object (VLISP ActiveX object).
When you refer to AutoCAD objects with ActiveX functions, you must specify a VLA-object type. For this reason, you cannot use entget to access an
object and then refer to that object with an ActiveX function. The entget
function returns an object of data type ename. Although you cannot use this
object directly with an ActiveX function, you can convert it to a VLA-object
using the vlax-ename->vla-object function. (See “Converting Object References” on page 190.)


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Using the Inspect Tool to View Object Properties
To view the properties associated with an Application object, you can select
the variable that points to the object (acadobject, in the previous example),
and choose the Inspect button on the VLISP View toolbar as follows:

You can readily identify many of the properties listed in the VLA-object
Inspect window. For example, FullName is the file name of the AutoCAD
executable file, Version is the current AutoCAD version, and Caption is the
contents of the AutoCAD window title bar. An [RO] following a property
name indicates the property is read-only; you cannot change it.
Any property identified as a #<VLA-OBJECT...> refers to another AutoCAD
ActiveX object. Look at the Preferences property, for example. If you refer to
the diagram of the AutoCAD object model, you’ll see that the Preferences
object is just below the Application object in the model hierarchy. To view
the properties associated with an object, double-click the object line in the
Inspect window (or right-click and choose Inspect). Here is the Inspect window for the Preferences object:

You may notice that the properties of the Preferences object correspond to
the tabs on the AutoCAD Options dialog box. Double-click on the Files property to display the following Inspect window:

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If you compare the properties shown in this window to the options available
under the Files tab in the AutoCAD Options dialog box, you’ll be able to see
the connection between the two. The following figure shows the Files
options:

For example, the AutoSavePath property corresponds to the Automatic Save
File Location option, and the HelpFilePath property would be a sub-option
under the Menu, Help, and Miscellaneous File Names option.
You’ll learn how to use ActiveX functions to access objects and modify properties in “Using Visual LISP Functions with ActiveX Methods” on page 170.


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Moving Forward from the Application Object
Following the AutoCAD object model hierarchy, the ActiveDocument
property of the Application object leads you to a Document object. This Document object represents the current AutoCAD drawing. The following
AutoLISP command returns the active document:
(setq acadDocument (vla-get-ActiveDocument acadObject))

The Document object has many properties. Access to non-graphical objects
(layers, linetypes, and groups, for example) is provided through like-named
properties such as Layers, Linetypes, and Groups. To get to the graphical
objects in the AutoCAD drawing, you must access either the drawing’s model
space (through the ModelSpace property) or paper space (through the
PaperSpace property). For example:
(setq mSpace (vla-get-ModelSpace acadDocument))

At this point, you have access to the AutoCAD drawing and can add objects
to the drawing. For example, you can add a circle to the model space with the
following command:
(setq mycircle (vla-addCircle mSpace
(vlax-3d-point '(3.0 3.0 0.0)) 2.0))

Summarizing the Process
In this section, you saw code examples that led to the drawing of a circle
object in an AutoCAD drawing using ActiveX Automation. The following
sequence of function calls was used:
(vl-load-com)
(setq acadObject
(vlax-get-acad-object))
(setq acadDocument (vla-get-ActiveDocument acadObject))
(setq mSpace
(vla-get-ModelSpace acadDocument))
(setq mycircle
(vla-addCircle mSpace
(vlax-3d-point '(3.0 3.0 0.0)) 2.0))

The statements in this example accomplished the following:
Loaded AutoLISP ActiveX support functions.
Returned a pointer to the Application object.
s Obtained a pointer to the current active Document object, using the ActiveDocument property of the Application object. This provided access to
the current AutoCAD drawing.
s Obtained a pointer to the ModelSpace object, using the ModelSpace property of the Document object.
s Drew a circle in the ModelSpace.
s
s

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The hierarchical path traversed in the AutoCAD object model is pictured
below:
AutoCAD
Application

Document

ModelSpace
Collection
Circle

Performance Considerations
Repeated calls to access the AutoCAD Application, active Document, and
Modelspace objects should be avoided, as they negatively impact performance. You should design your applications to obtain these objects one time,
and refer to the obtained object pointers throughout the application.
The following code examples illustrate three functions you can define to
return the Application, active Document, and Modelspace objects, respectively:
(setq *acad-object* nil)
; Initialize global variable
(defun acad-object ()
(cond (*acad-object*)
; Return the cached object
(t
(setq *acad-object* (vlax-get-acad-object))
)
)
)
(setq *active-document* nil) ; Initialize global variable
(defun active-document ()
(cond (*active-document*)
(t
(setq *active-document* (vla-get-activedocument (acad-object)))
)
)
)
(setq *model-space* nil)
; Initialize global variable
(defun model-space ()
(cond (*model-space*)
(t
(setq *model-space* (vla-get-modelspace (active-document)))
)
)
)


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For example, you can draw a circle using the following function call:
(vla-addCircle (model-space) (vlax-3d-point '(3.0 3.0 0.0)) 2.0)

The model-space function returns the model space of the active document,
using the active-document function to access the Document object, if necessary. The active-document function, in turn, calls acad-object to obtain
the Application object, if necessary.

Using Visual LISP Functions with ActiveX
Methods
VLISP adds a set of functions to the AutoLISP language that provides access
to ActiveX objects. The function names are prefixed with vla-: for example,
vla-addCircle, vla-get-ModelSpace, vla-getColor. These functions can be
further categorized as follows:

vla- functions correspond to every ActiveX method. Use these functions
to invoke the method (for example, vla-addCircle invokes the Addcircle
method).
s vla-get- functions correspond to every property, enabling you to retrieve
the value of that property (for example, vla-get-Color obtains an object’s
color property).
s vla-put- functions correspond to every property, enabling you to update
the value of that property (for example, vla-put-Color updates an
object’s color property).
s

VLISP also adds a set of ActiveX-related functions whose names are prefixed
with vlax-. These are more general ActiveX functions, each of which can be
applied to numerous methods, objects, or properties. For example, with the
vlax-get-property function, you can obtain any property of any ActiveX
object. If your drawing contains custom ActiveX objects, or if you need to
access objects from other applications, such as a Microsoft Excel spreadsheet,
you can use the vlax-invoke-method, vlax-get-property, and
vlax-put-property functions to access their methods and properties; you’ll
see examples using these functions in “Using ActiveX without Importing a
Type Library” on page 198.

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Determining the Visual LISP Function You Need
The VLISP ActiveX functions actually provide access to ActiveX methods. For
example, look at the following AutoLISP statement, which was entered at the
VLISP Console prompt:
_$ (setq mycircle (vla-addCircle mSpace
(vlax-3d-point '(3.0 3.0 0.0)) 2.0))
#<VLA-OBJECT IAcadCircle 03ad067c>

This command adds a circle to a drawing, using the Addcircle method. The
function called to draw the circle is vla-addCircle.
If you do not know what function adds a circle to an AutoCAD drawing, you
can figure it out by looking in the ActiveX and VBA Reference. If you look up
the definition for a Circle object, here’s what the entry looks like:

Sometimes, as in this Circle entry, there is descriptive text that identifies the
method you need. Often, though, you’ll need to look through the list of
methods to find the one that matches the action you want to take.

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Once you find the name of the method, add a vla- prefix to the method name
to get the name of the VLISP function that implements the method. In this
example, it is vla-AddCircle. Note in VLISP the function name is not casesensitive; vla-addcircle is the same as vla-AddCircle.

Determining How to Call a Function
Once you identify the VLISP function you need, you still must determine
how to call the function. You need to know the arguments to specify and the
data type of those arguments. The ActiveX and VBA Reference contains the
information required for coding calls to ActiveX functions.
For example, from the reference page for the Circle object, choose the
AddCircle hyperlink to view the definition of this method:

Note that you can also get to this page by choosing the Methods button near
the top of the Help window, then choosing AddCircle from a list of methods.
The syntax definitions in the reference were designed for Visual Basic users,
so they may take some getting used to. For AddCircle, the syntax is defined
as follows:
RetVal = object.AddCircle(Center, Radius)

Substituting the variable names used in this chapter’s examples, the
syntax is:
mycircle = mspace.AddCircle(Center, Radius)

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The AutoLISP syntax required for the same operation is:
(setq myCircle (vla-addCircle mSpace
(vlax-3d-point '(3.0 3.0 0.0)) 2.0))

The return value ( RetVal, in Visual Basic) is straightforward. The ActiveX and
VBA Reference defines this as a Circle object. In VLISP, whenever an AutoCAD
object is returned by an ActiveX function, it is stored as a VLA object data
type.
The object referred to before the method name (object.AddCircle) is always
the first argument in a vla function call. This is the AutoCAD object you are
viewing or modifying. For example, add a circle to the drawing model space
with the following:
(vla-addCircle

mSpace ...)

In this example, mspace refers to the ModelSpace object. Recall from the discussion on the AutoCAD object model (in “Accessing AutoCAD Objects” on
page 165), that you use the properties of one AutoCAD object to access
another object in a hierarchical manner. The ModelSpace object provides
access to the model space of the current drawing.
The Center and Radius arguments refer to data types that may be unfamiliar
to LISP users. The following section explains these data types.
Note that some ActiveX methods require arguments that are described as
output only. See “Using ActiveX Methods That Return Values in Arguments”
on page 184 for information on how to code these arguments.

Converting AutoLISP Data Types to ActiveX
Data Types
When adding a circle to a drawing, you must specify the center point of the
circle and the radius of the circle. In the definition for the AddCircle method
in the ActiveX and VBA Reference, these arguments are referred to as Center
and Radius. Center is defined as a variant (three-element array of doubles),
and Radius is listed as a double:
RetVal = object.AddCircle (Center, Radius)

Elements
Center
Radius

Variant (three-element array of doubles); input only.
A 3D WCS coordinate specifying the circle’s center.
Double; input only.
The radius of the circle. Must be a positive number.


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The reference explains what these parameters are used for, but the data types
indicated for these parameters may be unfamiliar to LISP users. Variants are
essentially self-defining structures that can contain different types of data.
For example, strings, integers, and arrays can all be represented by variants.
Stored along with the data is information identifying the type of data. This
self-defining feature makes variants useful for passing parameters to ActiveX
servers, because it enables servers based on any language to understand the
data value.

Working with Variants
Several AutoLISP functions introduced in AutoCAD 2000 allow you to create
and work with variants:
creates a variant.
returns the data type of a variant.
s vlax-variant-value returns the value of a variant variable.
s vlax-variant-change-type changes the data type of a variant variable.
s vlax-make-variant
s vlax-variant-type

The vlax-make-variant function accepts two arguments: value and type.
The value argument is the value to be assigned to the variant. The type argument specifies the type of data to be stored in the variant. For type, specify
one of the following constants:

vlax-vbEmpty
vlax-vbNull

Integer

vlax-vbLong

Long integer

vlax-vbSingle

Single-precision floating-point number

vlaxvbDouble

Double-precision floating-point number

vlax-vbString

String

vlax-vbObject

Object

vlaxvbBoolean

Boolean

vlax-vbArray

|

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vlaxvbInteger

174

Uninitialized (default value)

Array

Chapter 6


The constants evaluate to integer values. Because these values may change in
future releases of AutoCAD, you should always refer to the constant, not the
integer the constant evaluates to. See the entry for vlax-make-variant in the
AutoLISP Reference for the current integer value assigned to each constant.
For example, the following function call creates an integer variant and sets
its value to 5:
_$ (setq varint (vlax-make-variant 5 vlax-vbInteger))
#<variant 2 5>

The return value indicates the variant’s data type (2, which is vbInteger) and
the variant’s value (5).
If you do not specify a data type to vlax-make-variant, the function assigns
a default type. For example, the following function call creates a variant and
assigns it a value of 5 but does not specify a data type:
_$ (setq varint (vlax-make-variant 5))
#<variant 3 5>

By default, vlax-make-variant assigned the specified integer value to a Long
Integer data type, not Integer, as you might expect. When assigning a
numeric value to a variant, you should explicitly state the data type you
want. Refer to vlax-make-variant in the AutoLISP Reference for a complete
list of default type assignments.
If you do not specify a value or data type, vlax-make-variant allocates an
uninitialized ( vlax-vbEmpty) variant.

Working with Safearrays
Arrays passed to ActiveX methods must be of the safearray type. These arrays
are safe because you cannot accidentally assign values outside the array
bounds and cause a data exception to occur. Use the vlax-make-safearray
function to create a safearray and use vlax-safearray-put-element or
vlax-safearray-fill to populate a safearray with data.


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The vlax-make-safearray function requires a minimum of two arguments.
The first argument identifies the type of data that will be stored in the array.
Specify one of the following constants for the data type:

vlaxvbInteger

Integer

vlax-vbLong

Long integer

vlax-vbSingle

Single-precision floating-point number

vlaxvbDouble

Double-precision floating-point number

vlax-vbString

String

vlax-vbObject

Object

vlaxvbBoolean

Boolean

vlaxvbVariant

Variant

The constants evaluate to integer values. Because these values may change in
future releases of AutoCAD, you should always refer to the constant, not the
integer to which the constant evaluates. See the entry for
vlax-make-safearray in the AutoLISP Reference for the current integer value
assigned to each constant.
The remaining arguments to vlax-make-safearray specify the upper and
lower bounds of each dimension of the array. You can create single or multidimensional arrays with vlax-make-safearray. The lower bound for an
index can be zero or any positive or negative integer.
For example, the following function call creates a single-dimension array
consisting of doubles, with a starting index of 0:
_$ (setq point (vlax-make-safearray vlax-vbDouble '(0 . 2)))
#<safearray...>

The upper bound specified in this example is 2, so the array will hold three
elements (element 0, element 1, and element 2).
Different dimensions can have different bounds. For example, the following
function call creates a two-dimension array of strings. The first dimension
starts at index 0 and contains two elements, while the second dimension
starts at index 1 and contains three elements:
_$ (setq mat2 (vlax-make-safearray vlax-vbString '(0 . 1) '(1 . 3)))
#<safearray...>

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You can use either vlax-safearray-fill or vlax-safearray-put-element to
populate arrays with data.

Using vlax-safearray-fill
The vlax-safearray-fill function requires two arguments: the variable
containing the array you are populating and a list of the values to be assigned
to the array elements. You must specify as many values as there are elements
in the array. For example, the following code populates a single-dimension
array of three doubles:
(vlax-safearray-fill point '(100 100 0))

You can display the contents of this array in list form with the
vlax-safearray->list function:
_$ (vlax-safearray->list point)
(100.0 100.0 0.0)

If you do not specify a value for every element in the array,
vlax-safearray-fill results in an error.
To assign values to a multi-dimensional array, specify a list of lists to
vlax-safearray-fill, with each list corresponding to a dimension. For

example, the following command assigns values to a two-dimension array of
strings that contains three elements in each dimension:
_$ (vlax-safearray-fill mat2 '(("a" "b" "c") ("d" "e" "f")))
#<safearray...>

Use the vlax-safearray->list function to confirm the contents of mat2:
_$ (vlax-safearray->list mat2)
(("a" "b" "c") ("d" "e" "f"))

Using vlax-safearray-put-element
The vlax-safearray-put-element function can be used to assign values to
one or more elements of a safearray. The number of arguments required by
this function depends on the number of dimensions in the array. The
following rules apply to specifying arguments to
vlax-safearray-put-element:
The first argument always names the safearray to which you are assigning
a value.
s The next set of arguments identifies index values pointing to the element
to which you are assigning a value. For a single-dimension array, specify
one index value; for a two-dimension array, specify two index values, and
so on.
s The final argument is always the value to be assigned to the safearray
element.
s


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For example, the following code populates a single-dimension array of three
doubles:
(vlax-safearray-put-element point 0 100)

To change the second element of the array to a value of 50, issue the following command:

The following example populates a two-dimension array of strings. The first
dimension of the array starts at index 0, while the second dimension starts
at index 1:
(vlax-safearray-put-element

mat2
mat2
mat2
mat2
mat2
mat2

0
0
0
1
1
1

1
2
3
1
2
3

"a")
"b")
"c")
"d")
"e")
"f")

You can use vlax-safearray->list to confirm the contents of the array:
_$ (vlax-safearray->list mat2)
(("a" "b" "c") ("d" "e" "f"))

Using Safearrays with Variants
Safearray data must be passed to ActiveX methods through variants. That is,
you create a safearray, then you assign the safearray to a variant before passing it to a method. For methods that require you to pass a three-element
array of doubles (typically to specify a point), you can use the vlax-3d-point
function to build the required data structure. For example, the following call
takes a list of points and converts the list into an array of three doubles:
_$ (setq circCenter (vlax-3d-point '(3.0 3.0 0.0)))
#<variant 8197 ...>

You can also pass vlax-3d-point two or three numbers, instead of a list. For
example:
$ (setq circCenter (vlax-3d-point 3.0 3.0))
#<variant 8197 ...>

When you omit the third point from your argument, vlax-3d-point sets it
to zero. You can use vlax-safearray->list to verify the contents of the variable set by vlax-3d-point:
$ (vlax-safearray->list (vlax-variant-value circcenter))
(3.0 3.0 0.0)

The vlax-TMatrix function perform s a similar task for transformation matrices, which are required by the vla-TransformBy function. It builds the

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transformation matrix from four lists of four numbers each, converting all
numbers to reals, if necessary. For example:
_$ (vlax-tmatrix '((1 1 1 0) (1 2 3 0) (2 3 4 5) (2 9 8 3)))
#<variant 8197 ...>

If you need to create a variant for an array containing anything other than
three doubles or a transformation matrix, you must build it yourself.

To create a variant containing an array of four doubles
1

Allocate space for the array:
(setq 4dubs (vlax-make-safearray vlax-vbDouble '(0 . 3)))

2 Populate the array:
(vlax-safearray-fill 4dubs '(3.0 6.0 7.2 1.0))

3 Store the safearray in a variant:
(setq var4dubs (vlax-make-variant 4dubs))

The var4dubs variable now contains a variant containing an array of doubles.

Converting Other AutoLISP Data Types for ActiveX Methods
The Radius argument to the AddCircle method requires a Double, but the
ActiveX functions make the necessary conversion if you specify a real in
AutoLISP. The following table identifies the AutoLISP data type that ActiveX
functions will accept in place of the required ActiveX data type. Each row in
the table represents a data type used by ActiveX functions. Each column in
the table represents an AutoLISP data type. Wherever the intersecting cells


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contain a plus (+) symbol, you can specify the corresponding AutoLISP data
type for the required ActiveX data type.

AutoLISP data types accepted in place of an ActiveX data type
Integer
Byte

Real

String

VLA-object Variant

Safearray

:vlax-true
:vlax-false

+

Boolean

+

Integer

+

Long

+

Single

+

+

Double

+

+

Object
String

+
+

Variant
Array

+
+

In some instances an AutoLISP ActiveX function will accept and convert a
data type that is not indicated as acceptable by the preceding table, but you
should never count on this.

Viewing and Updating Object Properties
VLISP provides AutoLISP functions for reading and updating object properties. You can use these functions to obtain the properties of existing drawing
objects (for example, the center point of a circle), and to modify drawing
objects (for example, moving the center point of the circle).

Reading Object Properties
Functions that read object properties are named with a vla-get prefix and
require the following syntax:
(vla-get-property object)

For example, vla-get-center returns the center point of a circle.

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To obtain an object’s property and apply the property to a new object
1 Enter the following at the VLISP Console prompt:
(setq myCircle (vla-addcircle mspace (vlax-3d-point
(getpoint "nPick the center point for a circle: ")) 2.0))

This function call prompts you to pick a center point for a circle, then
invokes the Addcircle method to draw the circle. The vlax-3d-point
function converts the point you pick into the data type required by
vla-addcircle.

2 Use vla-get-center to draw a second circle concentric to the first:
(vla-addCircle mSpace (vla-get-center myCircle) 1.0)

The AutoCAD drawing window now contains the following objects:

Updating Object Properties
Functions that update properties are prefixed with vla-put and use the following syntax:
(vla-put-property object new-value)

For example, vla-put-center changes the center point of a circle.

To change the X axis of a circle
1 Obtain the current center point of the circle:
_$ (setq myCenter (vla-get-center myCircle))
#<variant 8197

The center point is returned in a variant of type safearray. The safearray contains three doubles (X, Y, and Z coordinates).

2

Save the center point in list form:
$ (setq centerpt (vlax-safearray->list
(vlax-variant-value myCenter)))
(17.8685 5.02781 0.0)

Converting the center point from a variant safearray to a list m akes it easier
to modify the coordinates.


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3 Subtract 1 from the X axis of the center point:
_$ (setq newXaxis (- (car centerpt) 1))
16.8685

The result is saved in variable newXaxis.

4 Construct a new point list for the center point, using the new X axis and the
original Y and Z values:
_$ (setq newcenter (list newXaxis
(caddr centerpt)))
(16.8685 4.52594 0.0)

(cadr centerpt)

The constructed list is saved in variable newcenter.

5 Use vla-put-center to update the circle with the new X axis:
_$ (vla-put-center myCircle (vlax-3d-point newcenter))
nil

Note that this command uses vlax-3d-point to convert the new center point
list into the data type required by vla-put-center.
The AutoCAD drawing window shows the result:

Note that changing an object’s property may not immediately affect the display of the object in the AutoCAD drawing. AutoCAD delays property
changes to allow you to change more than one property at a time. If you need
to update the drawing window explicitly, issue the vla-update function:
(vla-update object)

Sometimes you can use pre-defined constants to update an object’s property.
For example, to set the fill color of a circle to red, you can use the constant
acRed instead of specifying a numeric index value:
(vla-put-color myCircle acRed)

The ActiveX and VBA Reference lists any predefined constants under the entry
describing the property. You can use these constants in VLISP ActiveX function calls.

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Determining Whether an Object Is Available for Updating
If other applications are working with any AutoCAD objects at the same time
as your program, those objects may not be accessible. This is especially
important to look out for if your application includes reactors, because reactors execute code segments in response to external events that cannot be
predicted in advance (see “Attaching Reactors to AutoCAD Drawings” on
page 202). Even a simple thing such as a locked layer can prevent you from
changing an object’s properties.
VLISP provides the following functions to test the accessibility of an object
before trying to use the object:
s vlax-read-enabled-p

tests whether you can read an object.
determines whether you can modify an object’s

s vlax-write-enabled-p

properties.
checks to see if an object has been erased. Erased objects
may still exist in the drawing database.

s vlax-erased-p

These test functions return T if true, nil if false. The following examples test
a line object:
Determine whether the line is readable:
$ (vlax-read-enabled-p WhatsMyLine)
T

Determine whether the line is modifiable:
$ (vlax-write-enabled-p WhatsMyLine)
T

See if the line has been erased:
$ (vlax-erased-p WhatsMyLine)
nil

Erase WhatsMyLine:
_$ (vla-delete WhatsMyLine)
nil

Issue vlax-read-enabled-p to see if WhatsMyLine is still readable:
$ (vlax-read-enabled-p WhatsMyLine)
nil

Issue vlax-erased-p again to confirm the object was deleted:
$ (vlax-erased-p WhatsMyLine)
T


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Using ActiveX Methods That Return Values in
Arguments
Some ActiveX methods require that you supply them with variables into
which the methods can place values. The GetBoundingBox method is an
example of this type of method. Here is how it is defined in the ActiveX and
VBA Reference:

Note that the MinPoint and MaxPoint parameters are described as output
only. You must provide output arguments as quoted variable names. The following example shows a VLISP function call to return the minimum and
maximum bounding points of a circle:
_$ (vla-getboundingbox myCircle 'minpoint 'maxpoint)
nil

The values output by vla-getboundingbox are stored in the minpoint and
maxpoint variables as safearrays of three doubles. You can view the values
using vlax-safearray->list:
_$ (vlax-safearray->list minpoint)
(1.0 1.0 -1.0e-008)
_$ (vlax-safearray->list maxpoint)
(5.0 5.0 1.0e-008)

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Note that the quoted symbol parameters you pass to the function become
AutoLISP variables just like the ones created through setq. Because of this,
you should include them as local variables in your function definition so
they do not become global variables by default.

Listing an Object’s Properties and Methods
Earlier in this chapter, you learned how to use the VLISP Inspect tool to display an object’s properties. Another way to view an object’s properties is to
call the vlax-dump-object function. You can invoke this function from the
VLISP Console window or from an application program. The
vlax-dump-object function prints a list of the properties of the specified
object and returns T. For example, the following code obtains the last object
added to the model space, then issues vlax-dumpObject to print the object’s
properties:
_$ (setq WhatsMyLine (vla-item mSpace (- (vla-get-count mspace) 1)))
#<VLA-OBJECT IAcadLWPolyline 036f1d0c>
_$ (vlax-dump-object WhatsMyLine)
; IAcadLWPolyline: AutoCAD Lightweight Polyline Interface
; Property values:
;
Application (RO) = #<VLA-OBJECT IAcadApplication 00a4ae24>
;
Area (RO) = 2.46556
;
Closed = 0
;
Color = 256
;
ConstantWidth = 0.0
;
Coordinate = ...Indexed contents not shown...
;
Coordinates = (8.49917 7.00155 11.2996 3.73137 14.8 5.74379 ... )
;
Database (RO) = #<VLA-OBJECT IAcadDatabase 01e3da44>
;
Elevation = 0.0
;
Handle (RO) = "53"
;
HasExtensionDictionary (RO) = 0
;
Hyperlinks (RO) = #<VLA-OBJECT IAcadHyperlinks 01e3d7d4>
;
Layer = "0"
;
Linetype = "BYLAYER"
;
LinetypeGeneration = 0
;
LinetypeScale = 1.0
;
Lineweight = -1
;
Normal = (0.0 0.0 1.0)
;
ObjectID (RO) = 28895576
;
ObjectName (RO) = "AcDbPolyline"
;
PlotStyleName = "ByLayer"
;
Thickness = 0.0
;
Visible = -1
T

There is an optional second argument you can supply to vlax-dump-object
that causes it to also list all the methods that apply to the object. Simply specify “T” following the object name:
(vlax-dump-object WhatsMyLine T)


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Note that vlax-dump-object displays the information in the window from
which you issued the command. However, the function returns T to the calling program, not the information displayed in the Command window.

Determining If a Method or Property Applies to an Object
Trying to use a method that does not apply to the specified object will result
in an error. Trying to reference a property that does not apply to an object
also results in an error. In instances where you are not sure what applies, use
the vlax-method-applicable-p and vlax-property-available-p functions
to test the objects. These functions return T if the method or property is available for the object, and nil if it is not.
The syntax for vlax-method-applicable-p is:
(vlax-method-applicable-p object method)

The following command checks to see if the Copy method can be applied to
the object referenced by WhatsMyLine:
_$ (vlax-method-applicable-p WhatsMyLine "Copy")
T

The following command determines whether or not the AddBox method can
be applied to the object:
_$ (vlax-method-applicable-p WhatsMyLine "AddBox")
nil

For vlax-property-available-p, the syntax is:
(vlax-property-available-p object property [T])

For example, the following commands determine if Color and Center are
properties of WhatsMyLine:
_$ (vlax-property-available-p WhatsMyLine "Color")
T
_$ (vlax-property-available-p WhatsMyLine "Center")
nil

Supplying the optional “T” argument to vlax-property-available-p
changes the meaning of the test. If you supply this argument, the function
returns T only if the object has the property and the property can be modified. If the object has no such property or the property is read-only,
vlax-property-available-p returns nil. For example, a circle contains an
Area property, but you cannot update it. If you check the property without
specifying the optional argument, the result is T:
_$ (vlax-property-available-p myCircle "area")
T

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If you supply the optional argument, the result is nil:
_$ (vlax-property-available-p myCircle "area" T)
nil

Working with Collection Objects
The concept of collections was introduced in “Understanding the AutoCAD
Object Model.” Recall that all ActiveX objects in the AutoCAD object model
are grouped in collections. For example, the Blocks collection is made up of
all blocks in an AutoCAD document. VLISP provides functions to help you
work with collections of AutoCAD objects. These functions are
vlax-map-collection and vlax-for.
The vlax-map-collection function applies a function to every object in a
collection. The syntax is:
(vlax-map-collection collection-object function)

For example, the following command displays all properties of every object
in a drawing’s model space:
$ (vlax-map-collection (vla-get-ModelSpace acadDocument)
'vlax-dump-Object)
; IAcadLWPolyline: AutoCAD Lightweight Polyline Interface
; Property values:
;
Application (RO) = #<VLA-OBJECT IAcadApplication 00b3b91c>
;
Area (RO) = 3.67152
;
Closed = -1
;
Color = 256
;
Coordinates = (9.59247 4.44872 9.25814 5.34715 4.1991 5.679 ...)
;
EntityName (RO) = "AcDbPolyline"
;
EntityType (RO) = 24
;
Handle (RO) = "4C"
;
Layer = "0"
; .
; .
; .
;
Thickness = 0.0
;
Visible = -1

(Note that the preceding example does not show every property returned by
vlax-dump-Object.)
To evaluate a series of functions with each object in a collection, use
vlax-for:
(vlax-for symbol collection [expressions] ...)

Like the foreach function, vlax-for returns the result of the last expression
evaluated inside the for loop. Note that modifying the collection (that is,
adding or removing members) while iterating through it may cause an error.


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The following example defines a function that uses vlax-for to show color
statistics for each object in the active drawing:
(defun show-Color-Statistics (/ objectColor colorSublist colorList)
(setq modelSpace (vla-get-ModelSpace
(vla-get-ActiveDocument (vlax-get-Acad-Object))
)
)
(vlax-for obj modelSpace
(setq objectColor (vla-get-Color obj))
(if (setq colorSublist (assoc objectColor colorList))
(setq colorList
(subst (cons objectColor (1+(cdr colorSublist)))
colorSublist
colorList
)
)
(setq colorList (cons (cons objectColor 1) colorList))
)
)
(if colorList
(progn (setq
colorList (vl-sort colorList
'(lambda (lst1 lst2) (< (car lst1) (car lst2)))
)
)
(princ "nColorList = ")
(princ colorList)
(foreach subList colorList
(princ "nColor ")
(princ (car subList))
(princ " is found in ")
(princ (setq count (cdr subList)))
(princ " object")
(princ (if (= count 1)
"."
"s."
)
)
)
)
)
(princ)
)

This function lists each color in the drawing and the number of objects
where the color is found.

Retrieving Member Objects in a Collection
The Item method retrieves a member object from a collection. The Count
property shows the number of items in a collection. Using the Item method
and Count property, you can individually process each object in a collection.
For example, you can look at each object in a model space, determine the

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type of object, and process only the types of objects you are interested in. The
following code prints the start angle for each arc object in a model space:
(setq index 0)
(repeat
(vla-get-count mspace)
(if (= "AcDbArc" (vla-get-objectname (vla-item mspace index)))
(progn
(princ "nThe start angle of the arc is ")
(princ (vla-get-startangle (vla-item mspace index)))
)
)
(setq index (+ index 1))
)

Note that Item and Count also apply to groups and selection sets.

Releasing Objects and Freeing Memory
Just as you can have different variables pointing to the same AutoCAD entity,
you can have multiple VLA-objects pointing to the same drawing object. You
can compare two VLA-objects with the equal function, which returns T if
both objects point to the same drawing object.
As long as a VLA-object points to a drawing object, AutoCAD will keep all the
memory needed for the object. When you no longer need to reference an
object, use the vlax-release-object function to indicate this to AutoCAD:
(vlax-release-object object)

After releasing an object, it is no longer accessible through the VLA-object
pointer. This is similar to closing a file. No memory is necessarily freed when
you issue vlax-release-object, but AutoCAD can reclaim the memory if
needed, once all references to the object have been released.
To test whether or not an object has been released, use the
vlax-object-released-p function:
(vlax-object-released-p object)

This function returns T if the object has been released, nil if it has not.


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Converting Object References
There are a number of ways to refer to AutoCAD drawing objects with
AutoLISP. These include the following:
VLA-objects, returned by ActiveX functions
Entity names (enames), returned by entget and entsel, identifying
objects in an open drawing
s Handles, returned by handent, which entities retain across AutoCAD sessions
s Object IDs, used by ARX to identify objects
s
s

AutoLISP provides functions to convert from one type of object identifier to
another.

Converting between Enames and VLA-objects
The vlax-ename->vla-object function allows you to convert entity names
(enames) obtained through functions, such as entget, to VLA-objects you
can use with ActiveX functions. For example, the following code sets a variable to an ename, then uses vlax-ename->vla-object to convert the ename
to a VLA-object:
_$ (setq ename-circle (car (entsel "nPick a Circle:")))
<Entity name: 27f0538>
_$ (setq vlaobject-circle (vlax-ename->vla-object ename-circle))
#<VLA-OBJECT IAcadCircle 03642c24>

To convert VLA-objects to enames, use vlax-vla-object->ename. For
example:
$ (setq new-ename-circle (vlax-vla-object->ename vlaobject-circle))

Obtaining One Object Identifier from Another
You may find the same drawing object represented by different identifiers
and data types such as a handle string, an ename, a VLA-object, or an ARX
object ID integer. To obtain the identifier with the data type your program
requires, use the following strategies:
s

To find the handle associated with an ename, use the DXF 5 group of the
ename’s association list:
_$ (setq handle-circle (cdr (assoc 5 (entget ename-circle))))
"4F"

s

To find the ename associated with a handle, use the handent function:
_$ (handent handle-circle)

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s

To find the VLA-object associated with a handle, use the
vla-handleToObject function:
$ (setq vla-circle (vla-handleToObject acadDocument
handle-circle))

s

To find the handle associated with a VLA-object, use vla-get-handle to
obtain the handle property:
$ (vla-get-handle vla-circle)
"4F"

s

To find the ARX Object ID of a VLA-object, use vla-get-objectid to get
the objectID property:
_$ (setq objid-Circle (vla-get-objectid vla-circle))
41878840

s

To find the VLA-object identified by an ARX Object ID, use the
ObjectIDtoObject method on the AutoCAD Document object:
_$ (vla-ObjectIDtoObject acadDocument objid-circle)

Handling Errors Returned by ActiveX Methods
When ActiveX methods fail, they raise exceptions rather than returning error
values that your program can interpret. If your program uses ActiveX methods, you must prepare it to catch exceptions, otherwise the program halts,
leaving the user at a Command prompt. You can use vl-catch-all-apply to
intercept errors returned by ActiveX methods.

To intercept errors returned by ActiveX methods
1 Load the following function and invoke it by issuing (init-motivate) at the
VLISP Console prompt:
(defun init-motivate ()
(vl-load-com)
(setq mspace
(vla-get-modelspace
(vla-get-activedocument (vlax-get-acad-object))
)
)
(vla-addray mspace (vlax-3d-point 0 0 0) (vlax-3d-point 1 1 0))
)

This function adds a ray object to the current model space. A ray has a finite
starting point and extends to infinity.

2 The GetBoundingBox method obtains two points of a box enclosing a specified object, returning those points in variables you supply to the method.
(See “Using ActiveX Methods That Return Values in Arguments” on page 184


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for an example using this.) The following code obtains a pointer to the last
object added to a drawing’s model space and uses vla-getboundingbox to
obtain the points enclosing the object:
(defun bnddrop (/ bbox)
(setq bbox (vla-getboundingbox
(vla-item mspace (- 1 (vla-get-count mspace)))
'll
'ur
)
)
(list "Do something with bounding box." bbox)
)

Load this code and run it by issuing (bnddrop) at the Console prompt.
Because a ray extends to infinity, it is not possible to enclose it with a box,
and GetBoundingBox results in the following error:
; error: Automation Error. Invalid extents

If this code were part of your application program, execution would halt at
this point.

3 By invoking vla-getboundingbox through the vl-catch-all-apply function, you can intercept errors returned by ActiveX. Load the following code
and run it by issuing (bndcatch) at the Console prompt:
(defun bndcatch (/ bbox)
(setq bbox (vl-catch-all-apply
'vla-getboundingbox
(list (vla-item mspace (- 1 (vla-get-count mspace)))
'll
'ur
)
)
)
(if (vl-catch-all-error-p bbox)
(list "Exception: " (vl-catch-all-error-message bbox))
(list "Do something with bounding box." bbox)
)
)

This function uses vl-catch-all-apply to call vla-getboundingbox. It passes
vl-catch-all-apply two arguments: the symbol naming the function being
called ('vla-getboundingbox) and a list of arguments to be passed to
vla-getboundingbox. If the GetBoundingBox method completes
successfully, vl-catch-all-apply stores the return value in variable bbox. If
the call is unsuccessful, vl-catch-all-apply stores an error object in bbox.
At this point in the bnddrop function, vla-getboundingbox was issued
directly, an error resulted, and execution halted. But in bndcatch,
vl-catch-all-apply intercepts the error and program execution continues.

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A call to vl-catch-all-error-p checks the return value from
vl-catch-all-apply and returns T if it is an error object, nil otherwise. If the
return value is an error object, as it would be in this example, the function
issues vl-catch-all-error-message to obtain the message from the error
object. Program execution continues from this point.
“Catching Errors and Continuing Program Execution” on page 257 includes
a non-ActiveX example that uses the vl-catch-* functions to intercept
errors. For additional information on these functions, see the AutoLISP Reference.

Using ActiveX to Interact with Other
Applications
The power of ActiveX extends beyond the ability to interact with standard
AutoCAD objects. Visual LISP provides AutoLISP functions that allow you to
access objects from other applications that support ActiveX. For example,
you can open a Microsoft ® Word document, retrieve text data from an
AutoCAD drawing, and copy the text into the Word document. Or you might
access cells in a Microsoft ® Excel spreadsheet and use the data with your
AutoCAD drawing.
To write AutoLISP code that interacts with other ActiveX applications, you’ll
need to refer to the documentation for those applications to learn the application’s object names and how to work with its methods and properties.
Typically, the online help for an ActiveX-enabled Windows application contains information on its ActiveX interface. For exam ple, AutoCAD provides
the ActiveX and VBA Reference, as well as the ActiveX and VBA Developer’s Guide
for working with ActiveX using Visual Basic for Applications™ (VBA).
The following topics in this section apply when you work with any ActiveX
application from AutoLISP. The code examples illustrate the process of
obtaining text from an AutoCAD drawing and then inserting the text into a
Microsoft Word document.

Importing a Type Library
VLISP provides an AutoLISP function that allows you to import the type
library of the ActiveX application you want to access. When you import a
type library, AutoCAD creates a set of wrapper functions that provide access
to the application’s methods and properties. In fact, the vla- functions you
have seen so far are wrapper functions created for the AutoCAD type library.

Using ActiveX to Interact with Other Applications

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Use the vlax-import-type-library function to import a type library. When
calling this function, identify the type library and tell AutoCAD what prefixes to use in naming the wrapper functions for the application’s methods
and properties. Also specify a prefix for the application’s constants. The
vlax-import-type-library function takes the following syntax:
(vlax-import-type-library :tlb-filename filename
[ :methods-prefix mprefix :properties-prefix pprefix :constantsprefix cprefix])

The filename argument is a string that names the type library. If you do not
specify a path, AutoCAD looks for the file in the Support File Search Path.
The mprefix argument specifies the prefix to be used for method wrapper
functions. For example, if the type library contains a Calculate method and
the mprefix parameter is set to "cc-", AutoCAD generates a wrapper function
named cc-Calculate. This parameter defaults to "".
The pprefix argument specifies the prefix to be used for property wrapper
functions, and the cprefix argument defines the prefix to be used for constants contained in the type library. These parameters also default to "".
Note the required use of keywords when passing arguments to
vlax-import-type-library. For example, the following code imports a

Microsoft Word type library, assigning the prefix mswm- to methods, mswpto properties, and mswc- to constants:
(if (equal nil mswc-wd100Words) ; check for a WinWord constant
(vlax-import-type-library
:tlb-filename "c:/Microsoft Office/Office/msword8.olb"
:methods-prefix "mswm-"
:properties-prefix "mswp-"
:constants-prefix "mswc-"
)
)

After importing the type library you can use the VLISP Apropos feature to list
the ActiveX wrapper functions resulting from the import. For example, enter
mswm in the Apropos Options dialog box and select the Match by Prefix
option to list all Microsoft Word ActiveX methods.
Importing an application’s type library enables you to use VLISP features
such as Apropos on the application’s properties and methods, but you can
access the application even if you do not import its type library. See “Using
ActiveX without Importing a Type Library” on page 198.

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Coding Hints for Using vlax-import-type-library
In AutoCAD 2000, vlax-import-type-library is executed at runtime rather
than at compiletime. In future AutoCAD releases, this may change. The following practices are recommended when using vlax-import-type-library:
If you want your code to run on different machines, avoid specifying an
absolute path in the tlb-filename parameter.
s If possible, avoid using vlax-import-type-library from inside any
AutoLISP expression (in other words, always call it from a top-level
position).
s In your AutoLISP source file, code the vlax-import-type-library call
before any code that uses method or property wrappers or constants
defined in the type library.
s

Establishing a Connection to an Application
If an instance of Microsoft Word is already running on your PC, use vlaxget-object to establish a connection to the application. For example, the
following function call establishes a connection to a Microsoft Word 97
application, and saves a pointer to the application in a variable named msw:
(setq msw (vlax-get-object "Word.Application.8"))

The vlax-create-object function creates a new instance of an application
object. For example, if the return value from vlax-get-object is nil,
indicating that the requested application does not exist, you can use
vlax-create-object to start the application. The following call starts
Microsoft Word 97 and saves a pointer to the application in variable msw:
(setq msw (vlax-create-object "Word.Application.8"))

Alternatively, you can use vlax-get-or-create-object to access an application. This function attempts to connect to an existing instance of an
application, and starts a new instance if it doesn’t find one.
The application object does not appear until you make it visible. You make
an object visible by setting its Visible property to TRUE. For example, the following call makes the Microsoft Word application visible:
(vla-put-visible msw :vlax-true)


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Coding a Sample Application
After accessing the application object, the remaining AutoLISP code is
specific to the application you’re working with and the tasks you want to
accomplish. For example, the following function call accesses the documents
collection object in Microsoft Word:
(setq docs (vla-get-documents msw))

The following command creates a new Word document:
(setq doc (mswm-add docs))

The following procedure creates an ActiveX application that works with
Microsoft Word 97 and an AutoCAD drawing that contains mtext.

To copy mtext from an AutoCAD drawing into an Microsoft Word document
1 Issue the following command to ensure that AutoLISP ActiveX support is
loaded:
(vl-load-com)

2 Obtain the AutoCAD application and current ModelSpace objects and save
their pointers:
(setq *AcadApp* (vlax-get-acad-object))
(setq *ModelSpace* (vla-get-ModelSpace
(vla-get-ActiveDocument *AcadApp*)))

; Get AutoCAD application
; Get model space

3 Import the Microsoft Word type library. Change the :tlb-filename argument in the following code to point to the msword8.olb file on your system,
then run the code:
(if (equal nil mswc-wd100Words) ; check for a Word constant
:tlb-filename "c:/Microsoft Office/Office/msword8.olb"
:methods-prefix "mswm-"
:properties-prefix "mswp-"
:constants-prefix "mswc-"
)
)

This code first checks to see if a known Microsoft Word constant is defined
with a value. If the constant has a value, it is assumed that the Word type
library has already been imported and no further action is necessary. If the
constant is nil, vlax-import-type-library is invoked.

4 Establish a connection to a Microsoft Word application by running the following code:
(setq msw (vlax-get-object "Word.Application.8"))
(if (equal nil msw)
(progn

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; Word is not running. Start it.
(setq msw (vlax-create-object "Word.Application.8"))
(vla-put-visible msw :vlax-true)
)
)

The code issues vlax-get-object to establish a connection to a running
Microsoft Word application. (In this example, version 8—Word 97—is
specified; if the 8 were omitted, any instance of Word would be accepted.) If
there is no running instance of Word, vlax-create-object is issued to start
one.

5 The remaining code follows. Comments in the code explain the processing.
(if (/= nil msw)
(progn
;; Get the document collection object.
(setq docs (vla-get-documents msw))
;; Add a new document
(setq doc (mswm-add docs))
;; Get the paragraphs of the document (to do some formatting)
(setq paragraphs (mswp-get-paragraphs doc))
;; Now iterate through the model space and export any mtext
;; every Mtext entity to Word.
(vlax-for ent *ModelSpace*
(if (equal (vla-get-ObjectName ent) "AcDbMText")
(progn
;; Get the following information from the Mtext entity:
;;
o the text string
;;
o the location of a corner of the text boundary
(setq text (vla-get-TextString ent)
textpos (vla-get-InsertionPoint ent)
arrayTextpos (vlax-variant-value textpos)
textinfo
(strcat
(rtos (vlax-safearray-get-element arrayTextpos 0) 2 2)
", "
", "
)
) ;_ end of setq
; Print some info (with formatting)
; Get the last paragraph in the document
(setq pg (mswp-get-last paragraphs))
; Obtain the range of the paragraph
(setq range (mswp-get-range pg))
; Do some formatting
(mswp-put-bold range 1)
;bold
(mswp-put-underline range mswc-wdUnderlineSingle) ;underline
; 4) Insert info about the text at the end of the paragraph
(mswm-InsertAfter range
(strcat "AcDbMText at position " textinfo "n"))


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; Now show the text string (from the ACAD text entity)
(setq pg (mswp-get-last paragraphs))
(setq range (mswp-get-range pg))
(mswp-put-bold range 0)
(mswp-put-underline range mswc-wdUnderlineNone)
(mswm-InsertAfter range (strcat text "nn"))
) ;_ end of progn
) ;_ end of if AcDbMText
) ;_ end of vlax-for
) ;_ end of progn
(princ "nNo Microsoft Word application found.n")
)

Load and run the code and look at the result in Microsoft Word.

Using ActiveX without Importing a Type Library
Importing an application type library and using the resulting ActiveX wrapper functions is convenient and provides access to VLISP features such as
Apropos, but it comes at a cost. Applications such as Microsoft Word and
Microsoft Excel contain hundreds of methods and properties, and creating
wrappers for each of these adds up to significant memory usage. Also, you
may need to use an ActiveX property or method for which there is no generated AutoLISP wrapper function. In this instance, and to avoid the overhead
involved in importing a type library, VLISP provides the following AutoLISP
functions:
s vlax-invoke-method
s vlax-get-property
s vlax-put-property

Calling an ActiveX Method with vlax-invoke-method
The vlax-invoke-method function calls an ActiveX method directly. The
function requires the following arguments:
The VLA-object the method is to work on
A symbol or string naming the method to be called
s One or more arguments to be passed to the method
s
s

The return value from vlax-invoke-method depends on the method being
invoked.
For example, the following invokes the AddCircle method to draw a circle in
the model space (represented by the mspace variable) of the current AutoCAD
drawing:
_$ (setq mycircle
(vlax-invoke-method mspace 'AddCircle circCenter 3.0))
#<VLA-OBJECT IAcadCircle 00bfd6e4>

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In this example, circCenter is a variant (containing a three-element array of
doubles) identifying the center of the circle, and 3.0 is the radius of the circle.
The method returns a VLA-object, the circle drawn.

Obtaining an ActiveX Property with vlax-get-property
The vlax-get-property function returns the property of an object. The function requires the following arguments:
s
s

A VLA-object identifying the object whose property you are interested in
A symbol or string naming the property to be retrieved

For example, there is no wrapper function available to obtain the
CommandBars property of an Microsoft Word application object, but the
following command achieves this:
_$ (setq ComBars (vlax-get-property msw 'CommandBars))
#<VLA-OBJECT CommandBars 0016763c>

You can use vlax-get-property (and vlax-invoke-method and
vlax-put-property) even if a wrapper function is available for the task. For
example, the following returns the AutoCAD’s ActiveDocument property:
_$ (vlax-get-property acadObject 'ActiveDocument)
#<VLA-OBJECT IAcadDocument 00302a18>

In this instance, you could have instead used vla-get-ActiveDocument to
obtain the ActiveDocument property.

Updating an ActiveX Property with vlax-put-property
The vlax-put-property function updates the property of an object. The
function requires the following arguments:
A VLA-object identifying the object whose property you are updating
A symbol or string naming the property to be set
s The value to set the property to
s
s

If vlax-put-property updates the property successfully, it returns nil.
The following function call changes the size of the Microsoft Word toolbar
buttons by updating the LargeButtons property of the CommandBars object:
_$ (vlax-put-property combars 'LargeButtons :vlax-true)
nil


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Advanced Topics

7

In This Chapter

VLISP not only makes program development easier and

s Attaching Reactors to AutoCAD
Drawings

faster, it also provides new functionality to AutoLISP
applications. For example, you can attach reactors to
entities in the AutoCAD drawing window, allowing your
application to respond to user actions on these entities.

201

Attaching Reactors to AutoCAD Drawings
A reactor is an object you attach to AutoCAD drawing objects to have
AutoCAD notify your application when events you are interested in occur.
For example, if a user moves an entity that your application has attached a
reactor to, your application will receive notification that the entity has
moved. If you design it to do so, your application can react to this notification with appropriate actions, such as moving other entities associated with
the one moved, or perhaps updating a text tag that records revision information on the altered drawing feature.
A reactor communicates with your application by calling a function you
have associated with the reactor. Such a function is referred to as a callback
function. There isn’t anything particularly unusual about reactor callback
functions—they are like other functions you write with VLISP. They become
callback functions when you attach them to reactor events.
Before you can use reactor functions with AutoLISP, you must load the supporting code that enables these functions. Issue the following function call
to load reactor support:
vl-load-com

This function first checks whether reactor support is already loaded; if reactor
support is loaded, the function does nothing, otherwise, it loads reactor support and other AutoLISP extended functions.

NOTE All applications that use reactors—including all callback functions—
should begin by calling vl-load-com.

Understanding Reactor Types and Events
There are many types of AutoCAD reactors. Each reactor type responds to one
or more AutoCAD events. The different types of reactors are grouped into the
following categories:

Database
Reactors
Document
Reactors

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Database reactors notify your application when specific
events occur to the drawing database, such as when an
object has been added to the database.
Document reactors notify your application of a change to
the current drawing document, such as opening a new
drawing document, activating a different document
window, and changing a document’s lock status.

Chapter 7

Advanced Topics

Editor Reactors

Editor reactors notify you each time an AutoCAD
command is invoked; a drawing opens, closes, or is saved;
a DXF file is imported or exported; or a system variable
changes value.

Linker Reactors

Linker reactors notify your application every time an ARX
application is loaded or unloaded.

Object
Reactors

Object reactors notify you each time a specific object is
changed, copied, or deleted.

With the exception of Editor reactors, there is one type of reactor for each
reactor category. The following table lists the name by which each reactor
type is identified in AutoLISP code:

General reactor types
Reactor type identifier

Description

:VLR-AcDb-Reactor

Database reactor

:VLR-DocManager-Reactor

Document management reactor

:VLR-Editor-Reactor

General Editor reactor—maintained for backwardcompatibility

:VLR-Linker-Reactor

Linker reactor

:VLR-Object-Reactor

Object reactor

Beginning with AutoCAD 2000, the broad class of Editor reactors is broken
down into more specific reactor types. The :VLR-Editor-Reactor type is
retained for backward-compatibility, but any new Editor reactors introduced
with AutoCAD 2000 cannot be referenced through :VLR-Editor-Reactor. The
following table lists the types of Editor reactors available beginning with
AutoCAD 2000.

Editor reactor types
Reactor type

Description

:VLR-Command-Reactor

Notifies of a command event

:VLR-DeepClone-Reactor

Notifies of a deep clone event

:VLR-DWG-Reactor

Notifies of a drawing event (for example, opening or
closing a drawing file)


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Editor reactor types (continued)
Reactor type

Description

:VLR-DXF-Reactor

Notifies of an event related to reading or writing of a
DXF file

:VLR-Insert-Reactor

Notifies of an event related to block insertion

:VLR-Lisp-Reactor

Notifies of a LISP event

:VLR-Miscellaneous-Reactor

Does not fall under any of the other editor reactor
types

:VLR-Mouse-Reactor

Notifies of a mouse event (for example, a doubleclick)

:VLR-SysVar-Reactor

Notifies of a change to a system variable

:VLR-Toolbar-Reactor

Notifies of a change to the bitmaps in a toolbar

:VLR-Undo-Reactor

Notifies of an undo event

:VLR-Wblock-Reactor

Notifies of an event related to writing a block

:VLR-Window-Reactor

Notifies of an event related to moving or sizing an
AutoCAD window

:VLR-XREF-Reactor

Notifies of an event related to attaching or modifying
XREFs

Use the vlr-types function to return the complete list of reactor types.

Reactor Callback Events
For each reactor type there are a number of events that can cause the reactor
to notify your application. These events are known as callback events,
because they cause the reactor to call a function you associate with the event.
For example, when you issue the Save command to save a drawing, a
:vlr-beginSave event occurs. When you complete the save process, a
:vlr-saveComplete event occurs. In designing a reactor-based application,
it is up to you to determine the events you are interested in, and to write the
callback functions to be triggered when these events occur.
The vlr-reaction-names function returns a list of all available events for a
given reactor type:
(vlr-reaction-names reactor type)

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For example, the following command returns a list of all events related to
Object reactors:
$ (vlr-reaction-names :VLR-Object-Reactor)
(:VLR-cancelled :VLR-copied :VLR-erased :VLR-unerased :VLR-goodbye
:VLR-openedForModify :VLR-modified :VLR-subObjModified :VLRmodifyUndone :VLR-modifiedXData :VLR-unappended :VLR-reappended
:VLR-objectClosed)

NOTE If this or any other vlr-* command fails with a “no function definition”
message, you may have forgotten to call vl-load-com, the function that loads
AutoLISP reactor support functions.
You can print out a list of all available reactor events, sorted by reactor type,
by loading and running the following code in VLISP:
(defun print-reactors-and-events ()
(foreach rtype (vlr-types)
(princ (strcat "n" (vl-princ-to-string rtype)))
(foreach rname (vlr-reaction-names rtype)
(princ (strcat "nt" (vl-princ-to-string rname)))))
(princ))

The AutoLISP Reference lists each event available for a reactor type. For each
reactor type, you can find this information by looking up the description of
the function you use to define a reactor of that type. These functions have
the same name as the reactor type, minus the leading colon. For example,
vlr-acdb-reactor creates a database reactor, vlr-toolbar-reactor creates a
toolbar reactor, and so on.

Defining Callback Functions
To add reactor functionality to your application, you first need to write a callback function that performs the tasks needed at the time of the reactor event.
After you define a callback function, you link the function to an event by creating a reactor object.
A callback function is a regular AutoLISP function, which you define using
defun. However, there are some restrictions on what you can do in a callback
function. You cannot call AutoCAD commands using the command function.
Also, to access drawing objects, you must use ActiveX functions; entget and
entmod are not allowed inside callback functions. See “Reactor Use Guidelines” on page 216 for more information.


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205

Callback functions for all reactors, other than Object reactors, must be
defined to accept two arguments:
s
s

The first argument identifies the Reactor object that called the function.
The second argument is a list of parameters set by AutoCAD.

The following example shows a function named saveDrawingInfo, which
displays file path and size information. This function will be attached to a
DWG Editor reactor that will fire when an AutoCAD drawing is saved.
(defun saveDrawingInfo (calling-reactor commandInfo / dwgname
filesize)
(vl-load-com)
(setq dwgname (cadr commandInfo)
filesize (vl-file-size dwgname)
)
(alert (strcat "The file size of " dwgname " is "
(itoa filesize) " bytes."
)
)
(princ)
)

In this example, the calling-reactor variable identifies the reactor that
invoked the function. The function retrieves the drawing name from the
commandInfo parameter, then uses the vl-file-size function to retrieve the
size of the drawing. Finally, the function displays the information in an alert
box in the AutoCAD window.
The parameters passed to a callback function depend on the type of event
associated with the function. For example, saveDrawingInfo will be
associated with a saveComplete event. This event indicates that a Save
command has been completed. For saveComplete events, AutoCAD passes
the callback function a string containing the name of the file the drawing
was saved in. On the other hand, a callback function that reacts to changes
to system variables (sysVarChanged event) receives a parameter list containing
the name of a system variable (a string) and a flag indicating if the change
was successful. You can find a list of events for each reactor type, and the
parameters associated with each event, in the AutoLISP Reference. The events
are listed under the description of the functions used to define each type of
reactor.
AutoCAD comes with two predefined callback functions. You can use these
functions when testing your reactors:
is a simple function that beeps your PC.
prints a list of arguments to the VLISP Trace window
each time a reactor fires this callback function.

s vlr-beep-reaction

s vlr-trace-reaction

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Defining Object Reactor Callback Functions
Unlike other AutoCAD reactors, object reactors are attached to specific
AutoCAD entities (objects). When you define an object reactor, you must
identify the entity the reactor is to be attached to. So callback functions for
object reactors must be defined to accept three arguments:
The first argument identifies the object that fired the notification.
The second argument identifies the Reactor object that called the
function.
s The third argument is a list of parameters specific to the callback
condition.
s
s

For example, the following code defines a callback function named
print-radius. This function can be used to print the radius of a circle:
(defun print-radius (notifier-object reactor-object parameter-list)
(vl-load-com)
(cond
(
(vlax-property-available-p
notifier-object
"Radius"
)
(princ "The radius is ")
(princ (vla-get-radius notifier-object))
)
)
)

Note that the code uses the vlax-property-available-p function to verify
that the drawing object that notified this function contains a radius property.

Creating Reactors
You link a callback function to an event when you create a reactor. There is
an AutoLISP function for creating each type of reactor. These functions have
the same name as the reactor type, minus the leading colon. For example,
vlr-acdb-reactor creates a database reactor, vlr-toolbar-reactor creates a
toolbar reactor, and so on. Except for object reactors, the reactor creation
functions require the following arguments:
s
s

AutoLISP data to be associated with the Reactor object
A list of pairs naming the event and the callback function to be associated
with that event (event-name . callback_function)


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For example, the following command defines a DWG Editor reactor. The
reactor will invoke the saveDrawingInfo function in response to a user issuing a Save command:
(vlr-dwg-Reactor nil '((:vlr-saveComplete . saveDrawingInfo)))

In this example, the first argument is nil because there is no applicationspecific data to attach to this reactor. The second argument is a list consisting
of dotted pair lists. Each dotted pair list identifies an event the reactor is to
be notified about, and the callback function to be run in response to that
event. In this case the reactor is notified of only one event,
:vlr-saveComplete.
Editor reactors are notified each time the user issues a command, whether
through the AutoCAD Command line, a menu, a toolbar, or an AutoLISP program. So, the callback function for this DWG reactor needs to determine
precisely what it is responding to. In the current example, save-drawingInfo
simply checks for the Save command.
Possible events for each reactor type are listed in the AutoLISP Reference. To
find the list of events for a reactor, refer to the entry in the AutoLISP Reference
that describes the function used to create the reactor. For example, to find the
list of possible events for a DWG reactor, refer to the entry for
vlr-DWG-reactor.
All reactor construction functions return a Reactor object.

Using Object Reactors
Unlike other AutoCAD reactors, object reactors are attached to specific
AutoCAD entities (objects). When you define an object reactor, you must
identify the entity the reactor is to be attached to. The vlr-object-reactor
function, which creates object reactors, requires the following arguments:
A list of VLA-objects identifying the drawing objects that are to fire notifications to the reactor. These objects are referred to as the reactor owners.
s AutoLISP data to be associated with the Reactor object.
s A list of pairs naming the event and the callback function to be associated
with that event (event-name . callback_function).
s

WARNING! You cannot modify an object in a callback function if it is
included in the object reactor’s owner list. Attempts to do so will generate an
error message and can crash AutoCAD.

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For example, the following statement defines an object reactor with a single
owner (the object identified by myCircle), then attaches the string “Circle
Reactor” to the reactor and tells AutoCAD to invoke the print-radius
function when a user modifies myCircle:
(setq circleReactor (vlr-object-reactor (list myCircle)
"Circle Reactor" '((:vlr-modified . print-radius))))

The Reactor object is stored in variable circleReactor; you can refer to the
reactor using this variable, as described in “Querying, Modifying, and
Removing Reactors” on page 211.
When defining a list of owners, you must specify VLA-objects only; Ename
objects are not allowed. VLA-objects are required because callback functions
can only use ActiveX methods to modify AutoCAD objects, and ActiveX
methods require a VLA-object to work on.
Note that, although you cannot use objects obtained through functions such
as entlast and entget with callback reactors, you can convert these Ename
objects into VLA-objects using the vlax-ename->vla-object function. See
the AutoLISP Reference for more information on vlax-ename->vla-object.

To see how an object reactor works
1 Load the following code to define a circle object; you will be prompted to
draw the circle:
(setq myCircle
; Prompt for the center point and radius:
(progn (setq ctrPt
(getpoint "nCircle center point: ")
radius (distance ctrPt
(getpoint ctrpt "nRadius: ")
)
)
; Add a circle to the drawing model space. Nest the function
; calls to obtain the path to the current drawing's model
; space: AcadObject > ActiveDocument > ModelSpace
(vla-addCircle
(vla-get-ModelSpace
(vla-get-ActiveDocument (vlax-get-acad-object))
)
(vlax-3d-point ctrPt)
radius
)
)
)

This code uses vla-addCircle to draw a circle, assigning the return value to
variable myCircle. The return value is a VLA-object, which contains a pointer
to the Circle object drawn.


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2 Load the print-radius callback function shown in “Defining Object Reactor
Callback Functions” on page 207.

3 Define the reactor with the following command:
(setq circleReactor (vlr-object-reactor (list myCircle)

4 In the AutoCAD drawing window, select the circle and change its size. The
print-radius function will display a message in the AutoCAD Command
window. For example, if you use the STRETCH command to enlarge the circle,

the message looks like the following:
Specify stretch point or [Base point/Copy/Undo/eXit]: The radius is
3.75803

Attaching Data to Reactor Objects
The object reactor creation example in “Using Object Reactors” included a
string, “Circle Reactor,” in the call to vlr-object-reactor. You do not have
to specify any data to be included with the reactor; you can specify nil
instead. However, an object may have several reactors attached to it. Include
an identifying text string, or other data your application can use, to allow
you to distinguish among the different reactors attached to an object.

Working with Reactors in Multiple Namespaces
The current implementation of AutoLISP supports working in one drawing
document at a time. Some AutoCAD APIs, such as ObjectARX and VBA, do
support the ability of an application to work simultaneously in multiple documents. As a result, an application may modify an open drawing that is not
currently active. This is not supported in AutoLISP. (Note that a VLX may run
in a separate-namespace from the document it is loaded from, but it is still
associated with that document and cannot manipulate objects in another
document.)
AutoLISP does provide limited support for reactor callback functions executing in a document that is not active. By default, a reactor callback function
will execute only if a notification event occurs when the document it was
defined in is the active document. You can alter this behavior using the
vlr-set-notification function.
To specify that a reactor should execute its callback function even if the document it was defined in is not active (for example, if an application in
another namespace triggers an event), issue the following function call:
(vlr-set-notification reactor-object 'all-documents)

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To modify a reactor so it only executes its callback function if an event occurs
when the document it was defined in is active, issue the following:
(vlr-set-notification reactor-object 'active-document-only)

The vlr-set-notification function returns the specified reactor object. For
example, the following sequence of commands defines a reactor and sets it
to respond to events whether or not its associated document is active:
_$ (setq circleReactor (vlr-object-reactor (list myCircle)
#<VLR-Object-Reactor>
_$ (vlr-set-notification circleReactor 'all-documents)

To determine the notification setting of a reactor, use the vlr-notification
function. For example:
_$ (vlr-notification circleReactor)
all-documents

The vlr-set-notification function affects only the specified reactor. All
reactors are created with the default notification set to
"active-document-only."

WARNING! If you choose to set a reactor to execute its callback function
even if triggered when its document is not active, the callback function should
do nothing other than set and read AutoLISP variables. Any other action may
cause system instability.

Querying, Modifying, and Removing Reactors
There are various ways to obtain information about reactors. VLISP supplies
AutoLISP functions to query reactors, and you can use standard VLISP data
inspection tools to view information on them.
To use AutoLISP to list all reactors in a drawing, call the vlr-reactors
function. The function returns a list of reactor lists. Each reactor list begins
with a symbol identifying the reactor type, followed by pointers to each
reactor of that type. For example:
_$ (vlr-reactors)
((:VLR-Object-Reactor #<VLR-Object-Reactor>) (:VLR-Editor-Reactor
#<VLR-Editor-Reactor>))

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To list all reactors of a given type, supply vlr-reactors with an argument
identifying the reactor type. Specify one of the values returned by the
vlr-types function; these are listed in “Understanding Reactor Types and
Events” on page 202. For example, the following lists all DWG reactors:
_$ (vlr-reactors :vlr-dwg-reactor)
((:VLR-DWG-Reactor #<VLR-DWG-Reactor> #<VLR-DWG-Reactor>))

In this case, the return value is a list containing one list. The one list identifies pointers to two DWG reactors.

Inspecting Reactors
You can examine reactors using the VLISP Inspect tool. For example, the
object reactor defined in “Using Object Reactors” on page 208 was returned
to the variable circleReactor. If you open an Inspect window for this variable, VLISP displays the following information:

The list items in the Inspect window show the following:
s
s
s
s
s

s

Objects owning the reactor
Event and associated callback function
Whether or not the reactor is active (yes if added-p is T, no if added-p is
nil)
User data attached to the reactor
Document range in which the reactor will fire (if 0, it fires only in the context of the drawing document it was created in; if 1, the reactor responds
in the context of any document (see “Working with Reactors in Multiple
Namespaces” on page 210 for more information on this topic)
The AutoCAD document attached to the object reactor

Double-click on the item that begins with {Owners} to view a list of the
owner objects:

Double-click on a list item to obtain detailed information about an owner.

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Querying Reactors Using Function Calls
VLISP also provides functions to inspect a reactor definition from within an
application program, or at the Console prompt:
s vlr-type

returns the type of the specified reactor. For example:

$ (vlr-type circleReactor)
:VLR-Object-Reactor

returns the name of the event that caused
the callback function to be called.
s vlr-data returns the application-specific data value attached to the reactor, as shown in the following example:
s vlr-current-reaction-name

$ (vlr-data circleReactor)
"Circle Reactor"

You can use this data to distinguish among multiple reactors that can fire
the same callback function.
returns a list of the objects in an AutoCAD drawing that fire
notifications to an object reactor. The following function call lists the
objects that fire notifications to circleReactor:

s vlr-owners

_$ (vlr-owners circleReactor)
(#<VLA-OBJECT IAcadCircle 03ad077c>)

returns the callback list of condition-function pairs of the
specified reactor. The following example returns information about
circleReactor:

s vlr-reactions

$ (vlr-reactions circleReactor)
((:vlr-modified . PRINT-RADIUS))

Modifying Reactors
VLISP provides functions to modify reactor definitions:
changes the callback function link for the specified
reactor event. The function syntax is:

s vlr-reaction-set

(vlr-reaction-set reactor callback-condition 'callback-function)

For example, the following command changes the circleReactor reactor
to call the print-area function when an object is modified:
$ (vlr-reaction-set circleReactor :vlr-modified 'print-area)
PRINT-AREA

changes the application-specific data associated with the
reactor. For example, the following call replaces the text string used to
identify the circleReactor reactor:

s vlr-data-set

$ (vlr-data-set circleReactor "Circle Area Reactor")
"Circle Area Reactor"

You can verify that the reactor has changed by using the VLISP Inspect feature. If the Inspect window shown in “Inspecting Reactors” on page 212


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is still displayed in your VLISP session, right-click in the window’s object
line and choose Update. If you’ve modified the circleReactor reactor as
shown in this section, the updated Inspect window will look like the following:

adds a database object to the list of owners of the specified
reactor. In the following example, an ARC object named archie is added
to the owner list of reactor circleReactor:

s vlr-owner-add

$ (vlr-owner-add circleReactor archie)
#<VLA-OBJECT IAcadArc 03ad0bcc>

Now, if a user modifies the archie object, the callback function defined
for reactor circleReactor is invoked. You can verify this by inspecting the
reactor. Update the Inspect window for the circleReactor reactor, then
right-click on the list item that begins with {Owners} and choose Inspect:

Both the Arc and Circle objects are listed in the Inspect window.
removes an Owner object from the list of reactor
owners. For example, the following command removes archie from the
circleReactor owner list:

s vlr-owner-remove

$ (vlr-owner-remove circleReactor archie)
#<VLA-OBJECT IAcadArc 03ad0bcc>

Removing Reactors
Use the vlr-remove function to disable a reactor. Disabling the reactor does
not delete it: the Reactor object still exists and you can activate it again using
the vlr-add function. To determine whether or not a reactor is active (registered to AutoCAD), use the vlr-added-p function:
_$ (vlr-added-p circleReactor)
T

The vlr-added-p function returns T if the reactor is active, nil if it is not.
The following command disables reactor circleReactor:
_$ (vlr-remove circleReactor)
#<VLR-Object-reactor>

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You can use vlr-added-p to verify the circleReactor object reactor has been
disabled:
$ (vlr-added-p circleReactor)
nil

To enable the circleReactor reactor, use vlr-add:
$ (vlr-add circleReactor)
#<VLR-Object-reactor>

You can use the vlr-remove-all function to disable all reactors in your
drawing. To disable all reactors of a particular type, specify the reactor type
when calling vlr-remove-all. The following function call disables all object
reactors:
$ (vlr-remove-all :vlr-object-reactor)
(#<VLR-Object-reactor>)

Transient versus Persistent Reactors
Reactors may be transient or persistent. Transient reactors are lost when a
drawing closes; this is the default reactor mode. Persistent reactors are saved
with the drawing and exist when the drawing is next opened.
Use the vlr-pers function to make a reactor persistent. To remove persistence from a reactor and make it transient, use vlr-pers-release. Each
function takes a Reactor object as its only argument. For example, the following command makes a reactor persistent:
_$ (vlr-pers circleReactor)

If successful, vlr-pers returns the specified Reactor object.
To determine whether a Reactor object is persistent or transient, issue
vlr-pers-p. For example:
_$ (vlr-pers-p circleReactor)

The vlr-pers-p function returns the Reactor object if it is persistent, nil if it
is not.

Opening a Drawing Containing Persistent Reactors
A reactor is only a link between an event and a callback function. While this
link remains, the callback function itself is not part of the reactor, and is normally not part of the drawing. The reactors saved in the drawing are only
usable if their associated callback functions are loaded in AutoCAD. You can
cause this to occur automatically when a drawing is opened if you define the
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If you open a drawing containing VLISP reactor information and the associated callback functions are not loaded, AutoCAD displays an error message.
You can use the vlr-pers-list function to return a list of all Persistent reactors in a drawing document.

Reactor Use Guidelines
When using reactors, try to adhere to the following guidelines. Reactors that
violate these guidelines can result in unpredictable results for your application if the internal implementation of reactors changes.
s

Do not rely on the sequence of reactor notifications.
It is recommended that, with a few exceptions, you do not rely on the
sequence of reactor notifications. For example, an OPEN command
triggers BeginCommand, BeginOpen, EndOpen, and EndCommand
events. However, they may not occur in that order. The only event
sequence you can safely rely on is that a Begin event will occur before the
corresponding End event. For example, commandWillStart() always
occurs before commandEnded(), and beginInsert() always occurs before
endInsert(). Relying on more complex sequences may result in problems
for your application if the sequence is changed as a result of new
notifications being introduced in the future and existing ones being
rearranged.

s

Do not rely on the sequence of function calls between notifications.
It is not guaranteed that certain functions will be called between certain
notifications. For example, when you receive :vlr-erased notification on
object A, all it means is that object A is erased. If you receive :vlr-erased
notification on A followed by a :vlr-erased notification on B, all it
means is that both objects A and B are erased; it does not ensure that B was
erased after A. If you tie your application to this level of detail, there is a
very high probability of your application breaking in future releases.
Instead of relying on sequences, rely on reactors to indicate the state of the
system.

s

Do not use any interactive functions in your reactor callback function (for
example, do not use getPoint, entsel).
Attempting to execute interactive functions from within a reactor callback
function can cause serious problem s, as AutoCAD may still be processing
a command at the time the event is triggered. Therefore, avoid the use of
input-acquisition methods such as getPoint, entsel, and getkword, as
well as selection set operations and the command function.

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s

Do not launch a dialog box from within an event handler.
Dialog boxes are considered interactive functions and can interfere with
the current operation of AutoCAD. However, message boxes and alert
boxes are not considered interactive and can be issued safely.

s

Do not update the object that issued the event notification.
The event causing an object to trigger a callback function may still be in
progress and the object still in use by AutoCAD when the callback function is invoked. Therefore, do not attem pt to update an object from a
callback function for the same object. You can, however, safely read information from the object triggering an event. For example, suppose you
have a floor filled with tiles and you attach a reactor to the border of the
floor. If you change the size of the floor, the reactor callback function will
automatically add or subtract tiles to fill the new area. The function will
be able to read the new area of the border, but it cannot attempt any
changes on the border itself.

s

Do not perform any action from a callback function that will trigger the
same event.
If you perform an action in your reactor callback function that triggers the
same event, you will create an infinite loop. For example, if you attempt
to open a drawing from within a BeginOpen event, AutoCAD will simply
continue to open more drawings until the maximum number of open
drawings is reached.

Verify that a reactor is not already set before setting it, or you may end up
with multiple callbacks on the same event.
s Remember that no events will be fired while AutoCAD is displaying a
modal dialog.
s


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Part 2
Using the AutoLISP
Language

219

AutoLISP Basics

8

In This Chapter

This chapter introduces the basic concepts of the
AutoLISP programming language. It describes the core

s AutoLISP Expressions
s AutoLISP Data Types
s AutoLISP Program Files

components and data types used in AutoLISP, and pre-

s AutoLISP Variables

sents examples of simple number-, string-, output-, and

s Number Handling
s String Handling

list-handling functions.
AutoLISP code does not need to be compiled, so you can

s Basic Output Functions
s Equality and Conditional
s List Handling

enter the code at a Command line and immediately see

s Symbol and Function Handling

the results. Some examples in this chapter are intended

s Error Handling

to be entered at the Visual LISP (VLISP) Console window
prompt (_$ ), while others are entered at the AutoCAD
Command prompt (Command:).

221

AutoLISP Expressions
An AutoLISP program consists of a series of expressions. AutoLISP expressions have the following form:
(function arguments)

Each expression begins with an open (left) parenthesis and consists of a function name and optional arguments to that function. Each argument can also
be an expression. The expression ends with a right parenthesis. Every expression returns a value that can be used by a surrounding expression. The value
of the last interpreted expression is returned to the calling expression.
For example, the following code example involves three functions:
(fun1 (fun2 arguments)(fun3 arguments))

If you enter this code at the Visual LISP Console prompt or the AutoCAD
Command prompt, the AutoCAD AutoLISP interpreter processes the code.
The first function, fun1, has two arguments, and the other functions, fun2
and fun3, each have one argument. The functions fun2 and fun3 are surrounded by function fun1, so their return values are passed to fun1 as
arguments. Function fun1 evaluates the two arguments and returns the value
to the window from which you entered the code.
The following example shows the use of the * (multiplication) function,
which accepts one or more numbers as arguments:

_$ (* 2 27)
54
Because this code example has no surrounding expression, AutoLISP returns
the result to the window from which you entered the code.
Expressions nested within other expressions return their result to the surrounding expression. The following example uses the result from the
+ (addition) function as one of the arguments for the * (multiplication)
function.

_$ (* 2 (+ 5 10))
30
If you enter the incorrect number of close (right) parentheses, AutoLISP displays the following prompt:

(_>

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The number of open parentheses in this prompt indicates how many levels
of open parentheses remain unclosed. If this prompt appears, you must enter
the required number of close parentheses for the expression to be evaluated.

_$ (* 2 (+ 5 10
((_> ) )
30
A common mistake is to omit the closing quotation mark (") in a text string,
in which case the close parentheses are interpreted as part of the string and
have no effect in resolving the open parentheses. To correct this condition,
press SHIFT + ESC to cancel the function, then re-enter it correctly.

AutoLISP Function Syntax
In this guide, the following conventions describe the syntax for AutoLISP
functions:
function name
required argument(s)
optional argument(s) in brackets

(foo string [number ...])
close parenthesis
possible additional arguments
denoted by ellipsis (...)

open parenthesis

In this example, the foo function has one required argument, string, and
one optional argument, number. Additional number arguments can be provided. Frequently, the name of the argument indicates the expected data
type. The examples in the following table show both valid and invalid calls
to the foo function.

Valid and invalid function call examples
Valid calls

Invalid calls

(foo "catch")

(foo 44 13)

(foo "catch" 22)

(foo "fi" "foe" 44 13)

(foo "catch" 22 31)

(foo)

AutoLISP Expressions

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AutoLISP Data Types
AutoLISP expressions are processed according to the order and data type of
the code within the parentheses. Before you can fully utilize AutoLISP, you
must understand the differences among the data types and how to use them .

Integers
Integers are whole numbers that do not contain a decimal point. AutoLISP
integers are 32-bit signed numbers with values ranging from +2,147,483,647
to –2,147,483,648. (Note, however, that the getint function only accepts
16-bit numbers ranging from +32767 to -32678.) When you explicitly use an
integer in an AutoLISP expression, that value is known as a constant. Numbers such as 2, –56, and 1,200,196 are valid AutoLISP integers.
If you enter a number that is greater than the maximum integer allowed
(resulting in integer overflow), AutoLISP converts the integer to a real number. However, if you perform an arithmetic operation on two valid integers,
and the result is greater than the maximum allowable integer, the resulting
number will be invalid. The following examples illustrate how AutoLISP handles integer overflow.
The largest positive integer value retains its specified value:
_$ 2147483647
2147483647

If you enter an integer that is greater than the largest allowable value,
AutoLISP returns the value as a real:
_$ 2147483648
2.14748e+009

An arithmetic operation involving two valid integers, but resulting in integer
overflow, produces an invalid result:
_$ (+ 2147483646 3)
-2147483647

In this example the result is clearly invalid, as the addition of two positive
numbers results in a negative number. But note how the following operation
produces a valid result:
_$ (+ 2147483648 2)
2.14748e+009

In this instance, AutoLISP converts 2147483648 to a valid real before adding
2 to the number. The result is a valid real.

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The largest negative integer value retains its specified value:
_$ -2147483647
-2147483647

If you enter a negative integer larger than the greatest allowable negative
value, AutoLISP returns the value as a real:
_$ -2147483648
-2.14748e+009

The following operation concludes successfully, because AutoLISP first converts the overflow negative integer to a valid real:
_$ (- -2147483648 1)
-2.14748e+009

Reals
A real is a number containing a decimal point. Numbers between –1 and 1
must contain a leading zero. Real numbers are stored in double-precision
floating-point format, providing at least 14 significant digits of precision.
Note that VLISP does not show you all the significant digits.
Reals can be expressed in scientific notation, which has an optional e or E followed by the exponent of the number (for example, 0.0000041 is the same
as 4.1e-6). Numbers such as 3.1, 0.23, –56.123, and 21,000,000.0 are valid
AutoLISP reals.

Strings
A string is a group of characters surrounded by quotation marks. Within
quoted strings the backslash () character allows control characters (or escape
codes) to be included. When you explicitly use a quoted string in an
AutoLISP expression, that value is known as a literal string or a string
constant.
Examples of valid strings are “string 1” and “nEnter first point:”.

Lists
An AutoLISP list is a group of related values separated by spaces and enclosed
in parentheses. Lists provide an efficient method of storing numerous related
values. AutoCAD expresses 3D points as a list of three real numbers.
Examples of lists are (1.0 1.0 0.0), (“this” “that” “the other”), and (1 “ONE”).

AutoLISP Data Types

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Selection Sets
Selection sets are groups of one or more objects (entities). You can interactively add objects to, or remove objects from, selection sets with AutoLISP
routines.
The following example uses the ssget function to return a selection set containing all the objects in a drawing.

_$ (ssget "X")
<Selection set: 1>

Entity Names
An entity name is a numeric label assigned to objects in a drawing. It is actually a pointer into a file maintained by AutoCAD, and can be used to find the
object’s database record and its vectors (if they are displayed). This label can
be referenced by AutoLISP functions to allow selection of objects for processing in various ways. Internally, AutoCAD refers to objects as entities.
The following example uses the entlast function to get the name of the last
object entered into the drawing.

_$ (entlast)
Entity names assigned to objects in a drawing are only in effect during the
current editing session. The next time you open the drawing, AutoCAD
assigns new entity names to the objects. You can use an object’s handle to
refer to it from one editing session to another; see “Entity Handles and Their
Uses” on page 307 for information on using handles.

VLA-objects
Objects in a drawing may be represented as Visual LISP ActiveX (VLA)
objects, a data type introduced with Visual LISP. When working with ActiveX
functions, you must refer to VLA-objects, not the ename pointer returned by
functions such as entlast. For information on working with ActiveX objects,
see “Using ActiveX Objects with AutoLISP” on page 162.

File Descriptors
A file descriptor is a pointer to a file opened by the AutoLISP open function.
The open function returns this pointer as an alphanumeric label. You supply

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the file descriptor as an argument to other AutoLISP functions that read or
write to the file.
The following example opens the myinfo.dat file for reading. The open function returns the file descriptor:

_$ (setq file1 (open "c:myinfo.dat" "r") )
#<file "c:myinfo.dat">
In this example, the file descriptor is stored in the file1 variable.
Files remain open until you explicitly close them in your AutoLISP program.
The close function closes a file. The following code closes the file whose file
descriptor is stored in the file1 variable:

_$ (close file1)
nil

Symbols and Variables
AutoLISP uses symbols to refer to data. Symbol names are not case-sensitive
and may consist of any sequence of alphanumeric and notation characters
except the following:

Characters restricted from symbol names
(

(Open Parenthesis)

)

(Close Parenthesis)

.

(Period)

’

(Apostrophe)

"

(Quote Symbol)

;

(Semicolon)

A symbol name cannot consist of only numeric characters.
Technically, AutoLISP applications consist of either symbols or constant values, such as strings, reals, and integers. For the sake of clarity, this guide uses
the term symbol to refer to a symbol name that stores static data, such as
built-in and user-defined functions. The term variable is used to refer to a
symbol name that stores program data. The following example uses the setq

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function to assign the string value "this is a string" to the str1 variable:

_$ (setq str1 "this is a string")
"this is a string"
Be kind to yourself and to others who need to read your code. Choose meaningful names for your program symbols and variables.

Protected Symbols
You may be warned if you attempt to change the value of some symbols used
by the AutoLISP language. These symbols are known as protected symbols,
and include items such as arithmetic operators (for example, +, -) and the
values T and nil. You can use the Visual LISP Symbol Service feature to determine if a symbol is protected.
When you first start AutoCAD, protected symbols receive no special protection. If you set a protected symbol at the AutoCAD Command prompt, you
receive no indication that the symbol has any special status. However, once
you start Visual LISP, this changes. From the moment you start Visual LISP
until the end of your AutoCAD session, AutoLISP intercepts any attempt to
modify a protected symbol. Processing of protected symbols depends on the
status of a Visual LISP environment option. You can specify one of the following options:
s
s

Transparent Protected symbols are treated like any other symbol.
Print message AutoLISP issues a warning message when you modify a
protected symbol but carries out the modification. For example, the following demonstrates what happens when you modify the symbol T:
Command: (setq t "look out")
; *U* WARNING: assignment to protected symbol: T <- "look out"
"look out"

s

Prompt to enter break loop This is the default option, resulting in
AutoLISP displaying the following message box when you attempt to
modify a protected symbol:

If you choose No, the symbol’s value is modified, and processing continues normally. If you choose Yes, processing is interrupted, and you enter
a Visual LISP break loop. Control switches to the Visual LISP Console
window. To set the symbol and continue processing, press the Continue

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button on the Visual LISP toolbar; to abort modification, press Reset.
s

Error This option prohibits modification of protected symbols. Any
attempt to modify a protected symbol results in an error message.

To specify how AutoLISP responds to attempts to modify protected symbols,
choose Tools ® Environment Options ® General Options from the Visual
LISP menu.

AutoLISP Program Files
Although you can enter AutoLISP code in the Visual LISP Console window or
at the AutoCAD Command prompt, testing and debugging a series of instructions are considerably easier when you save AutoLISP code in a file rather
than re-entering it each time you make a refinement. AutoLISP source code
is usually stored in ASCII text files with an .lsp extension. However, you can
load AutoLISP code from any ASCII text file.
To create a new source file in VLISP, choose New File from the VLISP File
menu.
To edit existing AutoLISP source code in VLISP, choose Open File from the
VLISP File menu, and use the Open File dialog box to select your file. VLISP
loads this file into its text editor and displays the contents in a new editor
window.

Formatting AutoLISP Code
The extensive use of parentheses in AutoLISP code can make it difficult to
read. The traditional technique for combatting this confusion is indentation.
The more deeply nested a line of code is, the farther to the right you position
the line.
If you use the VLISP text editor to enter your code, VLISP automatically formats the code as you enter it. VLISP also has features to reformat a selection
or an entire file. This improves the appearance of your code, making it more
readable. For information on using these features, see “Formatting Code with
Visual LISP” on page 50.

Spaces in AutoLISP Code
In AutoLISP, multiple spaces between variable names, constants, and function names are equivalent to a single space. The end of a line is also treated
as a single space.

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The following two expressions produce the same result:
(setq test1 123 test2 456)
(setq
test1 123
test2 456
)

Comments
It is good practice to include comments in AutoLISP program files. Comments are useful to both the programmer and future users who may need to
revise a program to suit their needs. Use comments to do the following:
Give a title, authorship, and creation date
Provide instructions on using a routine
s Make explanatory notes throughout the body of a routine
s Make notes to yourself during debugging
s
s

Comments begin with one or more semicolons (;) and continue through the
end of the line.
; This entire line is a comment
(setq area (* pi r r)) ; Compute area of circle

Any text within ;| ... |; is ignored. Therefore, comments can be included
within a line of code or extend for multiple lines. This type of comment is
known as an in-line comment.
(setq tmode ;|some note here|; (getvar "tilemode"))

The following example shows a comment that continues for multiple lines:
(setvar "orthomode" 1) ;|comment starts here
and continues to this line,
but ends way down here|; (princ "nORTHOMODE set On.")

It is recommended that you use comments liberally when writing AutoLISP
programs. The tutorial files provided with VLISP contain good examples of
commenting style. If you’ve installed the AutoCAD samples files, you’ll find
the VLISP tutorial code in the TutorialVisualLISP directory.

Visual LISP Comment Styles
The VLISP code formatter recognizes five types of comments and positions
each comment according to its type. Refer to “Applying Visual LISP Comment Styles” on page 58 for a description of each com ment style.
Regardless of your commenting style, it is more important that comments be
present rather than they obey any particular layout rules.

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Color Coding
VLISP provides an additional solution to make AutoLISP text easier to read:
color coding. VLISP looks at each word of text and tries to determine what
type of AutoLISP language element the word represents (for example, a builtin function, a number, or a string). Every type of element is assigned its own
color, so you can easily distinguish among them when viewing the code. See
“Understanding Visual LISP Color Coding” on page 42 for more information
on the VLISP color coding feature.
Keep in mind that color coding is a VLISP text editor feature, and it is possible
that someone who does not have access to VLISP may need to read your code
some day. For this reason, you should still use indentation and alignment to
enhance your program’s readability.

AutoLISP Variables
An AutoLISP variable assumes the data type of the value assigned to it. Until
they are assigned new values, variables retain their original values. You use
the AutoLISP setq function to assign values to variables.
(setq variable_name1 value1 [variable_name2 value2 ...])

The setq function assigns the specified value to the variable name given. It
returns the value as its function result. If you issue setq at the Visual LISP
Console prompt, the result is displayed in the Console window:

_$ (setq val 3 abc 3.875)
3.875
_$ (setq layr "EXTERIOR-WALLS")
"EXTERIOR-WALLS"
_$

Displaying the Value of a Variable
To display the current value of a variable when working in Visual LISP, just
enter the variable name at the Console prompt as follows:

_$ abc
3.875

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To display the value of a variable from the AutoCAD Command prompt, you
must precede the variable name with an exclamation point (!). For example:

Command: !abc
3.875

Nil Variables
An AutoLISP variable that has not been assigned a value is said to be nil.
This is different from blank, which is considered a character string, and different from 0, which is a number. So, in addition to checking a variable for
its current value, you can test to determine if the variable has been assigned
a value.
Each variable consumes a small amount of memory, so it is good programming practice to reuse variable names or set variables to nil when their
values are no longer needed. Setting a variable to nil releases the memory
used to store that variable’s value. If you no longer need the val variable, you
can release its value from memory with the following expression:

_$ (setq val nil)
nil
Another efficient programming practice is to use local variables whenever
possible. See “Local Variables in Functions” on page 251 on this topic.

Predefined Variables
The following predefined variables are commonly used in AutoLISP applications:
PAUSE

Defined as a string consisting of a double backslash ()
character. This variable is used with the command function
to pause for user input.

PI

T

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Defined as the constant π (pi). It evaluates to
approximately 3.14159.
Defined as the constant T. This is used as a non-nil value.

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NOTE You can change the value of these variables with the setq function.
However, other applications might rely on their values being consistent; therefore, it is recommended that you do not modify these variables. Visual LISP, by
default, protects these variables from redefinition. You can override this protection through the VLISP Symbol Service feature or by setting a VLISP environment
option.

Number Handling
AutoLISP provides functions for working with integers and real numbers. In
addition to performing complex mathematical computations in applications, you can use the number-handling functions to help you in your daily
use of AutoCAD. If you are drawing a steel connection detail that uses a 2.5"
bolt that is 0.5" in diameter, how many threads are there if the bolt has 13
threads per inch? Use the * (multiplication) function at the Console prompt,
as in the following example:

_$ (* 2.5 13)
32.5
The arithmetic functions that have a number argument (as opposed to num or
angle, for example) return different values if you provide integers or reals as
arguments. If all arguments are integers, the value returned is an integer.
However, if one or all the arguments are reals, the value returned is a real. To
ensure your application passes real values, be certain at least one argument is
a real.

_$ (/ 12 5)
2
_$ (/ 12.0 5)
2.4
A complete list of number-handling functions is in appendix A, “AutoLISP
Function Synopsis,” under the heading “Arithmetic Functions.” These functions are described in the AutoLISP Reference.

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String Handling
AutoLISP provides functions for working with string values. For example, the
strcase function returns the conversion of all alphabetic characters in a
string to uppercase or lowercase. It accepts two arguments: a string and an
optional argument that specifies the case in which the characters are
returned. If the optional second argument is omitted, it evaluates to nil and
strcase returns the characters converted to uppercase.

_$ (strcase "This is a TEST.")
"THIS IS A TEST."
If you provide a second argument of T, the characters are returned as lowercase. AutoLISP provides the predefined variable T to use in similar situations
where a non-nil value is used as a type of true/false toggle.

_$ (strcase "This is a TEST." T)
"this is a test."
The strcat function combines multiple strings into a single string value.
This is useful for placing a variable string within a constant string. The following code sets a variable to a string value and then uses strcat to insert
that string into the middle of another string.

_$ (setq str "BIG") (setq bigstr (strcat "This is a " str " test."))
"This is a BIG test."
If the variable bigstr is set to the preceding string value, you can use the
strlen function to find out the number of characters (including spaces) in
that string.

_$ (strlen bigstr)
19
The substr function returns a substring of a string. It has two required arguments and one optional argument. The first required argument is the string.
The second argument is a positive integer that specifies the first character of
the string you want to include in the substring. If the third argument is provided, it specifies the number of characters to include in the substring. If the
third argument is not provided, substr returns all characters including and
following the specified start character.
As an example, you can use the substr function to strip off the three-letter
extension from a file name (note that you can actually use the

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vl-filename-base function to do this). First, set a variable to a file name.

_$ (setq filnam "bigfile.txt")
"bigfile.txt"
You need to get a string that contains all characters except the last four (the
period and the three-letter extension). Use strlen to get the length of the
string and subtract 4 from that value. Then use substr to specify the first
character of the substring and its length.

_$ (setq newlen (- (strlen filnam) 4))
7
_$ (substr filnam 1 newlen)
"bigfile"
If your application has no need for the value of newlen, you can combine
these two lines of code into one.

_$ (substr filnam 1 (- (strlen filnam) 4))
"bigfile"
Additional string-handling functions are listed in appendix A, “AutoLISP
Function Synopsis,” under the heading “String-Handling Functions.” These
functions are described in the AutoLISP Reference.
AutoLISP also provides a number of functions that convert string values into
numeric values and numeric values into string values. These functions are
discussed in “Conversions” on page 279.

Basic Output Functions
AutoLISP includes functions for controlling the AutoCAD display, including
both text and graphics windows. Some functions also display information in
the Visual LISP Console window. The major text display functions are:
s
s
s
s

prin1
princ
print
prompt

These functions are discussed in the following sections. The remaining display functions are covered in chapter 9, “Using AutoLISP to Communicate
with AutoCAD”, beginning with the “Display Control” topic.


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Displaying Messages
When entered from VLISP, the prompt function displays a message (a string)
in the AutoCAD Command window and returns nil to the VLISP Console
window. The princ, prin1, and print functions all display an expression
(not necessarily a string) in the AutoCAD Command window and return the
expression to the VLISP Console window. Optionally, these functions can
send output to a file. The differences are as follows:
princ displays strings without the enclosing quotation marks.
prin1 displays strings enclosed in quotation marks.
s print displays strings enclosed in quotation marks but places a blank line
before the expression and a space afterward.
s
s

The following examples demonstrate the differences between the four basic
output functions and how they handle the same string of text. If you enter
the examples from VLISP, the text following prints is what you see at the
AutoCAD Command prompt; text following returns appears within the VLISP
Console window or within an application. See the following section for an
explanation of the control characters used in the example.
(setq str "The "allowable" tolerance is 261 274"")
(prompt str)

prints
and returns

The "allowable" tolerance is
nil

(princ str)

prints
and returns

The "allowable" tolerance is
1/4"
"The "allowable" tolerance is

1/4""

prints
and returns

1/4""

1/4""

(prin1 str)
(print str)

prints
and returns

1/4"

<blank line>
1/4"" <space>
1/4""

Note that the write-char and write-line functions can also display output
to a Command window. Refer to the AutoLISP Reference for information on
these functions.

Exiting Quietly
If you invoke the princ function without passing an expression to it, it
displays nothing and has no value to return. So if you write an AutoLISP
expression that ends with a call to princ without any arguments, the ending
nil is suppressed (because it has nothing to return). This practice is called
exiting quietly.

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Control Characters in Strings
Within quoted strings, the backslash () character allows control characters
(or escape codes) to be included. The following table shows the currently recognized control characters:

AutoLISP control characters
Code

Description

character

"

" character

e

Escape character

n

Newline character

r

Return character

t

Tab character

nnn

Character whose octal code is nnn

The prompt and princ functions expand the control characters in a string
and display the expanded string in the AutoCAD Command window.
If you need to use the backslash character () or quotation mark (") within a
quoted string, it must be preceded by the backslash character ( ). For example, if you enter

_$ (princ "The "filename" is: D:ACADTEST.TXT. ")
the following displays in the AutoCAD Command window:

The "filename" is: D:ACADTEST.TXT
You will also see this output in the VLISP Console window, along with the
return value from the princ function (which is your original input, with the
unexpanded control characters).
To force a line break at a specific location in a string, use the newline
character (n).

_$ (prompt "An example of the nnewline character. ")
An example of the
newline character.


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You can also use the terpri function to cause a line break.
The return character (r) returns to the beginning of the current line. This is
useful for displaying incremental information (for example, a counter showing the number of objects processed during a loop).
The Tab character (t) can be used in strings to indent or to provide alignment with other tabbed text strings. In this example, note the use of the
princ function to suppress the ending nil.

_$ (prompt "nNametOfficen– – – – –t– – – – –
(_> nSuet101nJoet102nSamt103n") (princ)

Name

Office

–––––

–––––

Sue

101

Joe

102

Sam

103

Wild-Card Matching
The wcmatch function enables applications to compare a string to a wild-card
pattern. You can use this facility when you build a selection set (in conjunction with ssget) and when you retrieve extended entity data by application
name (in conjunction with entget).
The wcmatch function compares a single string to a pattern. The function
returns T if the string matches the pattern, and nil if it does not. The wildcard patterns are similar to the regular expressions used by many system and
application programs. In the pattern, alphabetic characters and numerals are
treated literally; brackets can be used to specify optional characters or a range
of letters or digits; a question mark (?) matches a single character; an asterisk
(*) matches a sequence of characters; and, certain other special characters
have special meanings within the pattern. When you use the * character at
the beginning and end of the search pattern, you can locate the desired portion anywhere in the string. For more information, see “wcmatch” in the
AutoLISP Reference.

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In the following examples, a string variable called matchme has been declared
and initialized:

_$ (setq matchme "this is a string - test1 test2 the end")
"this is a string - test1 test2 the end"
The following code checks whether or not matchme begins with the four characters "this":

_$ (wcmatch matchme "this*")
T
The following code illustrates the use of brackets in the pattern. In this case,
wcmatch returns T if matchme contains "test4", "test5", "test6" (4-6), or
"test9" (note the use of the * character):

_$ (wcmatch matchme "*test[4-69]*")
nil
In this case, wcmatch returns nil because matchme does not contain any of the
strings indicated by the pattern.
However,

_$ (wcmatch matchme "*test[4-61]*")
T
because the string contains "test1".
The pattern string can specify multiple patterns, separated by commas. The
following code returns T if matchme equals "ABC", or if it begins with "XYZ",
or if it ends with "end".

_$ (wcmatch matchme "ABC,XYZ*,*end")
T


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Equality and Conditional
AutoLISP includes functions that provide equality verification as well as conditional branching and looping. The equality and conditional functions are
listed in appendix A, “AutoLISP Function Synopsis,”under the heading
“Equality and Conditional Functions.” These functions are described in the
AutoLISP Reference.
When writing code that checks string and symbol table names, keep in mind
that AutoLISP automatically converts symbol table names to upper case in
some instances. When testing symbol names for equality, you need to make
the comparison insensitive to the case of the names. Use the strcase function to convert strings to the same case before testing them for equality.

List Handling
AutoLISP provides functions for working with lists. This section provides
examples of the append, assoc, car, cons, list, nth, and subst functions. A
summary of all list-handling functions is in appendix A, “AutoLISP Function
Synopsis,” under the heading “List Manipulation Functions.” Each listhandling function is described in the AutoLISP Reference.
Lists provide an efficient and powerful method of storing numerous related
values. After all, LISP is so-named because it is the LISt Processing language.
Once you understand the power of lists, you’ll find that you can create more
powerful and flexible applications.
Several AutoLISP functions provide a basis for programming twodimensional and three-dimensional graphics applications. These functions
return point values in the form of a list.
The list function provides a simple method of grouping related items. These
items do not need to be of similar data types. The following code groups
three related items as a list:

_$ (setq lst1 (list 1.0 "One" 1))
(1.0 "One" 1)
You can retrieve a specific item from the list in the lst1 variable with the nth
function. This function accepts two arguments. The first argument is an integer that specifies which item to return. A 0 specifies the first item in a list,

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1 specifies the second item, and so on. The second argument is the list itself.
The following code returns the second item in lst1.

_$ (nth 1 lst1)
“One”
The cdr function returns all elements, except the first, from a list. For example:

_$ (cdr lst1)
("One" 1)
The car function provides another way to extract items from a list. For more
examples using car and cdr, and combinations of the two, see “Point Lists”
on page 242.
Three functions let you modify an existing list. The append function returns
a list with new items added to the end of it, and the cons function returns a
list with new items added to the beginning of the list. The subst function
returns a list with a new item substituted for every occurrence of an old item.
These functions do not modify the original list, they return a modified list.
To modify the original list, you must explicitly replace the old list with the
new list.
The append function takes any number of lists and runs them together as one
list. Therefore, all arguments to this function must be lists. The following
code adds another "One" to the list lst1. Note the use of the quote (or ')
function as an easy way to make the string "One" into a list.

_$ (setq lst2 (append lst1 '("One")))
(1.0 "One" 1 "One")
The cons function combines a single element with a list. You can add another
string "One" to the beginning of this new list, lst2, with the cons function.

_$ (setq lst3 (cons "One" lst2 ))
("One" 1.0 "One" 1 "One")
You can substitute all occurrences of an item in a list with a new item with
the subst function. The following code replaces all strings "One" with the
string "one".

_$ (setq lst4 (subst "one" "One" lst3))
("one" 1.0 "one" 1 "one")

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Point Lists
AutoLISP observes the following conventions for handling graphics coordinates. Points are expressed as lists of two or three numbers surrounded by
parentheses.

2D points

Expressed as lists of two real numbers (X and Y,
respectively), as in
(3.4 7.52)

3D points

Expressed as lists of three real numbers (X, Y, and Z,
respectively), as in
(3.4 7.52 1.0)

You can use the list function to form point lists, as shown in the following
examples:

_$ (list 3.875 1.23)
(3.875 1.23)
_$ (list 88.0 14.77 3.14)
(88.0 14.77 3.14)
To assign particular coordinates to a point variable, you can use one of the
following expressions:

_$ (setq pt1 (list 3.875 1.23))
(3.875 1.23)
_$ (setq pt2 (list 88.0 14.77 3.14))
(88.0 14.77 3.14)
_$ (setq abc 3.45)
3.45
_$ (setq pt3 (list abc 1.23))
(3.45 1.23)
The latter uses the value of variable abc as the X component of the point.
If all members of a list are constant values, you can use the quote function to
explicitly define the list, rather than the list function. The quote function
returns an expression without evaluation, as follows:

_$ (setq pt1 (quote (4.5 7.5)))
(4.5 7.5)

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The single quotation mark (') can be used as shorthand for the quote function. The following code produces the same result as the preceding code.

_$ (setq pt1 '(4.5 7.5))
(4.5 7.5)
You can refer to X, Y, and Z components of a point individually, using three
additional built-in functions called car, cadr, and caddr. The following
examples show how to extract the X, Y, and Z coordinates from a 3D point
list. The pt variable is set to the point ( 1.5 3.2 2.0):

_$ (setq pt '(1.5 3.2 2.0))
(1.5 3.2 2.0)
The car function returns the first member of a list. In this example it returns
the X value of point pt to the x_val variable.

_$ (setq x_val (car pt))
1.5
The cadr function returns the second member of a list. In this example it
returns the Y value of the pt point to the y_val variable.

_$ (setq y_val (cadr pt))
3.2
The caddr function returns the third member of a list. In this example it
returns the Z value of point pt to the variable z_val.

_$ (setq z_val (caddr pt))
2.0
You can use the following code to define the lower-left and upper-right (pt1
and pt2) corners of a rectangle, as follows:

_$ (setq pt1 '(1.0 2.0) pt2 ' (3.0 4.0))
(3.0 4.0)
You can use the car and cadr functions to set the pt3 variable to the upperleft corner of the rectangle, by extracting the X component of pt1 and the Y
component of pt2, as follows:

_$ (setq pt3 (list (car pt1) (cadr pt2)))
(1.0 4.0)
The preceding expression sets pt3 equal to point (1.0,4.0).

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AutoLISP supports concatenations of car and cdr up to four levels deep. The
following are valid functions:
caaaar

cadaar

cdaaar

cddaar

caaadr

cadadr

cdaadr

cddadr

caaar

cadar

cdaar

cddar

caadar

caddar

cdadar

cdddar

caaddr

cadddr

cdaddr

cddddr

caadr

caddr

cdadr

cdddr

caar

cadr

cdar

cddr

These concatenations are the equivalent of nested calls to car and cdr. Each
a represents a call to car, and each d represents a call to cdr. For example:
(caar x)
(cdar x)
(cadar x)
(cadr x)
(cddr x)
(caddr x)

is equivalent to
is equivalent to
is equivalent to
is equivalent to
is equivalent to
is equivalent to

(car
(cdr
(car
(car
(cdr
(car

(car
(car
(cdr
(cdr
(cdr
(cdr

x))
x))
(car x)))
x))
x))
(cdr x)))

Dotted Pairs
Another way AutoCAD uses lists to organize data is with a special type of list
called a dotted pair. This list must always contain two members. When representing a dotted pair, AutoLISP separates the members of the list with a
period (.). Most list-handling functions will not accept a dotted pair as an
argument, so you should be sure you are passing the right kind of list to a
function.
Dotted pairs are an example of an "improper list." An improper list is one in
which the last cdr is not nil. In addition to adding an item to the beginning
of a list, the cons function can create a dotted pair. If the second argument
to the cons function is anything other than another list or nil, it creates a
dotted pair.

_$ (setq sublist (cons 'lyr "WALLS"))
(LYR . "WALLS")
The car, cdr, and assoc functions are useful for handling dotted pairs. The
following code creates an association list, which is a list of lists, and is the
method AutoCAD uses to maintain entity definition data. (Entity definition

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data is discussed in chapter 10, “Using AutoLISP to Manipulate AutoCAD
Objects.”) The following code creates an association list of dotted pairs:

_$ (setq wallinfo (list sublist(cons 'len 240.0) (cons 'hgt 96.0)))
( (LYR . “WALLS”) (LEN . 240.0) (HGT . 96.0) )
The assoc function returns a specified list from within an association list
regardless of the specified list’s location within the association list. The assoc
function searches for a specified key element in the lists, as follows:

_$ (assoc 'len wallinfo)
(LEN . 240.0)
_$ (cdr (assoc 'lyr wallinfo))
"WALLS"
_$ (nth 1 wallinfo)
(LEN . 240.0)
_$ (car (nth 1 wallinfo))
LEN

Symbol and Function Handling
AutoLISP provides a number of functions for handling symbols and variables. The symbol-handling functions are listed in appendix A, “AutoLISP
Function Synopsis,” under the heading “Symbol-Handling Functions.” Each
symbol-handling function is described in the AutoLISP Reference.
AutoLISP provides functions for handling one or more groups of functions.
This section provides examples of the defun function. The remaining function-handling functions are listed in appendix A, “AutoLISP Function
Synopsis,”under the heading “Function-Handling Functions.” The functions
are described in the AutoLISP Reference.

Using defun to Define a Function
With AutoLISP you can define your own functions. Once defined, you can
use these functions at the AutoCAD Command prompt, the Visual LISP
Console prompt, or within other AutoLISP expressions, just as you use the
standard functions. You can also create your own AutoCAD commands,
because commands are just a special type of function.
The defun function (see “defun” in the AutoLISP Reference) combines a group
of expressions into a function or command. This function requires at least
three arguments, the first of which is the name of the function (symbol
name) to define. The second argument is the argument list (a list of argu-


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ments and local variables used by the function). The argument list can be nil
or an empty list (). Argument lists are discussed in greater detail in “Functions with Arguments” on page 252. If local variables are provided, they are
separated from the arguments by a slash ( / ). Local variables are discussed in
“Local Variables in Functions” on page 251. Following these arguments are
the expressions that make up the function; there must be at least one expression in a function definition.
(defun symbol_name ( args / local_variables )
expressions
)

The following code defines a simple function that accepts no arguments and
displays “bye” in the AutoCAD Command window. Note that the argument
list is defined as an empty list ( () ):

_$ (defun DONE ( ) (prompt "nbye! "))
DONE
Now that the DONE function is defined, you can use it as you would any other
function. For example, the following code prints a message, then says “bye”
in the AutoCAD Command window:

_$ (prompt “The value is 127.”) (DONE) (princ)
The value is 127
bye!
Note how the previous example invokes the princ function without any
arguments. This suppresses an ending nil and achieves a quiet exit.
Functions that accept no arguments may seem useless. However, you might
use this type of function to query the state of certain system variables or conditions and to return a value that indicates those values.
AutoCAD can autom atically load your functions each time you start a new
AutoCAD session or open a new AutoCAD drawing file; see “Automatic Loading and Execution of AutoLISP Routines” in the AutoCAD Customization
Guide for further information on automatic loading.
Any code in an AutoLISP program file that is not part of a defun statement
is executed when that file is loaded. You can use this to set up certain
parameters or to perform any other initialization procedures in addition to
displaying textual information, such as how to invoke the loaded function.

Compatibility of defun with Previous Versions of AutoCAD
The internal implementation of defun changed in AutoCAD 2000. This
change will be transparent to the great majority of AutoLISP users upgrading
from earlier versions of AutoCAD. The change only affects AutoLISP code

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that manipulated defun definitions as a list structure, such as by appending
one function to another, as in the following code:
(append s::startup (cdr mystartup))

For situations like this, you can use defun-q to define your functions. An
attempt to use a defun function as a list results in an error. The following
example illustrates the error:
_$ (defun foo (x) 4)
foo
_$ (append foo '(3 4))
; error: Invalid attempt to access a compiled function definition.
You may want to define it using defun-q: #<SUBR @024bda3c FOO>

The error message alerts you to the possibility of using defun-q instead of
defun.
The defun-q function is provided strictly for backward compatibility with
previous versions of AutoLISP and should not be used for other purposes. For
more information on using defun-q, and the related defun-q-list-set and
defun-q-list-ref functions, see the AutoLISP Reference.

C:XXX Functions
If an AutoLISP function is defined with a name of the form C:XXX, it can be
issued at the AutoCAD Command prompt in the same manner as a built-in
AutoCAD command. This is true regardless of whether you define and load
the function in VLISP or at the AutoCAD Command prompt. You can use this
feature to add new commands to AutoCAD or to redefine existing
commands.
To use functions as AutoCAD commands, be sure they adhere to the
following rules:
The function name must use the form C:XXX (upper- or lowercase characters). The C: portion of the name must always be present; the XXX portion
is a command name of your choice. C:XXX functions can be used to
override built-in AutoCAD commands. (See “Redefining AutoCAD Commands” on page 249.)
s The function must be defined with no arguments. However, local variables are permitted and it is a good programming practice to use them.
s

A function defined in this manner can be issued transparently from within
any prompt of any built-in AutoCAD command, provided the function
issued transparently does not call the command function. (This is the AutoLISP
function you use to issue AutoCAD commands; see the entry on “command”
in the AutoLISP Reference.) When issuing a C:XXX defined command transpar-


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ently, you must precede the XXX portion with a single quotation mark (').
You can issue a built-in command transparently while a C:XXX command is
active by preceding it with a single quotation mark ('), as you would with all
commands that are issued transparently. However, you cannot issue a C:XXX
command transparently while a C:XXX command is active.

NOTE When calling a function defined as a command from the code of
another AutoLISP function, you must use the whole name, including the parentheses; for example, (C:HELLO). You also must use the whole name and the
parentheses when you invoke the function from the VLISP Console prompt.

Adding Commands
Using the C:XXX feature, you can define a command that displays a simple
message.

_$ (defun C:HELLO () (princ "Hello world. n") (princ))
C:HELLO
HELLO is now defined as a command, in addition to being an AutoLISP func-

tion. This means you can issue the command from the AutoCAD Command
prompt.

Command: hello
Hello world.
This new command can be issued transparently because it does not call the
command function itself. At the AutoCAD Command prompt, you could do
the following:

Command: line
From point: 'hello
Hello world.
From point:
Remember: to run this function from the VLISP Console window, you need
to issue the function call with the parentheses because VLISP does not recognize AutoCAD commands.

_$ (c:hello)
Hello world.

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If you follow your function definition with a call to the setfunhelp function,
you can associate a Help file and topic with a user-defined command. When
help is requested during execution of the user-defined command, the topic
specified by setfunhelp displays. See the AutoLISP Reference for more information on using setfunhelp.
You cannot usually use an AutoLISP statement to respond to prompts from
an AutoLISP-implemented command. However, if your AutoLISP routine
makes use of the initget function, you can use arbitrary keyboard input
with certain functions. This allows an AutoLISP-implemented command
to accept an AutoLISP statement as a response. Also, the values returned by
a DIESEL expression can perform some evaluation of the current drawing
and return these values to AutoLISP. See “Keyword Options” on page 272 for
more information on using initget, and refer to the AutoCAD Customization
Guide for information on the DIESEL string expression language.

Redefining AutoCAD Commands
Using AutoLISP, external comm ands, and the alias feature, you can define
your own AutoCAD commands. You can use the UNDEFINE command to
redefine a built-in AutoCAD command with a user-defined command of the
same name. To restore the built-in definition of a command, use the REDEFINE command. The UNDEFINE command is in effect for the current editing
session only.
You can always activate an undefined command by specifying its true name,
which is the command name prefixed by a period. For example, if you undefine QUIT, you can still access the command by entering .quit at the
AutoCAD Command prompt. This is also the syntax that should be used
within the AutoLISP command function.
Consider the following example. Whenever you use the LINE command, you
want AutoCAD to remind you about using the PLINE command. You can
define the AutoLISP function C:LINE to substitute for the normal LINE
command as follows:

_$ (defun C:LINE ( )
(_> (princ "Shouldn’t you be using PLINE?n")
(_> (command ".LINE") (princ) )
C:LINE
In this example, the function C:LINE is designed to issue its message and
then to execute the normal LINE command (using its true name, . LINE).
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must undefine the built-in LINE command. Enter the following to undefine
the built-in LINE command:

_$ (command "undefine" "line")
Now, if you enter line at the AutoCAD Command prompt, AutoCAD uses the
C:LINE AutoLISP function:

Command: line
Shouldn’t you be using PLINE?
.LINE Specify first point: Specify first point:
The previous code example assumes the CMDECHO system variable is set to 1
(On). If CMDECHO is set to 0 (Off), AutoCAD does not echo prompts during
a command function call. The following code uses the CMDECHO system variable to prevent the LINE command prompt from repeating:

_$ (defun C:LINE ( / cmdsave )
(_> (setq cmdsave (getvar "cmdecho"))
(_> (setvar "cmdecho" 0)
(_> (princ "Shouldn’t you be using PLINE?n")
(_> (command ".LINE")
(_> (setvar "cmdecho" cmdsave)
(_> (princ) )
C:LINE
Now if you enter line at the AutoCAD Command prompt, the following
displays:

Shouldn’t you be using PLINE?
Specify first point:
You can use this feature in a drawing management system, for example. You
can redefine the NEW, OPEN, and QUIT commands to write billing information to a log file before you terminate the editing session.
It is recommended that you protect your menus, scripts, and AutoLISP programs by using the period-prefixed forms of all commands. This ensures that
your applications use the built-in command definitions rather than a redefined command.
See the “Command Search Procedure” topic in the AutoCAD Customization
Guide for a description of the steps AutoCAD takes to evaluate command
names.

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Local Variables in Functions
AutoLISP provides a method for defining a list of symbols (variables) that are
available only to your function. These are known as local variables.

Local Variables versus Global Variables
The use of local variables ensures that the variables in your functions are
unaffected by the surrounding application and that your variables do not
remain available after the calling function has completed its task.
Many user-defined functions are used as utility functions within larger applications. User-defined functions also typically contain a number of variables
whose values and use are specific to that function.
The danger in using global variables, instead of local variables, is you may
inadvertently modify them outside of the function they were declared in and
intended for. This can lead to unpredictable behavior, and it can be very difficult to identify the source of this type of problem.
Another advantage of using local variables is that AutoCAD can recycle the
memory space used by these variables, whereas global variables keep accumulating within AutoCAD memory space.
There are some legitimate uses for global variables, but these should be kept
to a minimum. It is also a good practice to indicate that you intend a variable
to be global. A common way of doing this is to add an opening and closing
asterisk to the variable name, for example, *default-layer*.

Example Using Local Variables
The following example shows the use of local variables in a user-defined
function (be certain there is at least one space between the slash and the local
variables).

_$ (defun LOCAL ( / aaa bbb)
(_> (setq aaa "A" bbb "B")
(_> (princ (strcat "naaa has the value " aaa ))
(_> (princ (strcat "nbbb has the value " bbb))
(_> (princ) )
LOCAL
Before you test the new function, assign variables aaa and bbb to values other
than those used in the LOCAL function.

_$ (setq aaa 1 bbb 2)
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You can verify that the variables aaa and bbb are actually set to those values.

_$ aaa
1
_$ bbb
2
Now test the LOCAL function.

_$ (local)
aaa has the value A
bbb has the value B
You will notice the function used the values for aaa and bbb that are local to
the function. You can verify that the current values for aaa and bbb are still
set to their nonlocal values.

_$ aaa
1
_$ bbb
2
In addition to ensuring that variables are local to a particular function, this
technique also ensures the memory used for those variables is available for
other functions.

Functions with Arguments
With AutoLISP you can define functions that accept arguments. Unlike many
of the standard AutoLISP functions, user-defined functions cannot have
optional arguments. When you call a user-defined function that accepts
arguments, you must provide values for all the arguments.
The symbols to use as arguments are defined in the argument list before the
local variables. Arguments are treated as a special type of local variable; argument variables are not available outside the function. You cannot define a
function with multiple arguments of the same name.
The following code defines a function that accepts two string arguments,
combines them with another string, and returns the resulting string.

_$ (defun ARGTEST ( arg1 arg2 / ccc )
(_> (setq ccc "Constant string")
(_> (strcat ccc ", " arg1 ", " arg2) )
ARGTEST

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The ARGTEST function returns the desired value because AutoLISP always
returns the results of the last expression it evaluates. The last line in ARGTEST
uses strcat to concatenate the strings, and the resulting value is returned.
This is one example where you should not use the princ function to suppress
the return value from your program.
This type of function can be used a number of times within an application
to combine two variable strings with one constant string in a specific order.
Because it returns a value, you can save the value to a variable for use later in
the application.

_$ (setq newstr (ARGTEST "String 1" "String 2") )
"Constant string, String 1, String 2"
The newstr variable is now set to the value of the three strings combined.
Note that the ccc variable was defined locally within the ARGTEST function.
Once the function runs to completion, AutoCAD recycles the variable,
recapturing the memory allocated to it. To prove this, check from the VLISP
Console window to see if there is still a value assigned to ccc.

_$ ccc
nil

Special Forms
Certain AutoLISP functions are considered special forms because they evaluate arguments in a different manner than most AutoLISP function calls. A
typical function evaluates all arguments passed to it before acting on those
arguments. Special forms either do not evaluate all their arguments, or only
evaluate some arguments under certain conditions.
The following AutoLISP functions are considered special forms:
s
s
s
s
s
s
s
s
s
s
s
s

AND
COMMAND
COND
DEFUN
DEFUN-Q
FOREACH
FUNCTION
IF
LAMBDA
OR
PROGN
QUOTE


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s
s
s
s
s
s

REPEAT
SETQ
TRACE
UNTRACE
VLAX-FOR
WHILE

You can read about each of these functions in the AutoLISP Reference.

Error Handling
The AutoLISP language provides several functions for error handling. You
can use these functions to do the following:
Provide information to users when an error occurs during the execution
of a program.
s Restore the AutoCAD environment to a known state.
s Intercept errors and continue program execution.
s

The complete list of error-handling functions is in appendix A, “AutoLISP
Function Synopsis,” under the heading “Error-Handling Functions.” Each
error-handling function is described in the AutoLISP Reference.
If your program contains more than one error in the same expression, you
cannot depend on the order in which AutoLISP detects the errors. For example, the inters function requires several arguments, each of which must be
either a 2D or 3D point list. A call to inters like the following:
(inters 'a)

is an error on two counts: too few arguments and invalid argument type. You
will receive either of the following error messages:
; *** ERROR: too few arguments
; *** ERROR: bad argument type: 2D/3D point

Your program should be designed to handle either error.
Note also that in AutoCAD 2000, AutoLISP evaluates all arguments before
checking the argument types. In previous releases of AutoCAD, AutoLISP
evaluated and checked the type of each argument sequentially. To see the
difference, look at the following code examples:

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(defun foo ()
(print "Evaluating foo")
'(1 2))
(defun bar ()
(print "Evaluating bar")
'b)
(defun baz ()
(print "Evaluating baz")
'c)

Observe how an expression using the inters function is evaluated in
AutoCAD 2000:
Command: (inters (foo) (bar) (baz))
"Evaluating foo"
"Evaluating bar"
"Evaluating baz"
; *** ERROR: too few arguments

Each argument was evaluated successfully before AutoLISP passed the results
to inters and discovered that too few arguments were specified.
In AutoCAD R14, the same expression evaluated as follows:
Command: (inters (foo) (bar) (baz))
"Evaluating foo"
"Evaluating bar" error: bad argument type

AutoLISP evaluated (foo), then passed the result to inters. Since the result
was a valid 2D point list, AutoLISP proceeds to evaluate (bar), where it determines that the evaluated result is a string, an invalid argument type for
inters.

Using the *error* Function
Proper use of the *error* function can ensure that AutoCAD returns to a particular state after an error occurs. Through this user-definable function you
can assess the error condition and return an appropriate message to the user.
If AutoCAD encounters an error during evaluation, it prints a message in the
following form:

Error: text
In this message, text describes the error. However, if the *error* function is
defined (that is, if it is not nil), AutoLISP executes *error* instead of printing the message. The *error* function receives text as its single argument.

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If *error* is not defined or is nil, AutoLISP evaluation stops and displays a
traceback of the calling function and its callers. It is beneficial to leave this
error handler in effect while you debug your program.
A code for the last error is saved in the AutoCAD system variable ERRNO,
where you can retrieve it by using the getvar function. See appendix C,
“AutoLISP Error Codes,” for a list of error codes and their meaning.
Before defining your own *error* function, save the current contents of
*error* so that the previous error handler can be restored upon exit. When
an error condition exists, AutoCAD calls the currently defined *error* function and passes it one argument, which is a text string describing the nature
of the error. Your *error* function should be designed to exit quietly after
an ESC (cancel) or an exit function call. The standard way to accomplish this
is to include the following statements in your error-handling routine.
(if
(or
(= msg "Function cancelled")
(= msg "quit / exit abort")
)
(princ)
(princ (strcat "nError: " msg))
)

This code examines the error message passed to it and ensures that the user
is informed of the nature of the error. If the user cancels the routine while it
is running, nothing is returned from this code. Likewise, if an error condition
is programmed into your code and the exit function is called, nothing is
returned. It is presumed you have already explained the nature of the error
by using print statements. Remember to include a terminating call to princ
if you don’t want a return value printed at the end of an error routine.
The main caveat about error-handling routines is they are normal AutoLISP
functions that can be canceled by the user. Keep them as short and as fast as
possible. This will increase the likelihood that an entire routine will execute
if called.
You can also warn the user about error conditions by displaying an alert box,
which is a small dialog box containing a message supplied by your program.
To display an alert box, call the alert function.
The following call to alert displays an alert box:
(alert "File not found")

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Catching Errors and Continuing Program
Execution
Your program can intercept and attempt to process errors instead of allowing
control to pass to *error*. The vl-catch-all-apply function is designed to
invoke any function, return a value from the function, and trap any error
that may occur. The function requires two arguments: a symbol identifying
a function or lambda expression, and a list of arguments to be passed to the
called function. The following example uses vl-catch-all-apply to divide
two numbers:
_$ (setq catchit (vl-catch-all-apply '/ '(50 5)))
10

The result from this example is the same as if you had used apply to perform
the division.
The value of vl-catch-all-apply is in catching errors and allowing your
program to continue execution.

To catch errors with vl-catch-all-apply
1 The following code defines a function named catch-me-if-you-can. Copy
the code into a VLISP text editor window:
(defun catch-me-if-you-can (dividend divisor / errobj)
(setq errobj (vl-catch-all-apply '/ (list dividend divisor)))
(if (vl-catch-all-error-p errobj)
(progn
(print (strcat "An error occurred: "
(vl-catch-all-error-message errobj)
)
)
(prompt "Do you want to continue? (Y/N) -> ")
(setq ans (getstring))
(if (equal (strcase ans) "Y")
(print "Okay, I'll keep going")
)
)
(print errobj)
)
(princ)
)

This function accepts two number arguments and uses vl-catch-all-apply
to divide the first number by the second number. The vl-catch-all-error-p
function determines whether the return value from vl-catch-all-apply is

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an error object. If the return value is an error object, catch-me-if-you-can
invokes vl-catch-all-error-message to obtain the message from the error
object.

2 Load the function.
3 Invoke the function with the following command:
(catch-me-if-you-can 50 2)

The function should return 25.

4 Intentionally cause an error condition by invoking the function with the following command:
(catch-me-if-you-can 50 0)

The function should issue the following prompt in the AutoCAD Command
window:
"An error occurred: divide by zero" Do you want to continue? (Y/N) ->

If you enter y, catch-me-if-you-can indicates that it will continue
processing.
Try modifying this example by changing vl-catch-all-apply to apply.
Load and run the example with a divide by zero again. When apply results
in an error, execution immediately halts and *error* is called, resulting in
an error message.
The vl-catch-* functions are especially important when you use ActiveX
with AutoLISP. Many of the AutoCAD ActiveX automation methods are
designed to be used in the “programming by exception” style. This means
they either return useful values if they succeed, or raise an exception if they
fail (instead of returning an error value). If your program uses ActiveX methods, you must prepare it to catch exceptions, otherwise the program halts,
leaving the user at a Command prompt. See “Handling Errors Returned by
ActiveX Methods” on page 191 for an example using vl-catch-all-apply
with ActiveX.

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Using AutoLISP to
Communicate with
AutoCAD

9

In This Chapter

AutoLISP provides various functions for examining the
contents of the currently loaded drawing. This chapter

s Query and Command Functions
s Display Control
s Getting User Input

introduces these functions and describes how to use

s Geometric Utilities

them in conjunction with other functions.

s Conversions
s File Handling
s Device Access and Control

259

Query and Command Functions
The query and command functions described in this section provide direct
access to AutoCAD commands and drawing services. Their behavior depends
on the current state of the AutoCAD system and environment variables, and
on the drawing that is currently loaded. See “Query and Command Functions” in appendix A, “AutoLISP Function Synopsis,” for a complete list of
query and command functions.

NOTE The AutoLISP examples in this chapter show code entered at the
AutoCAD Command prompt, not the Visual LISP Console window.

Command Submission
The command function sends an AutoCAD command directly to the AutoCAD
Command prompt. The command function has a variable-length argument
list. These arguments must correspond to the types and values expected by
that command’s prompt sequence; these may be strings, real values, integers,
points, entity names, or selection set names. Data such as angles, distances,
and points can be passed either as strings or as the values themselves (as
integer or real values, or as point lists). An empty string ("") is equivalent to
pressing the SPACEBAR or ENTER on the keyboard.
There are some restrictions on the commands that you can use with the
command function. See the AutoLISP Reference definition of this function for
information on these restrictions.
The following code fragment shows representative calls to command.
(command "circle" "0,0" "3,3")
(command "thickness" 1)
(setq p1 '(1.0 1.0 3.0))
(setq rad 4.5)
(command "circle" p1 rad)

If AutoCAD is at the Command prompt when these functions are called,
AutoCAD performs the following actions:

1 The first call to command passes points to the CIRCLE command as strings
(draws a circle centered at 0.0,0.0 and passes through 3.0,3.0).

2 The second call passes an integer to the THICKNESS command (changes the
current thickness to 1.0).

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3 The last call uses a 3D point and a real (floating-point) value, both of which
are stored as variables and passed by reference to the CIRCLE command. This
draws an extruded circle centered at (1.0,1.0,3.0) with a radius of 4.5.

Foreign Language Support
If you develop AutoLISP programs that can be used with a foreign language
version of AutoCAD, the standard AutoCAD commands and keywords are
automatically translated if you precede each command or keyword with an
underscore (_).
(command "_line" pt1 pt2 pt3 "_c")

If you are using the dot prefix (to avoid using redefined commands), you can
place the dot and underscore in either order. Both "._line" and "_.line" are
valid.

Pausing for User Input
If an AutoCAD command is in progress and the predefined symbol PAUSE is
encountered as an argument to command, the command is suspended to allow
direct user input (usually point selection or dragging). This is similar to the
backslash pause mechanism provided for menus.
The PAUSE symbol is defined as a string consisting of a single backslash.
When you use a backslash () in a string, you must precede it by another
backslash ().
Menu input is not suspended by an AutoLISP pause. If a menu item is active
when the command function pauses for input, that input request can be satisfied by the menu. If you want the menu item to be suspended as well, you
must provide a backslash in the menu item. When valid input is found, both
the command function and the menu item resume.

NOTE You can use a backslash instead of the PAUSE symbol. However, the
pause mechanism might require a different trigger value in future versions of
AutoLISP, so it is recommended that you always use the PAUSE symbol rather
than an explicit backslash. Also, if the command function is invoked from a menu
item, the backslash suspends the reading of the menu item, which results in partial evaluation of the AutoLISP expression.
If you issue a transparent command while a command function is suspended,
the command function remains suspended. Therefore, users can ’ZOOM and
’PAN while at a command pause. The pause remains in effect until AutoCAD
gets valid input, and no transparent command is in progress. For example,
the following code begins the CIRCLE comm and, sets the center point at


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(5,5), and then pauses to let the user drag the circle’s radius. When the user
specifies the desired point (or types in the desired radius), the function
resumes, drawing a line from (5,5) to (7,5), as follows:
(command "circle" "5,5" pause "line" "5,5" "7,5" "")

If PAUSE is encountered when a command is expecting input of a text string
or an attribute value, AutoCAD pauses for input only if the TEXTEVAL system
variable is nonzero. Otherwise, AutoCAD does not pause for user input but
uses the value of the PAUSE symbol (a single backslash) text.
When the command function pauses for user input, the function is considered
active, so the user cannot enter another AutoLISP expression to be evaluated.
The following is an example of using the PAUSE symbol (the layer NEW_LAY
and the block MY_BLOCK must exist in the drawing prior to testing this code):
(setq blk "MY_BLOCK")
(setq old_lay (getvar "clayer"))
(command "layer" "set" "NEW_LAY" "")
(command "insert" blk pause "" "" pause)
(command "layer" "set" old_lay "")

The preceding code fragment sets the current layer to NEW_LAY, pauses for
user selection of an insertion point for the block MY_BLOCK (which is
inserted with X and Y scale factors of 1), and pauses again for user selection
of a rotation angle. The current layer is then reset to the original layer.
If the command function specifies a PAUSE to the SELECT command and a
PICKFIRST set is active, the SELECT command obtains the PICKFIRST set without pausing for the user.

WARNING! The Radius and Diameter subcommands of the Dim prompt
issue additional prompts in some situations. This can cause a failure of AutoLISP
programs written prior to Release 11 that use these commands.

Passing Pick Points to AutoCAD Commands
Some AutoCAD commands (such as TRIM, EXTEND, and FILLET) require the
user to specify a pick point as well as the object itself. To pass such pairs of
object and point data by means of the command function without the use of a
PAUSE, you must first store them as variables. Points can be passed as strings
within the command function or can be defined outside the function and
passed as variables, as shown in the following example. This code fragment
shows one method of passing an entity name and a pick point to the command
function.

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(command "circle" "5,5" "2")
(command "line" "3,5" "7,5" "")
(setq el (entlast))
(setq pt ’(5 7))
(command "trim" el "" pt "")

Draws circle
Draws line
Gets last entity name
Sets point pt
Performs trim

If AutoCAD is at the Command prompt when these functions are called,
AutoCAD performs the following actions:

1 Draws a circle centered at (5,5) with a radius of 2.
2 Draws a line from (3,5) to (7,5).
3 Creates a variable el that is the name of the last object added to the database.
(See “Using AutoLISP to Manipulate AutoCAD Objects” for more discussion
of objects and object-handling functions.)

4 Creates a pt variable that is a point on the circle. (This point selects the portion of the circle to be trimmed.)

5 Performs the TRIM command by selecting the el object and by selecting the
point specified by pt.

Undoing Commands Issued with the command Function
An UNDO group is explicitly created around each command used with the
command function. If a user enters U (or UNDO) after running an AutoLISP routine, only the last command will be undone. Additional entries of UNDO will
step backward through the commands used in that routine. If you want a
group of commands to be considered a group (or the entire routine), use the
UNDO Begin and UNDO End options.

System and Environment Variables
With the getvar and setvar functions, AutoLISP applications can inspect
and change the value of AutoCAD system variables. These functions use a
string to specify the variable name. The setvar function specifies a value of
the type that the system variable expects. AutoCAD system variables come in
various types: integers, real values, strings, 2D points, and 3D points. Values
supplied as arguments to setvar must be of the expected type. If an invalid
type is supplied, an AutoLISP error is generated.
The following code fragment ensures that subsequent FILLET commands use
a radius of at least 1:
(if (< (getvar "filletrad") 1)
(setvar "filletrad" 1)
)


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See the Command Reference for a list and description of each AutoCAD system
variable.
An additional function, getenv, provides AutoLISP routines with access to
the currently defined operating system environment variables.

Configuration Control
AutoCAD uses the acadxx .cfg file to store configuration information (the xx
in the file name refers to the AutoCAD release number). The AppData section
of this file is provided for users and developers to store configuration information pertaining to their applications. The getcfg and setcfg functions
allow AutoLISP applications to inspect and change the value of parameters
in the AppData section.

Display Control
AutoLISP includes functions for controlling the AutoCAD display in both
text and graphics windows. Some functions prompt for, or depend on, input
from the AutoCAD user.
The prompt, princ, prin1, and print functions are the primary text output
functions. These functions were described in the “AutoLISP Basics” chapter,
under the heading, “Basic Output Functions.”
See “Display Control Functions” in appendix A, “AutoLISP Function
Synopsis,” for a complete list of display control functions.

Controlling Menus
The menucmd function controls the display of the graphics window menus. It
displays, modifies, or queries one of the submenus of the current menu, and
accepts a string argument that specifies the submenu and the action to
perform on that submenu.
The menucmd function takes a string argument that consists of two fields,
separated by an equal sign, in the following form:
"menu_area=action"

This syntax can load a submenu into a specified menu area, or perform an
action on a menu item or a currently loaded menu area. The menu_area field
specifies which part of the menu is to receive the action. This field can specify
a menu area, such as P0 (for the shortcut menu) or S (for the screen menu),
or a specific menu item. The action field specifies the action to perform on

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the menu area or menu item, or a submenu to load into the menu area. The
menu areas that can receive an action are the same as those used in menu file
submenu references.
Every menu area has a currently loaded submenu. By default, the first submenu following a menu section label is loaded into that menu area.
If menu_area specifies a pull-down menu or image tile menu, action can be
an asterisk (*). This causes the menu to display (pull-down menus and image
tile menus are not automatically displayed when they are called). In Windows, only the P0 (cursor) menu and image tile menus are displayed with the
asterisk.

NOTE Do not include the dollar sign that introduces the similar instructions in
a menu file in the string argument. Also, do not include the asterisks that precede submenu labels in the menu file in the action field of the string argument.
The following menucmd function call causes the **OSNAP screen submenu
defined in the current menu file to be displayed (assuming the screen menu
is currently enabled).
(menucmd "S=OSNAP")

In Windows, you can reference the menu group. This can be useful if there
are multiple menus loaded that contain the sam e submenu name. The following code displays the **OSNAP screen submenu in the ACAD menu group.
(menucmd "S=ACAD.OSNAP")

The menucmd function can load submenus into the BUTTONS and AUX menu
areas. You might want your digitizer buttons to function differently depending on whether Tablet mode is on or off. You can have two submenus defined
in the ***BUTTONS1 section, **DIG-BUTTONS and **TAB-BUTTONS, and switch
between them with the following code.
(menucmd "B1=DIG-BUTTONS")
(menucmd "B1=TAB-BUTTONS")

Enables the DIG-BUTTONS submenu
Enables the TAB-BUTTONS submenu

The following code loads the ***POP0 menu into the P0 (cursor) menu area
and displays it.
(menucmd "P0=POP0")
(menucmd "P0=*")

Loads the ***POP0 menu into the P0 menu area
Displays it

If you are sure the correct menu is loaded into a particular menu area, you do
not need to load it specifically each time you want to display it.

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The following call displays the pull-down menu currently loaded in the P1
(first pull-down menu) location.
(menucmd "P1=*")

Using "P1=*" without previously loading the menu can result in unexpected
behavior. Although you can load virtually any menu at a pull-down or shortcut menu location, it is best to use only menus specifically designed for that
menu area. For example, if you have a submenu called **MORESTUFF, you can
load it at the P1 location with the following code:
(menucmd "P1=MORESTUFF")
(menucmd "P1=*")

Loads the **MORESTUFF menu in the
P1 menu location
Displays it

This menu remains in this location until you replace it by loading another
menu, as in the following:
(menucmd "P1=POP1")

If your menu uses the disabling (graying-out) and marking features, you can
retrieve and change the state of a menu label with the menucmd function. The
following call retrieves the current state of the fourth label in the pull-down
menu P2.
(menucmd "P2.4=#?")

If disabled returns

"P2.4=~"

These function calls enable and disable that same label:
(menucmd "P2.4=")
(menucmd "P2.4=~")

Enables the label
Disables the label

You can also place and remove marks to the left of menu labels.
The previously described method of menu item handling works relatively
well with a single static menu. However, it becomes unreliable when menu
item locations change when you load multiple partial menu files. You can
make use of the menu-group and name-tag features to keep track of menu
items. Instead of specifying a menu item by its location in the menu file, you
specify the menu group and name tag associated with the menu item.
When you use the menu group to enable, disable, and mark menu labels, you
must precede the group name with a G, as shown in the following examples.
(menucmd "Gacad.ID_New=~")
(menucmd "Gacad.ID_New=")

Disables the label
Enables the label

Not only can an AutoLISP function enable and disable menu labels, it can
also modify the text displayed in the label by placing a DIESEL string expression in the label. Because DIESEL accepts only strings as input, you can pass
information to the DIESEL expression through a USERS1–5 system variable
that has been set to a value returned by your function.

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You can also use the menucmd function to evaluate DIESEL string expressions
within an AutoLISP function. The following routine returns the current time:
(defun C:CTIME ( / ctim)
(setq ctim
(menucmd "M=$(edtime,$(getvar,date),H:MMam/pm)"))
(princ (strcat "nThe current time is " ctim ))
(princ)
)

For information on the use of DIESEL expressions with AutoLISP and a
catalog of DIESEL functions, see the Customization Guide. Refer also to the
Customization Guide for further information on menus.

Control of Graphics and Text Windows
You can control the display of the graphics and text windows from an
AutoLISP application. On single-screen AutoCAD installations, a call to
graphscr displays the graphics window, and a call to textscr displays the
text window. Using these functions is equivalent to toggling the Flip Screen
function key. The function textpage is like textscr, but textpage clears the
text window before displaying the next text window (as the AutoCAD STATUS
and LIST commands do).
The redraw function is similar to the AutoCAD REDRAW command but provides more control over what is displayed. It not only redraws the entire
graphics area but can also specify a single object to be redrawn or undrawn
(that is, blanked out). If the object is a complex object such as an old-style
polyline or a block, redraw can draw (or undraw) either the entire object or
its header. The redraw function can also highlight and unhighlight specified
objects.

Control of Low-Level Graphics
AutoLISP provides functions that control the low-level graphics and allow
direct access to the AutoCAD graphics screen and input devices.
The grtext function displays text directly in the status or menu areas, with
or without highlighting. The grdraw function draws a vector in the current
viewport with control over color and highlighting. The grvecs function
draws multiple vectors.

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NOTE Because these functions depend on code in AutoCAD, their operation
can be expected to change from release to release. There is no guarantee that
applications calling these functions will be upward compatible. Also, they
depend on current hardware configurations. In particular, applications that call
grtext are not likely to work the same on all configurations unless the developer
is very careful to use them as described (see the Customization Guide) and to
avoid hardware-specific features. Finally, because they are low-level functions,
they do almost no error reporting and can alter the graphics screen display unexpectedly (see the following example for a way to fix this).
The following sequence restores the default graphics window display caused
by incorrect calls to grtext, grdraw, or grvecs:
(grtext)
(redraw)

Restores standard text

Getting User Input
Several functions enable an AutoLISP application to prompt the user for
input of data. See “User Input Functions” in appendix A, “AutoLISP Function
Synopsis,” for a complete list of user input functions.

The getxxx Functions
Each user-input getxxx function pauses for data entry of the indicated type
and returns the value entered. The application specifies an optional prompt
to display before the function pauses. The following table lists the getxxx
functions and the type of user input requested.

Allowable input to the getxxx user-input functions
Function name

getint

A real or integer value on the Command line

getstring

A string on the Command line

getpoint

A point value on the Command line or selected from the screen

getcorner

|

An integer value on the Command line

getreal

268

Type of user input

A point value (the opposite corner of a box) on the Command line or
selected from the screen

Chapter 9


Allowable input to the getxxx user-input functions (continued)
Function name

Type of user input

getdist

A real or integer value (of distance) on the Command line or
determined by selecting points on the screen

getangle

An angle value (in the current angle format) on the Command line or
based on selected points on the screen

getorient

An angle value (in the current angle format) on the Command line or
based on selected points on the screen

getkword

A predefined keyword or its abbreviation on the Command line

NOTE Although the getvar, getcfg, and getenv functions begin with the letters g, e, and t, they are not user-input functions. They are discussed in “Query
and Command Functions” on page 260.
The functions getint, getreal, and getstring pause for user input on the
AutoCAD Command line. They return a value only of the same type as that
requested.
The getpoint, getcorner, and getdist functions pause for user input on the
Command line or from points selected on the graphics screen. The getpoint
and getcorner functions return 3D point values, and getdist returns a real
value.
Both getangle and getorient pause for input of an angle value on the Command line or as defined by points selected on the graphics screen. For the
getorient function, the 0 angle is always to the right: “East” or “3 o’clock.”
For getangle, the 0 angle is the value of ANGBASE, which can be set to any
angle. Both getangle and getorient return an angle value (a real) in radians
measured counterclockwise from a base (0 angle), for getangle equal to
ANGBASE, and for getorient to the right.
For example, ANGBASE is set to 90 degrees (north), and ANGDIR is set to 1
(clockwise direction for increasing angles). The following table shows what

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getangle and getorient return (in radians) for representative input values
(in degrees).

Possible return values from getangle and getorient
Input
(degrees)

getangle

getorient

0

0.0

1.5708

–90

1.5708

3.14159

180

3.14159

4.71239

90

4.71239

0.0

ANGBASE = 90
input
angle = 0
input
angle = -90

ANGDIR = 1 (clockwise)

input
angle = 90
input
angle = 180

The getangle function honors the settings of ANGDIR and ANGBASE when
accepting input. You can use getangle to obtain a rotation amount for a
block insertion, because input of 0 degrees always returns 0 radians. The
getorient function honors only ANGDIR. You use getorient to obtain angles
such as the baseline angle for a text object. For example, given the preceding
settings of ANGBASE and ANGDIR, for a line of text created at an angle of 0,
getorient returns an angle value of 90.
The user-input functions take advantage of the error-checking capability of
AutoCAD. Trivial errors are trapped by AutoCAD and are not returned by the
user-input function. A prior call to initget provides additional filtering
capabilities, lessening the need for error-checking.
The getkword function pauses for the input of a keyword or its abbreviation.
Keywords must be defined with the initget function before the call to
getkword. All user-input functions (except getstring) can accept keyword

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values in addition to the values they normally return, provided that initget
has been called to define the keywords.
All user-input functions allow for an optional prompt argument. It is recommended you use this argument rather than a prior call to the prompt or princ
functions. If a prompt argument is supplied with the call to the user-input
function, that prompt is reissued in the case of invalid user input. If no
prompt argument is supplied and the user enters incorrect information, the
following message appears at the AutoCAD prompt line:

Try again:
This can be confusing, because the original prompt may have scrolled out of
the Command prompt area.
The AutoCAD user cannot typically respond to a user-input function by
entering an AutoLISP expression. If your AutoLISP routine makes use of the
initget function, arbitrary keyboard input is permitted to certain functions
that can allow an AutoLISP statement as response to a command implemented in AutoLISP. This is discussed in “Arbitrary Keyboard Input” on page
273.

Control of User-Input Function Conditions
The initget function provides a level of control over the next user-input
function call. The initget function establishes various options for use by the
next entsel, nentsel, nentselp, or getxxx function (except getstring,
getvar, and getenv). This function accepts two arguments, bits and string,
both of which are optional. The bits argument specifies one or more control
bits that enable or disable certain input values to the following user-input
function call. The string argument can specify keywords that the following
user-input function call will recognize.
The control bits and keywords established by initget apply only to the next
user-input function call. They are discarded after that call. The application
doesn’t have to call initget a second time to clear special conditions.

Input Options for User-Input Functions
The value of the bits argument restricts the types of user input to the following user-input function call. This reduces error-checking. These are some of
the available bit values: 1 disallows null input, 2 disallows input of 0 (zero),
and 4 disallows negative input. If these values are used with a following call
to the getint function, the user is forced to enter an integer value greater
than 0.

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To set more than one condition at a time, add the values together (in any
combination) to create a bits value between 0 and 255. If bits is not included
or is set to 0, none of the control conditions applies to the next user-input
function call. (For a complete listing of initget bit settings, see “initget” in
the AutoLISP Reference.)
(initget (+ 1 2 4))
(getint "nHow old are you? ")

This sequence requests the user’s age. AutoCAD displays an error message
and repeats the prompt if the user attempts to enter a negative or zero value,
press ENTER only, or enter a string (the getint function rejects attempts to
enter a value that is not an integer).

Keyword Options
The optional string argument specifies a list of keywords recognized by the
next user-input function call.
The initget function allows keyword abbreviations to be recognized in
addition to the full keywords. The user-input function returns a predefined
keyword if the input from the user matches the spelling of a keyword (not
case sensitive), or if the user enters the abbreviation of a keyword. There are
two methods for abbreviating keywords; both are discussed in the initget
topic in the AutoLISP Reference.
The following user-defined function shows a call to getreal, preceded by a
call to initget, that specifies two keywords. The application checks for these
keywords and sets the input value accordingly.
(defun C:GETNUM (/ num)
(initget 1 "Pi Two-pi")
(setq num (getreal "Pi/Two-pi/<number>: "))
(cond
((eq num "Pi") pi)
((eq num "Two-pi") (* 2.0 pi))
(T num)
)
)

This initget call inhibits null input (bits = 1) and establishes a list of two
keywords, "Pi" and "Two-pi". The getreal function is then used to obtain a
real number, issuing the following prompt:

Pi/Two-pi/<number>:
The result is placed in local symbol num. If the user enters a number, that
number is returned by C:GETNUM. However, if the user enters the keyword Pi
(or simply P ), getreal returns the keyword Pi. The cond function detects this

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and returns the value of p in this case. The Two-pi keyword is handled
similarly.

NOTE You can also use initget to enable entsel, nentsel, and nentselp to
accept keyword input. For more information on these functions, see “Object
Handling” on page 305 and the entsel, nentsel, and nentselp function definitions in the AutoLISP Reference.

Arbitrary Keyboard Input
The initget function also allows arbitrary keyboard input to most getxxx
functions. This input is passed back to the application as a string. An application using this facility can be written to permit the user to call an AutoLISP
function at a getxxx function prompt.
These functions show a method for allowing AutoLISP response to a getxxx
function call:
(defun C:ARBENTRY ( / pt1)
(initget 128)
(setq pt1 (getpoint "nPoint: "))
(if (= 'STR (type pt1))
(setq pt1 (eval (read pt1)))
pt1

;
;
;
;
;
;

Sets arbitrary entry bit
Gets value from user.
If it's a string, convert it
to a symbol, try evaluating
it as a function; otherwise,
just return the value.

)
)
(defun REF ( )
(setvar "LASTPOINT" (getpoint "nReference point: "))
(getpoint "nNext point: " (getvar "LASTPOINT"))
)

If both the C:ARBENTRY and REF functions are loaded into the drawing, the
following command sequence is acceptable.

Command: arbentry
Point: (ref)
Reference point: Select a point
Next point: @1,1,0

Input Validation
You should protect your code from unintentional user errors. The AutoLISP
user input getxxx functions do much of this for you. However, it’s dangerous
to forget to check for adherence to other program requirements that the
getxxx functions do not check for. If you neglect to check input validity, the
program’s integrity can be seriously affected.

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Geometric Utilities
A group of functions allows applications to obtain pure geometric information and geometric data from the drawing. See “Geometric Functions” in
appendix A, “AutoLISP Function Synopsis,” for a complete list of geometric
utility functions.
The angle function finds the angle in radians between a line and the X axis
(of the current UCS), distance finds the distance between two points, and
polar finds a point by means of polar coordinates (relative to an initial
point). The inters function finds the intersection of two lines. The osnap
and textbox functions are described separately.
The following code fragment shows calls to the geometric utility functions:
(setq
(setq
(setq
(setq

pt1 ’(3.0 6.0 0.0))
pt2 ’(5.0 2.0 0.0))
base ’(1.0 7.0 0.0))
rads (angle pt1 pt2))

(setq len
(setq endpt

(distance pt1 pt2))

; Angle in XY plane of current UCS
; (value is returned in radians)
; Distance in 3D space

(polar base rads len))

The call to polar sets endpt to a point that is the same distance from (1,7) as
pt1 is from pt2, and at the same angle from the X axis as the angle between
pt1 and pt2.

Object Snap
The osnap function can find a point by using one of the AutoCAD Object
Snap modes. The Snap modes are specified in a string argument.
The following call to osnap looks for the midpoint of an object near pt1:
(setq pt2 (osnap pt1 "midp"))

The following call looks for the midpoint, the endpoint, or the center of an
object nearest pt1:
(setq pt2 (osnap pt1 "midp,endp,center"))

In both examples, pt2 is set to the snap point if one is found that fulfills the
osnap requirements. If more than one snap point fulfills the requirements,
the point is selected based on the setting of the SORTENTS system variable.
Otherwise, pt2 is set to nil.

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NOTE The APERTURE system variable determines the allowable proximity of a
selected point to an object when you use Object Snap.

Text Extents
The textbox function returns the diagonal coordinates of a box that encloses
a text object. It takes an entity definition list of the type returned by entget
(an association list of group codes and values) as its single argument. This list
can contain a complete association list description of the text object or just
a list describing the text string.
The points returned by textbox describe the bounding box (an imaginary
box that encloses the text object) of the text object, as if its insertion point
were located at (0,0,0) and its rotation angle were 0. The first list returned is
the point (0.0 0.0 0.0), unless the text object is oblique or vertical or it contains letters with descenders (such as g and p). The value of the first point list
specifies the offset distance from the text insertion point to the lower-left
corner of the smallest rectangle enclosing the text. The second point list specifies the upper-right corner of that box. The returned point lists always
describe the bottom-left and upper-right corners of this bounding box,
regardless of the orientation of the text being measured.
The following example shows the minimum allowable entity definition list
that textbox accepts. Because no additional information is provided,
textbox uses the current defaults for text style and height.

Command: (textbox '((1 . "Hello world")) )
((0.0 0.0 0.0) (2.80952 1.0 0.0))
The actual values returned by textbox will vary depending on the current
text style.

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275

The following example demonstrates one method of providing the textbox
function with an entity definition list.

Command: dtext
Justify/Style/<Start point>: 1,1
Height <1.0000>: ENTER
Rotation angle <0>: ENTER
Text: test
Text: ENTER
Command: (setq e (entget (entlast)))
((-1 . <Entity name: 1ba3568>) (0 . "TEXT") (330 . <Entity name: 1ba34f8>) (5 .
"2D") (100 . "AcDbEntity") (67 . 0) (410 . "Model") (8 . "0") (100 .
"AcDbText") (10 1.0 1.0 0.0) (40 . 1.0) (1 . "test") (50 . 0.0) (41 . 1.0) (51
. 0.0) (7 . "Standard") (71 . 0) (72 . 0) (11 0.0 0.0 0.0) (210 0.0 0.0 1.0)
(100 . "AcDbText") (73 . 0))
Command: (textbox e)
((0.0 0.0 0.0) (0.8 0.2 0.0))
The following figure shows the results of applying textbox to a text object
with a height of 1.0. The figure also shows the baseline and insertion point
of the text.

top right:
(5.5,1.0)
insertion
point: (0,0)

baseline

bottom left: (0,–0.333333)

If the text is vertical or rotated, pt1 is still the bottom-left corner and pt2 is
the upper-right corner; the bottom-left point may have negative offsets if
necessary.
The following figure shows the point values (pt1 and pt2) that textbox
returns for samples of vertical and aligned text. In both samples, the height
of the letters is 1.0. (For the aligned text, the height is adjusted to fit the
alignment points.)

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pt2 = 9.21954,1.38293,0.0

alignment points entered when text was created
pt1 = 0.263416,0.0,0.0

When using vertical text styles, the points are still returned in left-to-right,
bottom-to-top order as they are for horizontal styles, so that the first point
list will contain negative offsets from the text insertion point.
insertion
point: (0,0)

pt2 = 1.0, 0.0

pt1 =
-0.5,-20.0

Regardless of the text orientation or style, the points returned by textbox are
such that the text insertion point (group code 10) directly translates to the
origin point of the object coordinate system (OCS) for the associated text
object. This point can be referenced when translating the coordinates
returned from textbox into points that define the actual extent of the text.
The two sample routines that follow use textbox to place a box around
selected text regardless of its orientation.

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The first routine uses the textbox function to draw a box around a selected
text object:
(defun C:TBOX ( / textent tb ll ur ul lr)
(setq textent (car (entsel "nSelect text: ")))
(command "ucs" "Object" textent)
(setq tb (textbox (list (cons -1 textent)))
ll (car tb)
ur (cadr tb)
ul (list (car ll) (cadr ur))
lr (list (car ur) (cadr ll))
)
(command "pline" ll lr ur ul "Close")
(command "ucs" "p")
(princ)
)

The second routine, which follows, accomplishes the same task as the first
routine by performing the geometric calculations with the sin and cos
AutoLISP functions. The result is correct only if the current UCS is parallel to
the plane of the text object.
(defun C:TBOX2 ( / textent ang sinrot cosrot
t1 t2 p0 p1 p2 p3 p4)
(setq textent (entget (car (entsel "nSelect text: "))))
(setq p0 (cdr (assoc 10 textent))
ang (cdr (assoc 50 textent))
sinrot (sin ang)
cosrot (cos ang)
t1 (car (textbox textent))
t2 (cadr (textbox textent))
p1 (list
(+ (car p0)
(- (* (car t1) cosrot)(* (cadr t1) sinrot))
)
(+ (cadr p0)
(+ (* (car t1) sinrot)(* (cadr t1) cosrot))
)
)
p2 (list
(+ (car p0)
)
(+ (cadr p0)
)
)
p3 (list
(+ (car p0)
)
(+ (cadr p0)
)
)

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p4 (list
(+ (car p0)
)
(+ (cadr p0)
)
)
)
(command "pline" p1 p2 p3 p4 "c")
(princ)
)

Conversions
The functions described in this section are utilities for converting data types
and units. See “Conversion Functions” in appendix A, “AutoLISP Function
Synopsis,” for a complete list of conversion functions.

String Conversions
The functions rtos (real to string) and angtos (angle to string) convert
numeric values used in AutoCAD to string values that can be used in output
or as textual data. The rtos function converts a real value, and angtos converts an angle. The format of the result string is controlled by the value of
AutoCAD system variables: the units and precision are specified by LUNITS
and LUPREC for real (linear) values and by AUNITS and AUPREC for angular
values. For both functions, the dimensioning variable DIMZIN controls how
leading and trailing zeros are written to the result string.
The following code fragments show calls to rtos and the values returned
(assuming the DIMZIN system variable equals 0). Precision (the third argument to rtos) is set to 4 places in the first call and 2 places in the others.
(setq x 17.5)
(setq str "nValue formatted as ")
(setq fmtval (rtos x 1 4))
(princ (strcat str fmtval))

; Mode 1 = scientific
; displays
Value formatted as 1.7500E+01


; Mode 2 = decimal
; displays
Value formatted as 17.50


; Mode 3 = engineering
; displays
Value formatted as 1’-5.50"


; Mode 4 = architectural
; displays
Value formatted as 1’-5 1/2"


; Mode 5 = fractional
; displays
Value formatted as 17 1/2

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279

When the UNITMODE system variable is set to 1 , specifying that units are displayed as entered, the string returned by rtos differs for engineering (mode
equals 3), architectural ( mode equals 4), and fractional (mode equals 5) units.
For example, the first two lines of the preceding sample output would be the
same, but the last three lines would appear as follows:

Value formatted as 1’5.50"
Value formatted as 1’5-1/2"
Value formatted as 17-1/2''
Because the angtos function takes the ANGBASE system variable into account,
the following code always returns "0":
(angtos (getvar "angbase"))

There is no AutoLISP function that returns a string version (in the current
mode/precision) of either the amount of rotation of ANGBASE from true zero
(East) or an arbitrary angle in radians.
To find the amount of rotation of ANGBASE from AutoCAD zero (East) or the
size of an arbitrary angle, you can do one of the following:
Add the desired angle to the current ANGBASE, and then check to see if the
absolute value of the result is greater than 2π (2 * pi). If so, subtract 2π; if
the result is negative, add 2π, then use the angtos function on the result.
s Store the value of ANGBASE in a temporary variable, set ANGBASE to 0, evaluate the angtos function, then set ANGBASE to its original value.
s

Subtracting the result of (atof (angtos 0)) from 360 degrees (2π radians or
400 grads) also yields the rotation of ANGBASE from 0.
The distof (distance to floating point) function is the complem ent of rtos.
Therefore, the following calls, which use the strings generated in the previous examples, all return the same value: 17.5. (Note the use of the backslash
() with modes 3 and 4.)
(distof "1.7500E+01" 1)

; Mode 1 = scientific

(distof "17.50" 2)

; Mode 2 = decimal

(distof "1’-5.50"" 3)

; Mode 3 = engineering

(distof "1’-5 1/2"" 4)

; Mode 4 = architectural

(distof "17 1/2" 5)

; Mode 5 = fractional

The following code fragments show similar calls to angtos and the values
returned (still assuming that DIMZIN equals 0). Precision (the third argument
to angtos) is set to 0 places in the first call, 4 places in the next three calls,
and 2 places in the last.

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(setq ang 3.14159 str2 "nAngle formatted as ")
(setq fmtval (angtos ang 0 0))
(princ (strcat str2 fmtval))

; Mode 0 = degrees
; displays Angle formatted as 180


; Mode 1 = deg/min/sec
; displays Angle formatted as 180d0’0"


; Mode 2 = grads
; displays Angle formatted as 200.0000g


; Mode 3 = radians
; displays Angle formatted as 3.1416r


; Mode 4 = surveyor’s
; displays Angle formatted as W

The UNITMODE system variable also affects strings returned by angtos when
it returns a string in surveyor’s units (mode equals 4). If UNITMODE equals 0, the
string returned can include spaces (for example, "N 45d E"); if UNITMODE
equals 1, the string contains no spaces (for example, "N45dE").
The angtof function complements angtos, so all of the following calls return
the same value: 3.14159.
(angtof
(angtof
(angtof
(angtof
(angtof

"180" 0)
"180d0’0"" 1)
"200.0000g" 2)
"3.14159r" 3)
"W" 4)

;
;
;
;
;

Mode
Mode
Mode
Mode
Mode

0
1
2
3
4

=
=
=
=
=

degrees
deg/min/sec
grads
radians
surveyor’s

When you have a string specifying a distance in feet and inches, or an angle
in degrees, minutes, and seconds, you must precede the quotation mark with
a backslash (") so it doesn’t look like the end of the string. The preceding
examples of angtof and distof demonstrate this action.

Angular Conversion
If your application needs to convert angular values from radians to degrees,
you can use the angtos function, which returns a string, and then convert
that string into a floating point value with atof.
(setq pt1 ’(1 1) pt2 ’(1 2))
(setq rad (angle pt1 pt2))
(setq deg (atof (angtos rad 0 2)))

returns

90.0

However, a more efficient method might be to include a Radian->Degrees
function in your application. The following code shows this:
; Convert value in radians to degrees
(defun Radian->Degrees (nbrOfRadians)
(* 180.0 (/ nbrOfRadians pi))
)

Conversions

|

281

After this function is defined, you can use the Radian->Degrees function
throughout your application, as in
(setq degrees (Radian->Degrees rad))

returns

90.0

You may also need to convert from degrees to radians. The following code
shows this:
; Convert value in degrees to radians
(defun Degrees->Radians (numberOfDegrees)
(* pi (/ numberOfDegrees 180.0))
) ;_ end of defun

ASCII Code Conversion
AutoLISP provides the ascii and chr functions that handle decimal ASCII
codes. The ascii function returns the ASCII decimal value associated with a
string, and chr returns the character associated with an ASCII decimal value.
To see your system’s characters with their codes in decimal, octal, and hexadecimal form, save the following AutoLISP code to a file named ascii.lsp.
Then load the file and enter the new ASCII command at the AutoCAD Command prompt. This command prints the ASCII codes to the screen and to a
file called ascii.txt. The C:ASCII function makes use of the BASE function. You
may find this conversion utility useful in other applications.
; BASE converts from a decimal integer to a string in another base.
(defun BASE ( bas int / ret yyy zot )
(defun zot ( i1 i2 / xxx )
(if (> (setq xxx (rem i2 i1)) 9)
(chr (+ 55 xxx))
(itoa xxx)
)
)
(setq ret (zot bas int) yyy (/ int bas))
(while (>= yyy bas)
(setq ret (strcat (zot bas yyy) ret))
(setq yyy (/ yyy bas))
)
(strcat (zot bas yyy) ret)
)
(defun C:ASCII ( / chk out ct code dec oct hex )
(initget "Yes")
(setq chk (getkword "nWriting to ASCII.TXT, continue? <Y>: "))
(if (or (= chk "Yes")(= chk nil))
(progn
(setq out (open "ascii.txt" "w") chk 1 code 0 ct 0)
(princ "n n CHAR
DEC OCT HEX n")
(princ "n n CHAR
DEC OCT HEX n" out)
(while chk
(setq dec (strcat " " (itoa code))
oct (base 8 code) hex (base 16 code))
(setq dec (substr dec (- (strlen dec) 2) 3))

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(if (< (strlen oct) 3)(setq oct (strcat "0" oct)))
(princ (strcat "n " (chr code) "
" dec " "
oct " " hex ) )
(princ (strcat "n " (chr code) "
" dec " "
oct " " hex ) out)
(cond
((= code 255)(setq chk nil))
((= ct 20)
(setq xxx (getstring
"n nPress 'X' to eXit or any key to continue: "))
(if (= (strcase xxx) "X")
(setq chk nil)
(progn
(setq ct 0)
(princ "n n CHAR
DEC OCT HEX n")
)
)
)
)
(setq ct (1+ ct) code (1+ code))
)
(close out)
(setq out nil)
)
)
(princ)
)

Unit Conversion
The acad.unt file defines various conversions between real-world units such
as miles to kilometers, Fahrenheit to Celsius, and so on. The function cvunit
takes a value expressed in one system of units and returns the equivalent
value in another system. The two systems of units are specified by strings
containing expressions of units defined in acad.unt.
The cvunit function does not convert incompatible dimensions. For example, it does not convert inches into grams.
The first time cvunit converts to or from a unit during a drawing editor session, it must look up the string that specifies the unit in acad.unt. If your
application has many values to convert from one system of units to another,
it is more efficient to convert the value 1.0 by a single call to cvunit and then
use the returned value as a scale factor in subsequent conversions. This works
for all units defined in acad.unt, except temperature scales, which involve an
offset as well as a scale factor.

Conversions

|

283

Converting from Inches to Meters
If the current drawing units are engineering or architectural (feet and inches),
the following routine converts a user-specified distance of inches into
meters:
(defun C:I2M ( / eng_len metric_len eng metric)
(princ "nConverting inches to meters. ")
(setq eng_len
(getdist "nEnter a distance in inches: "))
(setq metric_len (cvunit eng_len "inches" "meters"))
(setq eng (rtos eng_len 2 4)
metric (rtos metric_len 2 4))
(princ
(strcat "nt" eng " inches = " metric " meters."))
(princ)
)

The Unit Definition File
With the AutoCAD unit definition file acad.unt, you can define factors to
convert data in one set of units to another set of units. The definitions in
acad.unt are in ASCII format and are used by the unit-conversion function
cvunit.
You can make new units available by using a text editor to add their definitions to acad.unt. A definition consists of two lines in the file—the unit name
and the unit definition. The first line must have an asterisk (*) in the first
column, followed by the name of the unit. A unit nam e can have several
abbreviations or alternate spellings, separated by commas. If a unit name has
singular and plural forms, you can specify these using the following format:
*[ [common] [ ( [singular.] plural) ] ]...

You can specify multiple expressions (singular and plural). They don’t have
to be located at the end of the word, and a plural form isn’t required. The following are examples of valid unit name definitions:
*inch(es)
*milleni(um.a)
*f(oot.eet) or (foot.feet)

The line following the *unit name line defines the unit as either fundamental
or derived.

Fundamental Units
A fundamental unit is an expression in constants. If the line following the
*unit name line begins with something other than an equal sign (=), it defines
fundamental units. Fundamental units consist of five integers and two real
numbers in the following form:
c, e, h, k, m, r1, r2

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The five integers correspond to the exponents of these five constants:

c

Velocity of light in a vacuum

e

Electron charge

h

Planck’s constant

k

Boltzman’s constant

m

Electron rest mass

As a group, these exponents define the dimensionality of the unit: length,
mass, time, volume, and so on.
The first real number (r1) is a multiplier, and the second (r2) is an additive
offset (used only for temperature conversions). The fundamental unit definition allows for different spellings of the unit (for example, meter and metre);
the case of the unit is ignored. An example of a fundamental unit definition
is as follows:
*meter(s),metre(s),m
-1,0,1,0,-1,4.1214856408e11,0

In this example, the constants that make one meter are as follows:

( 1 x h x 1 ) x (4.1214856 x 1011)
c
m
Derived Units
A derived unit is defined in terms of other units. If the line following the
*unit name line begins with an equal sign (=), it defines derived units. Valid
operators in these definitions are * (multiplication), / (division),
+ (addition), – (subtraction), and ^ (exponentiation). You can specify a
predefined unit by naming it, and you can use abbreviations (if provided).
The items in a formula are multiplied together unless some other arithmetic
operator is specified. For example, the units database defines the dimensionless multiple and submultiple names, so you can specify a unit such as
micro-inches by entering micro inch. The following are examples of derived
unit definitions.
; Units of area
*township(s)
=93239571.456 meter^2

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|

285

The definition of a township is given as 93,239,571.456 square meters.
; Electromagnetic units
*volt(s),v
=watt/ampere

In this example, a volt is defined as a watt divided by an ampere. In the
acad.unt, both watts and amperes are defined in terms of fundamental units.

User Comments
To include comments, begin the line with a semicolon. The comment continues to the end of the line.
; This entire line is a comment.

List the acad.unt file itself for more information and examples.

Coordinate System Transformations
The trans function translates a point or a displacement from one coordinate
system into another. It takes a point argument, pt, that can be interpreted as
either a 3D point or a 3D displacement vector, distinguished by a displacement argument called disp. The disp argument must be nonzero if pt is to
be treated as a displacement vector; otherwise, pt is treated as a point. A from
argument specifies the coordinate system in which pt is expressed, and a to
argument specifies the desired coordinate system. The following is the syntax
for the trans function:
(trans pt from to [disp])

The following AutoCAD coordinate systems can be specified by the from and
to arguments:

WCS

UCS

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|

World coordinate system—the reference coordinate
system. All other coordinate systems are defined relative
to the WCS, which never changes. Values measured
relative to the WCS are stable across changes to other
coordinate systems.
User coordinate system—the working coordinate system.
The user specifies a UCS to make drawing tasks easier. All
points passed to AutoCAD commands, including those
returned from AutoLISP routines and external functions,
are points in the current UCS (unless the user precedes
them with a * at the Command prompt). If you want your
application to send coordinates in the WCS, OCS, or DCS
to AutoCAD commands, you must first convert them to
the UCS by calling the trans function.

Chapter 9


OCS

Object coordinate system—point values returned by
entget are expressed in this coordinate system, relative to
the object itself. These points are usually converted into
the WCS, current UCS, or current DCS, according to the
intended use of the object. Conversely, points must be
translated into an OCS before they are written to the
database by means of the entmod or entmake functions.
This is also known as the entity coordinate system.

DCS

Display coordinate system—the coordinate system into
which objects are transformed before they are displayed.
The origin of the DCS is the point stored in the AutoCAD
system variable TARGET, and its Z axis is the viewing
direction. In other words, a viewport is always a plan view
of its DCS. These coordinates can be used to determine
where something will be displayed to the AutoCAD user.
When the from and to integer codes are 2 and 3, in either
order, 2 indicates the DCS for the current model space
viewport and 3 indicates the DCS for paper space (PSDCS).
When the 2 code is used with an integer code other than
3 (or another means of specifying the coordinate system),
it is assumed to indicate the DCS of the current space,
whether paper space or model space. The other argument
is also assumed to indicate a coordinate system in the
current space.

PSDCS

Paper space DCS—this coordinate system can be
transformed only to or from the DCS of the currently
active model space viewport. This is essentially a 2D
transformation, where the X and Y coordinates are always
scaled and are offset if the disp argument is 0. The Z
coordinate is scaled but is never translated. Therefore, it
can be used to find the scale factor between the two
coordinate systems. The PSDCS (integer code 2) can be
transformed only into the current model space viewport.
If the from argument equals 3, the to argument must
equal 2, and vice versa.

Conversions

|

287

Both the from and to arguments can specify a coordinate system in any of the
following ways:
As an integer code that specifies the WCS, current UCS, or current DCS (of
either the current viewport or paper space).
s As an entity name returned by one of the entity name or selection set
functions described in “Using AutoLISP to Manipulate AutoCAD Objects.”
This specifies the OCS of the named object. For planar objects, the OCS
can differ from the WCS, as described in the AutoCAD User’s Guide. If the
OCS does not differ, conversion between OCS and WCS is an identity
operation.
s As a 3D extrusion vector. Extrusion vectors are always represented in
World coordinates; an extrusion vector of (0,0,1) specifies the WCS itself.
s

The following table lists the valid integer codes that can be used as the to and
from arguments:

Coordinate system codes
Code

Coordinate system

0

World (WCS)

1

User (current UCS)

2

Display; DCS of current viewport when used with code 0 or
1, DCS of current model space viewport when used with
code 3

3

Paper space DCS, PSDCS (used only with code 2)

The following example translates a point from the WCS into the current
UCS.
(setq pt ’(1.0 2.0 3.0))
(setq cs_from 0)
(setq cs_to 1)
(trans pt cs_from cs_to 0)

; WCS
; UCS
; disp = 0 indicates that pt is a point

If the current UCS is rotated 90 degrees counterclockwise around the World
Z axis, the call to trans returns a point (2.0,–1.0,3.0). However, if you swap
the to and from values, the result differs as shown in the following code:
(trans pt cs_to cs_from 0) ; the result is (–2.0,1.0,3.0)

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Point Transformations
If you are doing point transformations with the trans function and you need
to make that part of a program run faster, you can construct your own
transformation matrix on the AutoLISP side by using trans once to transform each of the basis vectors (0 0 0), (1 0 0), (0 1 0), and (0 0 1). Writing
matrix multiplication functions in AutoLISP can be difficult, so it may not be
worthwhile unless your program is doing a lot of transformations.

File Handling
AutoLISP provides functions for handling files and data I/O. See “FileHandling Functions” in appendix A, “AutoLISP Function Synopsis,” for a
complete list of file-handling functions.

File Search
An application can use the findfile function to search for a particular file
name. The application can specify the directory to search, or it can use the
current AutoCAD library path.
In the following code fragment, findfile searches for the requested file
name according to the AutoCAD library path:
(setq refname "refc.dwg")
(setq fil (findfile refname))
(if fil
(setq refname fil)
(princ (strcat "nCould not find file " refname ". " ))
)

If the call to findfile is successful, the variable refname is set to a fully qualified path name string, as follows:
"/home/work/ref/refc.dwg"

When specifying a path name, you must precede the backslash () with
another backslash so the path name will be recognized by AutoLISP. Alternatively, you can use the slash character ( /) as a directory separator.
The getfiled function displays a dialog box containing a list of available
files of a specified extension type in the specified directory. This gives
AutoLISP routines access to the AutoCAD Get File dialog box.
A call to getfiled takes four arguments that determine the appearance and
functionality of the dialog box. The application must specify the following
string values, each of which can be nil: a title, placed at the top of the dialog

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|

289

box; a default file name, displayed in the edit box at the bottom of the dialog
box; and an extension type, which determines the initial files provided for
selection in the list box. The final argument is an integer value that specifies
how the dialog box interacts with selected files.
This simple routine uses getfiled to let you view your directory structure
and select a file:
(defun C:DDIR ( )
(setq dfil (getfiled "Directory Listing" "" "" 2))
(princ (strcat "nVariable 'dfil' set to selected file " dfil ))
(princ)
)

This is a useful utility command. The dfil variable is set to the file you select,
which can then be used by other AutoLISP functions or as a response to a
Command line prompt for a file name. To use this variable in response to a
Command line prompt, enter !dfil.

NOTE You cannot use !dfil in a dialog box. It is valid only at the command
line.
For more information, see “getfiled” in the AutoLISP Reference.

Accessing Help Files
The help function provides access to both AutoCAD Help files (.ahp ) and
Windows Help files (.hlp). Depending on the Help file’s extension, the help
function calls the AutoCAD or the Windows Help viewer with the specified
file. You can use this function to add a Help facility to your applications. The
following code fragment calls the default AutoCAD Help file and provides
information about the LINE command.
(help "" "line")

You can create a Help file that provides information about your applications
or about procedures you use in your business. The following user-defined
command displays the morehelp.hlp Help file as follows:
(defun C:MYHELP ( )
(help "morehelp.hlp")
(princ)
)

See the Customization Guide for information on creating and modifying help
files.
The setfunhelp function provides help for user-defined commands. After
the definition of your new command, adding a call to setfunhelp associates

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a specific help file and topic with that command. The following example
assigns the help topic “Mycmd” in the file morehelp.hlp to the user-defined
MYCMD command:
(defun C:MYCMD ( )
.
. Command definition
.
)
(setfunhelp c:mycmd "morehelp.hlp" "mycmd")

Device Access and Control
AutoLISP provides the grread and tablet functions for accessing data from
the various input devices.
Note that the read-char and read-line file-handling functions can also read
input from the keyboard input buffer. See the AutoLISP Reference for more
information on these functions.

Accessing User Input
The grread function returns raw user input, whether from the keyboard or
from the pointing device (m ouse or digitizer). If the call to grread enables
tracking, the function returns a digitized coordinate that can be used for
things such as dragging.

NOTE There is no guarantee that applications calling grread will be upward
compatible. Because it depends on the current hardware configuration, applications that call grread are not likely to work in the same way on all configurations.

Calibrating Tablets
AutoCAD users can calibrate a digitizing tablet by using the TABLET command (see the Command Reference for a description of this command). The
tablet function enables applications to manage calibration by setting the
calibrations directly and by saving those settings for future use.
The first argument to the tablet function is an integer code. If code is equal
to 0, the function returns the current calibration. If code is equal to 1, the
calibration is set according to the remaining arguments. Calibrations are
expressed as four 3D points (in addition to the code). The first three points—
row1, row2 , and row3 —are the three rows of the tablet’s transformation


|

291

matrix. The fourth point, direction , is a vector that is normal to the plane in
which the tablet’s surface is assumed to lie (expressed in WCS, the World
Coordinate System). When the calibration is set with the TABLET command,
the tablet’s surface is assumed to lie in the XY plane of the current UCS.

NOTE The TABMODE system variable controls whether Tablet mode is turned
on (1) or off (0). You can control it by using the setvar function.
The following sample routine retrieves the current tablet calibration and
stores it in the variable tcal:
(defun C:TABGET ( )
(setq tcal (tablet 0))
(if tcal
(princ
(strcat "nConfiguration saved, "
"use TABSET to retrieve calibration.")
)
(princ "nCalibration not obtainable ")
)
(princ)
)

If the preceding routine was successful, the symbol tcal now contains the list
returned by the tablet function. This list might appear as follows:
(1 (0.00561717 -0.000978942 -7.5171)
(0.000978942 0.00561717 -9.17308)
(0.0 0.0 1.0)
(0.0 0.0 1.0)
)

To reset the calibration to the values retrieved by the preceding routine, you
can use the C:TABSET routine, as follows:
(defun C:TABSET ( )
(if (not (apply ’tablet tcal))
(princ "nUnable to reset calibration. ")
(progn
(princ "nTablet calibration reset. ")
(setvar "tabmode" 1)
(if (= (getvar "tabmode") 0)
(princ "nUnable to turn on tablet mode ")
)
)
)
(princ)
)

The transformation matrix passed as row1, row2, and row3 is a 3×3 transformation matrix that is meant to transform a 2D point. The 2D point is

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expressed as a column vector in homogeneous coordinates (by appending
1.0 as the third element), so the transformation looks like this:
M00 M01 M02

X'
Y'
D'

=

X'

M10 M11 M12

Y'

M20 M21 1.0

1.0

The calculation of a point is similar to the 3D case. AutoCAD transforms the
point by using the following formulas:

X' = M00X + M01Y + M02
Y' = M10X + M11Y + M12
D' = M20X + M21Y + 1.0
To turn the resulting vector back into a 2D point, the first two components
are divided by the third component (the scale factor D’) yielding the point
(X’/D’,Y’/D’).
For projective transformations, the most general case, tablet does the full
calculation. But for affine and orthogonal transformations, M 20 and M 21 are
both 0, so D’ would be 1.0. The calculation of D’ and the division are omitted; the resulting 2D point is simply (X’,Y’).
As the previous paragraph implies, an affine transformation is a special, uniform case of a projective transformation. An orthogonal transformation is a
special case of an affine transformation: not only are M 20 and M 21 zero, but
M 00 = M 11 and M 10 = –M 01.

NOTE When you set a calibration, the list returned does not equal the list provided if the direction isn’t normalized. AutoCAD normalizes the direction vector
before it returns it. Also, it ensures the third element in the third column
(row3 [Z]) is equal to 1. This situation should not arise if you set the calibration
by using values retrieved from AutoCAD by means of tablet. However, it can
happen if your program calculates the transformation itself.


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293

Using AutoLISP to
Manipulate AutoCAD
Objects
In This Chapter

Most AutoLISP functions that handle selection sets and
objects identify a set or an object by the entity name.

10

s Selection Set Handling
s Object Handling
s Extended Data—xdata

For selection sets, which are valid only in the current

s Xrecord Objects

session, the volatility of names poses no problem, but it

s Symbol Table and Dictionary
Access

does for objects because they are saved in the drawing
database. An application that must refer to the same
objects in the same drawing (or drawings) at different
times can use the objects’ handle.
AutoLISP uses symbol tables to maintain lists of graphic
and non-graphic data related to a drawing, such as the
layers, linetypes, and block definitions. Each symbol
table entry has a related entity name and handle and
can be manipulated in a manner similar to the way
other AutoCAD entities are manipulated.

295

Selection Set Handling
AutoLISP provides a number of functions for handling selection sets. For a
complete list of selection set functions, see “Selection Set Manipulation
Functions” in appendix A, “AutoLISP Function Synopsis.”
The ssget function provides the most general means of creating a selection
set. It can create a selection set in one of the following ways:
Explicitly specifying the objects to select, using the Last, Previous, Window, Implied, WPolygon, Crossing, CPolygon, or Fence options
s Specifying a single point
s Selecting the entire database
s Prompting the user to select objects
s

With any option, you can use filtering to specify a list of attributes and conditions that the selected objects must match.

NOTE Selection set and entity names are volatile. That is, they apply only to
the current drawing session.
The first argument to ssget is a string that describes which selection option
to use. The next two arguments, pt1 and pt2, specify point values for the relevant options (they should be left out if they don’t apply). A point list,
pt-list, must be provided as an argument to the selection methods that
allow selection by polygons (that is, Fence, Crossing Polygon, and Window
Polygon). The last argument, filter-list, is optional. If filter-list is supplied, it specifies the list of entity field values used in filtering. For example,
you can obtain a selection set that includes all objects of a given type, on a
given layer, or of a given color. Selection filters are described in more detail
in “Selection Set Filter Lists” on page 298.
See the ssget entry in the AutoLISP Reference for a list of the available selection methods and the arguments used with each.

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The following table shows examples of calls to ssget:

SSGET Examples
Function call
(setq pt1
pt2
pt3
pt4

Effect
'(0.0
'(5.0
'(4.0
'(2.0

0.0
5.0
1.0
6.0

0.0)
0.0)
0.0)
0.0))

Sets pt1, pt2, pt3, and pt4 to point values

(setq ss1 (ssget))

Asks the user for a general object selection and
places those items in a selection set

(setq ss1 (ssget "P"))

Creates a selection set from the most recently
created selection set

(setq ss1 (ssget "L"))

Creates a selection set of the last object added to
the database that is visible on the screen

(setq ss1 (ssget pt2))

Creates a selection set of an object passing
through point (5,5)

(setq ss1 (ssget "W" pt1 pt2)) Creates a selection set of the objects inside the
window from (0,0) to (5,5)
(setq ss1 (ssget "F" (list pt2 Creates a selection set of the objects crossing the
pt3 pt4)))
fence and defined by the points (5,5), (4,1),
and (2,6)
(setq ss1 (ssget "WP" (list
pt1 pt2 pt3)))

Creates a selection set of the objects inside the
polygon defined by the points (0,0), (5,5),
and (4,1)

(setq ss1 (ssget "X"))

Creates a selection set of all objects in the
database

When an application has finished using a selection set, it is important to
release it from memory. You can do this by setting it to nil:
(setq ss1 nil)

Attempting to manage a large number of selection sets simultaneously is not
recommended. An AutoLISP application cannot have more than 128 selection sets open at once. (The limit may be lower on your system.) When the
limit is reached, AutoCAD refuses to create more selection sets. Keep a minimum number of sets open at a time, and set unneeded selection sets to nil


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as soon as possible. If the maximum number of selection sets is reached, you
must call the gc function to free unused memory before another ssget will
work.

Selection Set Filter Lists
An entity filter list is an association list that uses DXF group codes in the
same format as a list returned by entget. (See the DXF Reference for a list of
group codes.) The ssget function recognizes all group codes except entity
names (group –1), handles (group 5), and xdata codes (groups greater than
1000). If an invalid group code is used in a filter-list, it is ignored by
ssget. To search for objects with xdata, use the –3 code as described in
“Filtering for Extended Data” on page 300.
When a filter-list is provided as the last argument to ssget, the function
scans the selected objects and creates a selection set containing the names of
all main entities matching the specified criteria. For example, you can obtain
a selection set that includes all objects of a given type, on a given layer, or of
a given color.
The filter-list specifies which property (or properties) of the entities are
to be checked and which values constitute a match.
The following examples demonstrate methods of using a filter-list with
various object selection options.

SSGET examples using filter lists
Function call
(setq ss1 (ssget '((0 . "TEXT")))
)

Creates a selection set containing all line
objects from the last selection set created.

(setq ss1 (ssget "W" pt1 pt2
'((8 . "FLOOR9")))
)

Creates a selection set of all objects inside
the window that are also on layer
FLOOR9.

(setq ss1 (ssget "X"
'((0 . "CIRCLE")))
)

|

Prompts for general object selection but
adds only text objects to the selection set.

(setq ss1 (ssget "P"
'((0 . "LINE")))
)

298

Effect

Creates a selection set of all objects in the
database that are Circle objects.

Chapter 10


SSGET examples using filter lists (continued)
Function call

Effect

(ssget "I" ‘((0 . "LINE")
(62 . 5)))

Creates a selection set of all blue Line
objects that are part of the Implied
selection set (those objects selected while
PICKFIRST is in effect).
Note that this filter picks up lines that
have been assigned color 5 (blue), but
not blue lines that have had their color
applied by the ByLayer or ByBlock
properties.

If both the code and the desired value are known, the list may be quoted as
shown previously. If either is specified by a variable, the list must be constructed using the list and cons function. For example, the following code
creates a selection set of all objects in the database that are on layer FLOOR3:
(setq lay_name "FLOOR3")
(setq ss1
(ssget "X"
(list (cons 8 lay_name))
)
)

If the filter-list specifies more than one property, an entity is included in
the selection set only if it matches all specified conditions, as in the following
example:
(ssget "X"

(list

(cons 0 "CIRCLE")(cons 8 lay_name)(cons 62 1)))

This code selects only Circle objects on layer FLOOR3 that are colored red.
This type of test performs a Boolean “AND” operation. Additional tests for
object properties are described in “Logical Grouping of Filter Tests” on page
302.
The ssget function filters a drawing by scanning the selected entities and
comparing the fields of each main entity against the specified filtering list. If
an entity’s properties match all specified fields in the filtering list, it is
included in the returned selection set. Otherwise, the entity is not included
in the selection set. The ssget function returns nil if no entities from those
selected match the specified filtering criteria.

NOTE The meaning of certain group codes can differ from entity to entity, and
not all group codes are present in all entities. If a particular group code is specified in a filter, entities not containing that group code are excluded from the
selection set that ssget returns.


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When ssget filters a drawing, the selection set it retrieves might include entities from both paper space and model space. However, when the selection set
is passed to an AutoCAD command, only entities from the space that is currently in effect are used. (The space to which an entity belongs is specified by
the value of its 67 group. Refer to the Customization Guide for further information.)

Wild-Card Patterns in Filter Lists
Symbol names specified in filtering lists can include wild-card patterns. The
wild-card patterns recognized by ssget are the same as those recognized by
the wcmatch function, and are described in “Wild-Card Matching” on page
238, and under “wcmatch” in the AutoLISP Reference.
When filtering for anonymous blocks, you must precede the * character with
a reverse single quotation mark ( `), also known as an escape character,
because the * is read by ssget as a wild-card character. For example, you can
retrieve an anonymous block named *U2 with the following:
(ssget "X" ’((2 . "`*U2")))

Filtering for Extended Data
Using the ssget filter-list, you can select all entities containing extended
data for a particular application. (See “Extended Data—xdata” on page 323.)
To do this, use the –3 group code, as shown in the following example:
(ssget "X" ’((0 . "CIRCLE") (-3 ("APPNAME"))))

This code will select all circles that include extended data for the " APPNAME"
application. If more than one application name is included in the –3 group’s
list, an AND operation is implied and the entity must contain extended data
for all of the specified applications. So, the following statement would select
all circles with extended data for both the " APP1" and "APP2" applications:
(ssget "X" ’((0 . "CIRCLE") (-3 ("APP1")("APP2"))))

Wild-card matching is permitted, so either of the following statements will
select all circles with extended data for either or both of these applications.
(ssget "X" ’((0 . "CIRCLE") (-3 ("APP[12]"))))
(ssget "X" ’((0 . "CIRCLE") (-3 ("APP1,APP2"))))

Relational Tests
Unless otherwise specified, an equivalency is implied for each item in the
filter-list. For numeric groups (integers, reals, points, and vectors), you
can specify other relations by including a special –4 group code that specifies
a relational operator. The value of a –4 group is a string indicating the test
operator to be applied to the next group in the filter-list.

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The following selects all circles with a radius (group code 40) greater than or
equal to 2.0:
(ssget "X" ’((0 . "CIRCLE") (-4 . ">=") (40 . 2.0)))

The possible relational operators are shown in the following table:

Relational operators for selection set filter lists
Operator

Description

"*"

Anything goes (always true)

"="

Equals

"!="

Not equal to

"/="

Not equal to

"<>"

Not equal to

"<"

Less than

"<="

Less than or equal to

">"

Greater than

">="

Greater than or equal to

"&"

Bitwise AND (integer groups only)

"&="

Bitwise masked equals (integer groups only)

The use of relational operators depends on the kind of group you are testing:
All relational operators except for the bitwise operators ("&" and "&=") are
valid for both real- and integer-valued groups.
s The bitwise operators "&" and "&=" are valid only for integer-valued
groups. The bitwise AND, "&", is true if ( (integer_group & filter)
/= 0)—that is, if any of the bits set in the mask are also set in the integer
group. The bitwise masked equals, "&=", is true if ((integer_group &
filter) = filter)—that is, if all bits set in the mask are also set in the
integer_group (other bits might be set in the integer_group but are not
checked).
s For point groups, the X, Y, and Z tests can be combined into a single
string, with each operator separated by commas (for example, ">,>,*"). If
s


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an operator is omitted from the string (for example, "=,<>" leaves out the
Z test), then the “anything goes” operator, "*", is assumed.
s Direction vectors (group type 210) can be compared only with the operators "*", "=", and "!=" (or one of the equivalent “not equal” strings).
s You cannot use the relational operators with string groups; use wild-card
tests instead.

Logical Grouping of Filter Tests
You can also test groups by creating nested Boolean expressions that use the
logical grouping operators shown in the following table:

Grouping operators for selection set filter lists
Starting
operator

Encloses

Ending
operator

"<AND"

One or more operands

"AND>"

"<OR"

One or more operands

"OR>"

"<XOR"

Two operands

"XOR>"

"<NOT"

One operand

"NOT>"

The grouping operators are specified by –4 groups, like the relational operators. They are paired and must be balanced correctly in the filter list or the
ssget call will fail. An example of grouping operators in a filter list follows:
(ssget "X"
’(
(-4 . "<OR")
(-4 . "<AND")
(0 . "CIRCLE")
(40 . 1.0)
(-4 . "AND>")
(-4 . "<AND")
(0 . "LINE")
(8 . "ABC")
(-4 . "AND>")
(-4 . "OR>")
)
)

This code selects all circles with a radius of 1.0 plus all lines on layer " ABC".
The grouping operators are not case-sensitive; for example, you can specify
"and>", "<or", instead of "AND>", "<OR".

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Grouping operators are not allowed within the –3 group. Multiple application names specified in a –3 group use an implied AND operator. If you want
to test for extended data using other grouping operators, specify separate –3
groups and group them as desired. To select all circles having extended data
for either application " APP1" or " APP2" but not both, enter the following:
(ssget "X"
’((0 . "CIRCLE")
(-4 . "<XOR")
(-3 ("APP1"))
(-3 ("APP2"))
(-4 . "XOR>")
)
)

You can simplify the coding of frequently used grouping operators by setting
them equal to a symbol. The previous example could be rewritten as follows
(notice that in this example you must explicitly quote each list):
(setq <xor ’(-4 . "<XOR")
xor> ’(-4 . "XOR>") )
(ssget "X"
(list
’(0 . "CIRCLE")
<xor
’(-3 ("APP1"))
’(-3 ("APP2"))
xor>
)
)

As you can see, this method may not be sensible for short pieces of code but
can be beneficial in larger applications.

Selection Set Manipulation
Once a selection set has been created, you can add entities to it or remove
entities from it with the functions ssadd and ssdel. You can use the ssadd
function to create a new selection set, as shown in the following example.
The following code fragment creates a selection set that includes the first and
last entities in the current drawing (entnext and entlast are described later
in this chapter).
(setq fname (entnext))
(setq lname (entlast))

;
;
;
;

Gets first entity in the
drawing.
Gets last entity in the
drawing.


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303

(if (not fname)
(princ "nNo entities in drawing. ")
(progn
(setq ourset (ssadd fname)) ; Creates a selection set of the
; first entity.
(ssadd lname ourset)
; Adds the last entity to the
; selection set.
)
)

The example runs correctly even if only one entity is in the database (in
which case both entnext and entlast set their arguments to the same entity
name). If ssadd is passed the name of an entity already in the selection set,
it ignores the request and does not report an error. The following function
removes the first entity from the selection set created in the previous
example:
(ssdel fname ourset)

If there is more than one entity in the drawing (that is, if fname and lname
are not equal), then the selection set ourset contains only lname, the last
entity in the drawing.
The function sslength returns the number of entities in a selection set, and
ssmemb tests whether a particular entity is a member of a selection set. Finally,
the function ssname returns the name of a particular entity in a selection set,
using an index to the set (entities in a selection set are numbered from 0).
The following code shows calls to ssname:
(setq sset (ssget))
(setq ent1 (ssname sset 0))
(setq ent4 (ssname sset 3))

;
;
;
;
;
;

Prompts the user to create a
selection set.
Gets the name of the first
entity in sset.
Gets the name of the fourth
entity in sset.

(if (not ent4)
(princ "nNeed to select at least four entities. ")
)
(setq ilast (sslength sset)) ; Finds index of the last entity
; in sset.
; Gets the name of the
; last entity in sset.
(setq lastent (ssname sset (1- ilast)))

Regardless of how entities are added to a selection set, the set never contains
duplicate entities. If the same entity is added more than once, the later additions are ignored. Therefore, sslength accurately returns the number of
distinct entities in the specified selection set.

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Passing Selection Sets between AutoLISP and
ObjectARX Applications
When passing selection sets between AutoLISP and ObjectARX applications,
the following should be observed:
If a selection set is created in AutoLISP and stored in an AutoLISP variable,
then overwritten by a value returned from an ObjectARX application, the
original selection set is eligible for garbage collection (it is freed at the next
automatic or explicit garbage collection).
This is true even if the value returned from the ObjectARX application was
the original selection set. In the following example, if the adsfunc
ObjectARX function returns the same selection set it was fed as an argument,
then this selection set will be eligible for garbage collection even though it is
still assigned to the same variable.
(setq var1 (ssget))
(setq var1 (adsfunc var1))

If you want the original selection set to be protected from garbage collection,
then you must not assign the return value of the ObjectARX application to
the AutoLISP variable that already references the selection set. Changing the
previous example prevents the selection set referenced by var1 from being
eligible for garbage collection.
(setq var1 (ssget))
(setq var2 (adsfunc var1))

Object Handling
AutoLISP provides functions for handling objects. The object-handling functions are organized into two categories: functions that retrieve the entity
name of a particular object, and functions that retrieve or modify entity data.
See “Object-Handling Functions” in appendix A, “AutoLISP Function
Synopsis,” for a complete list of the object-handling functions.

Entity Name Functions
To operate on an object, an AutoLISP application must obtain its entity name
for use in subsequent calls to the entity data or selection set functions. Two
functions described in this section, entsel and nentsel, return not only the
entity’s name but additional information for the application’s use.

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305

Both functions require the AutoCAD user to select an object interactively by
picking a point on the graphics screen. All the other entity name functions
can retrieve an entity even if it is not visible on the screen or if it is on a
frozen layer. The entsel function prompts the user to select an object by
picking a point on the graphics screen, and entsel returns both the entity
name and the value of the point selected. Some entity operations require
knowledge of the point by which the object was selected. Examples from the
set of existing AutoCAD commands include: BREAK, TRIM , and EXTEND. The
nentsel function is described in detail in “Entity Context and Coordinate
Transform Data” on page 307. These functions accept keywords if they are
preceded by a call to initget.
The entnext function retrieves entity names sequentially. If entnext is called
with no arguments, it returns the name of the first entity in the drawing database. If its argument is the name of an entity in the current drawing, entnext
returns the name of the succeeding entity.
The following code fragment illustrates how ssadd can be used in conjunction with entnext to create selection sets and add members to an existing set.
(setq e1 (entnext))
(if (not e1)
; Sets e1 to name of first entity.
(princ "nNo entities in drawing. ")
(progn
(setq ss (ssadd))
; Sets ss to a null selection set.
(ssadd e1 ss)
; Returns selection set ss with
; e1 added.
(setq e2 (entnext e1))
; Gets entity following e1.
(ssadd e2 ss)
; Adds e2 to selection set ss.
)
)

The entlast function retrieves the name of the last entity in the database.
The last entity is the most recently created main entity, so entlast can be
called to obtain the name of an entity that has just been created with a call
to command.
You can set the entity name returned by entnext to the same variable name
passed to this function. This “walks” a single entity name variable through
the database, as shown in the following example:
(setq one_ent (entnext))
(while one_ent
.
.
.
(setq one_ent (entnext one_ent))
)

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; Gets name of first entity.

; Processes new entity.
; Value of one_ent is now nil.


Entity Handles and Their Uses
The handent function retrieves the name of an entity with a specific handle .
As with entity names, handles are unique within a drawing. However, an
entity’s handle is constant throughout its life. AutoLISP applications that
manipulate a specific database can use handent to obtain the current name
of an entity they must use. You can use the DDMODIFY command to get the
handle of a selected object.
The following code fragment uses handent to obtain and display an entity
name.
(if (not (setq e1 (handent "5a2")))
(princ "nNo entity with that handle exists. ")
(princ e1)
)

In one particular editing session, this code fragment might display the
following:

<Entity name: 60004722>
In another editing session with the same drawing, the fragment might
display an entirely different number. But in both cases the code would be
accessing the same entity.
The handent function has an additional use. Entities deleted from the database (with entdel, described in the following section) are not purged until
the current drawing ends. This means that handent can recover the names of
deleted entities, which can then be restored to the drawing by a second call
to entdel.

NOTE Handles are provided for block definitions, including subentities.
Entities in drawings that are cross-referenced by way of XREF Attach are not
actually part of the current drawing; their handles are unchanged but cannot
be accessed by handent. However, when drawings are combined by means of
INSERT, INSERT *, XREF Bind (XBIND), or partial DXFIN, the handles of entities
in the incoming drawing are lost, and incoming entities are assigned new
handle values to ensure each handle in the current drawing remains unique.

Entity Context and Coordinate Transform Data
The nentsel and nentselp functions are similar to entsel, except they
return two additional values to handle entities nested within block
references.

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307

Another difference between these functions is that when the user responds
to a nentsel call by selecting a complex entity or a complex entity is selected
by nentselp, these functions return the entity name of the selected subentity
and not the complex entity’s header, as entsel does.
For example, when the user selects a 3D polyline, nentsel returns a vertex
subentity instead of the polyline header. To retrieve the polyline header, the
application must use entnext to step forward to the seqend subentity, and
then obtain the name of the header from the seqend subentity’s –2 group.
The same applies when the user selects attributes in a nested block reference.
Selecting an attribute within a block reference returns the name of the
attribute and the pick point. When the selected object is a component of a
block reference other than an attribute, nentsel returns a list containing the
following elements:
The selected entity’s name.
A list containing the coordinates of the point used to pick the object.
s The Model to World Transformation Matrix. This is a list consisting of four
sublists, each of which contains a set of coordinates. This matrix can be
used to transform the entity definition data points from an internal coordinate system called the model coordinate system (MCS), to the World
Coordinate System (WCS). The insertion point of the block that contains
the selected entity defines the origin of the MCS. The orientation of the
UCS when the block is created determines the direction of the MCS axes.
s A list containing the entity name of the block that contains the selected
object. If the selected object is in a nested block (a block within a block),
the list also contains the entity names of all blocks in which the selected
object is nested, starting with the innermost block and continuing outward until the name of the block that was inserted in the drawing is
reported.
s
s

The list returned from selecting a block with nentsel is summarized as
follows:
(<Entity Name: ename1>
(Px Py Pz)
( (X0 Y0 Z0)
(X1 Y1 Z1)
(X2 Y2 Z2)
(X3 Y3 Z3)
)
(<Entity name: ename2>
.
.
.
<Entity name: enamen>)
)

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; Name of entity.
; Pick point.
; Model to World Transformation Matrix.

; Name of most deeply nested block
; containing selected object.
; Name of outermost block
; containing selected object.


In the following example, create a block to use with the nentsel function.

Command: line
Specify first point: 1,1
Specify next point or [Undo]: 3,1
Specify next point or [Undo]: 3,3
Specify next point or [Close/Undo]: 1,3
Specify next point or [Close/Undo]: c
Command: -block
Enter block name or [?]: square
Specify insertion base point: 2,2
Select objects: Select the four lines you just drew
Select objects: ENTER
Then, insert the block in a UCS rotated 45 degrees about the Z axis:

Command: ucs
Current ucs name: *WORLD*
Enter option[New/Move/orthoGraphic/Prev/Restore/Save/Del/Apply/?/World]
<World>: z
Specify rotation angle about Z axis <0>: 45
Command: -insert
Enter block name or [?]: square
Specify insertion point or [Scale/X/Y/Z/Rotate/PScale/PX/PY/PZ/PRotate]: 7,0
Enter X scale factor, specify opposite corner, or [Corner/XYZ] <1>: ENTER
Enter Y scale factor <use X scale factor>: ENTER
Specify rotation angle <0>: ENTER
Use nentsel to select the lower-left side of the square.
(setq ndata (nentsel))

This code sets ndata equal to a list similar to the following:
(<Entity Name: 400000a0>
(6.46616 -1.0606 0.0)
((0.707107 0.707107 0.0)
(-0.707107 0.707107 0.0)
(0.0 -0.0 1.0)
(4.94975 4.94975 0.0)
)
(<Entity name:6000001c>)

;
;
;
;

Entity name.
Pick point.
Model to World
Transformation Matrix.

; Name of block containing
; selected object.

)

Once you obtain the entity name and the Model to World Transformation
Matrix, you can transform the entity definition data points from the MCS to
the WCS. Use entget and assoc on the entity name to obtain the definition
points expressed in MCS coordinates. The Model to World Transformation

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309

Matrix returned by nentsel is a 4 × 3 matrix—passed as an array of four
points—that uses the convention that a point is a row rather than a column.
The transformation is described by the following matrix multiplication:

M00 M01 M02
X' Y' Z' 1.0

=

M10 M11 M12

X Y Z 1.0

M20 M21 M22
M30 M31 M32

So the equations for deriving the new coordinates are as follows:

X' = XM00 + YM10 + ZM20 + M30
Y' = XM01 + YM11 + ZM21 + M31
Z' = XM02 + YM12 + ZM22 + M32
The Mij, where 0 ≤ i, j ≤ 2, are the Model to World Transformation Matrix
coordinates; X , Y, Z is the entity definition data point expressed in MCS coordinates, and X ', Y', Z' is the resulting entity definition data point expressed
in WCS coordinates.
To transform a vector rather than a point, do not add the translation vector
(M30 M31 M32 from the fourth column of the transformation matrix).

NOTE This is the only AutoLISP function that uses a matrix of this type. The
nentselp function is preferred to nentsel because it returns a matrix similar to
those used by other AutoLISP and ObjectARX functions.

Using the entity name previously obtained with nentsel, the following
example illustrates how to obtain the MCS start point of a line (group
code 10) contained in a block definition:

Command: (setq edata (assoc 10 (entget (car ndata))))
(10 -1.0 1.0 0.0)

The following statement stores the Model to World Transformation Matrix
sublist in the symbol matrix.

Command: (setq matrix (caddr ndata))
((0.707107 0.707107 0.0)
(-0.707107 0.707107 0.0)
(0.0 -0.0 1.0)
(4.94975 4.94975 0.0)
)

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;
;
;
;

X transformation
Y transformation
Z transformation
Displacement from WCS origin


The following command applies the transformation formula for X ’ to change
the X coordinate of the start point of the line from an MCS coordinate to a
WCS coordinate:
(setq answer
(+
(* (car (nth 0 matrix))(cadr edata))
(* (car (nth 1 matrix))(caddr edata))
(* (car (nth 2 matrix))(cadddr edata))
(car (nth 3 matrix))
)
)

;
;
;
;
;

add:
M00 * X
M10 * Y
M20 * Z
M30

This statement returns 3.53553, the WCS X coordinate of the start point of
the selected line.

Entity Access Functions
The entity access functions are relatively slow. It is best to get the contents of
a particular entity (or symbol table entry) once and keep that information
stored in memory, rather than repeatedly ask AutoCAD for the same data. Be
sure the data remains valid. If the user has an opportunity to alter the entity
or symbol table entry, you should reissue the entity access function to ensure
the validity of the data.

Entity Data Functions
The functions described in this section operate on entity data and can be
used to modify the current drawing database.

Deleting an Entity
The entdel function deletes a specified entity. The entity is not purged from
the database until the end of the current drawing session, so if the application calls entdel a second time during that session and specifies the same
entity, the entity is undeleted.
Attributes and old-style polyline vertices cannot be deleted independently of
their parent entities. The entdel function operates only on main entities. If
you need to delete an attribute or vertex, you can use command to invoke the
AutoCAD ATTEDIT or PEDIT commands.

Obtaining Entity Information
The entget function returns the definition data of a specified entity. The data
is returned as a list. Each item in the list is specified by a DXF group code. The
first item in the list contains the entity’s current name.

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In this example, the following (default) conditions apply to the current
drawing:
Layer is 0
Linetype is CONTINUOUS
s Elevation is 0
s
s

The user has drawn a line with the following sequence of commands:

Command: line
From point: 1,2
To point: 6,6
To point: ENTER
An AutoLISP application can retrieve and print the definition data for the
line by using the following AutoLISP function:
(defun C:PRINTDXF ( )
(setq ent (entlast))
; Set ent to last entity.
(setq entl (entget ent)) ; Set entl to association list of
; last entity.
(setq ct 0)
; Set ct (a counter) to 0.
(textpage)
; Switch to the text screen.
(princ "nentget of last entity:")
(repeat (length entl)
; Repeat for number of members in list:
(print (nth ct entl)) ; Print a newline, then each list
; member.
(setq ct (1+ ct))
; Increments the counter by one.
)
(princ)
; Exit quietly.
)

This would print the following:

entget of last entity:
(-1 . <Entity name: 1bbd1c8>)
(0 . "LINE")
(330 . <Entity name: 1bbd0c8>)
(5 . "69")
(100 . "AcDbEntity")
(67 . 0)
(410 . "Model")
(8 . "0")
(100 . "AcDbLine")
(10 1.0 2.0 0.0)
(11 6.0 6.0 0.0)
(210 0.0 0.0 1.0)

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The –1 item at the start of the list contains the name of the entity. The entmod
function, which is described in this section, uses the name to identify the
entity to be modified. The individual dotted pairs that represent the values
can be extracted by using assoc with the cdr function.
Sublists for points are not represented as dotted pairs like the rest of the values returned. The convention is that the cdr of the sublist is the group’s
value. Because a point is a list of two or three reals, the entire group is a three(or four-) element list. The cdr of the group is the list representing the point,
so the convention that cdr always returns the value is preserved.
The codes for the components of the entity are those used by DXF. As with
DXF, the entity header items (color, linetype, thickness, the attributes-follow
flag, and the entity handle) are returned only if they have values other than
the default. Unlike DXF, optional entity definition fields are returned
whether or not they equal their defaults and whether or not associated X, Y,
and Z coordinates are returned as a single point variable, rather than as separate X (10), Y (20), and Z (30) groups.
All points associated with an object are expressed in terms of that object’s
object coordinate system (OCS). For point, line, 3D line, 3D face,
3D polyline, 3D mesh, and dimension objects, the OCS is equivalent to the
WCS (the object points are World points). For all other objects, the OCS can
be derived from the WCS and the object’s extrusion direction (its 210 group).
When working with objects that are drawn using coordinate systems other
than the WCS, you may need to convert the points to the WCS or to the current UCS by using the trans function.
When writing functions to process entity lists, make sure the function logic
is independent of the order of the sublists; use assoc to guarantee this. The
assoc function searches a list for a group of a specified type. The following
code returns the object type " LINE" (0) from the list entl.
(cdr (assoc 0 entl))

If the DXF group code specified is not present in the list (or if it is not a valid
DXF group), assoc returns nil.

WARNING! Before performing an entget on vertex entities, you should read
or write the polyline entity’s header. If the most recently processed polyline
entity is different from the one to which the vertex belongs, width information
(the 40 and 41 groups) can be lost.

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Modifying an Entity
The entmod function modifies an entity. It passes a list that has the same format as a list returned by entget but with some of the entity group values
(presumably) modified by the application. This function complements
entget. The primary mechanism by which an AutoLISP application updates
the database is by retrieving an entity with entget, modifying its entity list,
and then passing the list back to the database with entmod.
The following code fragment retrieves the definition data of the first entity
in the drawing and changes its layer property to MYLAYER.
(setq en (entnext))
(setq ed (entget en))

;
;
;
;

Sets en to first entity name
in the drawing.
Sets ed to the entity data
for entity name en.

(setq ed
(subst (cons 8 "MYLAYER")
(assoc 8 ed)
; Changes the layer group in ed.
ed
; to layer MYLAYER.
)
)
(entmod ed)
; Modifies entity en’s layer in
; the drawing.

There are restrictions on the changes to the database that entmod can make;
entmod cannot change the following:
The entity’s type or handle.
Internal fields. (Internal fields are the values that AutoCAD assigns to certain group codes: –2, entity name reference; –1, entity name; 5, entity
handle.) Any attempt to change an internal field—for example, the main
entity name in a seqend subentity (group –2)—is ignored.
s Viewport entities. An attempt to change a viewport entity causes an error.
s
s

Other restrictions apply when modifying dimensions and hatch patterns.
AutoCAD must recognize all objects (except layers) that the entity list refers
to. The name of any text style, linetype, shape, or block that appears in an
entity list must be defined in the current drawing before the entity list is
passed to entmod. There is one exception: entmod accepts new layer names.

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If the entity list refers to a layer name that has not been defined in the
current drawing, entmod creates a new layer. The attributes of the new layer
are the standard default values used by the New option of the AutoCAD
LAYER command.
The entmod function can modify subentities such as polyline vertices and
block attributes.
If you use entmod to modify an entity in a block definition, this affects all
INSERT or XREF references to that block. Also, entities in block definitions

cannot be deleted by entdel.

Adding an Entity to a Drawing
An application can add an entity to the drawing database by calling the
entmake function. Like that of entmod, the argument to entmake is a list
whose format is similar to that returned by entget. The new entity that the
list describes is appended to the drawing database (it becomes the last entity
in the drawing). If the entity is a complex entity (an old-style polyline or a
block), it is not appended to the database until it is complete.
The following code fragment creates a circle on the MYLAYER layer:
(entmake '((0 . "CIRCLE")
(8 . "MYLAYER")
(10 5.0 7.0 0.0)
(40 . 1.0)
) )

;
;
;
;

Object type
Layer
Center point
Radius

The following entmake restrictions apply to all entities:
The first or second member in the list must specify the entity type. The
type must be a valid DXF group code. If the first member does not specify
the type, it can specify only the name of the entity: group –1 (the name is
not saved in the database).
s AutoCAD must recognize all objects that the entity list refers to. There is
one exception: entmake accepts new layer names.
s Any internal fields passed to entmake are ignored.
s entmake cannot create viewport entities.
s

For entity types introduced in AutoCAD Release 13 and later releases, you
must also specify subclass markers (DXF group code 100) when creating the
entity. All AutoCAD entities have the AcDbEntity subclass marker, and this
must be explicitly included in the entmake list. In addition, one or more
subclass marker entries are required to identify the specific sub-entity type.

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315

These entries must follow group code 0 and must precede group codes that
are specifically used to define entity properties in the entmake list. For
example, the following is the minimum code required to entmake an MTEXT
entity:
(entmake '(
(0 . "MTEXT")
(100 . "AcDbEntity")
(8 . "ALAYER")
(100 . "AcDbMText")
(10 4.0 4.0 0.0)
(1 . "SomePtext")
)
)

; Required for all post-R12 entities.
; Identifies the entity as MTEXT.

The following table identifies the entities that do not require subentity
marker entries in the list passed to entmake:

DXF names of entities introduced prior to AutoCAD Release 13
3DFACE

ARC

ATTDEF

ATTRIB

CIRCLE

DIMENSION

INSERT

LINE

POINT

POLYLINE (old-style)

SEQEND

SHAPE

SOLID

TEXT

TRACE

VERTEX

VIEWPORT

The entmake function verifies that a valid layer name, linetype name, and
color are supplied. If a new layer name is introduced, entmake automatically
creates the new layer. The entmake function also checks for block names,
dimension style names, text style names, and shape names, if the entity type
requires them. The function fails if it cannot create valid entities. Objects created on a frozen layer are not regenerated until the layer is thawed.

Creating Complex Entities
To create a complex entity (an old-style polyline or a block), you make multiple calls to entmake, using a separate call for each subentity. When entmake

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first receives an initial component for a complex entity, it creates a temporary file in which to gather the definition data and extended data, if present.
(See “Extended Data—xdata” on page 323.) For each subsequent entmake
call, the function checks if the temporary file exists. If it does, the new subentity is appended to the file. When the definition of the complex entity is
complete (that is, when entmake receives an appropriate seqend or endblk
subentity), the entity is checked for consistency; if valid, it is added to the
drawing. The file is deleted when the complex entity is complete or when its
creation has been canceled.
No portion of a complex entity is displayed on your drawing until its definition is complete. The entity does not appear in the drawing database until
the final seqend or endblk subentity has been passed to entmake. The
entlast function cannot retrieve the most recently created subentity for a
complex entity that has not been completed. You can cancel the creation of
a complex entity by entering entmake with no argum ents. This clears the
temporary file and returns nil.
As the previous paragraphs imply, entmake can construct only one complex
entity at a time. If a complex entity is being created and entmake receives
invalid data or an entity that is not an appropriate subentity, both the invalid
entity and the entire complex entity are rejected. You can explicitly cancel
the creation of a complex entity by calling entmake with no arguments.
The following example contains five entmake functions that create a single
complex entity, an old-style polyline. The polyline has a linetype of DASHED
and a color of BLUE. It has three vertices located at coordinates (1,1,0),
(4,6,0), and (3,2,0). All other optional definition data assume default values.
(For this example to work properly, the linetype DASHED must be loaded.)
(entmake '((0 . "POLYLINE")
(62 . 5)
(6 . "dashed")
(66 . 1)
) )
(entmake '((0 . "VERTEX")
(10 1.0 1.0 0.0)
) )
(10 4.0 6.0 0.0)
) )
(10 3.0 2.0 0.0)
) )
(entmake '((0 . "SEQEND")))

;
;
;
;

Object type
Color
Linetype
Vertices follow

; Object type
; Start point
; Object type
; Second point
; Object type
; Third point
; Sequence end

When defining dotted pairs, as in the above example, there must be a space
on both sides of the dot. Otherwise, you will get an invalid dotted pair error
message.

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317

Block definitions begin with a block entity and end with an endblk subentity.
Newly created blocks are automatically entered into the symbol table where
they can be referenced. Block definitions cannot be nested, nor can they reference themselves. A block definition can contain references to other block
definitions.

NOTE Before you use entmake to create a block, you should use tblsearch to
ensure that the name of the new block is unique. The entmake function does not
check for name conflicts in the block definitions table, so it can redefine existing
blocks. See “Symbol Table and Dictionary Access” on page 332 for information
on using tblsearch.
Block references can include an attributes-follow flag (group 66). If present
and equal to 1, a series of attribute (attrib) entities is expected to follow the
insert object. The attribute sequence is terminated by a seqend subentity.
Old-style polyline entities always include a vertices-follow flag (also group
66). The value of this flag must be 1, and the flag must be followed by a
sequence of vertex entities, terminated by a seqend subentity.
Applications can represent polygons with an arbitrarily large number of sides
in polyface meshes. However, the AutoCAD entity structure imposes a limit
on the number of vertices that a given face entity can specify. You can represent more complex polygons by dividing them into triangular wedges.
AutoCAD represents triangular wedges as four-vertex faces where two adjacent vertices have the same value. Their edges should be made invisible to
prevent visible artifacts of this subdivision from being drawn. The PFACE
command performs this subdivision automatically, but when applications
generate polyface meshes directly, the applications must do this themselves.
The number of vertices per face is the key parameter in this subdivision
process. The PFACEVMAX system variable provides an application with the
number of vertices per face entity. This value is read-only and is set to 4.
Complex entities can exist in either model space or paper space, but not
both. If you have changed the current space by invoking either MSPACE or
PSPACE (with command) while a complex entity is being constructed, a subsequent call to entmake cancels the complex entity. This can also occur if the
subentity has a 67 group whose value does not match the 67 group of the
entity header.

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Working with Blocks
There is no direct method for an application to check whether a block listed
in the BLOCK table is actually referenced by an insert object in the drawing.
You can use the following code to scan the drawing for instances of a block
reference:
(ssget "x" '((2 . "BLOCKNAME")) )

You must also scan each block definition for instances of nested blocks.

Anonymous Blocks
The block definitions ( BLOCK) table in a drawing can contain anonymous
blocks (also known as unnamed blocks), which AutoCAD creates to support
hatch patterns and associative dimensioning. The entmake function can create anonymous blocks other than *Dnnn (dimensions) and *Xnnn (hatch
patterns). Unreferenced anonymous blocks are purged from the BLOCK definition table when a drawing is opened. Referenced anonymous blocks (those
that have been inserted) are not purged. You can use entmake to create a block
reference (insert object) to an anonymous block. (You cannot pass an anonymous block to the INSERT command.) Also, you can use entmake to redefine
the block. You can modify the entities in a block (but not the block object
itself) with entmod.
The name (group 2) of an anonymous block created by AutoLISP or
ObjectARX has the form *Unnn, where nnn is a number generated by
AutoCAD. Also, the low-order bit of an anonymous block’s block type flag
(group 70) is set to 1. When entmake creates a block whose name begins with
* and whose anonymous bit is set, AutoCAD treats this as an anonymous
block and assigns it a name. Any characters following the * in the name
string passed to entmake are ignored.

NOTE Anonymous block names do not remain constant. Although a referenced anonymous block becomes permanent, the numeric portion of its name
can change between drawing sessions.

Entity Data Functions and the Graphics Screen
Changes to the drawing made by the entity data functions are reflected on
the graphics screen, provided the entity being deleted, undeleted, modified,
or made is in an area and on a layer that is currently visible. There is one
exception: When entmod modifies a subentity, it does not update the image
of the entire (complex) entity. If, for example, an application modifies
100 vertices of an old-style polyline with 100 calls to entmod, the time

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319

required to recalculate and redisplay the entire polyline is unacceptably slow.
Instead, an application can perform a series of subentity modifications, and
then redisplay the entire entity with a single call to the entupd function.
Consider the following: If the first entity in the current drawing is an oldstyle polyline with several vertices, the following code modifies the second
vertex of the polyline and regenerates its screen image.
(setq e1 (entnext))
(setq v1 (entnext e1))
(setq v2 (entnext v1))
(setq v2d (entget v2))
(setq v2d
(subst
’(10 1.0 2.0 0.0)
(assoc 10 v2d)
v2d
)
)
(entmod v2d)
(entupd e1)

;
;
;
;

Sets
Sets
Sets
Sets

e1 to the polyline’s entity name.
v1 to its first vertex.
v2 to its second vertex.
v2d to the vertex data.

; Changes the vertex’s location in v2d
; to point (1,2,0).
; Moves the vertex in the drawing.
; Regenerates the polyline entity e1.

The argument to entupd can specify either a main entity or a subentity. In
either case, entupd regenerates the entire entity. Although its primary use is
for complex entities, entupd can regenerate any entity in the current
drawing.

NOTE To ensure that all instances of the block references are updated, you
must regenerate the drawing by invoking the AutoCAD REGEN command (with
command). The entupd function is not sufficient if the modified entity is in a block
definition.

Old-Style Polylines and Lightweight Polylines
A lightweight polyline (lwpolyline) is defined in the drawing database as a
single graphic entity. The lwpolyline differs from the old-style polyline,
which is defined as a group of subentities. Lwpolylines display faster and
consume less disk space and RAM.
As of Release 14 of AutoCAD, 3D polylines are always created as old-style
polyline entities, and 2D polylines are created as lwpolyline entities, unless
they are curved or fitted with the PEDIT command. When a drawing from an
earlier release is opened in Release 14 or a later release, all 2D polylines convert to lwpolylines automatically, unless they have been curved or fitted or
contain xdata.

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Processing Curve-Fit and Spline-Fit Polylines
When an AutoLISP application uses entnext to step through the vertices of
an old-style polyline, it might encounter vertices that were not created
explicitly. Auxiliary vertices are inserted automatically by the PEDIT command’s Fit and Spline options. You can safely ignore them, because changes
to these vertices will be discarded the next time the user applies PEDIT to fit
or to spline the polyline.
The old-style polyline entity’s group 70 flags indicate whether the polyline
has been curve-fit (bit value 2) or spline-fit (bit value 4). If neither bit is set,
all the polyline’s vertices are regular user-defined vertices. However, if the
curve-fit bit (2) is set, alternating vertices of the polyline have the bit value 1
set in their 70 group to indicate that they were inserted by the curve-fitting
process. If you use entmod to move the vertices of such a polyline with the
intent of refitting the curve by means of PEDIT, ignore these vertices.
Likewise, if the old-style polyline entity’s spline-fit flag bit (bit 4) is set, an
assortment of vertices will be found—some with flag bit 1 (inserted by curve
fitting if system variable SPLINESEGS was negative), some with bit value 8
(inserted by spline fitting), and all others with bit value 16 (spline framecontrol point). Here again, if you use entmod to move the vertices and you
intend to refit the spline afterward, move only the control-point vertices.

Non-Graphic Object Handling
AutoCAD uses two types of non-graphic objects: dictionary objects and symbol table objects. Although there are similarities between these object types,
they are handled differently.
All object types are supported by the entget, entmod, entdel, and entmake
functions, although object types individually dictate their participation in
these functions and may refuse any or all processing. With respect to
AutoCAD built-in objects, the following rules apply. (All rules and restrictions that apply to graphic objects apply to non-graphic objects as well.)
Non-graphic objects cannot be passed to the entupd function.
When using entmake, the object type determines where the object will reside.
For example, if a layer object is passed to entmake, it automatically goes to
the layer symbol table. If a graphic object is passed to entmake, it will reside
in the current space (model or paper).

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321

Symbol Table Objects
The following rules apply to symbol tables:
s

s
s

s
s
s

Symbol table entries can be created through entmake with few restrictions,
other than being valid record representations, and name conflicts can
only occur in the VPORT table. *ACTIVE entries cannot be created.
Symbol table entries cannot be deleted with entdel.
Symbol table and symbol table entry object states may be accessed with
entget by passing the entity name. The tblobjname function can be used
to retrieve the entity name of a symbol table entry.
Symbol tables themselves cannot be created with entmake, however,
symbol table entries can be created with entmake.
Handle groups (5, 105) may not be changed in entmod, nor specified in
entmake.
Symbol table entries that are not in the APPID table can have many of
their fields modified with entmod. To be passed to entmod, a symbol table
record list must include its entity name, which can be obtained from
entget but not from the tblsearch and tblnext functions. The 70 group
of symbol table entries is ignored in entmod and entmake operations.

Renaming symbol table entries to duplicate names is not acceptable, except
for the VPORT symbol table. The following entries may not be modified or
renamed, except that most LAYER entries can be renamed and xdata can be
modified on all symbol table entries.

Symbol table entries that cannot be modified or renamed
Table
VPORT

CONTINUOUS

LAYER

|

*ACTIVE

LINETYPE

322

Entry name

Entries may not be modified, except for xdata, but renaming is
allowed

Chapter 10


The following entries may not be renamed but are otherwise modifiable, subject to restriction:

Symbol table entries that cannot be renamed
Table

Entry name

STYLE

STANDARD

DIMSTYLE

STANDARD

BLOCKS

*MODEL_SPACE

BLOCKS

*PAPER_SPACE

APPID

No entries may be renamed

Dictionary Objects
The following rules apply to dictionary objects:
Dictionary objects can be examined with entget and their xdata modified
with entmod. Their entries cannot be altered with entmod. All access to
their entries are made through the dictsearch and dictnext functions.
s Dictionary entry contents cannot be modified through entmod, although
xdata can be modified.
s Dictionary entries that begin with ACAD* cannot be renamed.
s

Extended Data—xdata
Several AutoLISP functions are provided to handle extended data (xdata),
which is created by applications written with ObjectARX or AutoLISP. If an
entity contains xdata, it follows the entity’s regular definition data.
You can retrieve an entity’s extended data by calling entget. The entget
function retrieves an entity’s regular definition data and the xdata for those
applications specified in the entget call.
When xdata is retrieved with entget, the beginning of extended data is indicated by a –3 code. The –3 code is in a list that precedes the first 1001 group.


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323

The 1001 group contains the application name of the first application
retrieved, as shown in the table and as described in the following sections.

Group codes for regular and extended data
Group code

Field

Type of data

(–1, –2
(0–239

Entity name)
Regular definition data fields)
.
.
.

Normal entity
definition data

Extended data sentinel
Registered application name 1)

Extended data

)
(–3
(1001
(1000,
1002–1071

(1001
(1000,
1002–1071

(1001

XDATA fields)
.
.
.
XDATA fields)
.
.
.
.
.

Organization of Extended Data
Extended data consists of one or more 1001 groups, each of which begins
with a unique application name. The xdata groups returned by entget follow
the definition data in the order in which they are saved in the database.
Within each application’s group, the contents, meaning, and organization of
the data are defined by the application. AutoCAD maintains the information
but does not use it. The table also shows that the group codes for xdata are
in the range 1000–1071. Many of these group codes are for familiar data
types, as follows:

String
Application
Name

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|

1000. Strings in extended data can be up to 255 bytes long
(with the 256th byte reserved for the null character).
1001 (also a string value). Application names can be up to
31 bytes long (the 32nd byte is reserved for the null
character) and must adhere to the rules for symbol table

Chapter 10


names (such as layer names). An application name can
contain letters, digits, and the special characters $ (dollar
sign), - (hyphen), and _ (underscore). It cannot contain
spaces.

Layer Name

1003. Name of a layer associated with the xdata.

Database
Handle

1005. Handle of an entity in the drawing database.

3D Point

1010. Three real values, contained in a point.

Real

1040. A real value.

Integer

1070. A 16-bit integer (signed or unsigned).

Long

1071. A 32-bit signed (long) integer. If the value that
appears in a 1071 group is a short integer or real value, it
is converted to a long integer; if it is invalid (for example,
a string), it is converted to a long zero ( 0L).

NOTE AutoLISP manages 1071 groups as real values. If you
use entget to retrieve an entity’s definition list that contains
a 1071 group, the value is returned as a real, as shown in the
following example:
(1071 . 12.0)
If you want to create a 1071 group in an entity with
entmake or entmod, you can use either a real or an integer
value, as shown in the following example:
(entmake
(entmake
(entmake
(entmake

’((.....
’((.....
’((.....
’((.....

(1071
(1071
(1071
(1071

.
.
.
.

12) .... )))
12.0) .... )))
65537.0) .... )))
65537) .... )))

But AutoLISP still returns the group value as a real:
(entmake ’((..... (1071 . 65537) .... )))

The preceding statement returns the following:
(1071 . 65537.0)

ObjectARX always manages 1071 groups as long integers.


|

325

Several other extended data groups have special meanings in this context (if
the application chooses to use them):

Control String

1002. An xdata control string can be either "{" or "}".
These braces enable the application to organize its data by
subdividing it into lists. The left brace begins a list, and
the right brace terminates the most recent list. Lists can be
nested.

NOTE If a 1001 group appears within a list, it is treated as a
string and does not begin a new application group.
Binary Data

1004. Binary data that is organized into variable-length
chunks, which can be handled in ObjectARX with the
ads_binary structure. The maximum length of each
chunk is 127 bytes.

NOTE AutoLISP cannot directly handle binary chuncks, so
the same precautions that apply to long (1071) groups apply
to binary groups as well.
World Space
Position

1011. Unlike a simple 3D point, the WCS coordinates are
moved, scaled, rotated, and mirrored along with the
parent entity to which the extended data belongs. The
WCS position is also stretched when the STRETCH
command is applied to the parent entity and when this
point lies within the select window.

World Space
Displacement

1012. A 3D point that is scaled, rotated, or mirrored along
with the parent, but not stretched or moved.

World
Direction

1013. A 3D point that is rotated or mirrored along with
the parent, but not scaled, stretched, or moved. The WCS
direction is a normalized displacement that always has a
unit length.

Distance

1041. A real value that is scaled along with the parent
entity.

Scale Factor

1042. Also a real value that is scaled along with the parent.

The DXF group codes for xdata are also described in the DXF Reference.

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Registration of an Application
To be recognized by AutoCAD, an application must register the name or
names that it uses. Application names are saved with the extended data of
each entity that uses them, and also in the APPID table. Registration is done
with the regapp function, which specifies a string to use as an application
name. If it successfully adds the name to APPID, it returns the nam e of the
application; otherwise it returns nil. A result of nil indicates that the name
is already present in the symbol table. This is not an actual error condition
but an expected return value, because the application name needs to be registered only once per drawing.
To register itself, an application should first check that its name is not already
in the APPID table. If the name is not there, the application must register it.
Otherwise, it can simply go ahead and use the data, as described later in this
section.
The following fragment shows the typical use of regapp. (The tblsearch
function is described in “Symbol Table and Dictionary Access” on page 332.)
(setq appname "MYAPP_2356")
; Unique application name.
(if (tblsearch "appid" appname)
; Checks if already registered.
(princ (strcat
"n" appname " already registered. "))
(if (= (regapp appname) nil)
; Some other problem.
(princ (strcat
"nCan’t register XDATA for " appname ". "))
)
)

The regapp function provides a measure of security, but it cannot guarantee
that two separate applications have not chosen the same name. One way of
ensuring this is to adopt a naming scheme that uses the company or product
name and a unique number (like your telephone number or the current date
and time).

Retrieval of Extended Data
An application can call entget to obtain the xdata that it has registered. The
entget function can return both the definition data and the xdata for the
applications it requests. It requires an additional argument, application,
that specifies the application names. The names passed to entget must correspond to applications registered by a previous call to regapp; they can also
contain wild-card characters.


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By default, associative hatch patterns contain extended data. The following
code shows the association list of this xdata.

Command: (entget (car (entsel)) ’("ACAD"))
Select object: Select an associative hatch
Entering the preceding code at the command line returns a list that looks
something like this:

((-1 . <Entity name: 600000c0>) (0 . "INSERT") (8 . "0") (2 . "*X0")
(10 0.0 0.0 0.0) (41 . 1.0) (42 . 1.0) (50 . 0.0) (43 . 1.0) (70 . 0) (71 . 0)
(44 . 0.0) (45 . 0.0) (210 0.0 0.0 1.0) (-3 ("ACAD" (1000 . "HATCH")
(1002 . "{") (1070 . 16) (1000 . "LINE") (1040 . 1.0) (1040 . 0.0)
(1002 . "}"))))
This fragment shows a typical sequence for retrieving xdata for two specified
applications. Note that the application argument passes application names
in list form:
(setq working_elist
(entget ent_name
’("MY_APP_1" "SOME_OTHER")
)
)
(if working_elist
(progn
...
(entmod working_elist)
)
)

; Only xdata from "MY_APP_1"
; and "SOME_OTHER" is retrieved.

;
;
;
;

Updates working entity groups.
Only xdata from registered
applications still in the
working_elist list are modified.

As the sample code shows, you can modify xdata retrieved by entget by
using a subsequent call to entmod, just as you can use entmod to modify
normal definition data. You can also create xdata by defining it in the entity
list passed to entmake.
Returning the extended data of only those applications specifically requested
protects one application from corrupting another application’s data. It also
controls the amount of memory that an application needs to use and simplifies the xdata processing that an application needs to perform.

NOTE Because the strings passed by application can include wild-card characters, an application name of "*" will cause entget to return all extended data
attached to an entity.

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Attachment of Extended Data to an Entity
You can use xdata to store any type of information you want. For example,
draw an entity (such as a line or a circle), then enter the following code to
attach xdata to the entity:
(setq lastent (entget (entlast)))

; Gets the association
; list of definition data
; for the last entity.
(regapp "NEWDATA")
; Registers the
; application name.
(setq exdata
; Sets the variable
’((-3 ("NEWDATA"
; exdata equal to the
(1000 . "This is a new thing!") ; new extended data—
)))
; in this case, a text
)
; string.
(setq newent
(append lastent exdata)) ; Appends new data list to
; entity’s list.
(entmod newent)
; Modifies the entity with the new
; definition data.

To verify that your new xdata has been attached to the entity, enter the following code and select the object:
(entget (car (entsel)) ’("NEWDATA"))

This example shows the basic method for attaching extended data to an
entity.

Management of Extended Data Memory Use
Extended data is currently limited to 16K per entity. Because the xdata of an
entity can be created and maintained by multiple applications, problems can
result when the size of the xdata approaches its limit. AutoLISP provides two
functions, xdsize and xdroom, to assist in managing the memory that xdata
occupies. When xdsize is passed a list of xdata, it returns the amount of
memory (in bytes) that the data will occupy. When xdroom is passed the
name of an entity, it returns the remaining number of free bytes that can still
be appended to the entity.
The xdsize function reads an extended data list, which can be large. This
function can be slow, so it is not recommended that you call it frequently. A
better approach is to use it (in conjunction with xdroom) in an error handler.
If a call to entmod fails, you can use xdsize and xdroom to find out whether
the call failed because the entity didn’t have enough room for the xdata.


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Handles in Extended Data
Extended data can contain handles (group 1005) to save relational structures
within a drawing. One entity can reference another by saving the other’s
handle in its xdata. The handle can be retrieved later from xdata and then
passed to handent to obtain the other entity. Because more than one entity
can reference another, xdata handles are not necessarily unique. The AUDIT
command does require that handles in extended data either be NULL or valid
entity handles (within the current drawing). The best way to ensure that
xdata entity handles are valid is to obtain a referenced entity’s handle
directly from its definition data by means of entget. The handle value is in
group 5.
When you reference entities in other drawings (for example, entities that are
attached with XREF), you can avoid protests from AUDIT by using extended
entity strings (group 1000) rather than handles (group 1005). The handles of
cross-referenced entities are either not valid in the current drawing, or they
conflict with valid handles. However, if an XREF Attach changes to an XREF
Bind or is combined with the current drawing in some other way, it is up to
the application to revise the entity references accordingly.
When drawings are combined by means of INSERT, INSERT*, XREF Bind
(XBIND), or partial DXFIN, handles are translated so they become valid in the
current drawing. (If the incoming drawing did not employ handles, new ones
are assigned.) Extended entity handles that refer to incoming entities are also
translated when these commands are invoked.
When an entity is placed in a block definition (with the BLOCK command),
the entity within the block is assigned new handles. (If the original entity is
restored by means of OOPS, it retains its original handles.) The value of any
xdata handles remains unchanged. When a block is exploded (with the
EXPLODE command), xdata handles are translated in a manner similar to the
way they are translated when drawings are combined. If the xdata handle
refers to an entity that is not within the block, it is unchanged. However, if
the xdata handle refers to an entity that is within the block, the data handle
is assigned the value of the new (exploded) entity’s handle.

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Xrecord Objects
Xrecord objects are used to store and manage arbitrary data. They are composed of DXF group codes with normal object groups (that is, non-xdata
group codes), ranging from 1 through 369 for supported ranges. This object
is similar in concept to xdata but is not limited by size or order.
Xrecord objects are designed to work in such a way as not to offend releases
R13c0 through R13c3. However, if read into a pre-R13c4 level of AutoCAD,
xrecord objects disappear.
The following examples provide methods for creating and listing xrecord
data.
(defun C:MAKEXRECORD( / xrec xname )
; create the xrecord’s data list.
(setq xrec ‘((0 . "XRECORD")(100 . "AcDbXrecord")
(1 . "This is a test xrecord list")
(10 1.0 2.0 0.0) (40 . 3.14159) (50 . 3.14159)
(62 . 1) (70 . 180))
)
; use entmakex to create the xrecord with no owner.
(setq xname (entmakex xrec))
; add the new xrecord to the named object dictionary.
(dictadd (namedobjdict) "XRECLIST" xname)
(princ)
)
(defun C:LISTXRECORD ( / xlist )
; find the xrecord in the named object dictionary.
(setq xlist (dictsearch (namedobjdict) "XRECLIST"))
; print out the xrecord’s data list.
(princ xlist)
(princ)
)

Xrecord Objects

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Symbol Table and Dictionary Access
AutoLISP provides functions for accessing symbol table and dictionary
entries. Examples of the tblnext and tblsearch functions are provided in
the following sections. For a complete list of the symbol table and dictionary
access functions, see “Symbol Table and Dictionary-Handling Functions” in
appendix A, “AutoLISP Function Synopsis.” Refer to the AutoLISP Reference
for more detailed information on the functions listed in the Synopsis.
For additional information on non-graphic objects see, “Non-Graphic Object
Handling” on page 321.

Symbol Tables
Symbol table entries can also be manipulated by the following functions:
s
s
s
s
s

entdel
entget
entmake
entmod
handent

The tblnext function sequentially scans symbol table entries, and the
tblsearch function retrieves specific entries. Table names are specified by
strings. The valid names are LAYER, LTYPE, VIEW, STYLE, BLOCK, UCS, VPORT,
DIMSTYLE, and APPID. Both functions return lists with DXF group codes that
are similar to the entity data returned by entget.
The first call to tblnext returns the first entry in the specified table. Subsequent calls that specify the same table return successive entries, unless the
second argument to tblnext ( rewind) is nonzero, in which case tblnext
returns the first entry again.
In the following example, the function GETBLOCK retrieves the symbol table
entry for the first block (if any) in the current drawing, and then displays it
in a list format.
(defun C:GETBLOCK (/ blk ct)
(setq blk (tblnext "BLOCK" 1)) ;
(setq ct 0)
;
(textpage)
;
(princ "nResults from GETBLOCK:

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Gets the first BLOCK entry.
Sets ct (a counter) to 0.
Switches to the text screen.
")


(repeat (length blk)
(print (nth ct blk))
(setq ct (1+ ct))
)
(princ)

;
;
;
;
;

Repeats for the number of
members in the list.
Prints a new line, then
each list member.
Increments the counter by 1.

; Exits quietly.

)

Entries retrieved from the BLOCK table contain a –2 group that contains the
name of the first entity in the block definition. If the block is empty, this is
the name of the block’s ENDBLK entity, which is never seen on occupied
blocks. In a drawing with a single block named BOX, a call to GETBLOCK
displays the following. (The name value varies from session to session.)

Results from GETBLOCK:
(0 . "BLOCK")
(2 . "BOX")
(70 . 0)
(10 9.0 2.0 0.0)
(–2 . <Entity name: 40000126>)
As with tblnext, the first argument to tblsearch is a string that names a
table, but the second argument is a string that names a particular symbol in
the table. If the symbol is found, tblsearch returns its data. This function
has a third argument, setnext, that you can use to coordinate operations
with tblnext. If setnext is nil, the tblsearch call has no effect on tblnext,
but if setnext is non-nil, the next call to tblnext returns the table entry following the entry found by tblsearch.
The setnext option is useful when you are handling the VPORT symbol table,
because all viewports in a particular viewport configuration have the same
name (such as *ACTIVE).
If the VPORT symbol table is accessed when TILEMODE is turned off, any
changes have no visible effect until TILEMODE is turned on. Do not confuse
VPORTS, which is described by the VPORT symbol table with paper space viewport entities.
The following processes all viewports in the 4VIEW configuration:
(setq v (tblsearch "VPORT" "4VIEW" T)) ; Finds first VPORT entry.
(while (and v (= (cdr (assoc 2 v)) "4VIEW"))
.
.
; ... Processes entry ...
.
(setq v (tblnext "VPORT"))
; Gets next VPORT entry.
)

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Dictionary Entries
A dictionary is a container object, similar to the symbol tables in functions.
Dictionary entries can be queried with the dictsearch and dictnext functions. Each dictionary entry consists of a text name key plus a hard ownership handle reference to the entry object. Dictionary entries may be removed
by directly passing entry object names to the entdel function. The text name
key uses the same syntax and valid characters as symbol table names.

Accessing AutoCAD Groups
The following is an example of one method for accessing the entities
contained in a group. This example assumes a group named G1 exists in the
current drawing.
(setq objdict (namedobjdict))
(setq grpdict (dictsearch objdict "ACAD_GROUP"))

This sets the grpdict variable to the entity definition list of the
ACAD_GROUP dictionary and returns the following:

((-1 . <Entity name: 8dc10468>) (0 . "DICTIONARY") (5 . "D")
(102 . "{ACAD_REACTORS") (330 . <Entity name: 8dc10460>)
(102 . "}") (100 . "AcDbDictionary") (3 . "G1")
(350 . <Entity name: 8dc41240>))
The following code sets the variable group1 to the entity definition list of the
G1 group:
(setq group1 (dictsearch (cdar grpdict) "G1"))

It returns the following:

((-1 . <Entity name: 8dc10518>) (0 . "GROUP") (5 . "23")
(102 . "{ACAD_REACTORS") (330 . <Entity name: 8dc10468>)
(102 . "}") (100 . "AcDbGroup") (300 . "line and circle") (70 . 0) (71 . 1)
(340 . <Entity name: 8dc10510>)(340 . <Entity name: 8dc10550>) )
The 340 group codes are the entities that belong to the group.

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Part 3
Working with
Programmable Dialog
Boxes

335


11

In This Chapter

Dialog boxes are defined by ASCII files written in dialog

s Dialog Box Components

control language (DCL). The elements in a dialog box,

s Using DCL to Define Dialog
Boxes

such as buttons and edit boxes, are known as tiles. The

s Displaying Dialog Boxes with
Visual LISP

size and functionality of each tile is controlled by the

s Adjusting the Layout of Dialog
Boxes

tile’s attributes. The size of the dialog box and the layout

s Design Guidelines

of its parts are set automatically with a minimum of
positioning information. VLISP provides a tool for viewing dialog boxes, and provides functions for controlling
dialog boxes from application programs.
This chapter introduces the elements that make up dialog boxes. It explains DCL file structure and syntax, and
presents sample AutoLISP and DCL code for a sample
dialog box. This chapter also provides some DCL coding
techniques for handling layout problems.

337

Dialog Box Components
The following figure shows a standard AutoCAD dialog box, with some of its
components labeled. In dialog box creation and customization these components are known as tiles.
columns

edit boxes
toggles

buttons
in a row

radio buttons
in a row

A dialog box consists of the box and the tiles within it. The basic tile types
are predefined by the programmable dialog box (PDB) facility.
You can create complex tiles, called subassemblies, by grouping tiles into
rows and columns, with or without an enclosing box or border. A row or column of tiles is referred to as a cluster. Subassemblies define groups of tiles or
clusters that can be used in many dialog boxes. For example, the OK, Cancel,
and Help buttons are grouped into a subassembly, defined as a row (cluster)
of three button tiles and some spacing separating the buttons.
Subassemblies are treated as single tiles. The tiles within a subassembly are
called children. DCL files are organized in a tree structure. At the top of the
tree is a (dialog) tile that defines the dialog box itself. The following diagram
shows a DCL file structure:

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dialog
toggle
boxed_column

edit box
edit box

row
button
button

the ok_cancel subassembly

text

The layout, appearance, and behavior of a tile or subassembly are specified in
DCL by the tile’s attributes. For example, the dialog itself, and most predefined tile types, has a label attribute that specifies the text associated with
the tile. The label of a dialog box defines the caption at the top of the dialog
box, the label of a button specifies the text inside the button, and so on.
DCL also enables you to define new tiles, called prototypes, that are not necessarily associated with a specific dialog box. This is useful when you want to
use the same component in several dialog boxes. You can reference prototype
tiles from other DCL files and change their attributes the same way you
change predefined tiles.
Before you program a dialog box, plan both the dialog box and the application in detail before you code and debug. The sequence in which the data is
entered will vary with each user. The need to anticipate a variety of user
actions imposes a program structure that is less linear than conventional programming, but is more reflective of the way users work.

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Using DCL to Define Dialog Boxes
You define dialog boxes by entering DCL descriptions in ASCII text files,
much like writing AutoLISP code. DCL files have a .dcl extension. A single
DCL file can contain the description of one or more dialog boxes, or it can
contain only prototype tiles and subassemblies for use by other DCL files. A
DCL file consists of the following three parts, which can appear in any order.
Depending on your application, only one or more of these parts is required.
s

References to other DCL files
These consist of include directives as described in “Referencing DCL Files”
on page 340.

s

Prototype tile and subassembly definitions
These are tile definitions you can refer to in subsequent tile definitions
(including dialog box definitions).

s

Dialog box definitions
These define the attributes of tiles or override the attributes defined in
prototype tiles and subassemblies.

The base.dcl and acad.dcl Files
The base.dcl and acad.dcl files are included with AutoCAD and are distributed
in the AutoCAD Support directory.
The base.dcl file shows the DCL definitions for the basic, predefined tiles and
tile types. It also contains definitions for commonly used prototypes. The
PDB feature does not allow you to redefine the predefined tiles. The acad.dcl
file contains the standard definitions of all the dialog boxes used by
AutoCAD.

WARNING! Any errors in base.dcl may disrupt the appearance of the
standard AutoCAD dialog boxes and customized dialog boxes from your application or other applications.

Referencing DCL Files
When you create dialog boxes, you must create a new, application-specific
DCL file. All DCL files can use the tiles defined in the base.dcl file. A DCL file
can also use tiles defined in another DCL file by naming the other file in what
is called an include directive. You can create your own hierarchy of DCL files,
as shown in the following figure:

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base.dcl

acad.dcl

user1.dcl

user2.dcl

@include “user1.dcl”
user3.dcl

In this figure, the user1.dcl and user2.dcl files are independent of each other,
but user3.dcl uses tiles defined in user1.dcl. The include directive has the form:
@include filename

where filename is a quoted string containing the full name of the other DCL
file. For example, the following directive includes a file named usercore.dcl:
@include "usercore.dcl"

If you specify only the file name, the PDB feature searches for the file first in
the current directory and then in the same directory as the DCL file itself (the
one that contains the include directive). If you specify a full path name, the
PDB feature searches only the directory specified in that path.

NOTE The DCL files you create cannot use the dialog boxes defined in
acad.dcl. You cannot specify @include "acad.dcl". However, if you want to
create similar dialog boxes, you can cut and paste the definitions into your own
DCL file.

DCL Syntax
This section describes the DCL syntax for specifying tiles, tile attributes, and
attribute values.
New tiles are created by tile definitions. If a tile definition appears outside a
dialog box definition, it is a prototype or a subassembly. Prototypes and
subassemblies can be used in dialog box definitions by tile references. Each
reference to a definition inherits the attributes of the original tile. When
referring to prototypes, you can change the values of the inherited attributes
or add new attributes. When referring to subassemblies, you cannot change
or add attributes.
If you need multiple instances of a tile with some attributes in common, it is
easiest to define and name a prototype that contains only the common


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attributes. Then, in each reference to the prototype, you can change
attributes or add new ones, but you do not have to list all the common
attributes each time you reference the tile. Because attributes are inherited,
you will more often need to create tile references — especially references to
the predefined tiles — than to define new tiles.

Tile Definitions
Tile definitions have the following form:
name : item1 [ : item2 : item3 ... ] {
attribute = value;
...
}

where each item is a previously defined tile. The new tile (name) inherits the
attributes of all the specified tiles ( item1, item2, item3, … The attribute defi).
nitions within the curly braces ({}) either supplement, or, if the attribute’s
name is identical, replace the inherited definitions. When the definition has
multiple parents, attributes take precedence in left-to-right order. In other
words, if more than one item specifies the same attribute, the first one
encountered is the one used.
If the new definition contains no children, it is a prototype, and you can alter
or augment its attributes when referring to it. If it is a subassembly with
children , its attributes cannot be altered.
The name of a tile or tile prototype can contain only letters, numbers, or the
underscore character ( _ ), and must begin with a letter.

NOTE Tile names are case-sensitive. For example, bigbutton is not the same
as BigButton or BIGBUTTON. Be careful when using capitalization.
This is the (internal) definition of a button:
button : tile {
fixed_height = true;
is_tab_stop = true;
}

The base.dcl file defines a default_button as follows:
default_button : button {
is_default = true;
}

The default_button inherits the button tile’s values for the fixed_height
and is_tab_stop attributes. It adds a new attribute, is_default, and sets it
to true.

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Tile References
Tile references have one of the following forms:
name;

or
: name {
attribute = value;
. . .
}

where name is the name of a previously defined tile. Tile names are case
sensitive. In the first instance, all the attributes defined in name are incorporated into the reference. In the second instance, the attribute definitions
within the curly braces either supplement or replace the definitions inherited
from name. Because this is a tile reference, as opposed to a definition, the
attribute changes apply only to this instance of the tile.

NOTE The format of the second instance can refer only to prototypes, not to
subassemblies.
The spacer tile is used for layout in a dialog box definition. It has no unique
attributes, so references to it specify only its name:
spacer;

The ok_cancel tile defined in base.dcl is a subassembly, so it too can be referenced only by name:
ok_cancel;

On the other hand, you have the option of redefining the attributes of an
individual tile. For example, the following statement creates a button with
the same properties as a previously defined button, but with different text:
: retirement_button {
label = "Goodbye";
}

For more information, see “Customizing Exit Button Text” on page 351.

Attributes and Attribute Values
Within the curly braces of a tile definition or reference, you specify attributes
and assign them values using the following form:
attribute = value ;

where attribute is a valid keyword and value is the value assigned to the
attribute. An equal sign (=) separates the attribute from the value, and a semi-


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343

colon ( ;) ends the assignment statement. For example, the key attribute
defines the name by which a program can refer to the tile, and the label
attribute defines the text displayed within the tile. See “Synopsis of Predefined Attributes” on page 394 for a complete list of DCL attributes.
As with tile names, attribute names and values are also case-sensitive. Width
and width are not the same thing; True and true do not produce the same
results.

Comments
A statement preceded by two forward slashes (//) is treated as a comment in
a DCL file. Anything that appears between the // and the end of the line is
ignored. DCL also allows C language style comments. These have the form
/* comment text */. The starting /* and ending */ can be on separate lines.

Displaying Dialog Boxes with Visual LISP
VLISP provides a tool for previewing dialog boxes defined with DCL. To see
how this works, copy the following DCL code into a new file in the VLISP
text editor:
hello : dialog {
label = "Sample Dialog Box";
: text {
label = "Hello, world";
}
: button {
key = "accept";
label = "OK";
is_default = true;
}
}

This DCL file defines a dialog box labeled “Sample Dialog Box.” It contains a
text tile and an OK button. Save the file as hello.dcl, and specify “DCL Source
Files” in the Save As Type field of the Save As dialog box.

NOTE You must include the file extension when you specify the file name.
VLISP does not automatically add a .dcl file extension for you.

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Note how the text editor color codes the statements in the DCL file. The
default color coding scheme is shown in the following table:

DCL default color coding
DCL element

Color

Tiles and tile attributes

Blue

Strings

Magenta

Integers

Green

Real numbers

Teal

Comments

Magenta, on gray background

Parentheses

Red

Preprocessor

Dark blue

Operators and punctuation

Dark red

Unrecognized items
(for example, user variables)

Black

Choose Tools ® Interface Tools ® Preview DCL in Editor to display the dialog box defined in the text editor window. Because you may have more than
one dialog box defined in a single .dcl file, VLISP prompts you to specify the
name of the dialog you want to view:

If your DCL file contains definitions for multiple dialog boxes, click the pulldown arrow and choose the one you want to preview. There is only one
dialog box defined in hello.dcl, so choose OK to view it:

Choose OK to complete previewing the dialog box.

Displaying Dialog Boxes with Visual LISP

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Although buttons are a good way to demonstrate dialog box attributes, there
are standard exit button subassemblies you should use in your dialog boxes.
You can create a dialog box that is virtually the same as the one shown in the
previous figure by using the ok_only subassembly. See “Dialog Box Exit Buttons and Error Tiles” on page 410.

Preview Error Handling
If your DCL code contains errors, the VLISP DCL previewer displays messages
indicating the offending line and keyword or symbol. For example, introduce an error into hello.dcl by removing the colon before “button,” then try
previewing the dialog box. You’ll see the following message:

Press OK to clear the message from your screen. VLISP may display additional
error messages, like the following:

Semantic Auditing of DCL Files
AutoCAD provides a choice of four levels (0–3) of semantic auditing for DCL
files (see the following table). Auditing attempts to detect code in the DCL
file that is likely to be problematic or unnecessary. These audits are done at
DCL load time. To set the audit level for a DCL file, include a line such as the
following anywhere within the DCL file, but not inside any tile definitions:
dcl_settings : default_dcl_settings { audit_level = 3; }

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If your DCL file references other DCL files with include directives, you should
define dcl_settings in only one file. The defined audit level is used in all
included files. The following table describes each audit level:

Semantic auditing levels
Level

Description

0

No checking. Use only if the DCL files have been audited and have not
been touched since the audit.

1

Errors. Finds DCL bugs that may cause AutoCAD to terminate. This level of
checking is the default and involves almost no delay. Errors can include
using undefined tiles and circular prototype definitions.

2

Warnings. Finds DCL bugs that result in dialog boxes with undesired layout
or behavior. A modified DCL file should be audited at this level at least
once. The warning level catches mistakes such as missing required
attributes and inappropriate attribute values.

3

Hints. Finds redundant attribute definitions.

To get the most out of the auditing facility, you should keep the audit_level
at 3 during program development. Remember to strip out the dcl_settings
line before shipping DCL files to users.

Adjusting the Layout of Dialog Boxes
Look again at the sample dialog box defined in the previous section. There is
a small problem with it:

Notice how the OK button occupies almost the full width of the dialog box.
To improve the appearance of this dialog box, you can edit the DCL file and
add two attributes to the button tile. To prevent the button from filling the
available space, add a fixed_width attribute and set it to true. This causes the
button’s border to shrink so that it is just slightly wider than the text inside.


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To center the button, add an alignment attribute that specifies centered.
Tiles in a column are left-justified by default. Now the DCL description is as
follows:
hello : dialog {
: text {
label = "Hello, world";
}
: button {
key = "accept";
label = "OK";
is_default = true;
fixed_width = true;
alignment = centered;
}
}

The dialog box now appears like the following:

Many common layout problems can be resolved with the techniques that
are described in the following subsections. If the default layout is not suitable
to the dialog box you are creating, adjust the layout by changing the defaults
at the prototype or subassembly level. Adjust individual tiles only when
necessary.

Distributing Tiles in a Cluster
When laying out tiles in a dialog box, you need to arrange them into rows
and columns based on the relative size of each tile. The following DCL
defines a row of three tiles that runs along the top of another tile:
: column {
: row {
: compact_tile {
}
: compact_tile {
}
: compact_tile {
}
}
: large_tile {
}
}

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If the compact_tile components have fixed_width and the large_tile is
wider than the minimum space required by the row of compact_tiles above
it, the default horizontal alignment of this assembly appears as follows:

The leading edge of the first compact_tile in the row aligns with the leading
edge of the large_tile, and the trailing edge of the last compact_tile aligns
with the trailing edge of the large_tile. Tiles in between are distributed
evenly. The situation with adjoining columns is analogous.
You can control the default distribution by using the spacer_0 and spacer_1
tiles, which are variants of the spacer tile defined in base.dcl . See “DCL Tile
Catalog” on page 410 for more information on these tiles.

Adjusting the Space between Tiles
If two adjoining columns differ greatly in the amount of space their tiles
occupy, then the tiles in the one that needs less space may appear to be
distributed too far apart. Their appearance can be improved if you set the
incongruous column’s fixed_height attribute to true. The result for vertical
tile distribution is shown in the following diagram:

tiles distributed
too sparsely

sparse distribution
corrected


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Adjusting Space at the Right Side or Bottom
A dialog box may contain unused space along its right side. You can define a
text tile and explicitly specify a width greater than the width required by its
current value. For example, the following code fragment defines a tile that
does not display anything (its value is null) until an application sets its
value:
: text {
key = "l_text";
width = 18;
fixed_width = true;
}

The width attribute reserves space for 18 characters in the dialog box. The
application can add text with a statement like the following:
(set_tile "l_text" "By layer")

Because "By layer" doesn’t need all 18 characters, the dialog box has surplus
space along its right side.
A similar situation occurs when you use an errtile to display error messages.
(See “Dialog Box Exit Buttons and Error Tiles” on page 410.) Unless an error
message is currently shown, it looks as if there is extra space at the bottom of
the dialog box. In this case, an extra spacer tile at the top of the dialog box
can help balance the vertical layout.

Fixing the Spacing Around a Boxed Row or
Column
If the label attribute of a boxed row or column is either blank (" ") or null
(""), the box encloses the cluster but no text is shown. A single blank does
not appear as a space in the box. However, there is a difference in the way
blank and null labels are laid out:
If the label is a single blank, any vertical space the text occupied inside
the box is lost, but any vertical space the label occupied above the box is
not lost.
s If the label is a null string, all vertical space is lost, whether above the box
or inside it.
s

In the following DCL code, the top lines of the boxes around the first two
columns are guaranteed to line up (with the same Y location), and the top
line of the box around the third column is guaranteed to have no spacing
above or below it, except for the default margins:

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: row {
: boxed_column {
label = "Some Text";
}
: boxed_column {
label = " ";
// single blank: the default
}
: boxed_column {
label = "";
// null string
}
}

Customizing Exit Button Text
For some dialog boxes, you may want to change the text of one of the exit
buttons. For example, if you create a dialog box capable of destroying data,
it’s safer to call the button Destroy instead of OK. To do this, use the
retirement_button prototype as follows:
destroy_button : retirement_button {
label = "&Destroy";
key = "destroy";
}

Notice the use of the ampersand (&) in the label attribute. This assigns a mnemonic to the tile. In this case the letter D is underscored in the button label
and becomes the mnemonic.

NOTE When customizing existing button subassemblies you should obtain
the proper DCL code from your base.dcl file rather than from the manual.
Once you have defined a custom exit button, you need to embed it in a subassembly that matches the appearance and functionality of the standard
clusters. The following example shows the current definition of
ok_cancel_help:
ok_cancel_help : column {
: row {
fixed_width = true;
ok_button;
: spacer { width = 2; }
cancel_button;
help_button;
}
}


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Create a new subassembly that replaces the ok_button with the new button
as follows:
destroy_cancel_help : column {
: row {
fixed_width = true;
destroy_button;
cancel_button;
help_button;
}
}

In the standard subassembly, the OK button is the default, but this attribute
wasn’t added to destroy_button. Where the dialog box’s action can be
destructive (or very time-consuming), it is strongly recommended to make
the Cancel button the default. In this case, it functions both as the default
and as the Abort button:
destroy_cancel_help : column {
: row {
fixed_width = true;
destroy_button;
: cancel_button { is_default = true; }
help_button;
}
}

Because an attribute has been changed, the original Cancel button is used as
a prototype, requiring a colon in front of cancel_button.

WARNING! When the Cancel button and the Default button are the same
(both is_default and is_cancel are true) and you neglect to assign an action
that calls done_dialog to any other button, then no other button can exit the
dialog box and it will always be canceled.

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Design Guidelines
To design a dialog box well, you must consider not only the practical purpose
of the box but also its aesthetics, the ergonomics of using it, and the GUI
standards for the Windows environment. The following subsections provide
some guidelines for GUI design, dialog box design, and predefined tiles and
clusters. Refer to the “Programmable Dialog Box Reference,” chapter 13, for
more examples of tiles and clusters.

Aesthetics and Ergonomics
The appearance of a dialog box is important. If the box is too cluttered, it is
ineffective and hard to use. Also, tiles should be arranged so they are easy to
use. Consider which tiles will be used most frequently, make them prominent in the design, and arrange them so it’s easy to move between them,
particularly when they are used in conjunction with each other.

Consistent Design and Clear Language
The user interface of an application should be internally consistent, and
consistent with related applications. An unfamiliar dialog box is easier to
understand if its design is consistent with other dialog boxes in the application, related applications, or the host system. One example of this is the
consistent placement of buttons such as OK and Cancel . The technique associated with each kind of tile— how you enter text in a text box and how you
select a list box item — should also be consistent. The best way to achieve
consistency is to reuse tiles and the code that controls them.
Standardization contributes to consistency. Use standard definitions for dialog box controls. This reduces your work, contributes to consistency, and
makes it easier for users to learn and use your dialog boxes.
Use language that is clear. Although dialog boxes are considered part of a
graphical interface, most of the tiles and information they present are textual. The labeling of dialog boxes, naming of buttons, and phrasing of
messages should be direct and unambiguous. Avoid jargon and technical
terms that users may not understand.

User Control
Give users some control over how they access the dialog box to enter input.
One advantage of using dialog boxes instead of a command line interface is
that boxes don’t confine users to a strict sequence of prompts. In a dialog

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box, users should be able to enter input in any sequence. Some constraints
are necessary— when selecting one option causes another to be unavailable,
for example — but build in only constraints that have underlying reasons in
the way your application works.
For example, the following figure shows the Object Grouping dialog box.
This dialog box contains a Group Name field, where users may enter a name
for a new group they are creating. If the Unnamed option is selected, a Group
Name cannot be specified.

Multiple dialog boxes should appear on top of one another rather than
require the user to exit the current box before calling another. Always let
users return to the dialog box that was initially displayed. This design doesn’t
commit users to a choice before they are ready to leave the dialog box.
Because the current dialog box appears on top of the previous one, it reminds
users of the context: where they have come from and where they’ll return to.
Whenever users do something to change the current status or options, provide them with immediate feedback. If users select something, show it or
describe it immediately. If one choice excludes other choices, be sure to make
the invalid choices unavailable immediately.
In the AutoCAD Color Selection dialog box, for example, an image tile shows
the color immediately after the user selects its number. In the sample Block
Definition dialog box, the number of selected objects is always displayed in
a message below the Select Objects button:

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Forgiving Errors
Make your dialog boxes forgiving, so users feel free to explore without fear of
making irreversible mistakes. Report minor errors by messages in an error tile
at the bottom of the dialog box. Report more serious errors by displaying an
alert box. The alert function displays a simple alert box (with a single OK
button). See “alert” in the AutoLISP Reference.
If the user selects a potentially destructive or time-consuming action, the dialog box should display an alert box that gives the user a choice of proceeding
with the operation or canceling it.
For example, in the Block Definition dialog box, an alert box appears when
users attempt to create a block that already exists. Users can then choose to
proceed and overwrite the original block, or cancel the operation without
making changes:

Nested dialog boxes that alert users should return to the previous dialog box.
Terminate the current nest of dialog boxes only in the case of serious or
potentially fatal errors.

Providing Help
You should provide a Help facility. How much online help you provide
depends on how complex your application is and how self-explanatory your
dialog boxes are. At the very least, it is recommended that the main dialog
box of your application have a Help button that displays a single dialog box
describing important information. In most cases, the Help button should call
the Help facility using the help function.
If your application is more sophisticated, consider developing a contextsensitive Help facility with multiple Help dialog boxes, each associated with
a particular dialog box.

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Users with Disabilities
Considerations intended for users with disabilities can make a program easier
for anyone to use. When designing your dialog boxes, consider the
following:

Color

Many people cannot distinguish between certain colors. If
you use color coding to present information, supplement
this by presenting the same information in some other
way (usually with text).
For example, the standard AutoCAD color dialog box
displays a text message that states the color’s name or
number as well as an image tile that displays the color.

Online Help

Many users have difficulty either reading the small print
in manuals or physically handling books. Even a single
Help button on the main dialog box can be useful.

Keyboard
Access

Some users may have difficulty with or be unable to use a
pointing device. Try to specify mnemonics so your dialog
boxes can be used with just the keyboard.

Clarity and
Simplicity

Carefully designed dialog boxes with clear and simple
language help users with verbal or cognitive impairments.
Don’t force users to remember many different things.
Instead, use consistent terminology and present choices
wherever possible.

Using Capitalization
The following are some general guidelines for capitalizing text within dialog
boxes:

Dialog Boxes,
Areas, and
Column
Headings
Control Labels

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Use headline capitalization: capitalize the first and last
words, and all other words except articles, prepositions,
and coordinating conjunctions. However, if the dialog
box is invoked from a menu (not from the Command
prompt), its title should match the menu item.
Use headline capitalization for labels of control tiles such
as buttons. Do not follow labels with a period. Follow the
labels of a text box or a drop-down list with a colon (:).
You may want to use sentence-style capitalization (in

Chapter 11


which you capitalize only the first word and proper
nouns) if the label is lengthy or phrased as a question.

Prompts and
Messages

Use sentence-style capitalization.

Avoiding Abbreviations
Abbreviations can be ambiguous and difficult to translate. If space constraints require you to abbreviate terms, abbreviate them consistently within
a group (such as a boxed column). Be consistent. Don’t spell some terms in
full and abbreviate others.

Layout
Arrange sections of the dialog box logically into rows or columns so users can
scan them from left to right or from top to bottom. Align related entry fields
(such as edit boxes or list boxes) both vertically and horizontally, so that
when users switch fields by pressing TAB , the cursor moves in a straight,
orthogonal line.
If there is a natural order for entering data—such as the X , Y, and Z of coordinates—order the fields in the same way. Align boxed areas both vertically
and horizontally. Do not leave a lot of white space around or between boxed
areas. Extend their width to the right, if necessary.

Size and Placement
To display information clearly, make the dialog box no larger than necessary.

NOTE Users may have a screen resolution as low as 640 × 480. If you are developing applications on displays using a higher resolution, remember to verify that
your dialog boxes display properly at lower resolutions.
By default, AutoCAD initially displays all dialog boxes in the center of the
graphics window. However, you can specify that dialog boxes display at an
alternate location (such as the last location specified by the user). The
new_dialog and done_dialog AutoLISP functions provide for dialog box
placement.

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Disabling Tiles
If a tile or an area is unavailable or irrelevant given the current option settings, disable it immediately so the tile or area is unavailable and the user
can’t select it. Try not to overuse the disabling tiles feature. Too many
unavailable tiles can be distracting.
If a tile displays a value, disabling the tile shouldn’t affect the value. The tile
should display the same value when it is enabled again. Values that change
magically create more work for the user, which is annoying and distracting.

Nesting Dialog Boxes
AutoCAD limits the number of nested dialog boxes to eight. For information
on how to handle nested dialog boxes, see “Nesting Dialog Boxes” on page
376.
Insert an ellipsis (… in the label of a button that displays a nested dialog box
)
unless the nested dialog box is an alert box. Don’t nest dialog boxes more
than three deep . Four levels of nesting are reasonable if the fourth-level dialog boxes are only alert boxes. Because dialog boxes appear initially in the
center of the screen, make the nested dialog boxes smaller than the main dialog box.

Hiding Dialog Boxes
If a user needs to make a selection from the graphics screen before the dialog
box has closed, you must close the dialog box momentarily so that the user
can see the screen and make the selection. Once the selection is made, you
need to display the dialog box again. This is known as hiding a dialog box.
The label of a button that causes the dialog box to be hidden should not contain an ellipsis. Instead, use a space followed by a less-than symbol (<) in the
label. When the dialog box hides itself, a prompt should be displayed that
explains what the user is expected to do.
In most cases you can get the input with one of the getxxx functions. These
functions have an argument with which you can specify a prompt.
When the dialog box reappears, it should contain feedback on the selection
process. This can be new information in the edit box fields, an updated list
box, a text message that indicates the status, or a combination of these.

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Providing Defaults
Provide reasonable defaults for all entries and options. Well-chosen defaults
can help users complete a dialog box quickly and easily.
It is recommended that you update the default values — in other words, that
you save the user’s previous settings and use them as the new defaults — each
time the dialog box is used. Even if the user has to change some of these, it
is less work than starting from the beginning each time.

Handling Keyboard Input
When you create a custom dialog box, you can specify how it handles keyboard shortcuts. Some keyboard shortcuts are common to all dialog boxes.
For example, the TAB key generally enables users to move from tile to tile,
and the SPACEBAR allows users to turn toggles off or on. Each active tile
should be a tab stop (the default).
Two keys commonly act as accelerator keys. The accept key (usually the
ENTER key) accepts the dialog box and values entered. The cancel key ( ESC ),
discards the dialog box and the values. When AutoCAD first displays a dialog
box, one of its tiles has the initial keyboard focus. What the user enters affects
this tile until the user moves focus to another tile.
To move from tile to tile, the user can press TAB , choose another tile, or enter
one of the keyboard shortcuts known as mnemonic keystrokes. For example,
in the Drawing Aids dialog box you can select one of the Isometric Snap/Grid
radio buttons by pressing L , T , or R . Moving between tiles changes focus but
doesn’t make a selection. To select a tile that has focus, users must press the
Accept key. For some kinds of tiles, a double-click is equivalent to pressing
the Accept key.

International Language Considerations
Words in other languages often require more characters than their English
equivalents. If your dialog boxes are going to be translated, leave as much
room as possible for them to grow. The following table shows some familiar
AutoCAD terms with their equivalents in French and German.

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Equivalent AutoCAD terms in English, French, and German
English

French

German

Line

Ligne

Linie

Arc

Arc

Bogen

Circle

Cercle

Kreis

3D Polylines

Polylignes 3D

3D-Polylinien

Diameter dimensioning

Cotation de diamètre

Durchmesserbemaßung

Layers

Calque

Layer

Linetypes

Types de ligne

Linientypen

Entity creation modes

Modes de création
des objets

Modus für Objekterzeugung

Select objects

Choix des objets

Objekte wählen

OK

OK

OK

Cancel

Annuler

Abbruch

Help

Aide

Hilfe

Guidelines for Predefined Tiles and Clusters
This section lists recommended conventions and design guidelines associated with particular kinds of predefined tiles and tile clusters.

Buttons
The action associated with a button should be visible to the user and should
take place immediately. The label of a button should be unambiguous. Usually, it should be a verb that describes the effect of pushing the button,
though another label — such as OK or Options — is acceptable if its meaning
is clear. For buttons that call other dialog boxes or hide the current dialog
box, see “Nesting Dialog Boxes” on page 358 and “Hiding Dialog Boxes” on
page 358.
Buttons in a column should be the same width. In other cases, buttons
should have a fixed width (either fixed_width = true;, or
children_fixed_width = true;) in their common parent cluster.

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Clusters
A boxed cluster (a row or column) is called a group box or an area. An area
provides a visual cue to users by isolating and naming controls that work
together. The area can contain as many tiles, rows, and columns (unboxed)
as necessary. The label of an area should indicate its purpose.
If controls relate to each other, put them in an area. The Base Point cluster in
the Block Definition sample dialog box demonstrates this technique with an
area formed from a cluster with a label and a border:

However, do not overuse areas. White space is also an effective way to group
tiles. Do not put a box around a list box; this looks too busy.

Edit Boxes
The length of the text-entry portion of an edit box should roughly equal the
length of an average entry. When in doubt, use a character width of 10 for
real number fields and 20 for text fields.
The label of an edit box should end with a colon (:).
If there are restrictions on what users can enter in the edit box, put a text tile
to the right of the edit box that briefly explains these restrictions. If users
need to enter a file name, for example, there’s no need to explain what a file
name is. But if the string is a number that cannot exceed 100, a reminder of
this limit is a good idea.
For data, such as points, provide two or three edit boxes rather than require
users to remember the Command line syntax of point entry. One exception
is an edit box intended specifically for entering advanced syntax, such as the
wild-card pattern edit box in the AutoCAD File Search dialog box.

Image Buttons and Image Tiles
If you use an image button or image tile as an icon to alert the user— for
example, a warning signal such as a stop sign — use it consistently in all
dialog boxes.

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When you use image buttons to represent selections, supplement the image
with text that briefly describes it, especially if the color of the image (or part
of the image) is a factor in selecting it.

List Boxes
Because DCL list boxes cannot be scrolled horizontally, the width of the list
box should accommodate the longest item in the list. Provide a label (or a
text tile) to explain the contents of the list box, unless the list box is the main
tile in the dialog box. In that case the dialog box’s label might be sufficient—
although you must give the list box a label if you want users to be able to
move to that list box by using a mnemonic.
Alphabetize the items in the list unless you have a logical reason to organize
them in some other way. If the length of the list is fixed and short, consider
using a radio column instead of a list box.

Radio Buttons, Radio Rows, and Radio Columns
Radio columns look better and are easier to use than radio rows. Radio rows
are appropriate only when they contain a small number of buttons (usually,
two to four) or if the labels are short.

If an option selected elsewhere makes the choices in the radio row or radio
column invalid or irrelevant, then disable the whole row or column. In some
situations, an option selected elsewhere may make certain radio buttons
invalid or irrelevant. In situations like this, you can disable buttons individually.

Sliders
The granularity of a slider should not be too coarse. For example, if a slider is
assigned only four incremental values but is laid out in a two-inch section of
the dialog box, users would have to move half an inch to see a change. Avoid
jumpiness like this by scaling the size of the slider.
If users need to know the value controlled by the slider, your dialog box
should also display the slider’s current value. Update this value whenever the
slider is moved. It is recommended you also display an edit box that enables
users to enter the value rather than use the slider. If you use an edit box this
way, update its value; otherwise, display the value in a text tile. The following
figure shows a typical combination of slider and edit box:

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Text
When labels are not sufficient, use text tiles to identify the purpose of individual tiles or dialog box areas. You can also use text tiles to display status
messages or reminders, including error messages and warnings.
Text should be direct and unambiguous. Describe options and entry fields in
terms your users would use. For example, the error message “Invalid entry”
in a list box conveys little information. A message such as “Layer does not
exist” is more helpful.
Align messages with the control tiles they describe.
Put text that identifies a group of control tiles or a section of the dialog box
above the tiles that the text describes.

Toggles
When the options controlled by toggles relate to the same topic, group them
together.
Use a single toggle that controls whether other tiles, often in a row or column, are active. In this case, the toggle should be prominent. When the
toggle controls only one other tile, you can also place it to the right of that
tile. The toggle in the following dialog box enables or disables another tile:

Error Handling
Dialog boxes can display error messages and warnings with a text tile known
as an error tile ( errtile), or with a nested alert box. The following guidelines
apply to both:
Error messages should be complete sentences, punctuated as such, with an
initial capital and a period at the end.
s Error messages should explain clearly the problem or potential problem.
s After reporting the error, shift the dialog box’s focus to the tile that triggered the error, if possible.
s

Error Tiles
Use an error tile for minor errors or warnings, especially those that arise from
typos and other input errors.

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Do not display errors in text tiles used for status messages. These are easy to
overlook.
Error tiles should appear at the bottom of a dialog box. Use the standard
errtile described in “Dialog Box Exit Buttons and Error Tiles” on page 410.

Alert Boxes
You can display a standard alert box with a single OK button by calling the
alert function. Use alert boxes for serious or potentially fatal errors, but do
not overuse them. Alert boxes require user input. Therefore, they can be
annoying, especially when they report minor errors or obscure the entry that
needs to be corrected.
Use alert boxes to warn users that the action about to begin can destroy data
or can be time consuming. Alert boxes of this sort should give users a choice
of proceeding or canceling the action. If the alert box offers users a choice,
such as Proceed or Cancel, you must construct it yourself.
If the alert box provides users with a choice, the text in the alert box should
first describe the problem and then pose the next action as a question. In
such cases it is important that the button for proceeding be labeled with a
verb that describes what will happen. In this context, Overwrite, for example, is less ambiguous than OK, and is an aid to experienced users who will
gloss over the text because they have seen this alert box many times.
Unless the error is truly fatal, provide a way for users to return to a previous
step or escape from the operation that triggered the alert box.
Usually the default button for a dialog box is OK or its equivalent, but when
the situation described by the alert box has serious consequences, make
Cancel or its equivalent the default.

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12

In This Chapter

With AutoCAD, you can design and implement dialog

s Controlling Dialog Boxes with
AutoLISP Programs

boxes to use with your applications. The appearance of

s Action Expressions and Callbacks

a dialog box is defined by dialog control language (DCL)

s Handling Tiles
s Nesting Dialog Boxes

files, as described in “Designing Dialog Boxes.” You
control the functionality of a dialog box with an
AutoLISP application. This chapter describes how to

s Hiding Dialog Boxes
s List Boxes and Pop-Up Lists
s Image Tiles and Buttons
s Application-Specific Data

control dialog boxes using AutoLISP. Although this

s DCL Error Handling

chapter shows some examples of DCL files, you may

s Dialog Box Function Summary

find it helpful to read “Designing Dialog Boxes” before
reading this chapter.

365

Controlling Dialog Boxes with AutoLISP
Programs
This chapter begins with an overview of the process you use to display dialog
boxes and respond to user input from an AutoLISP program.

Quick Overview
This example starts with a simple dialog box:

The following DCL defines the dialog box:
hello : dialog {
: text { label = "Hello, world."; }
ok_only;
}

This DCL defines a dialog box labeled Sample Dialog Box that contains a text
tile and a single OK button. The DCL resides in a file named hello.dcl .

To display the dialog box and respond to the user pressing OK
1 Use the load_dialog function to load the DCL file into memory. For example:
(setq dcl_id (load_dialog "hello.dcl"))

The load_dialog function returns a DCL identification number. You need
this to identify the dialog in subsequent function calls.

2 Call the new_dialog function and pass it the dialog name and DCL identification number as arguments, as follows:
(new_dialog "hello" dcl_id)

3 Initialize the dialog box by setting up tile values, lists, and images.
The DCL example above uses a predefined tile named ok_only, so you do not
have to initialize the tile unless you want to override its default values. The
ok_only tile also has an action named done_dialog assigned to it. If the user
presses the OK button, AutoCAD passes the done_dialog call to your
AutoLISP application and ends the dialog.

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4 Call start_dialog to pass control of the dialog to AutoCAD for display to the
user:
(start_dialog)

5 Call unload_dialog to remove the dialog from memory after the user
responds.
Steps 3, 4, and 5 are dependent on the new_dialog function returning a nonnil value. For the sake of simplicity, no error processing is included in this
example.
You can use the following function to call the sample dialog box:
(defun C:HELLO( / dcl_id )
(setq dcl_id (load_dialog "hello.dcl")) ; Load the DCL file.
(if (not (new_dialog "hello" dcl_id))
; Initialize the dialog.
(exit)
; Exit if this doesn’t
; work.
)
(start_dialog)
; Display the dialog
; box.
(unload_dialog dcl_id)
; Unload the DCL file.
(princ)
)

Enter this code into a new VLISP text editor window and load the program
by choosing Tools ® Load Text in Editor from the VLISP menu. To display
the dialog box, enter (c:hello) at the VLISP Console prompt.
Note that the start_dialog call remains active until the user selects a tile
(usually a button) whose associated action expression calls done_dialog. The
done_dialog call can be issued explicitly by the tile. The done_dialog call is
also issued by the selected tile if its is_cancel attribute is set to true.

WARNING! In theory, the dialog box facility takes control of input at the time
you call start_dialog, but in Windows it takes control when you call
new_dialog. This has no effect on writing programs. However, if you invoke
these functions interactively (at the AutoCAD Command prompt or a VLISP window), you must enter them as one statement. Enclose them within a progn or
another function. If you don’t, the interactive call to new_dialog can freeze the
screen. Calling new_dialog and start_dialog interactively can be useful during debugging. (For an example of using these functions interactively, see “DCL
Error Handling” on page 386.)

Functions Restricted When a Dialog Box Is Open
While a dialog box is active — that is, during the start_dialog call — you
cannot call any function that requires user input on the AutoCAD command
line, or affects the display outside the dialog box (for example, in the

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AutoCAD graphics window). This restriction includes functions that write
text, such as print, princ, and prin1.
You can issue ssget calls, as long as you do not use any options that require
user input.
If your program calls one of the restricted functions between the
start_dialog and done_dialog calls, AutoCAD terminates all dialog boxes
and displays the following error message:
AutoCAD rejected function

You can test the CMDACTIVE system variable to determine if a dialog box is
active. If CMDACTIVE is greater than 7, a dialog box is active. The CMDACTIVE
system variable has bit-coded values that indicate command, script, and dialog box activity.

NOTE If your application requires users to enter input based on the graphics
screen rather than on the dialog box itself (for example, to specify a point or
select an object), you must hide the dialog box. That is, you must call
done_dialog so the graphics screen is visible again, and then restart the dialog
box after the user has made the selection. For more information, see “Hiding
Dialog Boxes” on page 377.
The term_dialog function terminates all current dialog boxes as if the user
had canceled each of them. This function can be used to cancel a series of
nested dialog boxes.

Action Expressions and Callbacks
To define the action taken when a certain tile in a dialog box is selected, you
associate an AutoLISP expression with that tile by calling the action_tile
function. This is known as an action expression. Within the action expression, you often need access to attributes in the DCL file. The get_tile and
get_attr functions provide this capability. The get_attr function retrieves
the user-defined attributes within the DCL file. The get_tile function gets
the current runtime value of a tile based on user input to that tile. Action
expressions must be defined following the new_dialog call and before the
start_dialog call.
Information relating to how the user has selected a tile or modified a tile’s
contents is returned to the action expression as a callback. In most cases,
every active tile within a dialog box can generate a callback. As with reactors,
the action expression that responds to the callback is often referred to as a

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callback function. This function should perform validity checking on the
associated tile and should update information in the dialog box that pertains
to the value of the tile. Updating the dialog box can include issuing an error
message, disabling other tiles, and displaying the appropriate text in an edit
box or list box.
Only the OK button (or its equivalent) should query the tile values to permanently save the settings that the user has finally selected. In other words, you
should update the variables associated with tile values within the callback for
the OK button, not the callback for an individual tile. If permanent variables
are updated within the individual tile callbacks, there is no way to reset the
values if the user selects the Cancel button. If the OK button’s callback
detects an error, it should display an error message and return focus to the
tile in error; it should not exit the dialog box.
When a dialog box includes several tiles whose handling is similar, it can be
convenient to associate those tiles with a single callback function. The principle of not committing to the user’s changes until the user chooses OK still
applies.
There are two ways to define actions other than calling action_tile. You can
define a default action for the entire dialog box when you call new_dialog,
and you can define an action by using a tile’s action attribute. These alternative means of defining actions, and the order in which they occur, are
described in “Default and DCL Actions” on page 372.

Action Expressions
An action expression can access the variables shown in the following table,
indicate which tile was selected, and describe the tile’s state at the time of the
action. The variable names are reserved. Their values are read-only and have
no meaning, unless they are accessed within an action expression.

Action expression variables
Variable

Description

$key

The key attribute of the tile that was selected.
This variable applies to all actions.

$value

The string form of the current value of the tile, such as the string from an
edit box, or a "1" or "0" from a toggle.
This variable applies to all actions.
If the tile is a list box (or pop-up list) and no item is selected, the $value
variable will be nil.


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Action expression variables (continued)
Variable

Description

$data

The application-managed data (if any) that was set just after new_dialog
time by means of client_data_tile.
This variable applies to all actions, but $data has no meaning unless your
application has already initialized it by calling client_data_tile. See
“Application-Specific Data” on page 386.

$reason

The reason code that indicates which user action triggered the action.
Used with edit_box, list_box, image_button, and slider tiles.
This variable indicates why the action occurred. Its value is set for any kind
of action, but you need to inspect it only when the action is associated
with an edit_box, list_box, image_button, or slider tile. See
“Callback Reasons” in the following section for details.

If edit1 is a text box, the action expression in the following action_tile call
is evaluated when the user exits the text box:
(action_tile "edit1" "(setq ns $value)")

The $value contains the string that the user entered, and the expression
saves this in the ns variable.
The next example saves the name of the selected tile so that the program can
refer to it:
(action_tile "edit1" "(setq newtile $key)")

The newtile variable is set to the key name of the selected tile, in this case
"edit1". The $key variable is very useful within a function that serves as the
action for several separate tiles.
When a tile is named in more than one action_tile call, only the last such
call (prior to start_dialog) has any effect. (It’s as if you were to assign multiple values to the same variable.) The programmable dialog box (PDB) feature allows only one action per tile.

Callback Reasons
The callback reason , returned in the $reason variable, specifies why the
action occurred. Its value is set for any kind of action, but you need to inspect

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it only when the action is associated with an edit_box, list_box,
image_button, or slider tile. The following table shows the possible values:

Callback reason codes
Code

Description

1

This is the value for most action tiles. The user has selected the tile (possibly
by pressing ENTER, if the tile is the default and the platform recognizes
accelerator keys).

2

Edit boxes: The user has exited the edit box, but has not made a final
selection.

3

Sliders: The user has changed the value of the slider by dragging the indicator
but has not made a final selection.

4

List boxes and image buttons: This callback reason always follows a code 1. It
usually means “commit to the previous selection.” It should never undo the
previous selection ; this confuses and annoys the user.

Code 1 is described fully in the table. The following text describes the codes
2, 3, and 4 in greater detail.

Code 2—Edit Boxes
The user has exited the edit box— by pressing the TAB key or by choosing a
different tile— but has not made a final selection. If this is the reason for an
edit box callback, your application should not update the value of the associated variable, but should check the validity of the value in the edit box.

Code 3—Sliders
The user has changed the value of the slider by dragging the indicator (or an
equivalent action), but has not made a final selection. If this is the reason for
a slider callback, your application should not update the value of the associated variable but should update the text that displays the slider’s status. For
more information, see “Sliders” on page 362. For code examples, see
“Handling Sliders” on page 375.

Code 4—List Boxes
The user has double-clicked on the list box. You can define the meaning of a
double-click in your application. If the main purpose of the dialog box is to
select a list item, a double-click should make a selection and then exit the dialog box. (In this case, the is_default attribute of the list_box tile should be
true.) If the list box is not the primary tile in the dialog box, then a doubleclick should be treated as equivalent to making a selection (code 1).


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List boxes that allow the user to select multiple items
(multiple_select = true) cannot support double-clicking.

Code 4—Image Buttons
The user has double-clicked on the image button. You can define the meaning of a double-click in your application. In many cases it is appropriate for
a single-click to select the button, but in others it is better for a single-click
(or a keyboard action) to highlight the button, and then have the ENTER key
or a double-click select it.

Default and DCL Actions
The action_tile function is not the only way to specify an action. A tile’s
DCL description can include an action attribute in AutoLISP, and the
new_dialog call can specify a default action for the dialog box as a whole. A
tile can have only a single action at a time. If the DCL and the application
specify more than one action, they supersede each other in the following
order of priority (lowest to highest):
The default action specified by the new_dialog call (used only if no action
is explicitly assigned to the tile).
s The action specified by the action attribute in the DCL file.
s The action assigned by the action_tile call (highest priority).
s

Handling Tiles
Your program has some control over the tiles that are in the current dialog
box at initialization time and action (callback) time. This section introduces
the tile-handling functions and shows how to initialize and modify the tiles’
modes and values.

Initializing Modes and Values
Initializing a tile can include the following:
Making it the initial keyboard focus of the dialog box
Disabling or enabling it
s Highlighting its contents, if it is an edit box or image
s
s

These operations are performed by mode_tile calls. You can set the value of
a tile by using set_tile.

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To display a default value—such as a surname—in an edit box and set the
dialog box’s initial focus to that box, use the following code:
(setq name_str "Kenobi")
(set_tile "lastname" name_str)
(mode_tile "lastname" 2)

; Default.
; Initializes field.
; 2 sets focus to tile.

An additional mode_tile call can highlight all the contents of an edit box, so
the user has the option to type immediately over the default contents, as
shown in the following example:
(mode_tile "lastname" 3)

; 3 selects box contents.

Changing Modes and Values at Callback Time
At callback time, you can check the value of a tile. If necessary, you can use
set_tile again to modify this value. During callbacks, you can also use
mode_tile to change the status of a tile. The following table shows the values
of the mode_tile mode argument:

Mode codes for mode_tile
Value

Description

0

Enable tile

1

Disable tile

2

Set focus to tile

3

Select edit box contents

4

Flip image highlighting on or off

When you use mode_tile to disable a tile that has the current focus, you must
call mode_tile again to set the focus to a different tile (in most cases, the next
tab stop in the dialog box). Otherwise, the focus will remain on a disabled
tile, which is illogical and can cause errors.
A good example of a tile disabling itself is a series of dialog box pages that the
user steps through by choosing a Next or Previous button. When the user
chooses Next on the next-to-last page, the button is disabled. The same thing
happens after choosing Previous on the second page. In both cases, the code
must disable the button that was chosen, and then set focus to a different
tile.

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Suppose the tile called group_on is a toggle that controls a cluster called
group. When the toggle is turned off, the tiles in the cluster are inactive and
should not be modified. In this case, you might define the following action
for the toggle. (Notice the use of the " control character, which allows quotation marks within an action_tile argument.)
(action_tile "group_on" "(mode_tile "group" (- 1 (atoi
$value)))")

The subtraction and atoi call in the action expression set the mode_tile
function’s mode argument. Because a toggle is 0 when it is turned off and 1
when it is turned on, the subtraction inverts its value and the mode controls
whether the cluster is enabled.
You can inspect attributes other than a tile’s value with the get_attr function. For example, you may want to retrieve the label of a button called
"pressme":
(get_attr "pressme" "label")

The get_attr function returns the value of the specified attribute as a string.

NOTE If you use get_attr to retrieve a value attribute, it gets the value
attribute saved in the DCL file (the initial value of the tile). The get_tile function, however, gets the current runtime value of the tile. The two values are not
necessarily the same.

Handling Radio Clusters
Radio buttons appear in radio clusters. The value of each radio button is
either "1" for On or "0" for Off. The value of the radio cluster is the key
attribute of the currently selected button. The PDB feature manages the values of radio buttons in a cluster and ensures that only one button is turned
on at a time. You can assign an action to each radio button, but it is more
convenient to assign an action to the radio cluster as a whole and then test
the cluster’s value to see which radio button was chosen.
Consider the following example: A radio cluster controls the view of a threedimensional object that is displayed after a user exits a dialog box. This
cluster contains four radio buttons:
(action_tile "view_sel" "(pick_view $value)")
.
.
.

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(defun pick_view (which)
(cond
((= which "front") (setq show_which 0))
((= which "top") (setq show_which 1))
((= which "left") (setq show_which 2))
((= which "right") (setq show_which 3))
)
)

These examples show each radio button associated with a single variable that
takes multiple values. These variables may also cause additional actions, such
as disabling selections in your dialog box. If the radio cluster is large, you can
store the associated values in a table. If you use a table, structure it so it
doesn’t depend on the order of the buttons within the cluster. The PDB feature does not impose this restriction, and the order can change if the DCL
definition changes.

Handling Sliders
When you handle actions and callbacks from sliders, your application should
check the reason code that it receives along with the callback. This is not
required, but it is a good idea because it can reduce processing.
A callback occurs when an increment boundary on a slider is crossed. For
example, if the slider is defined with a minimum value of 0, a maximum
value of 10, and both small and big increments of 1, a callback is issued
10 times as the user traverses from one end of the slider to the other.
The following function shows the basic scheme of a function to handle a
slider. It is called from an action expression associated with the slider tile. The
slider_info tile used by the function displays the slider’s current value in
decimal form . Often such a tile is an edit box as well, which gives users the
choice of either manipulating the slider or entering its value directly. If a user
enters a value in slider_info, your edit box callback should update the value
of the slider as follows:
(action_tile
"myslider"
"(slider_action $value $reason)"
)
(action_tile
"slider_info"
"(ebox_action $value $reason)"
)
.
.
.

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(defun slider_action(val why)
(if (or (= why 2) (= why 1))
(set_tile "slider_info" val)
)
)
(defun ebox_action(val why)
(if (or (= why 2) (= why 1))
( set_tile "myslider" val)
)
)

; Check reason code.
; Show interim result.

; Check reason code.
; Show interim result.

Handling Edit Boxes
Actions and callbacks to handle edit boxes are similar to those for sliders.
However, because characters in edit boxes are already visible, there is no need
for action on interim results. Edit boxes only return a callback code when the
focus to that tile is lost. The following code example checks the value but
doesn’t redisplay it:
(action_tile "myeditbox" "(edit_action $value $reason)")
.
.
.
(defun edit_action (val why)
(if (or (= why 2) (= why 4))
. ; Do range checking on
. ; transient value here.
.
)
)

Nesting Dialog Boxes
You create and manage nested dialog boxes by calling new_dialog and
start_dialog from within an action expression or callback function. For
example, by including the following statement, a function can display the
“Hello, world” box when the user chooses the button called button_1:
(action_tile "button_1" "(c:hello)")

The user must exit the nested dialog box before using the previous dialog box
again.
AutoCAD imposes a limit of no more than eight nested dialog boxes, but to
avoid confusion it is recommended you nest dialog boxes no deeper than
four levels.

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WARNING! If you display nested dialog boxes by multiple new_dialog calls,
be careful to balance each new_dialog call with a corresponding done_dialog
call (whether called from a callback or not). Otherwise, your application may fail.
The term_dialog function terminates all current dialog boxes as if the user
had canceled each of them. You can use this function if you need to cancel a
series of nested dialog boxes.

Hiding Dialog Boxes
A user cannot make an interactive selection while a dialog box is active. If
you want the user to make a selection from the graphics screen, you must
hide your dialog box and then restore it. Hiding the box is the same as ending
it with done_dialog, except your callback function must use the done_dialog
status argument to indicate that the dialog box is hidden — as opposed to
ended or canceled. Set status to an application-defined value.
The start_dialog function returns the application-defined status when the
dialog box disappears. Your program must then examine the status returned
by start_dialog and determine what to do next. For standard and application-defined status values, see “done_dialog” in the AutoLISP Reference.
For example, here is a simple dialog box that may require a user to pick a
point in the AutoCAD graphics window:

The dialog box is defined with the following DCL:
hidedcl : dialog
{ label="Hide Example";
: column
{ : text
{ key="message";
label="Click PickMe to pick a point";
fixed_width=true;
fixed_height=true;
alignment=centered;
}

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:row
{ ok_only;
:retirement_button
{ label
= "PickMe";
key
= "hide";
mnemonic = "H";
}}}}

The function controlling the dialog box displays the window until the user
presses OK or closes the window. If the user chooses PickMe, the code hides
the dialog box and prompts the user to select a point. The following AutoLISP
code controls the dialog box:
(defun c:hidedcl (/ dcl_id what_next cnt)
(setq dcl_id (load_dialog "hidedcl.dcl"))
(setq what_next 2)
(setq cnt 1)
(while (>= what_next 2)
(if (null (new_dialog "hidedcl" dcl_id))
(exit)
); endif
;
;
;
;
;

;Load the dialog box.
;Begin display loop.
;Initialize dialog
;box, exit if nil
;returned.

Set action to take if a button is pressed. Either button
results in a done_dialog call to close the dialog box.
Each button associates a specific status code with
done_dialog, and this status code is returned by
start_dialog.

(action_tile "accept" "(done_dialog 1)") ;Set action for OK.
(action_tile "hide" "(done_dialog 4)")
;Set action for
;PickMe.
(setq what_next (start_dialog))
;Display dialog box.
;
(cond
((= what_next 4)
;Prompt user to
(getpoint "npick a point")
;pick pt.
)
((= what_next 0)
(prompt "nuser cancelled dialog")
)
)
)
(princ)
)

NOTE The term_dialog function terminates all dialog boxes at once but does
not return a status code, so there is no way for an application to distinguish
between hiding a nested box and canceling boxes due to an error condition.

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Requesting a Password
The following examples show how to use a simple dialog box to request a
password from users.
The getpass.dcl file defines a dialog box named passdlg, which contains two
tiles: the edit_box tile where the user enters the password, and the ok_cancel
tile. It uses the password_char DCL attribute to mask the text a user enters:
// GETPASS.DCL
//
passdlg : dialog {
label = "Password Protected";
: edit_box {
label = "Password:";
edit_width = 20;
key = "password";
password_char = "?";
}
ok_cancel;
}

The getpass.lsp file defines the GETPASS function. This function loads the
getpass.dcl file and displays the passdlg dialog box. When a user enters text
into the edit box, it is masked by the password_char character defined in the
DCL file. The action assigned to the edit box ensures that the characters
entered by the user are set to the pass variable:
;; GETPASS.LSP
;;
(defun GETPASS ( / dcl_id pass )
(setq dcl_id (load_dialog "getpass.dcl"))
(if (new_dialog "passdlg" dcl_id)
(progn
(action_tile "password" "(setq pass $value)")
(start_dialog)
)
(princ "Error: Unable to load GETPASS.DCL. ")
)
pass
)

The GETPASS function returns the string entered by the user.

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List Boxes and Pop-Up Lists
The following functions handle list boxes and pop-up lists in dialog boxes:
s
s
s

start_list
add_list
end_list

You set up the lists displayed in list boxes and pop-up lists by using a
sequence of calls to these functions.

List Operations
A dialog box list operation always begins with a start_list function call.
The function syntax is as follows:
(start_list key [operation [index]])

The key argument is a string that identifies the dialog box tile. The key argument is case-sensitive. The operation argument is an integer value that
indicates whether you are creating a new list, changing a list, or appending
to a list. The following are valid operation arguments:

Operation codes for start_list
Value

Description

1

Change selected list contents

2

Append new list entry

3

Delete old list and create new list (the default)

The index argum ent is only used in change operations. The index indicates
the list item to change by a subsequent add_list call. The first item in a list
is index 0.
If you don’t specify operation, it defaults to 3 (create a new list). If you do
not specify an index, the index value defaults to 0.

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You implement the list operations as follows:

Creating a
New List (3)

After the start_list call, call add_list repeatedly to add
new items to the list. End list handling by calling
end_list.

Changing an
Item in a
List (1)

After calling start_list, call add_list once to replace the
item whose index was specified in the start_list call. (If
you call add_list more than once, it replaces the same
item again.) End list handling by calling end_list.

Appending an
Item to a
List (2)

After calling start_list, call add_list to append an item
to the end of the list. If you continue to call add_list,
more items are appended until you call end_list.

Regardless of which list operation you are doing, you must call the three
functions in sequence: start_list, then add_list (possibly m ore than
once), and then end_list.
The mapcar function is useful for turning a “raw” AutoLISP list into a list box
display. In the following example, the appnames list contains strings that you
want to appear in a list box called selections. You can use this code fragment to set up the list and display it as follows:
(start_list "selections")
(mapcar ’ add_list appnames)
(end_list)

;Specify the name of the list box.
;Specify the AutoLISP list.

Because list creation (3) is the default, this example doesn’t specify it.
The value of a list_box tile is the index of the selected item (or the indexes
of selected items, if multiple selections are allowed). If your program needs
to know the actual text associated with an index, it must save the original
list. It must also track changes to the list.
Appending list items is similar to creating a new list. If, for example,
appnames has 12 items in it, and you want to append another list, called
newnames, you could use the following code:
(start_list "selections" 2)
(mapcar ’add_list newnames)
(end_list)

Changing a single item requires only one add_list call. In this case, you
specify the index of the item to change:
(start_list "selections" 1 5) ;Change the sixth item in the list.
(add_list "SURPRISE!")
;Remember that the first index is 0.
(end_list)

You cannot delete a list item or insert an item without rebuilding the list
from scratch.

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Processing List Elements
Because the value of a list_box tile can contain leading spaces (especially if
you are retrieving multiple items), do not test the value as a string comparison. Convert list_box value to an integer first with the atoi function, before
processing the list box. You can also use the read function, which converts a
token to an integer automatically. For example, for a list named justone that
accepts only a single selection, the following code fragment checks to see if
the third item in the list was selected:
(setq index ( get_tile "justone"))
(cond
((/= index "")
;See if string is empty.
(= 2 (atoi index))
; Process the third entry.
...
)
)

It is necessary to first check if the string is empty, because the atoi functions
return 0 for an empty string as well as the string "0".
The value of a pop-up list never has a leading space, so you don’t have to convert the value. Pop-up lists do not allow for multiple selection.
If the list box supports multiple selection, your program must do the conversion and step through the multiple values in the value string. The following
definition of MK_LIST returns a list containing only items the user has
selected from the original displist. (In this example, the display list
displist is maintained as a global variable.) The MK_LIST function expects
to be called with the current $value of the list box:
(defun MK_LIST (readlist / count item retlist)
(setq count 1)
(while (setq item (read readlist))
(setq retlist (cons (nth item displist) retlist))
(while (and (/= " " (substr readlist count 1))
(/= "" (substr readlist count 1)))
(setq count (1+ count))
)
(setq readlist (substr readlist count))
)
(reverse retlist)
)

Both preceding examples also work for the case of a single selection.

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Image Tiles and Buttons
AutoLISP provides functions for handling image tiles and image buttons.
Examples for how to use these functions are provided in this section.

Creating Images
The calling sequence to create images for image tiles and image buttons is
similar to the list-handling sequence. The start_image function begins the
creation of an image, and end_image ends it. However, the type of image to
draw is specified in separate function calls, instead of arguments:

vector_image

Draws a vector (a single, straight line) in the current
image.

fill_image

Draws a filled rectangle in the current image.

slide_image

Draws an AutoCAD slide in the image.

Vectors and filled rectangles are useful for simple images, such as the color
swatches (filled rectangles) that the AutoCAD Select Color dialog box uses to
display the user’s choice of color. For complicated images, slides are more
convenient. However, displaying slides can be time-consuming. If you use
slides, keep them simple.

NOTE If you use slides with filled objects (such as wide polylines, solids, and
3D faces) in image tiles, the images will appear as outlines unless you make the
slides from an image created with the SHADE command.
The vector_image function requires that you specify absolute coordinates,
while fill_image and slide_image require that you specify a starting coordinate along with a relative width and height. To do this correctly you must
know the exact dimensions of the image tile or image button. Because these
dimensions are usually assigned when the dialog box is laid out, the PDB feature provides functions that return the width and height of a particular tile.
These dimension functions are dimx_tile and dimy_tile. You should call
them before you begin creating an image. The origin of a tile, (0,0), is always
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Colors can be specified as AutoCAD color numbers or as one of the logical
color numbers shown in the following table. (The values and mnemonics are
defined by the Autodesk Device Interface [ADI].)

Dialog box color attribute
Color number

ADI mnemonic

Meaning

–2

BGLCOLOR

Current background of the AutoCAD graphics
screen

–15

DBGLCOLOR

Current dialog box background color

–16

DFGLCOLOR

Current dialog box foreground color (for text)

–18

LINELCOLOR

Current dialog box line color

In the following example, "cur_color" is an image tile you want to fill
entirely with a patch of red as follows:
(setq width (dimx_tile "cur_color")
height (dimy_tile "cur_color"))
(start_image "cur_color")
(fill_image 0 0 width height 1)
;1 = AutoCAD red.
(end_image)

You can use the image-drawing functions in conjunction with each other.
The following code fills an image and then draws a vertical stripe over it:
(setq width (dimx_tile "stripe")
height (dimy_tile "stripe"))
(start_image "stripe")
(fill_image 0 0 width height 3) ;3 = AutoCAD green.
(setq x (/ width 2))
;Center the vector vertically.
(vector_image x 0 x height 4)
;4 = AutoCAD cyan.
(end_image)

The slides you display with slide_image can be standalone slide (SLD) files,
or part of a slide library (SLB) file. If the slide is in an SLD file, you specify its
name without the .sld extension (for example, "frntview"). If the slide is in
a slide library, you specify the name of the library, followed by the name of
the slide enclosed in parentheses. Note that the library and slide names are
also specified without extensions—for example, "allviews(frntview)". The
slide_image function searches for the slide or slide library file according to
the current AutoCAD library search path. (See “load” in the AutoLISP Reference.)

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In the following example, the slide is in a single file called topview.sld:
(setq x (dimx_tile "view")
y (dimy_tile "view"))
(start_image "view")
( slide_image 0 0 x y "topview")
(end_image)

Vectors in slides are often drawn in white (color number 7), which is the
default background color of an image. If your image tile is blank when you
first display a slide, try changing its color attribute to graphics_background.
(You can also change the background of the image by preceding the
slide_image call with a fill_image call.)

Handling Image Buttons
You can handle an image button simply as a button — that is, you can use it
to trigger a single action. However, you can also use the PDB feature to define
regions of the button. With regions defined, the action taken depends on the
part of the image button the user selects. The mechanism for this is straightforward: an image button’s action or callback returns the ( X,Y) location that
the user selected. The coordinates are within the range of the particular
image button tile (as returned by the dimension functions). Your application
must assign a meaning to select locations by implicitly defining regions of
the image. The DDVPOINT dialog box makes good use of this feature. You can
view this by loading and running the ddvpoint.lsp file in the AutoCAD Support
directory.
In the following example, your image button has two color swatches created
by fill_image. You want to select either one or the other, depending on
which region the user selects. If the image button is divided horizontally
(dark above and light below), your action needs to test only the one
dimension:
(action_tile "image_sel" "(pick_shade $key $value $y)")
...
(defun pick_shade (key val y)
(setq threshold
(/ ( dimy_tile key) 2)) ;Image is divided horizontally.
(if (> y threshold)
;Remember that the origin is at
(setq result "Light")
;upper left.
(setq result "Dark") )
)


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Application-Specific Data
The client_data_tile function assigns application-specific data to a tile.
The data is available at callback time as the $data variable and must be a
string. Client data is not represented in DCL; it is valid only while your application is running. Using client data is comparable to using user-defined
attributes. The main difference is that user-defined attributes are read-only,
while client data can change at runtime. Also, end-users can inspect userdefined attributes in the application’s DCL file, but client data is invisible to
them.
Because your program must maintain the list displayed by a list box (or popup list), client data is good for handling this information. The following
modification to the MK_LIST function (shown in “Processing List Elements”
on page 382) makes the list an argument:
(defun MK_LIST (readlist displist / )

This code eliminates the need for a global list variable. The following calls in
the main part of the dialog box handler associate a short list with the tile by
calling client_data_tile, and then pass that list to MK_LIST by means of an
action expression as follows:
(client_data_tile
"colorsyslist"
"Red-Green-Blue Cyan-Magenta-Yellow Hue-Saturation-Value"
)
(action_tile
"colorsyslist"
"(setq usrchoice (mk_list $value $data))"
)

DCL Error Handling
The PDB feature checks a DCL file for errors the first time you load it. If
AutoCAD encounters a syntax error, a misuse of attributes, or any other error
(such as failure to specify a key attribute for an active tile), the PDB does not
load the DCL file. Instead, AutoCAD either displays one or more dialog boxes
alerting you to the error, or writes a list of errors to a text file called acad.dce.
If AutoCAD writes the error messages to acad.dce, it alerts you to this with a
message similar to the following:

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You can inspect the contents of acad.dce to find the problem. AutoCAD
places the acad.dce file in the current working directory. When AutoCAD
reads a DCL file successfully, it deletes the acad.dce file.
If your application uses multiple DCL files, the acad.dce file is overwritten (or
deleted if no errors occur) when each new file is loaded. When you test the
program, acad.dce shows errors (if any) from only the DCL file most recently
read. It is recommended that you use the VLISP DCL Preview feature to debug
your DCL files (see “Displaying Dialog Boxes with Visual LISP” on page 344).
You can also load and debug each file manually in AutoCAD with the
load_dialog function. The following load_dialog function loads the DCL
file hellofile.dcl :

Command:
3

(load_dialog "hellofile")

If the dialog box loads successfully, load_dialog returns a positive integer
that identifies the DCL file. You pass this value to the new_dialog function
to initialize individual dialog boxes in the file.
The new_dialog function returns T if it succeeds; otherwise it returns nil. If
new_dialog returns T, call the start_dialog function to display the dialog
box.
Once you’ve debugged each DCL file, you can load your program and test the
dialog boxes in combination. If your program calls a restricted function
between the start_dialog and done_dialog calls, AutoCAD terminates all
dialog boxes and displays the following error message:

AutoCAD rejected function
See “Functions Restricted When a Dialog Box Is Open” on page 367 for information on which functions are restricted.

Setting the Auditing Level to Affect Error
Messages
The level of semantic auditing affects which messages AutoCAD issues for a
DCL file (see “Semantic Auditing of DCL Files” on page 346). For example,
the hidedcl dialog box defined in “Hiding Dialog Boxes” on page 377 dis-

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387

plays without any warnings, if you use the default audit level. If you set the
audit level to 3, though, AutoCAD displays an alert dialog box with a warning message. You can see this for yourself by inserting the following line at
the beginning of hidedcl:
dcl_settings : default_dcl_settings { audit_level = 3; }

Try using the VLISP DCL Preview feature to view the dialog box defined in
hidedcl. You will be alerted to view the acad.dce file, which contains the following messages:
=== DCL semantic audit of C:/PROGRA~1/AUTOCA~1/VLISP/$vld$.dcl ===
Hint in "hidedcl". (widget type = text, key = "message")
fixed_height = true is probably redundant.

At lower (less discriminating) levels of semantic auditing, AutoCAD does not
look for redundant attribute definitions and the dialog box displays normally.
Remove the fixed_height = true statement from the DCL to correct the situation AutoCAD is warning you about.

Dialog Box Function Summary
This section summarizes the steps required in a typical dialog box handling
function. It also describes a sample application you can refer to when designing and implementing your own dialog box functions.

Function Sequence
The following demonstrates the typical function sequence:

1 Load the DCL file with a load_dialog call.
2 Call new_dialog to display a particular dialog box.
Be sure to check the value returned by new_dialog. Calling start_dialog
when the new_dialog call has failed can have unpredictable results.

3 Initialize the dialog box by setting up tile values, lists, and images. Initialize
also when you call action_tile to set up action expressions or callback functions. Other functions typically called at this time are set_tile and
mode_tile for general tile values and states, start_list, add_list, and
end_list for list boxes, and the dimension functions with start_image,
vector_image, fill_image, slide_image, and end_image for images. At this
time you can also call client_data_tile to associate application-specific
data with the dialog box and its components.

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4 Call start_dialog to turn control over to the dialog box, so that the user can
enter input.

5 Process user input from within your actions (callbacks). Process input when
you are most likely to use get_tile, get_attr, set_tile, and mode_tile.
The user presses an exit button, causing an action to call done_dialog, which
causes start_dialog to return a value. At this point, unload the DCL file by
calling unload_dialog.
This scheme handles only one dialog box and one DCL file at a time. Applications usually have multiple dialog boxes. The easiest and quickest way to
handle these dialog boxes is to save all of them in a single DCL file. The
load_dialog call then loads all dialog boxes at once, and you can call
new_dialog for any dialog box. If memory is limited, however, you may need
to create multiple DCL files and use unload_dialog to remove one set of
dialog boxes from memory before you load another set.

The Sample Block Definition Dialog Box
The sample application bmake.lsp and its associated bmake.dcl file illustrate a
number of useful dialog box techniques. These files are in the AutoCAD Support directory. The bmake application is essentially an interactive interface to
the entmake function. You can use it to define new blocks and to view the
names of existing blocks. Some of the techniques illustrated by bmake are
Hiding dialog boxes by defining special status codes for done_dialog to
pass to start_dialog. See the main loop of the C:BMAKE function (following the load_dialog and action_tile calls).
s Using a toggle to enable or disable another tile. See the definition of the
DO_UNNAMED function.
s Building a list for a list box. See the PAT_MATCH and SORT functions.
s Displaying the standard AutoCAD Help dialog box. See the DO_HELP
function.
s

Aside from demonstrating dialog box techniques, bmake illustrates good
design.

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Programmable Dialog Box
Reference

13

In This Chapter

This chapter lists and describes all the dialog control
language (DCL) tiles and their associated attributes, and

s Tile Attributes
s Synopsis of Predefined Attributes
s DCL Attribute Catalog

summarizes the VLISP functions available for working

s Functional Synopsis of DCL Tiles

with programmable dialog boxes.

s DCL Tile Catalog
s Programmable Dialog Box
Function Synopsis

391

Tile Attributes
A tile’s attributes define its layout and functionality. An attribute is similar to
a programming language variable: it consists of a name and a value.

Attribute Types
The value of an attribute must be one of the following data types:

Integer

Numeric values (both integers and real numbers) that
represent distances, such as the width or height of a tile,
are expressed in character-width or character-height
units.

Real Number

A fractional real number must have a leading digit: for
example, 0.1, not .1.

Quoted String

A quoted string consists of text enclosed in quotation
marks ( ""). Attribute values are case-sensitive: B1 is not
the same as b1. If the string must contain a quotation
mark, precede the quotation mark character with a
backslash ( "). Quoted strings can contain other control
characters as well. The characters recognized by DCL are
shown in the following table:

Control characters allowed in DCL
strings
Control
character
"

Chapter 13

newline

t

|

backslash

n

392

quote (embedded)

Reserved Word

Meaning

horizontal tab

A reserved word is an identifier made up of alphanumeric
characters, beginning with a letter. For example, many
attributes require a value of either true or false. Reserved
words are also case-sensitive: True does not equal true.

Programmable Dialog Box Reference

Like reserved words and strings, attribute names are case-sensitive; for example, you cannot assign a width by calling it Width.
Application programs always retrieve attributes as strings. If your application
uses numeric values, it must convert them to and from string values. For
more information on handling tile values within an AutoLISP program, see
“Handling Tiles” on page 372.
Some attributes, such as width and height, are common to all tiles. Attribute
specifications are optional. Many attributes have default values that are used
if the attribute is not specified. Other attributes are specifically meant for certain kinds of tiles — for example, the background color of an image. If you
attempt to assign this attribute to a different kind of tile, AutoCAD may
report an error. Usually, it ignores the attribute.

Restricted Attributes
Do not use the following tile attributes in your DCL files:
s horizontal_margin
s vertical_margin
s type

User-Defined Attributes
When defining tiles, you can assign your own attributes. The name of the
attribute can be any valid name that does not conflict with the standard, predefined attributes described in the previous subsection and summarized in
“Synopsis of Predefined Attributes” on page 394. An attribute name, like a
keyword, can contain letters, numbers, or the underscore (_), and must begin
with a letter.
If a user-defined attribute name conflicts with a predefined attribute, the PDB
feature does not recognize the attribute as a new one, and attempts to use the
value you assign it with the standard attribute. This can be very hard to
debug.
The values you assign to the attribute, and their meanings, are defined by
your application. Values for user-defined attributes must conform to the
types described in “Tile Attributes” on page 392.
Defining attributes is comparable to defining application-specific client data.
Both techniques enable the PDB feature to manage data you supply. Userdefined attributes are read-only, that is, they are static while the dialog box
is active. If you need to change the values dynamically, you must use client

Tile Attributes

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393

data at runtime. Also, end users can inspect the value of user-defined
attributes in the application’s DCL file, but client data remains invisible.
The definition of the AutoCAD Drawing Aids dialog box defines its own
attribute, errmsg, which has a unique string value for each tile. A common
error handler uses the value of errmsg when it displays a warning. For example, the tile could assign the following value to errmsg:
errmsg = "Grid Y Spacing";

If the user enters an unusable value, such as a negative number, AutoCAD
displays the following error message:

Invalid Grid Y Spacing.
The word Invalid and the trailing period (.) are supplied by the error handler.
User-defined attributes also can be used for limits on the value of a tile and
the name of a subdialog box that the tile activates (see “Nesting Dialog
Boxes” on page 376).

Synopsis of Predefined Attributes
This section lists the attributes defined by the PDB feature. The following
table summarizes the predefined attributes in alphabetical order. The
attributes are described in detail in “User-Defined Attributes” on page 393.

Predefined attributes
Attribute name

All active tiles

AutoLISP action expression

alignment

All tiles

Horizontal or vertical position in
a cluster

allow_accept

edit_box, image_button,
list_box

Activates is_default button when
this tile is selected

aspect_ratio

image, image_button

Aspect ratio of an image

big_increment

|

Meaning (if specified or true)

action

394

Associated with

slider

Incremental distance to move

Chapter 13


Predefined attributes (continued)
Attribute name

Associated with


children_alignment

row, column, radio_row,
radio_column, boxed_row,
boxed_column,
boxed_radio_row,
boxed_radio_column

Alignment of a cluster’s children

children_fixed_
height

boxed_column,
boxed_radio_row,
boxed_radio_column

Height of a cluster’s children
doesn’t grow during layout

children_fixed_
width

boxed_column,
boxed_radio_row,
boxed_radio_column

Width of a cluster’s children
doesn’t grow during layout

color

image, image_button

Background (fill) color of an
image

edit_limit

edit_box

Maximum number of characters
users can enter

edit_width

edit_box, popup_list

Width of the edit (input) portion
of the tile

fixed_height

All tiles

Height doesn’t grow during
layout

fixed_width

All tiles

Width doesn’t grow during
layout

fixed_width_font

list_box, popup_list

Displays text in a fixed pitch font

height

All tiles

Height of the tile

initial_focus

Dialog

Key of the tile with initial focus

is_bold

Text

Displays as bold

is_cancel

Button

Button is activated when the
cancel key—usually ESC— is
pressed

is_default

Button

Button is activated when the
accept key —usually ENTER —
is pressed

Synopsis of Predefined Attributes

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395

Predefined attributes (continued)
Attribute name

All active tiles

Tile is initially enabled

is_tab_stop

All active tiles

Tile is a tab stop

key

All active tiles

Tile name used by the
application

label

boxed_row, boxed_column, Displayed label of the tile
boxed_radio_row,
boxed_radio_column, button,
dialog, edit_box, list_box,
popup_list, radio_button,
text, toggle

layout

slider

Whether the slider is horizontal
or vertical

list


Initial values to display in list

max_value

slider

Maximum value of a slider

min_value

slider

Minimum value of a slider

mnemonic

all active tiles

Mnemonic character for the tile

multiple_select

list_box

List box allows multiple items to
be selected

password_char

edit_box

Masks characters entered in
edit_box

small_increment

slider

Incremental distance to move

tabs


Tab stops for list display

tab_truncate


Truncates text that is larger than
the associated tab stop

value

Text, active tiles (except
buttons and image buttons)

Tile’s initial value

width

|


is_enabled

396

Associated with

All tiles

Width of the tile

Chapter 13


DCL Attribute Catalog
DCL tile attributes are described in detail in this section. The attributes are
listed alphabetically.

action
action = "(function)";
Specifies an AutoLISP expression to perform an action when this tile is
selected. Also known as a callback. For some kinds of tiles, an action can also
occur when the user switches focus to a different tile.
The possible value is a quoted string that is a valid AutoLISP expression. A tile
can have only one action. If the application assigns it an action (with
action_tile), this overrides the action attribute.

NOTE You cannot call the AutoLISP command function from the action
attribute.

alignment
alignment = position;
Specifies the horizontal or vertical positioning (justification) of a tile within
its cluster.
For a tile that is a child of a column, the possible values are left, right, or
centered (default is left).
For a tile that is a child of a row, the possible values are top, bottom, or
centered (default is centered).
You cannot specify the alignment along the long axis of a cluster. The first
and last tiles in the cluster always align themselves with the ends of the column or row. Other tiles in the cluster are distributed evenly unless you adjust
the distribution by using padding insertion points (see “spacer_0” on page
426).


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397

allow_accept
allow_accept = true-false;
Specifies whether the tile is activated when the user presses the accept key
(usually ENTER ). If true and the user presses the accept key, the default button (if any) is pressed. The default button is the button tile whose is_default
attribute is set to true. The allow_accept attribute defaults to false.

aspect_ratio
aspect_ratio = real;
Specifies the ratio of the width of the image to its height (width divided by
height). If zero (0.0), the tile is fitted to the size of the image.
Possible values are floating-point values (default: none).

big_increment
big_increment = integer;
Specifies the value used by the slider’s incremental controls. The default
value of big_increment is one-tenth of the total range. The value must be
within the range specified by min_value and max_value.

children_alignment
children_alignment = position;
Specifies the default alignment (similar to alignment) for all tiles in a cluster.
Does not override a child’s alignment attribute, if alignment is specified
explicitly.
For columns, possible values are left, right, or centered (default: left).
For rows, possible values are top, bottom, or centered (default: centered).

children_fixed_height
children_fixed_height = true-false;
Specifies the default height (similar to height) for all tiles in a cluster. Does
not override a child’s height attribute, if it is specified explicitly.

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Possible values are true or false (default: false).

NOTE Use the fixed_ attributes with discretion. Inconsistent overriding of
defaults results in inconsistent layouts.

children_fixed_width
children_fixed_width = true-false;
Specifies the default width (similar to width) for all tiles in a cluster. Does not
override a child’s width attribute, if it is specified explicitly.

NOTE Use the fixed_ attributes with discretion. Inconsistent overriding of
defaults results in inconsistent layouts.

color
color = colorname;
Specifies the background (fill) color of the image. Possible values are an integer or reserved word (default: 7) specified as an AutoCAD color number or as
one of the symbolic names shown in the following table:

Symbolic names for colors
Symbolic name

Meaning

dialog_line

Current dialog box line color

dialog_foreground

Current dialog box foreground color (for text)

dialog_background

Current dialog box background color

graphics_background

Current background of the AutoCAD graphics screen
(usually equivalent to 0)

black

AutoCAD color = 0 (black) (appears light on a black
background)

red

AutoCAD color = 1 (red)


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Symbolic names for colors (continued)
Symbolic name

Meaning

yellow

AutoCAD color = 2 (yellow)

green

AutoCAD color = 3 (green)

cyan

AutoCAD color = 4 (cyan)

blue

AutoCAD color = 5 (blue)

magenta

AutoCAD color = 6 (magenta)

white
graphics_foreground

AutoCAD color = 7 (white)
(appears black on a light background)

The symbolic names graphics_background and graphics_foreground are
provided as alternatives to the names black and white. The use of a specific
color can be confusing because the color that is actually displayed varies
depending on the current AutoCAD configuration. Also, vectors in slides that
you display in an image are often drawn in black or white. If your image tile
is blank when you first display it, try changing its color to
graphics_background or graphics_foreground.

edit_limit
edit_limit = integer;
Specifies the maximum number of characters a user is allowed to enter in the
edit box. A possible value is an integer (default: 132). When the user reaches
this limit, AutoCAD rejects additional characters (except for BACKSPACE or
DEL ). The maximum edit limit allowed is 256 characters.

edit_width
edit_width = number;
Specifies the width in character-width units of the edit (input) portion of the
box — the actual boxed portion of the edit_box tile. Possible values are an
integer or a real number. If edit_width is not specified or is zero, and the
width of the tile is not fixed, the box expands to fill the available space. If
edit_width is nonzero, then the box is right-justified within the space occu-

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pied by the tile. If it’s necessary to stretch the tile for layout purposes, the
PDB feature inserts white space between the label and the edit portion of
the box.

fixed_height
fixed_height = true-false;
Specifies if a tile’s height is allowed to fill the available space. If this attribute
is true, the tile does not fill the extra space that becomes available in the layout/alignment process.

fixed_width
fixed_width = true-false;
Specifies if a tile’s width is allowed to fill the available space. If this attribute
is true, the tile does not fill the extra space that becomes available in the layout/alignment process.

fixed_width_font
fixed_width_font = true-false;
Specifies whether a list box or pop-up list will display text in a fixed pitch
font. This allows for easier spacing and tab alignment of columns.

height
height = number;
Specifies the height of a tile. Possible values are an integer or a real number
representing the distance in character height units. Do not specify this value
unless the assigned defaults do not have an acceptable appearance. You must
specify, however, the height of image tiles and image buttons.


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The height attribute specifies the minimum height of a tile. This dimension
can be expanded when the tile is laid out, unless the height is fixed by one
of the fixed_ attributes. Defaults are dynamically assigned based on layout
constraints.
Character-height units are defined as the maximum height of screen characters (including line spacing).

initial_focus
initial_focus = "string";
Specifies the key of the tile within the dialog box that receives the initial keyboard focus. Possible value is a quoted string (no default).

is_bold
is_bold = true-false;
Specifies whether the text is displayed in bold characters. Possible values are
true or false (default: false). If true, the text is displayed in bold
characters.

is_cancel
is_cancel = true-false;
Specifies whether the button is selected when the user presses the ESC key.
If the action expression for buttons with the is_cancel attribute set to true
does not exit the dialog box (does not call done_dialog), the dialog box is
automatically terminated after the action expression has been carried out,
and the DIASTAT system variable is set to 0.
Only one button in a dialog box can have the is_cancel attribute set to true.

is_default
is_default = true-false;
Specifies whether the button is the default button selected (“pushed”) when
the user presses the accept key. Possible values are true or false (default:
false). If the user is in an edit_box, list_box, or image_button that has the

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allow_accept attribute set to true, the default button is also selected if the
user presses the accept key or (for list boxes and image buttons) double-clicks.
The default button is not selected by the accept key if another button has
focus. In this case, the button that has focus is the one selected.

Only one button in a dialog box can have the is_default attribute set
to true.

is_enabled
is_enabled = true-false;
Specifies whether or not the tile is initially available. Possible values are
true or false (default: true). If false, the tile is unavailable and appears
grayed out.

is_tab_stop
is_tab_stop = true-false;
Specifies whether the tile receives keyboard focus when the user moves
between tiles by pressing the TAB key. Possible values are true or false
(default: true). If the tile is disabled, it is not a tab stop even if this attribute
is true. If false, the tile is not a tab stop.

key
key = "string";
Specifies a name that the program uses to refer to this specific tile. Possible
value is a quoted string (no default). Within a particular dialog box, each key
value must be unique. This string is case-sensitive: if you specify the key as
BigTile, you cannot reference it as bigtile.
Because the value of a key is not visible to the user, its name can be whatever
you choose (as long as it is unique to the dialog box). For the same reason,
key attributes do not need to be translated for applications offered in multiple languages.


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label
label = "string";
Specifies the text displayed within the tile. Possible value is a quoted string
(default: a blank string, " "). The placement of label text is tile-specific.
The label attribute can specify a mnemonic character for the tile. The mnemonic is underlined in the tile’s label.
If a character in the label string is preceded by an ampersand (&), that character becomes the mnemonic. The character doesn’t have to be unique to the
dialog box. If more than one tile has the same mnemonic, the user presses
that key to cycle through the tiles sequentially.
Mnemonics change focus but do not select a tile. If the user specifies a mnemonic key for a tile that contains a group of items, such as a cluster or a list
box, the focus is put on the first item in the tile that is a tab stop. Any active
tile is a tab stop unless its is_tab_stop attribute is set to false.

NOTE The mnemonic attribute also specifies a mnemonic character.

layout
layout = position;
Specifies the orientation of a slider. Possible values are horizontal or
vertical (default: horizontal). For horizontal sliders, the value increases
from left to right. For vertical sliders, the value increases from bottom to top.

list
list = "string";
Specifies the initial set of lines (choices) to be placed in the popup_list or
list_box. Possible value is a quoted string (no default). Lines are separated
by a new line symbol ( n). Tab characters ( t) can occur within each line.

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max_value
max_value = integer;
Specifies the upper range of values that a slider returns. Default maximum
value is 10000. This value must be a signed, 16-bit integer no greater than
32767.

min_value
min_value = integer;
Specifies the lower range of values that a slider returns. Default minimum
value is 0. This value must be a signed, 16-bit integer no less than -32768. The
min_value can be greater than the max_value.

mnemonic
mnemonic = "char";
Specifies a keyboard mnemonic character for the tile. The mnemonic is
underlined in the tile’s label. A possible value is a quoted string of a single
character (no default). The character must be one of the letters in the tile’s
label. The character doesn’t have to be unique to the dialog box. If more than
one tile has the same mnemonic, the user presses that key to cycle through
the tiles sequentially.
From the user’s point of view, mnemonics aren’t case-sensitive. For example,
if a button’s mnemonic character is A , entering a or A both gives the A button
focus. However, in the DCL file the mnemonic must be one of the characters
in the tile’s label, and it must be capitalized as it appears in the label string.
Mnemonics change focus. If the user specifies a mnemonic key for a tile that
contains a group of items, such as a cluster or a list box, the focus is put on
the first item in the tile that is a tab stop. Any active tile is a tab stop unless
its is_tab_stop attribute is set to false.

NOTE The label attribute can also specify a mnemonic character.


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405

multiple_select
multiple_select = true-false;
Specifies whether multiple items in the list_box can be selected (highlighted) at the same time. Possible values are true or false (default: false).
If true, multiple items can be selected at a time.

password_char
password_char = "char";
Specifies the character to be used to mask user input. If password_char is
specified and is not null, that character is displayed in the edit box instead of
the characters entered by the user. The use of this attribute has no effect on
your application’s retrieval of the value entered by the user; it alters only the
display of the characters in the edit box.
For an example of using the password_char attribute in an application, see
“Requesting a Password” on page 379.

small_increment
small_increment = integer;
Specifies the value used by the slider’s incremental controls. Default value of
small_increment is one one-hundredth the total range. The value must be
within the range specified by min_value and max_value. This attribute is
optional.

tabs
tabs = "string";
Specifies the placement of tabs in character width units. Possible value is a
quoted string containing integers or floating-point numbers, separated by
spaces (no default). These values are used for vertically aligning columns of
text in a popup_list or list_box.
For example, the following code specifies a tab stop at every 8 characters.
tabs = "8 16 24 32";

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tab_truncate
tab_truncate = true-false;
Specifies whether the text in a list box or pop-up list is truncated if it is larger
than the associated tab stop. Possible values are true or false (default:
false).

value
value = "string";
Specifies the initial value of a tile. Possible value is a quoted string. The meaning of a tile’s value varies depending on the kind of tile. The value of a tile
can change at runtime through user input or set_tile calls.
The value attribute of a tile is not considered when the dialog box is laid out.
After the layout is finished and the dialog box has been displayed,
new_dialog uses the value attributes to initialize each tile in the dialog box.
A tile’s value attribute has no effect on the size or spacing of tiles in the
dialog box.

width
width = number;
Specifies the width of a tile. Possible values are an integer or a real number
representing the distance in character-width units. Do not specify this value
unless the assigned defaults don’t provide acceptable appearance. You must
specify, however, the width of image tiles and image buttons.
The width of a tile specifies a minimum width. This dimension can be
expanded when the tile is laid out unless the width is fixed by one of the
fixed_ attributes. Defaults are dynamically assigned based on layout
constraints.
Character width units is defined as the average width of all uppercase and
lowercase alphabetic characters, or the screen width divided by 80, whichever is less (average width is (width(A .. Z) + width (a .. z)))/52 ).


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Functional Synopsis of DCL Tiles
This section presents the DCL tiles in functional groupings.

Predefined Active Tiles
The AutoCAD PDB feature has a set of built-in, or predefined, tiles that can
be used by themselves or as the basis for more complex tiles. Their definitions
appear as comments within the base.dcl file. (See “The base.dcl and acad.dcl
Files” on page 340.)
When the user chooses an active tile—a button, for example— the dialog box
responds by notifying the application controlling the dialog box. Any predefined active tile can have an associated action. The effect of an action can
be visible to the user or can be purely internal (for example, a status update).
Actions are accompanied by a reason code that indicates what triggered the
action. The meaning of the reason depends on which kind of tile triggered it.
The following tiles are selectable, active tiles:

button

popup_list

edit_box

radio_button

image_button

slider

list_box

toggle

Tile Clusters
You can group tiles into composite rows or columns (known collectively as
clusters). For layout purposes, a cluster is treated as a single tile. The row or
column can be boxed, with an optional label (a cluster without a box cannot
be labeled).
Users cannot select a cluster, only individual tiles within the cluster. Clusters
cannot have actions assigned to them, with the exception of radio rows and
radio columns. The following tiles define clusters:

boxed_column
boxed_radio_column

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dialog
radio_column

Chapter 13


boxed_radio_row

radio_row

boxed_row

row

column

Decorative and Informative Tiles
The tiles listed below do not cause actions and cannot be selected. They are
provided to display information or for visual emphasis, or to assist you in laying out the dialog box.

image

spacer_0

text

spacer_1

spacer

Text Clusters
A text tile is surrounded by margin space (like any other kind of tile), which
presents a problem when you want to combine pieces of text. For example,
assume you want to display the following message:

The time is now 0800 hours and 37 seconds.
The actual values (0800 and 37) are supplied by your program. You can do
this by creating a concatenated line of text built out of text_part tiles. You
can also use text parts vertically to create a paragraph that doesn’t have too
much space between the lines.
The following text cluster tiles are prototypes defined in the base.dcl file.
concatenation

text_part

paragraph

Functional Synopsis of DCL Tiles

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409

Dialog Box Exit Buttons and Error Tiles
The base.dcl file provides standard button subassemblies for exiting (or “retiring”) a dialog box. Use these standard versions to maintain a consistent
appearance across applications.
errtile

ok_cancel_help

ok_only

ok_cancel_help_errtile

ok_cancel

ok_cancel_help_info

You can customize the text in these buttons by using the prototype
retirement_button as described in “Customizing Exit Button Text” on page

351.

Restricted Tiles
Your DCL files should not use the tiles cluster or tile. Also, do not use the
basic exit button types ( cancel_button, help_button, info_button, and
ok_button) unless you redefine the standard exit button subassemblies as
described in this section in “Dialog Box Exit Buttons and Error Tiles” on page
410.

DCL Tile Catalog
This section describes all the predefined DCL tiles. The syntax statement,
which follows the tile name, lists all the attributes associated with that tile.
Any specific attribute functionality is noted following the tile’s description.

boxed_column
: boxed_column {
alignment children_alignment
children_fixed_height children_fixed_width
fixed_height fixed_width height label width
}

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Chapter 13


A boxed column has a border around it. A dialog box is laid out like a boxed
column. If a boxed column is assigned a label, the label appears embedded in
the top border. If the label is absent, blank (" "), or null (""), only the box is
displayed.
label

Appears as a title. Spacing between a blank and a null label
might be different. (See “Fixing the Spacing Around a
Boxed Row or Column” on page 350.)

boxed_radio_column
: boxed_radio_column {
}

A boxed radio column has a border around it. Treat the label the same way
that you would treat the label of a boxed column.
label

Appears as a title. If the label is absent, blank (the default),
or null (""), only the box appears. Spacing between a
blank and a null label might be different. (See “Fixing the
Spacing Around a Boxed Row or Column” on page 350.)

value

Specifies the key of the currently selected radio button
(the one whose value is "1").

DCL Tile Catalog

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boxed_radio_row
: boxed_radio_row {
}

A boxed radio row has a border around it. You treat the label the same way
that you would treat the label of a boxed row.
label


value

Specifies the key of the currently selected radio button
(the one whose value is " 1").

boxed_row
: boxed_row {
}

A boxed row has a border around it. If a boxed row has a label, the label
appears embedded in it.
label

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button
: button {
action alignment fixed_height fixed_width
height is_cancel is_default is_enabled
is_tab_stop key label mnemonic width
}

A button tile resembles a push button. The button’s label specifies text that
appears inside the button. Buttons are appropriate for actions that are immediately visible to the user such as leaving the dialog box, or going into a subdialog box.
Dialog boxes must include an OK button (or its equivalent) for the user to
press after using (or reading) the box. Many dialog boxes also include a
Cancel button that enables the user to leave the dialog box without making
any changes.
Dialog boxes should use the standard exit button subassemblies described in
“Dialog Box Exit Buttons and Error Tiles” on page 410. These subassemblies
guarantee that the attributes described in this section are correctly assigned.

NOTE If you make the default button and the cancel button the same, you
must make sure at least one other exit button is associated with an action that
calls done_dialog. Otherwise, the dialog box is always canceled.
label

Specifies the text that appears in the button.

column
: column {
}

DCL Tile Catalog

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413

Tiles in a column are laid out vertically in the order in which they appear in
the DCL file. A column can contain any kind of tile (except for solitary radio
buttons), including rows and other columns.
A column without a box has no additional attributes beyond the standard
layout attributes.

concatenation
: concatenation {
}
A concatenation is a line of text made up of multiple, concatenated
text_part tiles. This is useful when you want to insert text that can change
at runtime into a standard message. There is a margin around the
concatenation as a whole.
The concatenation tile is defined in the base.dcl file. See “paragraph” on page
419 for an example that uses concatenation.

dialog
: dialog {
initial_focus
}

label

value

A dialog is the tile that defines the dialog box. You should not specify both a
label and value attribute: the value attribute overrides the label attribute.
label

Specifies the optional title displayed in the title bar of the
dialog box.

value

Specifies a string to display as the optional dialog box title.
However, the value isn’t inspected at layout time, so if you
assign the title this way, make sure the dialog box is wide
enough or the text might be truncated.
For a dialog, the label and value are equivalent except
for layout considerations. To change the title at runtime ,
use the set_tile function (see “set_tile” in the AutoLISP
Reference).

initial_focus

Specifies the key of the tile that receives the initial
keyboard focus.

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edit_box
: edit_box {
action alignment allow_accept edit_limit
edit_width fixed_height fixed_width height
is_enabled is_tab_stop key label mnemonic
value width password_char
}

An edit box is a field that enables the user to enter or edit a single line of text.
An optional label can appear to the left of the box. If the entered text is
longer than the length of the edit box, the edit box scrolls horizontally.
Left-justifying the label and right-justifying the edit box makes it easier to
align edit_box tiles vertically.
label

Appears as a title. If specified, the label is left-justified
within the width of the edit_box tile.

value

The initial ASCII value placed in the box. It is displayed
left-justified within the edit (input) part of the box. The
value of an edit box is terminated by the null character. If
the user enters more characters than the edit_limit and
the string is truncated, the null character is appended.

errtile
errtile;
An error tile is a text tile that appears at the bottom of a dialog box. By default
it is blank, but programs can display messages in it by setting the value of the
tile whose key is "error". For example:
(set_tile "error" "You can only select one option")

The errtile tile is defined in the base.dcl file.

DCL Tile Catalog

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415

image
: image {
action alignment aspect_ratio color
fixed_height fixed_width height is_enabled
is_tab_stop key mnemonic value width
}

An image is a rectangle in which a vector graphic picture is displayed. Images
are used to display icons, linetypes, text fonts, and color patches in AutoCAD
dialog boxes. See “Creating Images” on page 383 for instructions on how to
generate images for image tiles.
You must assign an image tile either an explicit width and height attribute,
or one of those attributes plus an aspect_ratio.

image_button
: image_button {
action alignment allow_accept aspect_ratio
color fixed_height fixed_width height
is_enabled is_tab_stop key mnemonic width
}

The image button tile is a button that displays a graphic image rather than a
label.
When the user selects an image button, the program obtains the coordinates
of the point that was selected. This is useful if you want to display a miniature drawing and assign different meanings to selecting different regions
in it.
See “Creating Images” on page 383 for instructions on how to generate
images for image buttons.

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You must assign an image button either an explicit width and height
attribute, or one of those attributes plus an aspect_ratio.

list_box
: list_box {
action alignment allow_accept fixed_height
fixed_width height is_enabled is_tab_stop
key label list mnemonic multiple_select tabs
value width
}

A list box contains a list of text strings, arranged in rows. Usually the list is
of variable length, but list boxes can be used for fixed-length lists when a different kind of tile, such as a set of radio buttons, takes up too much space in
the dialog box. When users select a row, it is highlighted. A list box can contain more rows than can fit in the box, so a scroll bar always appears to the
right of the list box. (The scroll bar is enabled only if the list has more items
than can appear at once.) By dragging the scroll bar cursor or clicking on its
arrows, users can scroll through the list box items. Some applications may
allow users to select multiple rows.
See “List Boxes and Pop-Up Lists” on page 380 for instructions on how to
manage lists for list boxes and pop-up lists.
label

Text displayed above the list box.

value

A quoted string containing zero ("") or more integers,
separated by spaces (no default). Each integer is a zerobased index that indicates a list item that is initially
selected. If multiple_select is false, value cannot
contain more than one integer.
If the value string is empty ( ""), then no items in the list
are initially selected. In this case, you don’t need to
specify the value attribute at all.

DCL Tile Catalog

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417

ok_only
ok_only;

The ok_only tile is a solitary OK button, such as the kind that alert boxes use.
The key of the OK button is "accept".
The ok_only tile is defined in the base.dcl file.

ok_cancel
ok_cancel;

The ok_cancel tile is a combination of the OK and Cancel buttons, and is the
standard combination for dialog boxes that can originate changes to data.
The key of the Cancel button is "cancel".
The ok_cancel tile is defined in the base.dcl file.

ok_cancel_help
ok_cancel_help;

This tile is the ok_cancel cluster combined with the Help button. The key of
the Help button is "help". Help buttons are recommended for the main dialog box of an application and for complex dialog boxes. The function that
handles the Help button can display the standard AutoCAD Help dialog box
by invoking the AutoLISP help function.
The ok_cancel_help tile is defined in the base.dcl file.

ok_cancel_help_errtile
ok_cancel_help_errtile;

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The ok_cancel_help_errtile tile provides a convenient way to specify the
exit buttons and error tile all at once.
The ok_cancel_help_errtile tile is defined in the base.dcl file.

ok_cancel_help_info
ok_cancel_help_info;

The ok_cancel_help_info tile does everything that the ok_cancel_help tile
does, but it also includes an information button for displaying additional
material. It might display the name of your application, the logo of your
firm, the application’s version number, how to obtain support, and so on.
The key of the Info button is "info".
The ok_cancel_help_info tile is defined in the base.dcl file.

paragraph
: paragraph {
}

A paragraph is a cluster of text_part or concatenation tiles that are arranged
vertically. You can construct paragraphs of running text either statically or at
runtime. There is a margin around the paragraph as a whole.
The paragraph tile is defined in the base.dcl file.
The illustration above was generated with the following DCL:
: paragraph
{
: concatenation
{
: text_part
{
label = "One";
}

DCL Tile Catalog

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419

: text_part
{
label = "good turn";
}
}
: text_part {
label = "Deserves another";
}
}

popup_list
: popup_list {
action alignment edit_width fixed_height
fixed_width height is_enabled is_tab_stop
key label list mnemonic tabs value width
}

A pop-up list, or simply pop-up, is functionally equivalent to a list box.
When a dialog box is first displayed, the pop-up is in a collapsed state and
looks like a button except for the downward-pointing arrow on the right.
When the user selects the text or the arrow, the list pops up and displays
more selections. A popped-up list has a scroll bar on the right that works like
the scroll bar of a list box. When a pop-up list is collapsed, the current selection appears in its display field. Pop-up lists do not allow multiple selection.
See “List Boxes and Pop-Up Lists” on page 380 for instructions on how to
manage lists for list boxes and pop-up lists.
label

edit_width

420

|

Appears as a title to the left of the pop-up list. If specified,
the label is left justified within the width of the
popup_list tile.
Specifies the width of the text portion of the list in
character-width units. It doesn’t include the optional
label on the left or the pop-up arrow (or scroll bar) on the
right. If edit_width isn’t specified or is zero, and the

Chapter 13


width of the tile isn’t fixed, the box expands to fill the
available space. Possible value is an integer or a real
number. If edit_width is nonzero, then the box is rightjustified within the space occupied by the tile. If it is
necessary to stretch the tile for layout purposes, the PDB
feature inserts white space between the label and the edit
portion of the box.
value

A quoted string containing an integer (default: "0"). The
integer is a zero-based index that indicates the currently
selected item in the list (the one that is displayed when
the list isn’t popped up).

radio_button
: radio_button {
action alignment fixed_height
height is_enabled is_tab_stop
mnemonic value width
}

fixed_width
key label

A radio button is one of a group of buttons composing a radio column or
radio row. These work like the buttons on a car radio: only one can be
selected at a time, and when one is pressed, any other button in the column
(or row) that is on is turned off. An optional label appears to the right of the
radio button. The PDB feature reports an error if you attempt to place a radio
button outside a radio column or radio row.
label

The text displayed to the right of the radio button.

value

A quoted string (no default). If the value is "1", the
radio_button is on; if it is "0", the radio_button is off; all
other values are equivalent to "0".
If by some chance more than one radio_button in a radio
cluster has value = " 1", only the last one is turned on.
(This can happen in a DCL file. Once the dialog box starts,
the PDB feature manages radio buttons and ensures that
only one per cluster is turned on at a time.)

DCL Tile Catalog

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421

radio_column
: radio_column {
}

A radio column contains radio button tiles, only one of which can be selected
at a time. Radio columns present the user with a fixed set of mutually exclusive choices. Radio columns, unlike ordinary columns, can be assigned an
action.
value

A quoted string containing the key of the currently
selected radio button (the one whose value is "1").

radio_row
: radio_row {
}

A radio row, like a radio column, contains radio button tiles, only one of
which can be selected at a time. Radio rows can be assigned an action.
value

A quoted string containing the key of the currently
selected radio button (the one whose value is "1").

NOTE Radio rows are not as easy to use as radio columns, because the mouse
has to travel farther. Use radio rows only if they specify two to four options, or if
the labels are short.

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row
: row {
}
A row is like a column, but its tiles are laid out horizontally instead of vertically, in the order they appear in the DCL file.
A row without a box has no additional attributes beyond the standard layout
attributes.

slider
: slider {
action alignment big_increment fixed_height
fixed_width height key label layout
max_value min_value mnemonic small_increment
value width
}

A slider obtains a numeric value. The user can drag the slider’s indicator to
the left or right (or up or down) to obtain a value whose meaning depends
on the application. This value is returned as a string containing a signed integer within a specified range (the integer is a 16-bit value, so the maximum
range is –32,768 to 32,767). The application can scale this value as required.
value

A quoted string that contains the current (integer) value
of the slider (default: min_value).

DCL Tile Catalog

|

423

text
: text {
alignment fixed_height fixed_width
is_bold key label value width
}

height

A text tile displays a text string for titling or informational purposes.
Because most tiles have their own label attribute for titling purposes, you
don’t always need to use text tiles. But a text tile that you usually keep blank
is a useful way to display feedback about user actions, error messages, or
warnings .
Alert boxes and error tiles are discussed in “Dialog Box Exit Buttons and Error
Tiles” on page 410 and “DCL Error Handling” on page 386.
If you intend the message to be static, specify it in the label attribute and
don’t specify a width or value. If you intend the message to change at runtime, specify it in the value attribute and assign a width long enough to contain any strings that you plan to assign the value. Once the dialog box is laid
out, the size of its tiles can’t change, so if you use set_tile to assign a string
longer than the width, the displayed text is truncated.
label

The displayed text. When a text tile is laid out, its width
is the larger of either its width attribute, if that is specified
in the DCL, or the width required by its label attribute, if
specified. At least one of these attributes must be
specified.

value

Like label, the value attribute specifies a string to display
in the text tile. However, it has no effect on the tile’s
layout.

text_part
: text_part {
label
}
A text part is a text tile that is part of a larger piece of text. The margins of a
text_part are suppressed, so it can be combined with other text_parts into
a concatenation or paragraph tile.
The text_part tile is defined in the base.dcl file. See “paragraph” on page 419
for an example that uses text_part.

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toggle
: toggle {
action
height
}

alignment fixed_height
is_enabled is_tab_stop

fixed_width
label width

A toggle controls a Boolean value ("0" or "1"). A toggle appears as a small box
with an optional label to the right of the box. A check mark or X appears (or
disappears) when the user selects the box. Toggles enable the user to view or
change the state of on/off options. Toggles are also known as check boxes.
label

The text displayed to the right of the toggle box.

value

A quoted string containing an integer (default: "0") and
specifying the initial state of the toggle. If the string is
"0", the toggle box is blank (without a check mark). If it is
"1", the box contains a check mark (or an X).

spacer
: spacer {
alignment fixed_height fixed_width
height width
}
A spacer is a blank tile. It is used only for layout purposes to affect the size
and layout of adjacent tiles. To ensure consistency with other dialog boxes,
use spacer tiles only in special cases, because the PDB feature handles spacing
automatically. See “Adjusting the Layout of Dialog Boxes” on page 347.
The spacer tile has no additional attributes beyond the standard layout
attributes.

DCL Tile Catalog

|

425

spacer_0
spacer_0;
A spacer_0, demonstrated in the following figure, is a spacer that normally
has no width. However, it indicates a point in a tile group where you want
space to be inserted, if the group has to be stretched during layout. If the
spacer_0 tiles in a group are assigned a positive width, all of them are
assigned an equal share of the spacing.
The spacer_0 tile is defined in the base.dcl file.
location of spacer_0 tile

spacer_1
spacer_1;
The spacer_1 tile, demonstrated in the following figure, is a spacer whose
width and height both equal one. It is used for the smallest kind of spacer
that will still be obvious to the user.
The spacer_1 tile is defined in the base.dcl file.
location of spacer_1 tile

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Programmable Dialog Box Function Synopsis
The programmable dialog box functions perform dialog box opening and
closing, tile and attribute handling, list box and pop-up list handling, image
tile handling, and application-specific data handling. This section lists each
PDB function available in Visual LISP, grouping them by the type of task each
performs. For detailed information on these functions, see the AutoLISP Reference.

Dialog Box Opening and Closing Functions
Dialog box opening and closing functions
Function name

Description

(done_dialog [status])

Terminates a dialog box

(load_dialog dclfile)

Loads a DCL file

(new_dialog dlgname dcl_id
[action [screen-pt]])

Begins a new dialog box and displays it, and can
also specify a default action

(start_dialog)

Displays a dialog box and begins accepting user
input

(term_dialog)

Terminates all current dialog boxes as if the user
cancels each of them


Unloads a DCL file


|

427

Tile- and Attribute-Handling Functions
Tile- and attribute-handling functions
Function name

Description

(action_tile key action-expression)

Assigns an action to evaluate when the user
selects the specified tile in a dialog box

(get_attr key attribute)

Retrieves the DCL value of a dialog box
attribute

(get_tile key)

Retrieves the current runtime value of a dialog
box tile

(mode_tile key mode)

Sets the mode of a dialog box tile

(set_tile key value)

Sets the value of a dialog box tile

List Box and Pop-Up List-Handling Functions
List box and pop-up list-handling functions
Function name
(add_list string)

Ends processing of the currently active dialog
box list

(start_list key [operation [index] ])

|

Adds or modifies a string in the currently active
dialog box list

(end_list)

428

Description

Starts the processing of a list in the list box or in
the pop-up list dialog box tile

Chapter 13


Image Tile-Handling Functions
Image tile-handling functions
Function name

Description

(dimx_tile key) and (dimy_tile key)

Retrieves the dimensions of a tile in dialog box
units

(end_image)

Ends creation of the currently active dialog box
image

(fill_image x1 y1 wid hgt color)

Draws a filled rectangle in the currently active
dialog box image tile

(slide_image x1 y1 wid hgt sldname)

Displays an AutoCAD slide in the currently active
dialog box image tile

(start_image key)

Starts the creation of an image in the dialog box
tile

(vector_image x1 y1 x2 y2 color)

Draws a vector in the currently active dialog box
image

Application-Specific Data-Handling Functions
Application-specific data-handling functions
Function name

Description

(client_data_tile key clientdata)

Associates application-managed data with a
dialog box tile


|

429

AutoLISP Function
Synopsis

A

In This Appendix

To find a function without knowing its name, use the
listings in this appendix. The AutoLISP functions in this

s Category Summary
s Basic Functions
s Utility Functions

synopsis are organized into functional groups, and
listed alphabetically within each function group. Each
function is briefly described by its signature and a single
sentence indicating the function’s purpose.

s Selection Set, Object, and Symbol
Table Functions
s Memory Management Functions
s Visual LISP Extensions to
AutoLISP
s Reactor Functions
s VLX Namespace Functions
s Namespace Communication
Functions
s Windows Registry Functions

433

Category Summary
Functions in this synopsis are organized into the following categories:

Basic: (application-handling, arithmetic, equality and conditional, errorhandling, function-handling, list manipulation, string-handling, and
symbol-handling functions)
s Utility: (conversion, device access, display control, file-handling, geometric, query and command, and user input functions)
s Selection Set, Object, and Symbol Table: (extended data-handling, objecthandling, selection set manipulation, and symbol table-handling
functions)
s

s
s

Memory Management
Visual LISP Extensions to AutoLISP: (collection manipulation, curve measurement, data conversion, dictionary-handling, object-handling, and
property-handling functions)

s
s

Reactor
VLX Namespace: (function exposure, document namespace variable

s

access, and error-handling functions)
Namespace Communication: (blackboard-addressing and multi-document
loading-functions)

s

Windows Registry Handling

Note that programmable dialog box functions are listed in the “Programmable Dialog Box Reference” section of this manual.
Functions are grouped by data type and by the action they perform. Detailed
information on each Visual LISP function is provided in the alphabetical listings in the AutoLISP Reference.
Note that any functions not described here or in other parts of the documentation are not officially supported and are subject to change in future
releases.

Basic Functions
Application-Handling Functions

(see page 439)

Error-Handling Functions

(see page 440)

Function-Handling Functions

(see page 441)

List Manipulation Functions

(see page 442)

String-Handling Functions

|

(see page 437)

Equality and Conditional Functions

434

(see page 436)

Arithmetic Functions

(see page 444)

Appendix A AutoLISP Function Synopsis

Symbol-Handling Functions

(see page 445)

Utility Functions
Conversion Functions

(see page 446)

Device Access Functions

(see page 447)

Display Control Functions

(see page 448)

File-Handling Functions

(see page 449)

Geometric Functions

(see page 450)


(see page 451)

User Input Functions

(see page 452)

Selection Set, Object, and Symbol Table Functions
Extended Data-Handling Functions

(see page 453)

Object-Handling Functions

(see page 453)

Selection Set Manipulation Functions

(see page 455)

Symbol Table and Dictionary-Handling Functions

(see page 455)

Memory Management Functions

(see page 457)

Visual LISP AutoLISP Extensions
ActiveX Collection Manipulation Functions

(see page 458)

ActiveX Data Conversion Functions

(see page 458)

ActiveX Method Invocation Functions

(see page 459)

ActiveX Object-Handling Functions

(see page 460)

ActiveX Property-Handling Functions

(see page 460)

Curve Measurement Functions

(see page 461)

Dictionary Functions

(see page 462)


(see page 463)

Reactor Functions

(see page 464)

VLX Namespace Functions

(see page 467)

Namespace Communication Functions

(see page 468)

Windows Registry Functions

(see page 469)

Category Summary

|

435

Basic Functions
The basic functions consist of the arithmetic, string-handling, equality and
conditional, list manipulation, symbol-handling, function-handling, errorhandling, and application-handling functions.

Application-Handling Functions
Application-handling functions
Function

Description

(arx)

Returns a list of the currently loaded ObjectARX
applications

(arxload application [onfailure])

Loads an ObjectARX application

(arxunload application [onfailure]) Unloads an ObjectARX application
(autoarxload filename cmdlist)

(autoload filename cmdlist)

Forces the display of the next command's dialog box

(load filename [onfailure])

Evaluates the AutoLISP expressions in a file

(startapp appcmd file)

Starts a Windows application

(vl-vbaload “filename”)

Loads a Visual Basic project

(vl-vbarun “macroname”)

Runs a Visual Basic macro

(vlax-add-cmd “global-name”
‘func-sym [“local-name” cmdflags])

|

Predefines command names to load an associated
AutoLISP file

(initdia [dialogflag])

436

Predefines command names to load an associated
ObjectARX file

Adds commands to AutoCAD’s built-in command set
NOTE VLISP extension: requires vl-load-com


Arithmetic Functions
Arithmetic functions
Function

Description

(+ [number number] ...)

Returns the sum of all numbers

(– [number number] ...)

Subtracts the second and following numbers from the
first and returns the difference

(* [number number] ...)

Returns the product of all numbers

(/ [number number] ...)

Divides the first number by the product of the
remaining numbers and returns the quotient

(~ int)

Returns the bitwise NOT (1’s complement) of the
argument

(1+ number)

Returns the argument increased by 1 (incremented)

(1– number)

Returns the argument reduced by 1 (decremented)

(abs number)

Returns the absolute value of the argument

(atan num1 [num2])

Returns the arctangent of a number in radians

(cos ang)

Returns the cosine of an angle expressed in radians

(exp number)

Returns the constant e (a real) raised to a specified
power (the natural antilog)

(expt base power)

Returns a number raised to a specified power

(fix number)

Returns the conversion of a real into the nearest smaller
integer

(float number)

Returns the conversion of a number into a real

(gcd int1 int2)

Returns the greatest common denominator of two
integers

(log number)

Returns the natural log of a number as a real

(logand [int int ...])

Returns the result of the logical bitwise AND of a list of
integers

(logior [int int ...])

Returns the result of the logical bitwise inclusive OR of a
list of integers

Basic Functions

|

437

Arithmetic functions (continued)
Function
(lsh [int numbits])

Returns the largest of the numbers given

(min [number number ...])

Returns the smallest of the numbers given

(minusp number)

Verifies that a number is negative

(rem [num1 num2 ...])

Divides the first number by the second, and returns the
remainder

(sin ang)

Returns the sine of an angle as a real expressed in
radians

(sqrt number)

Returns the square root of a number as a real

(zerop number)

|

Returns the logical bitwise shift of an integer by a
specified number of bits

(max [number number ...])

438

Description

Verifies that a number evaluates to zero


Equality and Conditional Functions
Equality and conditional functions
Function

Description

(= numstr [numstr] ...)

Returns T if all arguments are numerically equal, and
returns nil otherwise

(/= numstr [numstr] ...)

Returns T if the arguments are not numerically equal,
and nil if the arguments are numerically equal

(< numstr [numstr] ...)

Returns T if each argument is numerically less than the
argument to its right, and returns nil otherwise

(<= numstr [numstr] ...)

Returns T if each argument is numerically less than or
equal to the argument to its right, and returns nil
otherwise

(> numstr [numstr] ...)

Returns T if each argument is numerically greater than
the argument to its right, and returns nil otherwise

(>= numstr [numstr] ...)

Returns T if each argument is numerically greater than
or equal to the argument to its right, and returns nil
otherwise

(and [expr ...])

Returns the logical AND of a list of expressions

(Boole func int1 [int2 ...])

Serves as a general bitwise Boolean function

(cond [(test result ...) ...])

Serves as the primary conditional function for AutoLISP

(eq expr1 expr2)

Determines whether two expressions are identical

(equal expr1 expr2 [fuzz])

Determines whether two expressions are equal

(if testexpr thenexpr [elseexpr])

Conditionally evaluates expressions

(or [expr ...])

Returns the logical OR of a list of expressions

(repeat int [expr ...])

Evaluates each expression a specified number of times,
and returns the value of the last expression

(while testexpr [expr ...])

Evaluates a test expression, and if it is not nil, evaluates
other expressions; repeats this process until the test
expression evaluates to nil

Basic Functions

|

439

Error-Handling Functions
Error-handling functions
Function
(alert string)

A user-definable error-handling function

(exit)

Forces the current application to quit

(quit)

Forces the current application to quit

(vl-catch-all-apply ‘function list)

Passes a list of arguments to a specified function and
traps any exceptions

(vl-catch-all-error-message
error-obj)

Returns a string from an error object

(vl-catch-all-error-p arg)

|

Displays an alert dialog box with the error or warning
message passed as a string

(*error* string)

440

Description

Determines whether an argument is an error object
returned from vl-catch-all-apply


Function-Handling Functions
Function-handling functions
Function

Description

(apply function lst)

Passes a list of arguments to a specified function

(defun sym ([arguments]
[/variables...]) expr ...)

Defines a function

(defun-q sym ([arguments]
[/variables...]) expr ...)

Defines a function as a list (intended for backwardcompatibility only)

(defun-q-list-ref ‘function)

Displays the list structure of a function defined with
defun-q

(defun-q-list-set ’sym list)

Defines a function as a list (intended for backwardcompatibility only)

(eval expr)

Returns the result of evaluating an AutoLISP expression

(lambda arguments expr ...)

Defines an anonymous function

(progn [expr] ...)

Evaluates each expression sequentially, and returns the
value of the last expression

(trace function ...)

Aids in AutoLISP debugging

(untrace function ...)

Clears the trace flag for the specified functions

Basic Functions

|

441

List Manipulation Functions
List manipulation functions
Function
(acad_strlsort lst)

Takes any number of lists and runs them together as one
list

(assoc item alist)

Searches an association list for an element and returns
that association list entry

(car lst)

Returns the first element of a list

(cdr lst)

Returns the specified list, except for the first element of
the list

(cons new-first-element lst)

The basic list constructor

(foreach name lst [expr ...])

Evaluates expressions for all members of a list

(last lst)

Returns the last element in a list

(length lst)

Returns an integer indicating the number of elements in
a list

(list [expr ...])

Takes any number of expressions and combines them
into one list

(listp item)

Verifies that an item is a list

(mapcar function list1 ... listn)

Returns a list of the result of executing a function with
the individual elements of a list or lists supplied as
arguments to the function

(member expr lst)

Searches a list for an occurrence of an expression and
returns the remainder of the list, starting with the first
occurrence of the expression

(nth n lst)

Returns the nth element of a list

(reverse lst)

Returns a list with its elements reversed

(subst newitem olditem lst)

Searches a list for an old item and returns a copy of the
list with a new item substituted in place of every
occurrence of the old item

(vl-consp list-variable)

|

Sorts a list of strings by alphabetical order

(append lst ...)

442

Description

Determines whether or not a list is nil


List manipulation functions (continued)
Function

Description

(vl-every predicate-function list
[more-lists]...)

Checks whether the predicate is true for every element
combination

(vl-list* object [more-objects]...)

Constructs and returns a list

(vl-list->string char-codes-list)

Combines the characters associated with a list of
integers into a string

(vl-list-length list-or-cons-object)

Calculates list length of a true list

(vl-member-if predicate-function
list)

Determines whether the predicate is true for one of the
list members

(vl-member-if-not predicatefunction list)

Determines whether the predicate is nil for one of the
list members

(vl-position symbol list)

Returns the index of the specified list item

(vl-remove element-to-remove
list)

Removes elements from a list

(vl-remove-if predicate-function
list)

Returns all elements of the supplied list that fail the test
function

(vl-remove-if-not predicatefunction list)

Returns all elements of the supplied list that pass the test
function

(vl-some predicate-function list
[more-lists]...)

Checks whether the predicate is not nil for one element
combination

(vl-sort list less?-function)

Sorts the elements in a list according to a given
compare function

(vl-sort-i list less?-function)

Sorts the elements in a list according to a given
compare function, and returns the element index
numbers

(vl-string->list string)

Converts a string into a list of character codes

Basic Functions

|

443

String-Handling Functions
String-handling functions
Function
(read [string])

Returns a string where all alphabetic characters have
been converted to uppercase or lowercase

(strcat [string1 [string2] ...)

Returns a string that is the concatenation of multiple
strings

(strlen [string] ...)

Returns an integer that is the number of characters in a
string

(subst string start [length])

Returns a substring of a string

(vl-prin1-to-string object)

Returns the string representation of any LISP object as if
it were output by the prin1 function

(vl-princ-to-string object)

Returns the string representation of any LISP object as if
it were output by the princ function

(vl-string->list string)

Converts a string into a list of character codes

(vl-string-elt string position)

Returns the ASCII representation of the character at a
specified position in a string

(vl-string-left-trim character-set
string)

Removes the specified characters from the beginning of
a string

(vl-string-mismatch str1 str2
[pos1 pos2 ignore-case-p])

Returns the length of the longest common prefix for
two strings, starting at specified positions

(vl-string-position char-code str
[start-pos [from-end-p]])

Looks for a character with the specified ASCII code in a
string

(vl-string-right-trim characterset string)

Removes the specified characters from the end of a
string

(vl-string-search pattern string
[start-pos])

Searches for the specified pattern in a string

(vl-string-subst new-str pattern
string [start-pos])

Substitutes one string for another, within a string

(vl-string-translate
source-set dest-set str)

|

Returns the first list or atom obtained from a string

(strcase string [which])

444

Description

Replaces characters in a string with a specified set of
characters


String-handling functions (continued)
Function

Description

(vl-string-trim char-set str)

Removes the specified characters from the beginning
and end of a string

(wcmatch string pattern)

Performs a wild-card pattern match on a string

Symbol-Handling Functions
Symbol-handling functions
Function

Description

(atom item)

Verifies that an item is an atom

(atoms-family format [symlist])

Returns a list of the currently defined symbols

(boundp sym)

Verifies whether a value is bound to a symbol

(not item)

Verifies that an item evaluates to nil

(null item)

Verifies that an item is bound to nil

(numberp item)

Verifies that an item is a real or an integer

(quote expr)

Returns an expression without evaluating it

(set sym expr)

Sets the value of a quoted symbol name to an
expression

(setq sym1 expr1
[sym2 expr2] ...)

Sets the value of a symbol or symbols to associated
expressions

(type item)

Returns the type of a specified item

(vl-symbol-name symbol)

Returns a string containing the name of a symbol

(vl-symbol-value symbol)

Returns the current value bound to a symbol

(vl-symbolp object)

Identifies whether or not a specified object is a symbol

Basic Functions

|

445

Utility Functions
The utility functions consist of query and command, display control, user
input, geometric, conversion, file-handling, and device access functions.

Conversion Functions
Conversion functions
Function

Description

(angtof string [mode])

Converts a string representing an angle into a real
(floating-point) value in radians

(angtos angle [mode [precision]]) Converts an angular value in radians into a string
(ascii string)

(atof string)

Returns the conversion of a string into an integer

(chr integer)

Returns the conversion of an integer representing an
ASCII character code into a single-character string

(cvunit value from to)

Converts a value from one unit of measurement to
another

(distof string [mode])

Converts a string that represents a real (floating-point)
value into a real value

(itoa int)

Returns the conversion of an integer into a string

(rtos number [mode [precision]])

Converts a number into a string

(trans pt from to [disp])

|

Returns the conversion of a string into a real

(atoi string)

446

Returns the conversion of the first character of a string
into its ASCII character code (an integer)

Translates a point (or a displacement) from one
coordinate system to another


Device Access Functions
Device access functions
Function

Description

(grread [track] [allkeys [curtype]]) Reads values from any of the AutoCAD input devices
(tablet code [row1 row2 row3
direction])

Retrieves and sets digitizer (tablet) calibrations

Utility Functions

|

447

Display Control Functions
Display control functions
Function

Description

(graphscr)

Displays the AutoCAD graphics screen

(grdraw from to color [highlight]) Draws a vector between two points, in the current
viewport
(grtext [box text [highlight]])
(grvecs vlist [trans])

Issues menu commands, or sets and retrieves menu
item status

(menugroup groupname)

Verifies that a menu group is loaded

(prin1 [expr [file-desc]])

Prints an expression to the command line or writes an
expression to an open file

(princ [expr [file-desc]])

Prints an expression to the command line, or writes an

(print [expr [file-desc]])

Prints an expression to the command line, or writes an

(prompt msg)

Displays a string on your screen’s prompt area

(redraw [ename [mode]])

Redraws the current viewport or a specified object
(entity) in the current viewport

(terpri)

Prints a newline to the Command line

(textpage)

Switches from the graphics screen to the text screen

(textscr)

Switches from the graphics screen to the text screen
(like the AutoCAD Flip Screen function key)

(vports)

|

Draws multiple vectors on the graphics screen

(menucmd string)

448

Writes text to the status line or to screen menu areas

Returns a list of viewport descriptors for the current
viewport configuration


File-Handling Functions
File-handling functions
Function

Description

(close file-desc)

Closes an open file

(findfile filename)

Searches the AutoCAD library path for the specified file

(open filename mode)

Opens a file for access by the AutoLISP I/O functions

(read-char [file-desc])

Returns the decimal ASCII code representing the
character read from the keyboard input buffer or from
an open file

(read-line [file-desc])

Reads a string from the keyboard or from an open file

(vl-directory-files [directory pattern Lists all files in a given directory
directories])
(vl-file-copy "source-filename"
Copies or appends the contents of one file to another
"destination-filename" [append?]) file
(vl-file-delete "filename")

Deletes a file

(vl-file-directory-p "filename")

Determines if a file name refers to a directory

(vl-file-rename "old-filename"
"new-filename")

Renames a file

(vl-file-size "filename")

Determines the size of a file, in bytes

(vl-file-systime "filename")

Returns last modification time of the specified file

(vl-filename-base "filename")

Returns the name of a file, after stripping out the
directory path and extension

(vl-filename-directory
"filename")

Returns the directory path of a file, after stripping out
the name and extension

(vl-filename-extension
"filename")

Returns the extension from a file name, after stripping
out the rest of the name

(vl-filename-mktemp ["pattern"
"directory" "extension"])

Calculates a unique file name to be used for a
temporary file

(write-char num [file-desc])

Writes one character to the screen or to an open file

(write-line string [file-desc])

Writes a string to the screen or to an open file

Utility Functions

|

449

Geometric Functions
Geometric functions
Function
(angle pt1 pt2)

Returns the 3D distance between two points

(inters pt1 pt2 pt3 pt4 [onseg])

Finds the intersection of two lines

(osnap pt mode)

Returns a 3D point that is the result of applying an
Object Snap mode to a specified point

(polar pt ang dist)

Returns the UCS 3D point at a specified angle and
distance from a point

(textbox elist)

|

Returns an angle in radians of a line defined by two
endpoints

(distance pt1 pt2)

450

Description

Measures a specified text object, and returns the
diagonal coordinates of a box that encloses the text


Query and command functions
Function

Description

(acad_colordlg colornum [flag])

Displays the standard AutoCAD Color Selection dialog
box

(acad_helpdlg helpfile topic)

Invokes the Help facility (obsolete)

(command [arguments] ...)

Executes an AutoCAD command

(getcfg cfgname)

Retrieves application data from the AppData section of
the acad.cfg file

(getcname cname)

Retrieves the localized or English name of an AutoCAD
command

(getenv “variable-name”)

Returns the string value assigned to a system
environment variable

(getvar varname)

Retrieves the value of an AutoCAD system variable

(help [helpfile [topic
[command]]])

Invokes the Help facility

(setcfg cfgname cfgval)

Writes application data to the AppData section of the
acad.cfg file

(setenv “varname” “value”)

Sets a system environment variable to a specified value

(setfunhelp “c:fname” [“helpfile” Registers a user-defined command with the Help facility
[“topic” [“command”]]])
so the appropriate help file and topic are called when
the user requests help on that command
(setvar varname value)

Sets an AutoCAD system variable to a specified value

(ver)

Returns a string that contains the current AutoLISP
version number

(vl-cmdf [arguments] ...)

Executes an AutoCAD command after evaluating
arguments

(vlax-add-cmd global-name
Adds commands to a group
func-sym [local-name cmd-flags]) NOTE VLISP extension: requires vl-load-com
(vlax-remove-cmd global-name)

Removes a single command or command group

Utility Functions

|

451

User Input Functions
User input functions
Function
(entsel [msg])

Pauses for user input of an angle, and returns that angle
in radians

(getcorner pt [msg])

Pauses for user input of a rectangle’s second corner

(getdist [pt] [msg])

Pauses for user input of a distance

(getfiled title default ext flags)

Prompts the user for a file name with the standard
AutoCAD file dialog box, and returns that file name

(getint [msg])

Pauses for user input of an integer, and returns that
integer

(getkword [msg])

Pauses for user input of a keyword, and returns that
keyword

(getorient [pt] [msg])

Pauses for user input of an angle, and returns that angle
in radians

(getpoint [pt] [msg])

Pauses for user input of a point, and returns that point

(getreal [msg])

Pauses for user input of a real number, and returns that
real number

(getstring [cr] [msg])

Pauses for user input of a string, and returns that string

(initget [bits] [string])

Establishes keywords for use by the next user input
function call

(nentsel [msg])

Prompts the user to select an object (entity) by
specifying a point, and provides access to the definition
data contained within a complex object

(nentselp [msg] [pt])

|

Prompts the user to select a single object (entity) by
specifying a point

(getangle [pt] [msg])

452

Description

Provides similar functionality to that of the nentsel
function without the need for user input


Selection Set, Object, and Symbol Table
Functions
The selection set, object, and symbol table functions consist of selection set
manipulation, object-handling, extended data-handling, and symbol
table–handling functions.

Extended Data-Handling Functions
Extended data-handling functions
Function

Description

(regapp application)

Registers an application name with the current
AutoCAD drawing in preparation for using extended
object data

(xdroom ename)

Returns the amount of extended data (xdata) space that
is available for an object (entity)

(xdsize lst)

Returns the size (in bytes) that a list occupies when it is
linked to an object (entity) as extended data

Object-handling functions
Function

Description

(entdel ename)

Deletes objects (entities) or restores previously deleted
objects

(entget ename [applist])

Retrieves an object’s (entity’s) definition data

(entlast)

Returns the name of the last nondeleted main object
(entity) in the drawing

(entmake [elist])

Creates a new entity (graphical object) in the drawing

(entmakex [elist])

Makes a new object or entity, gives it a handle and
entity name (but, does not assign an owner), and then
returns the new entity name

(entmod elist)

Modifies the definition data of an object (entity)


|

453

Object-handling functions (continued)
Function
(entnext [ename])

Updates the screen image of an object (entity)

(handent handle)

Returns an object (entity) name based on its handle

(vlax-dump-object obj)

Lists an object’s methods and properties

(vlax-erased-p obj)

Determines whether an object was erased

(vlax-get-acad-object)

Retrieves the top-level AutoCAD application object for
the current AutoCAD session

(vlax-method-applicable-p obj
method)

Determines whether an object supports a particular
method

(vlax-object-released-p obj)

Determines whether an object has been released

(vlax-read-enabled-p obj)

Determines whether an object can be read

(vlax-release-object obj)

Releases a drawing object

(vlax-typeinfo-available-p obj)

Determines whether TypeLib information is present for
the specified type of object

(vlax-write-enabled-p obj)

|

Returns the name of the next object (entity) in the
drawing

(entupd ename)

454

Description

Determines whether an AutoCAD drawing object can
be modified


Selection Set Manipulation Functions
Selection set manipulation functions
Function

Description

(ssadd [ename [ss]])

Adds an object (entity) to a selection set, or creates a
new selection set

(ssdel ename ss)

Deletes an object (entity) from a selection set

(ssget [mode] [pt1 [pt2]] [pt-list]
[filter-list])

Prompts the user to select objects (entities), and returns
a selection set

(ssgetfirst)

Determines which objects are selected and gripped

(sslength ss)

Returns an integer containing the number of objects
(entities) in a selection set

(ssmemb ename ss)

Tests whether an object (entity) is a member of a
selection set

(ssname ss index)

Returns the object (entity) name of the indexed element
of a selection set

(ssnamex ss index)

Retrieves information about how a selection set was
created

(sssetfirst gripset [pickset])

Sets which objects are selected and gripped

Symbol Table and Dictionary-Handling Functions
Symbol table and dictionary-handling functions
Function

Description

(dictadd ename symbol newobj)

Adds a non-graphical object to the specified dictionary

(dictnext ename symbol [rewind]) Finds the next item in a dictionary
(dictremove ename symbol)

Removes an entry from the specified dictionary

(dictrename ename oldsym
newsym)

Renames a dictionary entry

(dictsearch ename symbol
[setnext])

Searches a dictionary for an item


|

455

Symbol table and dictionary-handling functions (continued)
Function

Description

(layoutlist)

Returns a list of all paper space layouts in the current
drawing

(namedobjdict)

Returns the entity name of the current drawing’s named
object dictionary, which is the root of all non-graphical
objects in the drawing

(setview view_description
[vport_id])

Establishes a view for a specified viewport

(snvalid sym_name)

Checks the symbol table name for valid characters

(tblnext table-name [rewind])

Finds the next item in a symbol table

(tblobjname table-name symbol) Returns the entity name of a specified symbol table
entry
(tblsearch table-name symbol
[setnext])
(vlax-ldata-delete dict key)

Retrieves LISP data from a drawing dictionary

(vlax-ldata-list dict)

Lists LISP data in a drawing dictionary

(vlax-ldata-put dict key data)

Stores LISP data in a drawing dictionary

(vlax-ldata-test data)

|

Erases LISP data from a drawing dictionary

(vlax-ldata-get dict key [defaultdata])

456

Searches a symbol table for a symbol name

Determines whether data can be saved over a session
boundary


Memory management functions
Function

Description

(alloc int)

Sets the segment size to a given number of nodes

(expand number)

Allocates node space by requesting a specified number
of segments

(gc)

Forces a garbage collection, which frees up unused
memory

(mem)

Displays the current state of memory in AutoLISP

Visual LISP Extensions to AutoLISP
The extended AutoLISP functions provided with VLISP consist of curve measurement, data conversion, object-handling, property-handling, collection
manipulation, and dictionary-handling functions. The function names are
prefixed with vlax-. These functions are in addition to the ActiveX methods
provided through vla-* functions.

NOTE Before you can use the AutoLISP extensions, you must issue the following command:
(vl-load-com)

The vl-load-com function also initializes ActiveX support for AutoLISP.


|

457

ActiveX Collection Manipulation Functions
Collection manipulation functions
Function

Description

(vlax-for symbol collection
[expression1 [expression2 ...]])

Iterates through a collection of objects, evaluating each
expression (VLISP Function)

(vlax-map-collection obj
function)

Applies a function to all objects in a collection

ActiveX Data Conversion Functions
Data conversion functions
Function
(vlax-3D-point list)
(vlax-3D-point x y [z])

Transforms entity to VLA-object

(vlax-make-safearray type
’(l-bound . u-bound)
[ ’(l-bound . u-bound)...)]

Creates a safearray

(vlax-make-variant value type)

Creates a variant data type

(vlax-safearray-fill var ‘
element-values)

Stores elements in a safearray

(vlax-safearray-get-dim var)

Returns the number of dimensions in a safearray object

(vlax-safearray-get-element var
element)

Returns an element from an array

(vlax-safearray-get-l-bound var
dim)

Returns the lower boundary (starting index) of a
dimension of an array

(vlax-safearray-get-u-bound var
dim)

Returns the upper boundary (end index) of a dimension
of an array

(vlax-safearray-put-element var
element value)

Adds or updates an element in an array

(vlax-safearray-type var)

|

Creates an ActiveX-compatible 3D point structure

(vlax-ename->vla-object
entname)

458

Description

Returns the data type of a safearray


Data conversion functions (continued)
Function

Description

(vlax-safearray->list var)

Returns the elements of a safearray in list form

(vlax-tmatrix list)

Returns a suitable representation for a 4x4
transformation matrix to be used in VLA methods

(vlax-variant-change-type var
type)

Returns the value of a variant after changing it from one
data type to another

(vlax-variant-type var)

Returns the data type of a variant

(vlax-variant-value var)

Returns the value of a variant

(vlax-vla-object->ename obj)

Transforms a VLA-object to an AutoLISP entity

ActiveX Method Invocation Functions
Method invocation functions
Function

Description

(vlax-invoke-method obj method Calls the specified method of an object
list)
method)

Determines if an object supports a particular method


|

459

ActiveX Object-Handling Functions
ActiveX Object-handling functions
Function

Description



(vlax-erased-p obj)




method)

Determines if an object supports a particular method


Determines if an object has been released








be modified

ActiveX Property-Handling Functions
Property-handling functions
Function
(vlax-get-property obj property)

Determines whether an object has a specified property

(vlax-put-property obj property
arg)

|

Low-level property get function. May be used for
custom ActiveX object

(vlax-property-available-p obj
prop [T])

460

Description

Low-level property set function


Curve Measurement Functions
Curve measurement functions
Function

Description

(vlax-curve-getArea curve-obj)

Returns the area inside the curve

(vlax-curve-getDistAtParam
curve-obj param)

Returns the length of the curve's segment from the
curve's beginning to the specified point

(vlax-curve-getDistAtPoint
curve-obj point)

Returns the length of the curve's segment between the
curve's start point and the specified point

(vlax-curve-getEndParam
curve-obj)

Returns the parameter of the endpoint of the curve

(vlax-curve-getEndPoint
curve-obj)

Returns the endpoint (in WCS coordinates) of the curve

(vlax-curve-getParamAtDist
curve-obj param)

Returns the distance along the curve from the
beginning of the curve to the location of the specified
parameter

(vlax-curve-getParamAtPoint
curve-obj point)

Returns the parameter of the curve at the point

(vlax-curve-getPointAtDist
curve-obj dist)

Returns the point (in WCS coordinates) along a curve at
the distance specified by the user

(vlax-curve-getPointAtParam
curve-obj param)

Determines the point on the curve that corresponds to
the param parameter and returns the point

(vlax-curve-getStartParam
curve-obj)

Returns the start parameter on the curve

(vlax-curve-getStartPoint
curve-obj)

Returns the start point (in WCS coordinates) of the
curve

(vlax-curve-isClosed
curve-obj)

Determines if the specified curve is closed (i.e., start
point is same as endpoint)

(vlax-curve-isPeriodic curve-obj)

Determines if the specified curve has an infinite range in
both directions and there is a period value dT, such that
there is a point on curve at (u + dT) = point on curve (u),
for any parameter u

(vlax-curve-isPlanar curve-obj)

Determines if there is a plane that contains the curve


|

461

Curve measurement functions (continued)
Function

Description

(vlax-curve-getClosestPointTo
curve-obj givenPnt [extend])

Returns the point (in WCS coordinates) on a curve that
is nearest to the specified point

(vlax-curvegetClosestPointToProjection
curve-obj givenPnt normal
[extend])

Returns the point (in WCS coordinates) on a curve that
is nearest to the specified point

(vlax-curve-getFirstDeriv
curve-obj param)

Returns the first derivative (in WCS coordinates) of a
curve at the specified location

(vlax-curve-getSecondDeriv
curve-obj param)

Returns the second derivative (in WCS coordinates) of a
curve at the specified location

Dictionary Functions
Dictionary functions
Function
(vlax-ldata-delete dict key)

Retrieves LISP data from a drawing dictionary

(vlax-ldata-list dict)

Lists LISP data in a drawing dictionary

(vlax-ldata-put dict key data)

Stores LISP data in a drawing dictionary

(vlax-ldata-test data)

|

Erases LISP data from a drawing dictionary

(vlax-ldata-get dict key
[default-data])

462

Description

Determines whether data can be saved over a session
boundary


Object-handling functions
Function

Description

(vlax-create-object “prog-id”)

Creates a new instance of an ActiveX object



(vlax-erased-p obj)




(vlax-get-object “prog-id”)

Returns a running instance of an ActiveX object

(vlax-get-or-create-object
“prog-id”)

Returns a running instance of an ActiveX object, if one
exists, otherwise starts a new instance of the object

:tlb-filename filename
[ :methods-prefix mprefix
:properties-prefix pprefix
:constants-prefix cprefix])

Imports information from a type library

method)

Determines whether an object supports a particular
method


Determines whether an object has been released








be modified


|

463

Reactor Functions
Reactor functions define, query, and delete reactors and reactor properties.

NOTE Before you can use these functions, you must load AutoLISP reactor
support by issuing the following command:
(vl-load-com)

The vl-load-com function initializes reactor support and a number of other
AutoLISP extensions.

Reactor functions
Function
(vl-load-com)

Constructs a database (global) reactor object

(vlr-add obj)

Enables a disabled reactor object

(vlr-added-p obj)

Tests to determine whether a reactor object is enabled

(vlr-beep-reaction [args])

Produces a beep sound

(vlr-current-reaction-name)

Returns the name (symbol) of the current event, if called
from within a reactor’s callback

(vlr-dataobj)

Returns application-specific data associated with a
reactor

(vlr-data-set obj data)

Overwrites application-specific data associated with a
reactor

(vlr-deepclone-reactor obj data)

Constructs an editor reactor object that notifies of deep
clone events

(vlr-docmanager-reactor
obj data)

Constructs a reactor object that notifies of MDI-related
events

(vlr-dwg-reactor obj data)

|

Loads AutoLISP reactor support functions and other
AutoLISP extensions

(vlr-acdb-reactor data callbacks)

464

Description

Constructs an editor reactor object that notifies of a
drawing event (for example, opening or closing a
drawing file)


Reactor functions (continued)
Function

Description

(vlr-dxf-reactor obj data)

Constructs an editor reactor object that notifies of an
event related to reading or writing of a DXF file

(vlr-editor-reactor data
callbacks)

Constructs an editor (global) reactor object

(vlr-linker-reactor data
callbacks)

Constructs a linker (global) reactor object

(vlr-miscellaneous-reactor
data callbacks)

Constructs an editor reactor object that does not fall
under any of the other editor reactor types

(vlr-mouse-reactor
data callbacks)

mouse event (for example, a double-click)

(vlr-notification reactor)

Determines whether or not a reactor’s callback function
will execute if its associated namespace is not active

(vlr-object-reactor owners
data callbacks)

Constructs an object reactor object

(vlr-owner-add reactor owner)

Adds an object to the list of owners of an object reactor

(vlr-owner-remove
reactor owner)

Removes an object from the list of owners of an object
reactor

(vlr-owners reactor)

Returns the list of owners of an object reactor

(vlr-pers reactor)

Makes a reactor persistent

(vlr-pers-list [reactor])

Returns a list of persistent reactors in the current
drawing

(vlr-pers-p reactor)

Determines whether or not a reactor is persistent

(vlr-pers-release reactor)

Makes a reactor transient

(vlr-reaction-names reactor-type) Returns a list of all callback conditions for this reactor
type
(vlr-reaction-set reactor event
function)

Adds or replaces a callback function in a reactor

(vlr-reactions reactor)

Returns a list of pairs (event-name . callback_function) for
the reactor

(vlr-reactors [reactor-type...])

Returns a list of reactors of the specified types

Reactor Functions

|

465

Reactor functions (continued)
Function
(vlr-remove reactor)

Disables all reactors of the specified type

(vlr-set-notification reactor
‘range)

Defines whether or not a reactor’s callback function will
execute if its associated namespace is not active

(vlr-sysvar-reactor data
callbacks)

change to a system variable

(vlr-toolbar-reactor data
callbacks)

change to the bitmaps in a toolbar

(vlr-trace-reaction)

A pre-defined callback function that prints one or more
callback arguments in the Trace window

(vlr-type reactor)

Returns a symbol representing the reactor type

(vlr-types)

Returns a list of all reactor types

(vlr-undo-reactor data
callbacks)

undo event

(vlr-wblock-reactor data
callbacks)

event related to writing a block

(vlr-window-reactor data
callbacks)

event related to moving or sizing an AutoCAD window

(vlr-xref-reactor data callbacks)

|

Disables a reactor

(vlr-remove-all reactor-type)

466

Description

event related to attaching or modifying XREF


The VLX namespace functions listed below apply to separate-namespace
VLX applications. These functions allow separate-namespace VLX functions
to be accessible from a document namespace, enable the retrieval and
updating of variables in the associated document namespace, and provide
error-handling routines for separate-namespace VLX functions.

VLX namespace functions
Function

Description

(vl-arx-import [function |
application]

Imports ADS-DEFUN functions into a separatenamespace VLX

(vl-doc-export ’function)

Makes a function loaded in a VLX namespace available
to the current document

(vl-doc-import [’function |
application])

Imports a function that was previously exported from
another separate-namespace VLX

(vl-doc-ref symbol)

Retrieves the value of a variable from the namespace of
the associated document

(vl-doc-set symbol value)

Sets the value of a variable in the associated document’s
namespace

(vl-exit-with-error “msg”)

Passes control from a VLX error handler to the *error*
function of the associated document namespace

(vl-exit-with-value value)

Returns a value to the document namespace from
which the VLX was invoked

(vl-list-exported-functions
[“appname”])

Lists all functions exported by the specified application,
or all exported functions if no application is specified

(vl-list-loaded-vlx)

Returns a list of all separate-namespace VLX files
associated with the current document

(vl-unload-vlx “appname”)

Unloads a VLX that is loaded in its own namespace (a
separate-namespace VLX)

(vl-vlx-loaded-p “appname”)

Determines whether a VLX is loaded in its own
namespace


|

467

Namespace Communication Functions
The namespace communication functions consist of blackboard addressing
and multi-document-loading functions.

Namespace communication functions
Function
(vl-bb-ref ’variable)

Sets the value of a variable in the blackboard namespace

(vl-load-all “filename”)

Loads a file into all open AutoCAD documents, and into
any document subsequently opened during the current
AutoCAD session

(vl-propagate ’variable)

|

Returns the value of a variable from the blackboard
namespace

(vl-bb-set ’variable value)

468

Description

Copies the value of a variable into all open AutoCAD
documents, and into any document subsequently
opened during the current AutoCAD session


Windows Registry functions query and update the Windows Registry.

Windows Registry functions
Function

Description

(vl-registry-delete reg-key
[val-name])

Deletes the specified key or value from the Windows
Registry

(vl-registry-descendents reg-key
[val-names])

Returns a list of subkeys or value names for the specified
Registry key

(vl-registry-read reg-key
[val-name])

Returns data stored in the Windows Registry for the
specified key/value pair

(vl-registry-write reg-key
[val-name val-data])

Creates a key in the Windows Registry

(vlax-product-key)

Returns the AutoCAD registry path
NOTE This is an extended function provided by VLISP.
You must issue vl-load-com before you can use the
function.


|

469

Visual LISP Environment
and Formatting Options

B

In This Appendix

This chapter describes the configuration options
available on the VLISP Tools menu. The Window

s Window Attributes
s Environment Options
s Save Settings

Attributes menu item sets color-coding options for the
VLISP text editor windows. The Environment Options
item allows you to set session-wide VLISP options (for
example, whether or not to create automatic backup
files, or how to treat protected symbols), diagnostic
options (such as what statistics to report during syntax
checking, or what level of detail to display when
inspecting drawing objects), formatting options for
AutoLISP code, and page layout options for printed
output.

471

Window Attributes
The Window Attributes submenu includes selections for customizing the
VLISP windowing environment, controlling attributes such as colors, fonts,
and code formatting. The Syntax Coloring, Current to Prototype, and All to
Prototype items are available only for text editor windows.
VLISP allows you to define prototype configurations for text editor windows.
The prototype becomes the default configuration for these windows. For
example, when you open a new file in the VLISP text editor, the editor
window assumes the attributes and properties of the prototype editor configuration. The window prototype includes
Color scheme
Lexical coloring flag
s Tab size
s Left margin indent
s
s

Every time you change and save any text editor window attribute settings,
VLISP will ask you if the modified setting should be used as a prototype for
this window type.

Syntax Coloring
The Syntax Coloring item determines the type of syntax coloring that will be
used for the current file being edited. This option is available when you edit
a file whose file type is not .lsp . When chosen, Syntax Coloring displays the
Color Style dialog box, which provides the following options:

None

No color coding.

AutoLISP

Use LISP syntax color coding. This color coding scheme is
used for all files of type .lsp.

C++

Use C++ syntax color coding. This is the default for all files
of type . cpp , .c++, .c, .hpp, .h++, and .h.

DCL

Use DCL syntax color coding. This is the default for all
files of type .dcl.

SQL

Use SQL syntax color coding. This is the default for all files
of type . sql .

If a file type does not have a default coloring style, the user is asked whether
to use the selected coloring style for all files of the same type.

472

|

Appendix B Visual LISP Environment and Formatting Options

NOTE All formatting and “smart” indent features require the AutoLISP lexical
coloring style.

Configure Current
This command allows you to configure the attributes of the current window.
It is applicable to the VLISP text editor and Console windows. The Configure
Current command displays the Window Attributes dialog box:

This dialog box lets you customize the tab width and left margin sizes, customize various text colors defined for the current window type, and control
the lexical coloring for that window (if applicable). To select the color with
the aid of the color selection control, click the mouse button in the rectangle
that is painted with the color you want to set.

Text Colors

The upper row of rectangles indicates foreground color,
the lower row indicates background color. When you
select a color, the color palette changes its color with
respect to your choice. Use the pull-down list to select the
attribute of the window whose colors you want to change.

Window Attributes

|

473

The available choices depend on which window is
current. The following are possible window attributes:
s

:Input-Zone. The input area following the Console

s

:Window-Text. Text displayed in the window (other

s

:Window-Selection. Selected text.

window prompt.
than input zone).
:Error-Highlight. Error m essages in the Build Output
window.
s :Console-Message. No effect (reserved for future use).
s :BPT-Active. Active breakpoint.
s :BPT-Disable. Disabled breakpoint.
s

The pull-down list may also provide options for changing
the lexical coloring of the following AutoLISP code
components:

s

:LEX-SPACE. Spaces.
:LEX-STR. Strings.
:LEX-SYM. Symbols.
:LEX-NUM. Reserved for future use.
:LEX-INT. Integers.
:LEX-REAL. Real numbers.
:LEX-COMM. Reserved for future use.
:LEX-COMM1. Comments that begin with one or more

s

:LEX-COMM2. Inline and multi-line comments

s

:LEX-PAREN. Parentheses.
:LEX-SPEC. Reserved for future use.
:LEX-SPEC1. Reserved for future use.
:LEX-UNKN. Unknown items.

s
s
s
s
s
s
s

semicolons.
(comments that begin with ;| and end with |;).
s
s
s

Transparent FG
Transparent
BG

If selected, VLISP applies the selected color coding
options. If you want to use the VLISP formatter but do not
want lexical coloring, turn this option off.

Tab Width

Sets tab spacing in the current window.

Left Margin

|

Transparent background.

Lexical Colors

474

Transparent foreground.

Sets the left margin of the current window.


When you change and save the configuration of a VLISP editor window, you
will be asked whether or not you want the configuration to become the prototype for all text editor windows. If you choose Yes, the configuration of the
current window becomes the new prototype for VLISP text editor windows,
and all open text editor windows assume the attributes of the prototype.

Set Current Window to Prototype
This command configures the current active window with the attributes of
the prototype window.

Set All Windows to Prototype
This command sets all open windows with the attributes of the prototype.

Font
This option opens a standard Windows Font dialog box for selecting the font
to be used in VLISP windows.
Note that for code formatting to work correctly, you must use a fixed (nonproportional) font.

Environment Options
The Environment Options menu item allows you to set session-wide VLISP
options. For example, you can tell VLISP whether to save text editor files at
set intervals automatically, whether to create automatic backup files, and
how you want to treat attempts to modify protected symbols. Environment
Options is also where you set diagnostic options, such as what statistics to
report during syntax checking, and what level of detail to display when
inspecting drawing objects. You can also set formatting options for AutoLISP
code, and page layout options for printed output.

General Options
The General Options menu item displays a tabbed dialog box containing
General and Diagnostic tabs.

General Options Tab
The General Options tab contains three groups of items: Editor Options,
Desktop Options, and SETQ to Protected Symbols.

Environment Options

|

475

The Editor Options group contains the following items:

Backup the File
Edited on First
Save

When this option is selected, VLISP creates a backup copy
of the file the first time you save it.

Make Backup
by Copy, Not
Rename

VLISP creates a copy of the original file. When this option
is not selected, the backup file is a renamed version of the
original file.

Group Typing
for Undo/Redo

VLISP groups keystrokes for the Undo and Redo Edit
commands. If not selected, Undo and Redo proceed one
character at a time.

The Desktop Options group contains the following items:

Save Editor
Windows
Settings

Autosave
Setting on Exit
Application

476

|

The VLISP text editor window settings (toolbar placement
and text/background color) will be saved along with
window sizes, placements, and editor configurations
upon issuing Save Settings. When the option is off, VLISP
editor window settings are not saved on Save Settings.
Options are saved automatically upon exiting VLISP. If
Save Editor Windows Settings is turned on, the VLISP text
editor window settings (toolbar placement and
text/background color) are saved along with window
sizes, placements, and editor configuration.


The SETQ to Protected Symbols group controls how VLISP responds to
attempts to redefine protected symbols. (See “Protected Symbols” on page
228.) The options are:

Transparent

Protected symbols are treated like any other symbol.

Print Message

AutoLISP issues a warning message when you modify a
protected symbol but carries out the modification.

Prompt to
Enter Break
Loop

This is the default option. AutoLISP displays a message
box asking whether or not to enter a break loop when you
attempt to modify a protected symbol. If you choose No,
the symbol’s value is modified and processing continues
normally. If you choose Yes, processing is interrupted and
you enter a VLISP break loop.
In a break loop, control switches to the VLISP Console
window. You can set the symbol and continue processing
by pressing the Continue button on the VLISP toolbar, or
abort modification by pressing Reset.

Error

Prohibits modification of protected symbols. Any attempt
to modify a protected symbol results in an error.

Diagnostic Options
The Diagnostic Options tab displays the following dialog box:

Environment Options

|

477

Diagnostic options are as follows:

Report
Statistics
During Syntax
Checking

If selected, the syntax checker and the file compiler report
the statistics after checking or compiling each top-level
form and after each file.

Print Top Level
Results On
Load

If selected, top-level expressions are evaluated and printed
in the Console window when the expressions are loaded.
A top-level expression is one that appears outside any
other expression (for example, an expression that appears
outside of defun). For example, the following call to list
is a top-level expression:
(list 1 2 3)
(defun foo (x) x)

Loading a file containing this code results in the following
being printed in the Console window, if Print Top Level
Results on Load is selected:
(1 2 3)
FOO

Print
Notification
Message After
Load
Echo PRINx
Output to
ACAD

If selected, the elements of an object are included in the
Inspect window for a drawing database object. If the
option is not selected, only the object line (containing the
entity name) appears in drawing object Inspect windows.

Do Not Debug
Top-Level

If selected and Stop Once mode is set, the break will not
occur before evaluating every top-level form (such as
defun) during the file load process.

Animation
Delay

|

If selected, the default output of functions print, princ
and prin1 is echoed to the AutoCAD Command window
and the VLISP Console window instead of only to the
VLISP Console window.

Inspect
Drawing
Objects
Verbosely

478

If selected, each call to the load function results in
messages printed to the VLISP Console window.

Determines the pause length between program steps in
Animate mode, measured in milliseconds. The default
is 100.


Visual LISP Format Options
The Visual LISP Format Options menu item displays the Format Options
dialog box used to set formatting and indentation options.

Additional formatting options are available by pressing the More Options
button. These options are covered in “Additional Formatting Options” on
page 481.
Pressing Revert to Default reverts the option settings to the previous saved
setting, or to the system default, if the user has not previously changed and
saved settings.
Note that the code formatter assumes that you are using a fixed font to
display or print formatted text.

Base Formatting Options
Right Text
Margin

Right margin for text. An expression prints on a single line
if its last character position does not exceed the right
margin.

Narrow Style
Indentation

Sets the standard indentation value used in the Narrow
Formatting Style for function arguments.

Environment Options

|

479

Maximum
Wide-Style Car
Length

Maximum length for function expressions in Wide
Formatting Style. For longer expressions, the formatter
always uses Narrow Formatting Style.

SingleSemicolon
Comment
Indentation

Identifies the left margin alignment for single-semicolon
comments.

The Closing Parenthesis Style group of options controls the position of closing parentheses for multi-line formatting styles. The effect of each option is
demonstrated by formatting the following code, where Right Text Margin is
set to 40 and Preserve Existing Line Breaks is not selected:
(cond
((/= (logand mask flg) 0)
(list (list txton)))
)

VLISP formats this code as follows:

Close at the
Same Line

(list (list txton))))

Close at the
New Line with
Inner
Indentation

(list (list txton))
)
)

Close at The
New Line with
Outer
Indentation

(list (list txton))
)
)

The remaining items in this dialog box concern tabs, saving the current setting, and the setting of several comment options.

Insert Tabs
Save
Formatting
Options in
Source File

480

|

The VLISP formatter inserts tab characters instead of
multiple space characters whenever possible.
The VLISP formatter appends comments containing the
current formatting settings to the end of the text in the
VLISP text editor window. If you save these comments
(and do not modify them), VLISP applies the saved
formatting options to the text editor the next time you
open the file.


Insert FormClosing
Comment

This option causes VLISP to add a closing comment to an
expression when Close at the New Line with Inner
Indentation or Close at the New Line with Outer
Indentation is selected. The comment takes the following
form at the end of a multi-line function:
;_ end of <function name>

VLISP does not add the comment if the line already
contains a comment.

Form-Closing
Comment
Prefix

Determines the text to be included when Insert Formclosing Comment is selected.

Additional Formatting Options
These options appear when you press the More Options button on the basic
formatting window.

Approximate
Line Length

The VLISP formatter checks this value when it chooses the
formatting style. If the number of characters in an
expression is greater than this value, the formatter prints
the expression as multi-line.

Preserve
Existing Line
Breaks

When this option is selected, the VLISP formatter inserts
new lines whenever a new line is detected in the text
being formatted. When the option is off, the formatter
can squeeze a multiple-line expression to the plane style,
if it fits within the right margin.

NOTE Selecting this option causes VLISP to ignore other
formatting options when those options would result in a
loss of existing line breaks. This is often the source of
unexpected formatting results.
Split
Comments

When this option is selected, the VLISP formatter splits
comments that exceed the right margin.

Environment Options

|

481

Casing for
Symbols

These options control whether or not the VLISP formatter
converts the case of alphabetic text in an AutoLISP symbol
name. The protected symbols subgroup controls the case
conversion of protected symbols (that is, symbols with
the ASSIGN-PROTECT flag set). The unprotected options
subgroup controls the case conversion of unprotected
AutoLISP symbols. The following options are available:

None: No case conversion.
downcase: The formatter converts all characters in a
symbol name to lowercase.
UPCASE: The formatter converts all characters in a symbol
name to uppercase.
The Long List format style option controls the formatting of long lists. Long
lists are lists of formal arguments in defun and lambda expressions, or in
quoted lists of atoms with more than five elements. The style option applies
to long lists that do not fit on a single line (that is, within the Right Text
Margin). Long List format style options are illustrated by formatting the
following statement with Right Text Margin set to 45:
(setq lista '("abc" "def" "ghi" "jkl" "mno" "pqr"))

The options are:

SingleColumn
Formatting

(setq lista '("abc"
"def"
"ghi"
"jkl"
"mno"
"pqr"
)
)

2-Column
Formatting

(setq listall '("abc"
"ghi"
"mno"
)
)

"def"
"jkl"
"pqr"

Multi-Column
Formatting

(setq listall '("abc"
"jkl"
)
)

"def"
"mno"

Fill-to-Margin
Formatting

(setq listall '("abc" "def" "ghi" "jkl" “mno”
"pqr"
)
)

482

|


"ghi"
"pqr"

Page Format Options
These options control the appearance of printed output from VLISP. The
options are:

Header and
Footer

Fields for specifying the content of the page header and
footer. The first input field contains the header line to
print at the top of the page, the second input field
contains the footer line to print at the bottom of the page.
Headers and footers may contain text strings and
variables. See “Justification and Substitution Codes” on
page 483 for more information on specifying headers and
footers.

Print Page
Margins

Select either inches or millimeters as the measuring unit,
then specify Top, Left, Bottom, and Right margins.

Press the Font button to open a dialog box for specifying the output font.

Justification and Substitution Codes
Only the ampersand character (&) is considered as an escape character. Both
the ampersand and the character that follows are not copied to the output
line. Instead, they either justify the following text, or VLISP replaces them
with variable information.
Justification codes indicate how header text is justified on the printed page.
You can specify any of the following:

&l

Left-justified (the default).

&c

Centered within the page margins.

&r

Right-justified.

Replace codes are variables for which VLISP substitutes values. Specify any of
the following:

&f

VLISP replaces this code with the title of the active VLISP
window. When invoked from a VLISP text editor window,
&f is the name of the file being edited, including directory
and extension.

&d

Current system date. To select a date format, choose
Edit ® Extra Commands ® Format Date/Time from the
VLISP menu.

&t

Current system time. To select a time format, choose
Edit ® Extra Commands ® Format Date/Time from the
VLISP menu.

&p

Current page number.

Environment Options

|

483

To include an ampersand character in your heading text, enter two in
succession.
The default heading is set to the following:
&cFile: &f &r&dt

The default footing is set as follows:
&r&p

The following is a sample printed page from an AutoLISP source file using the
default page layout settings:
File: REACTORSTUFF.LSP

12/11/98

(defun saveDrawingInfo (calling-reactor commandInfo / dwgname
filesize)
(setq dwgname (cadr commandInfo)
filesize (vl-file-size dwgname)
)
(alert (strcat "The file size of “ dwgname “ is “))
.
.
.
(princ)
)
2

Save Settings
The Save Settings tools option saves the desktop configuration and options
settings. Note that the desktop configuration concerning the child windows
attributes (their presence on the screen, color, position, files loaded) is saved
only when the Save Editor Windows Settings option is on. This option is
available through the Desktop Options tab of the General Options
dialog box.

484

|


AutoLISP Error Codes

C

In This Appendix

This appendix lists the AutoLISP error codes.

s Error Codes

485

Error Codes
The following table shows the values of error codes generated by AutoLISP.
The ERRNO system variable is set to one of these values when an AutoLISP
function call causes an error that AutoCAD detects. AutoLISP applications
can inspect the current value of ERRNO with (getvar "errno").
The ERRNO system variable is not always cleared to zero. Unless it is inspected
immediately after an AutoLISP function has reported an error, the error that
its value indicates may be misleading. This variable is always cleared when
starting or opening a drawing.

NOTE The possible values of ERRNO, and their meanings, may change in future
releases of AutoCAD.

Online program error codes
Value
0

Invalid symbol table name

2

Invalid entity or selection set name

3

Exceeded maximum number of selection sets

4

Invalid selection set

5

Improper use of block definition

6

Improper use of xref

7

Object selection: pick failed

8

End of entity file

9

End of block definition file

10

Failed to find last entity

11

Illegal attempt to delete viewport object

12

|

No error

1

486

Meaning

Operation not allowed during PLINE

Appendix C AutoLISP Error Codes

Online program error codes (continued)
Value

Meaning

13

Invalid handle

14

Handles not enabled

15

Invalid arguments in coordinate transform request

16

Invalid space in coordinate transform request

17

Invalid use of deleted entity

18

Invalid table name

19

Invalid table function argument

20

Attempt to set a read-only variable

21

Zero value not allowed

22

Value out of range

23

Complex REGEN in progress

24

Attempt to change entity type

25

Bad layer name

26

Bad linetype name

27

Bad color name

28

Bad text style name

29

Bad shape name

30

Bad field for entity type

31

Attempt to modify deleted entity

32

Attempt to modify seqend subentity

33

Attempt to change handle

34

Attempt to modify viewport visibility

35

Entity on locked layer

Error Codes

|

487

Value
36

Bad polyline entity

38

Incomplete complex entity in block

39

Invalid block name field

40

Duplicate block flag fields

41

Duplicate block name fields

42

Bad normal vector

43

Missing block name

44

Missing block flags

45

Invalid anonymous block

46

Invalid block definition

47

Mandatory field missing

48

Unrecognized extended data (XDATA) type

49

Improper nesting of list in XDATA

50

Improper location of APPID field

51

Exceeded maximum XDATA size

52

Entity selection: null response

53

Duplicate APPID

54

Attempt to make or modify viewport entity

55

Attempt to make or modify an xref, xdef, or xdep

56

ssget filter: unexpected end of list

57

ssget filter: missing test operand

58

|

Bad entity type

37

488

Meaning

ssget filter: invalid opcode (–4) string


Value

Meaning

59

ssget filter: improper nesting or empty conditional clause

60

ssget filter: mismatched begin and end of conditional clause

61

ssget filter: wrong number of arguments in conditional clause (for NOT or
XOR)

62

ssget filter: exceeded maximum nesting limit

63

ssget filter: invalid group code

64

ssget filter: invalid string test

65

ssget filter: invalid vector test

66

ssget filter: invalid real test

67

ssget filter: invalid integer test

68

Digitizer is not a tablet

69

Tablet is not calibrated

70

Invalid tablet arguments

71

ADS error: Unable to allocate new result buffer

72

ADS error: Null pointer detected

73

Cannot open executable file

74

Application is already loaded

75

Maximum number of applications already loaded

76

Unable to execute application

77

Incompatible version number

78

Unable to unload nested application

79

Application refused to unload

80

Application is not currently loaded

81

Not enough memory to load application

Error Codes

|

489

Value
82

ADS error: Invalid symbol name

84

ADS error: Invalid symbol value

85

|

ADS error: Invalid transformation matrix

83

490

Meaning

AutoLISP/ADS operation prohibited while a dialog box was displayed


Index

Symbols
! (exclamation point), for viewing AutoCAD
variable values, 18, 25
* (asterisk)
as Apropos wild-card character, 44
by file name in text editor status bar, 14
*obj* system variable
copying Inspect objects to , 103
copying symbol name from Apropos, 47
copying trace stack elements to, 88
copying value from Frame Binding window
to, 88
copying value from Inspect window, 102
copying value from Watch window, 84
; (semicolon) in VLISP comment styles, 58
_ (underscore)
for foreign-language support, 261
for VLISP comments , 58
(backslash)
for control characters in quoted strings,
237–238
using within quoted strings, 237
*error* function
for document namespaces, 134, 135
overview, 254 –257
" (quotation marks)
and parentheses in expressions, 223
' (single quotation mark), forming point lists,
243
// (slashes) for DCL comments, 344
._xx files, 139
| (vertical bar) for VLISP comments, 58

A
acad.dcl file, 340
acad.unt. See unit definition file
:ACAD-REQUEST trace keyword frame, 89
accessing
AutoCAD groups , 334
AutoCAD objects with ActiveX , 165–169
circle object example, 168–169

accessing (continued)
moving forward from the application
object, 168
overview, 165 , 168–169
returning pointer to AutoCAD object,
165
specifying VLA-object type, 165
using Inspect tool to view object
properties, 166–169
dictionary entries , 334
entities, 311
help files, 290 –291
symbol table entries, 332–333
user input, 291
calibrating tablets, 291–293
summarized, 447
:ACMD-CALLBACK trace keyword frame, 90
action (DCL attribute), 397
action expressions (dialog boxes). See dialog box
management, action expressions and
callbacks
action_tile function, 372 , 374
activating. See starting
active document, changing, 28
ActiveX, 161 –199
accessing AutoCAD objects, 165–169
object, 168
overview, 165 , 168–169
165
AutoCAD object model, 162–164
collections of objects, 164
object methods , 164
object properties, 164
AutoLISP functions and, 162
connecting to application objects, 165
connecting to applications, 195

491

ActiveX (continued)
data types
converting from AutoLISP to ActiveX,
173–180
enabling AutoLISP support for, 22
errors, handling of using AutoLISP,
191–193
interacting with other applications ,
193–199
calling ActiveX methods with
vlax-invoke-method,
198–199
establishing connection to
application, 195
importing a type library, 193–195
obtaining properties with
vlax-get-property, 199
overview, 193
sample application, 196–198
updating properties with
vlax-put-property, 199
without importing a type library,
198–199
intercepting errors returned from, 191–193
languages and environments supporting,
162
loading ActiveX support for AutoLISP, 22,
165
methods , 164–173 , 198 –199
in ActiveX and VBA Reference, 164,
171–174, 193
objects. See objects
overview, 162
properties of objects
in ActiveX and VBA Reference, 164
changing, 181 –183
getting, 180–181
listing, 185–187
reading, 180–181
updating, 181–183
viewing, 180 –181
safearrays, using
creating, 175–177
creating variants containing, 178–179
displaying contents of, 177
populating with data , 175–178
with variants , 178–179
using AutoLISP functions with ActiveX
methods , 170–191
applying object's property to new
object, 181
AutoLISP data types accepted in place of
ActiveX data type, 180
changing X axis of circle, 181–183
converting AutoLISP data types to
ActiveX data types, 173 –180
converting object references, 190–191

492

|

Index

ActiveX (continued)
determining function needed, 172
determining how to call functions,
172–173
determining if method or property
applies to object, 186–187
determining if object is available for
updating, 183
listing object properties and methods,
185–187
reading object properties , 180–181
releasing objects and freeing memory,
189
updating object properties, 181–183
using ActiveX methods that return
values in arguments,
184–185
vla- functions , 170
vla-get functions, 170
vla-put functions, 170
vlaxfunctions , 170
working with collection objects,
187–189
variants, using, 174–175
changing data type of, 174
creating, 174–175
returning data type of, 174
returning value of, 174
safearrays and, 178–179
ActiveX and VBA Developer's Guide, 193
ActiveX and VBA Reference, 8, 164, 171–174,
193
Add File command (Project window shortcut
menu), 146
Add Lisp Source Files to Project dialog box , 120
Add to Watch command
Apropos results window shortcut menu, 47
Frame Binding window shortcut menu, 89
Add Watch command
Console window shortcut menu, 29
text editor shortcut menu, 33
add_list function, 380–381
adsfunc function, 305
aesthetics in dialog box design, 353
:AFTER-EXP trace keyword frame, 90
alert function, 256, 355, 364
alignment (DCL attribute), 397–426
All (Apropos filter value), 44
allow_accept (DCL attribute), 398
angles
converting radians and degrees, 281 –282
converting to strings, 280
finding angle between line and X axis, 274
angtof function, 281
angtos function, 280, 281
angular values, converting radians or degrees ,
281–282

Animate command (VLISP Debug menu), 74
Animate mode, 74
anonymous blocks , 319
append function, 241
Append With text formatting option, 59
appending information to existing Console log
file, 30
Application Compilation Options dialog box,
122–123
Application Directory dialog box, 118
application modules, making. See making
application modules
Application Option dialog box, 118
Application Properties dialog box, 124
Application Wizard. See Make Application Wizard
application-handling functions , 436
applications
building. See building applications
managing. See managing VLISP applications
running, 114–115 , 124
separate-namespace, 129–136
Apropos dialog box , 43–44
Apropos dialog box options , 43–44
Apropos feature, 43–47
Apropos dialog box , 43–44
calling from Watch window, 85
Complete Word by Apropos feature, 48 –49
Copy to Trace/Log feature, 46
Downcase Symbols option, 44
Filter Flags option, 44
Filter Values option, 44
inserting symbols from results window, 46
invoking from Console window shortcut
menu, 29
invoking from text editor shortcut menu,
33
invoking from Watch window shortcut
menu, 85
Match by Prefix option, 45
opening Apropos window, 29, 33, 43
overview, 43
results window, 45–47
searching for AutoLISP symbols by prefix,
45
shortcut menu options, 46–47
Use WCMATCH option , 44
using search results , 45–47
Apropos Window command (VLISP View
menu), 43
arbitrary data management, 331
arithmetic functions , 437–438
:ARQ-SUBR-CALLBACK trace keyword frame, 90
Arrange Files command (Project window shortcut
menu), 146
arranging files in Project window, 146
arrays. See safearrays
ARX applications. See ObjectARX applications

ARX Object ID, 190 , 191
ASCII code conversions, 282 –283
aspect_ratio (DCL attribute), 398
assoc function, 244, 245
association lists , 244
associative searches. See searching
asterisk (*)
as Apropos wild-card character, 44
by file name in text editor status bar, 14
atoi function, 382
attaching data
extended data to entities, 329
to reactor objects , 210
attaching reactors to AutoCAD drawings. See
reactors
attributes, DCL. See DCL
AutoCAD
accessing AutoCAD groups, 334
active document, 28
blocks, viewing with VLISP, 106–107
commands
issuing with AutoLISP 260 –261
,
redefining, 249–250
configuration control, 264
coordinate systems , 286–287
device access and control functions,
291–293
display control, 264 –268
graphics and text windows , 267
low-level graphics , 267–268
overview, 264
entities, viewing with VLISP 104 –105
,
exiting, 22
foreign-language support, 261
geometric utilities , 274–279
finding angle between line and X axis,
274
finding distance between two points ,
274
finding intersection of two lines, 274
finding polar coordinates of points ,
274
overview, 274
getting user input from, 291
handling user input, 268–273
pausing for input, 261–262
help files, accessing, 290–291
inspecting and changing system and
environment variables, 263 –264
menus, controlling, 264–267
object snap, 274–275
objects, manipulating, 295–334
extended data, 323–330
object-handling, 305–323
selection set handling, 296–305

Index

|

493

AutoCAD (continued)
symbol table and dictionary access,
332–334
xrecord objects , 331
passing pick points to commands , 262–263
pausing for user input, 261–262
query and command functions, 260 –264
receiving user input from, 291
redefining AutoCAD commands, 249–250
related publications, 8
running with VLISP, 3, 20
sending commands to AutoCAD prompt,
260–261
text extents, 275–279
undoing commands issued with command
function, 263
user input functions, 268–273
accessing user input from devices , 291
allowable input, 268–269
arbitrary keyboard input, 273
controlling user-input function
conditions, 271–273
getting user input, 268–271
getxxx functions, 268–271
input options , 271–272
keyword options, 272–273
validating input, 273
viewing drawing entities , 104–108
blocks in the drawing database,
106–107
controlling amount of Inspect
information, 104
entities in the drawing database,
104–105
extended data associated with objects,
105, 107–108
selected objects in drawings, 107
symbol tables in the drawing
database, 105
AutoCAD command window
Console window compared to , 18 , 25–26,
28
starting Visual LISP, 12
AutoCAD drawing database, viewing
blocks in, 106–107
entities in, 104–105
extended data, 108
symbol tables in, 105
AutoCAD groups, accessing, 334
AutoCAD mode command (Console window
shortcut menu), 29
AutoCAD object model, 162–164
collections of objects, 164
object methods , 164
object properties, 164

494

|

Index

AutoCAD objects. See objects
AutoCAD Runtime Extension. See ARX
Autodesk World Wide Web site, 8
AutoLISP
accessing AutoCAD groups, 334
accessing user input with, 291
application-handling functions , 436
arithmetic functions , 437–438
AutoCAD display control, 264–268
menus , 264–267
overview, 264
calibrating tablets with, 291 –293
closing files in programs, 227
collection manipulation functions , 458
comments in program files , 230
communicating with AutoCAD, 259–293
converting data types and units,
279–289
device access and control, 291–293
display control, 264 –268
file-handling functions , 289–291
query and command functions,
260–264
compiling and linking AutoLISP programs,
110–116
Application Compilation Options
dialog box, 122–123
choosing a compilation mode, 111,
154, 155
choosing build options , 144, 153–155
compile example, 113–114
compiling programs from files ,
111–113
defining build options , 153–155
linking function calls, 111, 116, 159
loading and running compiled
programs , 114–115
localizing variables, 155
Make Application output, 123
Merge Files mode, 154
naming an output file, 113
optimization during compiling, 111
project source files, 146–147
recompiling project source files, 148
report detail level, 155
safe optimization, 155, 157–160
using Application Wizard, 117–123
using the compiler, 110
using VLISP integrated project
management facilities , 110
conditional branching and looping, 240
control characters in strings, 237 –238
controlling dialog boxes with, 366–368

AutoLISP (continued)
converting data types and units, 279–289
angular values from radians or
degrees, 281 –282
coordinate system transformations,
286–289
measurement unit conversions,
283–286
point transformations , 289
string conversions , 279–281
synopsis of functions , 446, 458–459
curve measurement functions, 461–462
data types, 224–229
entity names , 226
file descriptors, 226–227
integers, 224–225
lists, 225
reals, 225
selection sets, 226
strings , 225
symbols and variables, 227–229
VLA-objects , 226
debugging AutoLISP code
break loop process , 76
Break on Error option, 75
breakpoint life cycle, 81
checking for syntax errors, 61–65
continuable break loops , 77–78
continuing program execution , 74, 77
Debug-on-Entry flag, 75, 94
disabling breakpoints temporarily, 80
displaying breakpoints , 80
example, 69–75
highlight colors for breakpoints, 79
listing breakpoints, 80
monitoring evaluation results of an
expression, 73 –74
non-continuable break loops , 78
optimization and bug introduction,
156
Quit Current Level option, 77
removing breakpoints, 79
Reset to Top Level option, 77
running in Animate mode, 74
semantic auditing of DCL files ,
346–347, 387–388
setting breakpoints, 70–71 , 79
starting debugging sessions , 76
starting Trace logging, 82
stepping through programs from
breakpoints, 71–72, 78
Stop Once mode, 75, 76
Top-Level debugging mode, 75
using Frame Binding window, 88–92
using Inspect windows , 95–108

using Symbol Service dialog box,
92–95
using Trace Stack window, 85–92
using Watch window, 83–85
VLISP debugging features, 68–69
developing AutoLISP programs, 24 –65
basic steps , 24
formatting code, 50 –60
using coding aids, 42 –50
using the Console window, 25 –30
using the text editor, 31–41
291–293
synopsis of, 447
dialog box management, 365–389
action expressions and callbacks,
368–372
application-specific data, 386
controlling dialog boxes with AutoLISP
DCL error handling, 386 –388
function sequence, 388–389
handling tiles, 372–376
hiding dialog boxes, 377 –379
image tiles and buttons, 383 –385
list boxes and pop-up lists, 380–382
nesting dialog boxes, 376–377
sample block definition dialog box,
389
dictionary functions , 334, 462
display-control functions , 448
displaying messages with, 236
dotted pairs, 244 –245
equality and conditional functions, 439
equality verification, 240
error codes, 485, 486
error handling, 254–257, 440
exiting quietly, 236
expressions, 222–223
extended data functions
attaching extended data to entities,
329
filtering selection sets for extended
data , 300
group codes for extended data,
323–324
handles in extended data, 330
managing memory use, 329
organization of extended data,
324–326
registration of applications , 327
retrieving extended data, 323,
327–328
synopsis of, 453

Index

|

495

file-handling functions
accessing help files , 290–291
file search, 289–290
synopsis of, 449
formatting code, 229–230
function synopsis (summary), 433–461
basic functions, 436–445
category summary, 434–436
memory management functions , 457
namespace communication
functions , 468
reactor functions , 464–466
selection set, object, and symbol table
functions , 453–457
utility functions, 446–452
Visual LISP extended functions , 457
VLX namespace functions, 467
Windows Registry functions, 469
function syntax, 223
function handling, 245–254
adding commands, 248–249
c:xxx functions , 247–250
defining functions , 245–247
defining functions with arguments ,
252–254
defun function, 245–253
defun-q function, 247
local variables in functions, 251 –252
redefining AutoCAD commands,
249–250
special forms, 253–254
synopsis of functions , 441
functions, as lists , 246
274
274
274
overview, 274
synopsis of, 450
history of, 2
integer overflow handling, 224–225
interacting with users, 291
issuing commands from Console window,
14
list processing functions, 240 –245
adding items to list beginning, 241,
241
combining lists, 241

496

|

Index

grouping related items , 240
point lists, 242–244
retrieving items from lists, 240–241
returning all but first element, 241
substituting items, 241, 241
synopsis of, 442–443
loading from text editor, 20
manipulating AutoCAD objects , 295–334
object handling, 305–323
332–334
matching parentheses , 222–223
MDI (multiple document interface), and
AutoLISP, 126–134
error-handling in MDI environment,
134–135
limitations, 136
namespaces overview, 126–129
running an application in its own
namespace, 128–130
sharing data between namespaces,
133–134
method invocation functions, 459
namespace communication functions, 468
number handling, 233
object-handling functions, 305–323
blocks and, 308–311
entity access functions, 311
entity data functions , 311–320
entity name functions, 305–311
non-graphic object-handling,
321–323
polylines (old-style and lightweight),
320–321
selection sets, 296–305
symbol table and dictionary entries,
332–334
synopsis of, 453–454, 463
output functions, 235–239
control characters in quoted strings,
237–238
displaying messages, 236
wild-card matching, 238–239
overview, 2
predefined variables, 232 –233
program files , 229–231
color coding, 231
comments, 230
creating new source files, 229
editing code in VLISP, 229

property-handling functions, 460
protected symbols , 94, 228–229
query and command functions, 260 –264
environment variables,
263–264
passing pick points to AutoCAD
commands, 262–263
sending commands to AutoCAD
prompt, 260–261
synopsis of, 451
undoing commands issued with
command function, 263
referring to entities for multiple sessions ,
226
relationship to Visual LISP, 1, 3
running from Console prompt, 20–21
running selected lines of code, 21
selection set handling functions , 296–305
adding entities, 303–304
creating selection sets , 296–297
deleting entities, 303 , 304
finding number of entities, 304
passing selection sets between AutoLISP
and ObjectARX
applications, 305
returning entity names , 304
selection set filter lists, 298–304
synopsis of, 455
testing whether an entity is a member,
304
selection set, object
and symbol table functions, 453–457
spaces in code, 229–230
string handling, 234–235 , 444 –445
symbol and function-handling, 245 –254
symbol table access functions, 332–333
symbol handling, 245, 445
function, 263
user input functions
getxxx functions , 268–271

synopsis of, 452
conversion functions, 446
device access functions , 447
display-control functions , 448
file-handling functions , 449
geometric functions, 450
query and command functions, 451
user input functions, 452
variables
assigning values to , 227–228 , 231
data type, 227–229, 231
displaying value of, 231–232
nil variables , 232
predefined, 232–233
Visual LISP extended functions , 22, 457
collection manipulation functions ,
458
curve measurement functions,
461–462
data conversion functions , 458–459
defined, 22
dictionary functions , 462
loading extended functions , 22
object-handling functions, 463
running, 22
vl-load-com and, 22
AutoLISP Format Options command (VLISP Tools
menu), 51–59
AutoLISP functions. See functions
AutoLISP Reference, 4, 205, 208
automatically backing up text editor files, 31–32
:AXVLO-IO-CALLBACK trace keyword frame, 90

B
backing up
files in text editor automatically, 31–32
restoring from backup files, 32
backslash ()
for control characters in quoted strings,
237–238
balance of parentheses, checking in VLISP,
61–65, 222–223
base.dcl file
default_button definition, 342
overview, 340
beeping your PC, 206
:BEFORE-EXP trace keyword frame, 90

Index

|

497

big_increment (DCL attribute), 398
blackboard namespace, 133
blackboard variables, 133 , 134
blocks
viewing with VLISP, 106–107
working with, 319
blocks in the drawing database, 106 –107
blocks of text
converting code to comments, 60
converting comments to active text, 60
indenting or unindenting, 59
saving to new file, 36, 60
sorting, 60
bold courier type in this manual, 7
boldface type in this manual, 7
bookmarking text, 40–41
adding bookmarks , 40
clearing, 41
deleting bookmarks , 41
moving to bookmarks , 40–41
overview, 40
selecting text using bookmarks , 41
boxed_column tile, 410 –411
boxed_radio_column tile, 411
boxed_radio_row tile, 412
boxed_row tile, 412
break loops
Break on Function Entry, 75, 94
entering, 75–77
exiting, 74, 77
overview of, 76
Prompt to enter break loop option for
protected symbols , 228
stepping through programs in , 71–72, 78
turning on, 75–77
Break on Error command (VLISP Debug menu),
75
Break on Function Entry command (VLISP Debug
menu), 75
Breakpoint Service dialog box , 80
:BREAK-POINT trace keyword frame, 90
breakpoints
clearing, 79
described, 68
disabling temporarily, 80
highlight colors for, 79
life cycle of, 81
listing and viewing, 80

498

|

Index

breakpoints (continued)
removing, 79
Reset to Top Level option, 77 , 92
resuming execution from, 77
setting, 70–71 , 79
stepping through programs from, 71 –72,
78
Toggle Breakpoint command, 33
turning on, 75–77
Breakpoints window, 80
Browse All Entities command (VLISP View
menu), 104
Browse Blocks command (VLISP View menu),
106
Browse Selection command (VLISP View menu),
107
Browse Tables command (VLISP View menu),
105
browsing. See displaying
Build Options dialog box , 154
Build Output window
error messages in, 65
finding location of syntax errors , 65
Build Project FAS button (Project window), 145,
148
building applications , 109–136
compiling and linking programs, 110–115
compiling programs from files ,
111–113
loading and running compiled
designing for multiple document
environments, 126–129
134–135
sharing data between namespaces,
133–134
making application modules , 117
changing application options,
124–125
including projects, 151–152
loading and running VLISP
applications, 124
rebuilding applications , 125
updating applications, 125 , 126

Built-in function (Apropos filter value), 44
button tile, 413
buttons (dialog box). See tiles (dialog box)

C
.c files , 140
caddr function, 243
cadr function, 243, 244
calibrating tablets , 291–293
Call Point Source command (Trace Stack window
shortcut menu), 88
call stack, 68
callback events for reactors, 204 –205
callback functions for dialog boxes. See dialog box
management, action expressions and
callbacks
callback functions for reactors , 205–207
calling ActiveX methods, 164–173, 198
capitalization. See case
Capitalize option, 60
car function
handling dotted pairs , 244
for point lists, 243, 244
retrieving items from lists, 241
case (of text and symbols)
Assign-Protect flag and, 57
automatic changing of by AutoLISP, 57, 234
conversion by Apropos, 48
converting selected text, 60
converting with strcase function, 234
DCL attributes and, 393
dialog box design guidelines, 356–357
equality checking and, 240
symbols, automatic case changing of, 57,
234
tile names, 342
case sensitivity
of Apropos search , 48
comparison functions and, 240
of Complete Word by Match, 48
of DCL attribute names and values, 344
of DCL tile names, 343
of equality functions, 240
of grouping operators, 302
of input functions , 272
of mnemonics (in DCL tiles), 405
of reserved words (in DCL tiles), 392
of search in text editor, 38
of symbol names, 227
.cch files, 140
cdr function
handling dotted pairs , 244
returning all but first list element, 241
Check command, 64–65
errors detected by, 64–65

Check command (continued)
finding location of errors , 65
running, 65
Check Selection command (VLISP Tools menu),
65
Check Syntax command (Project window
shortcut menu), 146
Check Text in Editor command (VLISP Tools
menu), 65
balance of parentheses, 61 –63
from Project window, 146
using Check command, 64–65
using color coding, 63
children_alignment (DCL attribute), 398
children_fixed_height (DCL attribute), 398–399
children_fixed_width (DCL attribute), 399
circles
changing X axis, 181–183
returning minimum and maximum
bounding points, 184 –185
Clear All Bookmarks command (VLISP Search
menu), 41
Clear All Breakpoints command (VLISP Debug
menu), 79
Clear Console window command (Console
window shortcut menu), 29
clear language in dialog box design, 353
clearing. See deleting
client_data_tile function, 386
Clipboard
Console window shortcut menu
commands, 29
text editor shortcut menu commands,
32–33
VLISP support for, 36
See also copying; moving text
close function, 227
Close Parenthesis Style options (Format Options
dialog box), 54
Close Project command (Project window shortcut
menu), 146
closing
all Inspect windows, 103
AutoCAD, 22
Console log file, 30
dialog box closing functions, 427
files in AutoLISP programs , 227
projects, 149
Visual LISP, 22
coding aids
Apropos feature, 43–47
color coding, 19, 42–43, 63
Complete Word by Match feature, 47–48
See also formatting text

Index

|

499

collection objects
applying function to every object in,
187–188
evaluating series of functions with each
object in, 187 , 187 –188
overview, 164
retrieving member objects, 188–189
working with, 187–189
color (DCL attribute), 399–400
color coding
for AutoLISP code, 231
changing colors, 42
of DCL files, 345
of files in text editor, 19 , 42–43
scheme for AutoLISP code, 42
for syntax error detection, 63
colors for breakpoints , 79
Column style, 53
column tile, 413–414
combining strings in AutoLISP, 234
command function
commands, 262–263
260–261
undoing commands, 263
command prompt, starting Visual LISP from, 12
commands
Console window shortcut menu
commands, 28
descriptions on status bar, 14
interrupting, 27
issuing from Console window, 14
issuing from VLISP menus , 15
retrieving previous commands , 18, 26 –27
text editor shortcut menu commands,
32–33
See also specific commands
Comment Block option, 60
comments
in AutoLISP program files, 230
in dialog control language (DCL), 344
Insert Form-Closing Comment option, 55
shortcut keys for, 60
Split Comments option, 56
in unit definition file, 286
VLISP comment styles , 58
Compilation mode option (Build Options dialog
box), 154
compilation report detail level, 155
compiling and linking programs
Application Compilation Options dialog
box, 122–123

500

|

Index

compiling and linking programs (continued)
build options, choosing, 144, 153–155
choosing a compilation mode, 111, 154,
155
compiling programs from files , 111–113
identifying the input file, 112
loading and running compiled programs,
114–115
localizing variables, 155
Merge Files mode, 154
optimization during compiling, 111
output file, naming, 113
recompiling project source files, 138,
145–146, 148
report detail level, 155
safe optimization, 155, 157–160
source files, identifying, 112–113
using Application Wizard, 117
using VLISP integrated project management
facilities, 110
vlisp-compile function, 111–113
See also Application Wizard; optimizing
application code
concatenating strings in AutoLISP, 234
concatenation tile, 414
COND-expression clauses, Column style for, 53
conditional branching and looping in AutoLISP,
240
Configure Current command (VLISP Tools
menu), 42, 79
connecting with ActiveX
to application objects, 165
to applications, 195
cons function
adding items to list beginning, 241, 241
creating dotted pairs , 244
consistency in dialog box design, 353
Console prompt
changing active document, 28
clearing, 18, 27
copying symbol name from Apropos
window, 46
copying text within the Console window,
25
displaying new prompt without evaluating
text, 18, 27
displaying variable values , 231–232
illustrated, 25

Console prompt (continued)
pasting text at, 25
resetting, 18, 27
running AutoLISP programs from, 20–21
Console window
AutoCAD command window compared to,
18, 25–26, 28
changing active document, 28
clearing Console prompt, 18
color coding of text, 42
continuing expression on new line, 25
copying text to the prompt, 25
displaying new prompt without evaluating
text, 18, 27
ENTER key and, 25–26
entering multiple expressions before
processing, 25
features , 18–19
interactive programming in , 25
interrupting commands , 27
loading AutoLISP programs from text
editor, 20
logging activity, 29–30
multiple AutoCAD drawings with, 28
overview, 14, 18–19 , 25 –26
printing Frame Binding window value to ,
88
printing Inspect window object to, 102
printing stack element to , 88
printing Watch window variable values, 85
retrieving previous commands , 18, 28
running AutoLISP programs , 20–21
searching input history, 18, 27
shortcut menu commands , 28
context-sensitive help. See help feature
Continue command (VLISP Debug menu), 74,
77
continuing expression on new line in Console
window, 25
control characters
in DCL strings, 392
in quoted strings, 237–238
controlling amount of Inspect information, 104
controlling AutoCAD display, 264–268
menus , 264–268
overview, 264
conversion functions, 279–289
angular values from radians or degrees ,
281–282

conversion functions (continued)
286–289
AutoCAD coordinate systems ,
286–287
overview, 286
specifying coordinate systems , 288
valid integer codes , 288
measurement unit conversions, 283–286
synopsis of, 446
converting AutoLISP data types to ActiveX data
types , 173–180
ActiveX and VBA Reference, 173–174
other AutoLISP data types, 179 –180
using safearrays with variants, 178 –179
working with safearrays, 175 –178
working with variants , 174–175
enames and VLA-objects, 190
obtaining one object identifier from
another, 190 –191
converting string case, 60, 234
coordinate system transformations
AutoCAD coordinate systems , 286–287
entity context and coordinate transform
data , 307–311
overview, 286
specifying coordinate systems , 288
valid integer codes , 288
Copy command
Trace Stack window shortcut menu, 88
Copy to Clipboard command (Apropos results
window shortcut menu), 46
Copy to Trace/Log feature (Apropos window), 46
Copy Value command (Watch window shortcut
menu), 84
copying
Apropos search results to Trace window and
log, 46
by dragging in text editor, 36
Clipboard support for, 36
from Console window, 25
from Frame Binding window to *obj* system
variable, 89
from Inspect window to *obj* system
variable, 103

Index

|

501

copying (continued)
from Inspect window to Trace window and
log, 102
from output windows, 15
selected text to new file, 36 , 60
stack elements to *obj* system variable, 88
symbol names from Apropos results
window, 46
symbols from Apropos results window, 46
undoing copy actions , 37
using Console window shortcut menu, 29
using text editor shortcut menu, 33
from Watch window to *obj* system
variable, 84
from Watch window to Trace window and
log, 84
See also printing
correcting text. See text editor
Courier type in this manual, 7
.cpp files, 140
creating
applications, 117–123
complex entities, 316–318
new instance of application object, 195
new source files, 31, 229
reactors , 207–210
safearrays , 175–177
selection sets, 296–297
variant with an array of four doubles , 179
variants , 174, 174–175
Current File option (Find dialog box), 37
Current Selection option (Find dialog box), 37
curve-fit polylines, processing, 321
Customization Guide, 8
Cut command, text editor shortcut menu, 33
cutting. See deleting; moving
cvunit function, 283–284

D
data inspection tools. See Frame Binding window;
Inspect feature; Symbol Service dialog
box; Trace Stack window
data types
AutoLISP
accepted in place of ActiveX data type,
180
converting to ActiveX data types,
173–180
entity names , 226
file descriptors, 226–227
integers, 224–225
lists, 225
reals, 225
selection sets, 226

502

|

Index

data types (continued)
strings , 225
symbols , 227–229
variables, 227–229 , 231
VLA-objects , 226
converting AutoLISP data types to ActiveX
data types, 173–180
ActiveX and VBA Reference, using,
173–174
other AutoLISP data types, 179 –180
using safearrays with variants,
178–179
working with safearrays, 175 –178
working with variants , 174–175
element list formats and, 97–102
extended data organization, 324–326
for tile attribute values , 392
Database reactors, 202
date
changing format for, 60
inserting current date, 60
DCL (dialog control language)
acad.dcl file, 340
actions, 372
adjusting layout, 347–352
centering buttons, 347–348
customizing exit button text, 351–352
distributing tiles in a cluster, 348 –349
example, 347–348
space around boxed row or column,
350–351
space at right side or bottom, 350
space between tiles, 349
attributes, 392 –394
case-sensitivity, 393
data types for values , 392
naming, 393
numeric values and, 393
restricted attributes , 393
synopsis of predefined attributes,
394–396
syntax, 343–344
user-defined attributes , 393–394
attributes listed by function
action expression specification, 397
aligning horizontally or vertically in a
cluster, 397–426
aspect ratio specification, 398
background color of image, 399 –400
bold text specification, 402
button is selected with ESC key (or
not), 402
callback specification, 397
character used to mask user input, 406
character width units for edit box
input, 400

DCL (dialog control language)
default alignment for all tiles in a
cluster, 398
default button specification , 402–403
default height for all tiles in a cluster,
398–399
default width for all tiles in a cluster,
399
fixed pitch font for list boxes or pop-up
lists, 401
initial availability of tile, 403
initial choices for list box or pop-up
list, 404
initial value of tile, 407
key of tile to receive initial keyboard
focus , 402
keyboard mnemonic character for tile,
405
maximum characters for edit box
input, 400
maximum value for slider, 405
minimum value for slider, 405
multiple selections allowed in list box
(or not), 406
slider incremental control value
specification, 398, 406
slider orientation specification, 404
specifying if tile is activated, 398
tab placement in character width
units, 406
text larger than tab stop truncated in
list box or pop-up list (or
not), 407
tile height allowed to fill space (or
not), 401
tile height specification, 401–402
tile name specification, 403
tile receives focus with TAB key (or
not), 403
tile text (label) specification , 404
tile width allowed to fill space (or not),
401
tile width specification , 407
attributes listed by name, 397–407
action, 397
alignment, 397 –426
allow_accept, 398
aspect_ratio, 398
big_increment, 398
children_alignment, 398
children_fixed_height, 398–399
children_fixed_width, 399
color, 399–400
edit_limit, 400
edit_width , 400
fixed_height, 401
fixed_width, 401

DCL (continued)
fixed_width_font, 401
height, 401–402
initial_focus, 402
is_bold, 402
is_cancel, 402
is_default, 402–403
is_enabled, 403
is_tab_stop, 403
key, 403
label, 404
layout, 404
list, 404
max_value, 405
min_value, 405
mnemonic, 405
multiple_select, 406
password_char, 406
small_increment, 406
tab_truncate, 407
tabs , 406
value, 407
width, 407
base.dcl file, 340
control characters in DCL strings , 392
DCL files , 340–341
DCL syntax, 341–344
attributes and attribute values ,
343–344
comments, 344
346–347
tile definitions, 342
tile references, 343
defining dialog boxes, 340–344
referencing DCL files, 340
displaying dialog boxes with VLISP
,
344–347
color coding in text editor, 345
example, 344
preview error handling, 346
selecting a dialog box from multiple
definitions , 342
346–347, 387–388
error handling
alert boxes , 355, 364
error tile guidelines, 363 –364
forgiving errors, 355
346–347
symbolic names for colors, 399 –400
tiles in functional groupings, 408–410
decorative and informative tiles, 409

Index

|

503

DCL (continued)
dialog box exit buttons and error tile,
410
predefined active tiles, 408
restricted tiles, 410
text clusters , 409
tile clusters , 408
tiles listed by name, 410–426
boxed_column, 410–411
boxed_radio_column, 411
boxed_radio_row, 412
boxed_row, 412
button, 413
column, 413 –414
concatenation , 414
DCL (dialog control language), 426
dialog, 414
edit_box, 415
errtile, 415
image, 416
image_button, 416–417
list_box, 417
ok_cancel, 418
ok_cancel_help, 418
ok_cancel_help_errtile, 418–419
ok_cancel_help_info , 419
ok_only, 418
paragraph, 419–420
popup_list, 420–421
radio_button, 421
radio_column, 422
radio_row, 422
row, 423
slider, 423
spacer, 425
spacer_0, 426
text, 424
text_part, 424
toggle, 425
DCL files
acad.dcl, 340
base.dcl, 340
color coding, 345
parts of, 340
referencing, 340
semantic auditing of, 346 –347, 387–388
specifying in VLISP, 344
:DCL-ACTION trace keyword frame, 89
De symbol flag, 94
Debug menu (VLISP)
Animate command, 74
Break on Error command, 75
Break on Function Entry command, 75, 94
Clear All Breakpoints command, 79
Continue command, 74, 77
Debug Top-Level mode command, 75

504

|

Index

Debug menu (VLISP)
overview, 17
Quit Current Level command, 77
Reset to Top Level command, 77, 92
Step Into command, 71, 78
Step Out command, 78
Step Over command, 72, 78
Stop Once command, 75, 76
Toggle Breakpoint command, 70, 79
Debug toolbar
Continue button, 77
Quit Current Level button, 77
Reset to Top Level button, 77 , 92
Step Indicator button, 71
Step Into button, 71, 78
Step Out button, 78
Step Over button, 72 , 78
Toggle Breakpoint button, 70 , 79
Debug Top-Level mode command (VLISP Debug
menu), 75
debugging programs
break loop process , 76
breakpoint life cycle, 81
breakpoints
clearing, 79
described, 68
disabling temporarily, 80
duration of, 81
highlight colors for, 79
life cycle of, 81
listing and viewing, 80
removing, 79
Reset to Top Level option, 77
resuming execution from, 77
setting, 70–71 , 79
stepping through programs from,
71–72, 78
turning on, 75–77
disabling breakpoints temporarily, 80
displaying breakpoints , 80
example, 69–75
listing breakpoints, 80

debugging programs (continued)
optimization and bug introduction, 156
removing breakpoints, 79
Reset to Top Level option, 77 , 92
running in Animate mode, 74
semantic auditing of DCL files , 346–347,
387–388
setting breakpoints, 70–71
starting debugging sessions , 76
starting Trace logging, 82
stepping through programs from
breakpoints, 71–72, 78
Top-Level debugging mode, 75
using Frame Binding window, 88–92
using Inspect windows , 95–108
using Symbol Service dialog box, 92–95
using Trace Stack window, 85–92
using Watch window, 83–85
VLISP debugging features, 68–69
See also break loop mode; checking for
syntax errors; errors; Frame
Binding window; Inspect feature;
Symbol Service dialog box; Trace
Stack window
Debug-on-Entry symbol flag, 75, 94
defining callback functions, 205–207
defining functions. See defun function
defining new units, 284
defining projects, 140–149
assigning properties, 141–144
overview, 140
sample files , 140
using the Project window, 145–148
compatibility with AutoCAD versions,
246–247
with arguments, 252–254
defun-q function, 281 –282
degrees, converting to radians, 282
Delete Blanks option, 60
Delete to EOL option, 60
deleting
bookmarks , 41
breakpoints, 79
clearing Console prompt, 18
determining if objects were erased, 183
disabling reactors, 214–215
entities, 311
project members, 145–146

deleting (continued)
reactor owner objects, 214
selection set entities , 303, 304
spaces from cursor to first non-blank
character, 60
stripping file extensions, 234–235
text from cursor to end of line, 60
trailing spaces, 36
trailing tab characters, 36
using text editor shortcut keys, 33
variables from Watch window, 84 , 85
derived units, 285–286
Descend command (Inspect window shortcut
menu), 102
designing dialog boxes. See dialog box design
designing for multiple document environments
AutoLISP limitations , 136
error-handling in MDI environment, 134,
135
limitations using AutoLISP, 136
sharing data between namespaces , 133–134
detecting syntax errors. See checking for syntax
errors
developing programs , 24–65
basic steps , 24
using coding aids, 42 –50
using the Console window, 25 –30
using the text editor, 31
device access and control functions, 291 –293
accessing user input, 291
synopsis of, 447
dialog box design, 337–364
acad.dcl file, 340
example, 347–348
layout guidelines, 357
space around boxed row or column,
350–351
base.dcl file, 340
defining dialog boxes, 340–344
tile definitions, 341–342
dialog box components , 338–339
displaying dialog boxes with VLISP
,
344–347

Index

|

505

dialog box design (continued)
example, 344
definitions , 342
346–347, 387–388
error handling
346–347, 387–388
guidelines , 353–364
abbreviations, avoiding, 357
capitalization, 356–357
consistency, 353
disabling tiles, 358
error handling, 363–364
handling keyboard input, 359
hiding dialog boxes, 358
international language
considerations, 359–360
layout, 357
nesting dialog boxes, 358
placement of dialog boxes , 357
predefined tiles and clusters, 360–364
providing defaults , 359
providing help, 355
size of dialog boxes , 357
user control over input, 353–354
for users with disabilities, 356
planning the design, 339
predefined tiles and clusters, 360–364
buttons, 360
clusters, 361
edit boxes, 361
image buttons and image tiles ,
361–362
list boxes, 362
radio buttons, radio rows, and radio
columns , 360–362
sliders, 362
text, 363
toggles, 363
user input
handling keyboard input, 359
user control over, 353–354
for users with disabilities, 356
action expressions and callbacks
for application-specific data , 386
callback reasons, 370–372
DCL actions, 372

506

|

Index

dialog box management (continued)
default actions, 372
for edit boxes , 376
for image buttons, 385
processing list elements, 382
for radio clusters , 374–375
for sliders, 375–376
variables, 369–370
functions handling, 429
callback reasons, 370–372
edit boxes, 371
image buttons , 372
list boxes, 371–372
reason codes, 371
sliders, 371
canceling dialog boxes
all dialog boxes, 368, 377, 378
if Cancel button and Default button the
same, 352
hiding dialog boxes and, 377
ok_cancel tiles , 343
displaying the dialog box and
responding to the user,
366–367
functions restricted when dialog box is
open, 367 –368
auditing level for error messages ,
387–388
for multiple DCL files, 387
testing dialog boxes with programs ,
387
when loading first time, 386–387
dialog box opening and closing functions,
427
displaying the dialog box and responding to
the user, 366–367
function synopsis , 427–429
application-specific data handling
functions , 429
dialog box opening and closing
functions , 427
image tile handling functions , 429
list box and pop-up list handling
functions , 428
tile and attribute handling functions,
428
open, 367 –368

dialog box management (continued)
changing modes and values at callback
time, 373–374
edit boxes, 376
initializing modes and values ,
372–373
mode codes for mode_tile function,
373
radio clusters, 374–375
sliders, 375–376
canceling all dialog boxes , 378
requesting a password, 379
user input and, 377–378
color attributes , 384
creating images , 383–385
handling image buttons, 385
image tile handling functions , 429
appending list items, 381
changing list items, 381
creating lists, 380–381
deleting list items, 381
functions handling, 380, 428
inserting list items, 381
list operations, 380–381
operation codes for start_list function,
380
nesting dialog boxes
canceling all dialog boxes , 368, 377,
378
managing, 376 –377
requesting passwords from users, 379
sample block definition dialog box, 389
dialog boxes
all dialog boxes, 368, 377, 378
if Cancel and Default button are the same,
352
ok_cancel tiles , 343
dialog control language. See DCL
dialog tile, 414
dictionary and symbol table handling
dictionary objects , 323
dictnext function, 334
dictsearch function, 334
DIESEL string expressions , 266–267
digitizing tablets, calibrating, 291 –293
directories
application directory, 118
for Console log file, 30

directories (continued)
for .fas files, 154
project home directory, 141
project source directory, 141
searching for text in , 38
Tmp directory for project files , 154
disabling
breakpoints temporarily, 80
display control functions , 448
Display Coordinate System, 287
displaying
AutoCAD drawing entities , 104–108
breakpoints, 80
menus , 264–268
overview, 264
current trace stack, 87
current value of variables, 18 , 25
dialog boxes with VLISP, 344–347
example, 344
definitions , 342
346–347, 387–388
error trace stack, 92
Frame Binding window for local variables ,
88
function call stack, 68
function definition for Symbol Service
dialog box, 94
messages in AutoLISP, 236
new Console prompt without evaluating
text, 18, 27
position of caller expression in Trace Stack
window, 88
shortcut menus, 28
source text for functions, 88
trace stack element information, 87 –88
variable values, 231–232
See also Inspect feature; printing
distof function, 280
Document object, 168
Document reactors, 202
dollar sign ($) prompt. See Console prompt
done_dialog function
nested dialog boxes and, 377
for OK button, 366
start_dialog calls and, 367

Index

|

507

done_dialog function (continued)
user input based on graphics screen and,
368
Windows and, 367
Down option (Find dialog box), 37
Downcase option, 60
Downcase Symbols option (Apropos dialog
box), 44
dragging text in text editor, 36
drawings
adding entities to, 315–316
AutoCAD drawing database
viewing blocks in, 106–107
viewing entities in, 104–105
viewing extended data, 108
viewing selected objects in drawings ,
107
viewing symbol tables in, 105
multiple AutoCAD drawings with Console
window, 28
opening drawings containing persistent
viewing drawing entities , 104–108
106–107
information, 104
104–105
105, 108
shortcut menu for object line, 105
database, 105
drawline function
loading from text editor, 20
Drop directives and Safe Optimization , 158, 160
.dsk files , 139
:DWF trace keyword frame, 90
:DWG trace keyword frame, 90
DXF codes. See DXF Reference
DXF object list (ENAME Inspect window), 101
DXF Reference, 8

E
Ea symbol flag, 95
edit boxes. See tiles (dialog box)
Edit command (Project window shortcut
menu), 146
Edit Global Declarations option (Build Options
dialog box), 154
Edit menu (VLISP)
Match Backward command, 61–63
Match Forward command, 61–63

508

|

Index

Edit menu (continued)
overview, 16
Redo command, 31
Select Backward command, 62
Select Forward command, 62
Undo command, 31
Edit toolbar
New File button, 31
Open button, 32
Redo button, 31
Undo button, 31
edit_box tile, 415
edit_limit (DCL attribute), 400
edit_width (DCL attribute), 400
editing. See text editor
Editor reactors , 203–204
enabling reactors, 215
ENAME Inspect window, 101
enames
converting to and from VLA-objects, 190
searching for associated handle, 190
end_image function, 383
end_list function, 381
entdel function, 311
ENTER key and Console window processing,
25–26
entget function, 165, 311–313, 323, 327–328
entities
adding to drawings, 315–316
blocks , 319
changing, 314 –315
complex, 311, 316
handles and use of, 307
modifying, 314–315
names, obtaining, 305–306
obtaining information on, 311–313
referring to across multiple sessions, 226
viewing in drawing database, 104–105
adding entities to drawings, 315 –316
creating complex entities, 316–318
deleting entities, 311
graphics screen and, 319 –320
modifying entities, 314–315
obtaining entity information, 311 –313
working with blocks, 319
entity filter lists for selection sets, 298–304
examples, 298–299
filtering for extended data, 300
logical grouping of filter tests , 302–303
relational tests, 300 –302
selection set manipulation, 303 –304
wild-card patterns in , 300

entity name data type
defined, 226
overview, 226
referring to entities across multiple
sessions , 226
entity context and coordinate transform
data , 307–311
entity handles and their uses, 307
retrieving entity names, 305 –306
setting entity name to variable name, 306
entlast function, 306
entmake function, 315–319, 321–322
entmod function
dictionary objects and, 323
graphics screen and, 319
modifying entities , 314–315
non-graphic object handling, 322
polylines and, 321
symbol table objects and, 322
entnext function, 306, 321
:ENTRY-NAMESPACE trace keyword frame, 90
entsel function, 305–306
entupd function, 319 –320
environment variables, inspecting and
changing, 264
equality and conditional functions, 439
equality verification in AutoLISP, 240
erasing. See deleting
ergonomics in dialog box design, 353
ERRNO system variable, 486
error codes
AutoLISP, 485
Error option for protected symbols, 229
:ERROR-BREAK trace keyword frame, 90
errors
AutoLISP error handling, 254–257
bug introduction during optimization , 156
catching and continuing execution,
257–258
continuing after, 257–258
dialog box error handling
for multiple DCL files, 387
preview errors , 346
346–347, 387–388
testing dialog boxes with programs ,
387
when loading first time, 386–387
*error* function, 135 , 255 –256

errors (continued)
error-handling functions, 134 –135,
254–256, 440
from ActiveX function calls, 191–193
handling for ActiveX methods, 191–193
handling for VLX application in its own
Inspect command error handling, 103
intercepting with vl-catch-all-apply,
257–258
MDI environment error-handling, 134–135
safe optimization warning messages, 158
separate-namespace VLX error handling,
135–136
viewing error trace stack, 92
vl-catch-all-apply, using, 257–258
VLX error handling, 134–135
See also debugging programs
escape codes in strings, 237 –238
establishing ActiveX connection to application,
195
events, callback
exclamation point (!), for viewing AutoCAD
variable values, 18, 25
executing. See loading; running; starting
Existing Application Properties command (VLISP
File menu), 124
exiting
AutoCAD, 22
quietly in AutoLISP, 236
Visual LISP, 22
See also closing
expanding
element list items in Inspect window, 97
selections using shortcut keys, 34 –35
Expert Wizard mode, 118, 119
exporting functions
to ACAD, 157
to document namespaces , 130–131
Export-to-ACAD symbol flag, 95
exposing functions. See exporting functions
expressions
AutoLISP, 222–223
form for, 222
formatting styles for, 52
function syntax, 223
matching parentheses , 222–223
monitoring evaluation results of, 73–74
quotation marks and parentheses, 223
EXRXSUBR Apropos filter value, 44
EXRXSUBR Inspect window, 97, 101
associated with objects , 105, 108
attaching to entities, 329
filtering selection sets for, 300

Index

|

509

extended data (continued)
group codes for, 323–324
handles in, 330
organization of, 324–326
retrieving, 323, 327–328
synopsis of, 453
viewing associated with objects, 105, 108
extensions to AutoLISP. See Visual LISP, extended
functions

F
FAS Directory option (Build Options dialog
box), 154
.fas files
described, 138–139
directory for, 154
loading, 138
loading from project, 145–147
file descriptor data type
defined, 226
file extensions
additional file types , 138–139
.fas , 138, 139
.lsp, 138, 139
for project files, 139
.vlx, 123, 125, 139
file extensions, stripping, 234 –235
FILE Inspect window, 97, 100
File menu (VLISP)
Load File command, 114 , 124 –125
Make Application submenu
Existing Application Properties
command, 124
Make Application command, 125
New Application Wizard command,
117, 152
Rebuild Application command, 125
New File command, 31
Open File command, 14
overview, 16
Toggle Console Log command, 30
Toggle Trace Log command, 82
file-handling functions , 289–291, 449
synopsis of, 449
files
AutoLISP program files, 229–231
color coding, 231
comments, 230
editing code in VLISP, 229

510

|

Index

files (continued)
backing up automatically in text editor,
31–32
closing in AutoLISP programs , 227
color coding in text editor, 19, 42–43
compiling programs from, 111–113
copying text to new file, 36
creating Console log file, 30
DCL files , 340–341
acad.dcl, 340
base.dcl, 340
color coding, 345
parts of, 340
referencing, 340
semantic auditing of, 346 –347,
387–388
specifying in VLISP, 344
FILE Inspect window, 97, 100
file-handling functions , 289–291, 449
synopsis of, 449
global declarations file, 154
input file for compiler, 112
inserting into text editor window, 60
LISP files to include in applications , 120
loading, 20
managing multiple LISP files, 138 –140
navigating in text editor, 35
opening in text editor, 32
output file from compiler, 113
resource files to include in applications, 121
restoring from backups, 32
Support File Search Path, 112
temporary files for projects , 154
types , 138–140
typographical conventions in this manual,
7
unit definition file, 284–286
.vlx files , 123, 125
See also DCL files
fill_image function, 383–385
Filter Flags option (Apropos dialog box), 44
filter lists for selection sets, 298 –304
examples, 298–299
logical grouping of filter tests , 302–303
Filter Values option (Apropos dialog box), 44

Find command
VLISP Search menu, 37
Find dialog box, 37–39
Cancel button, 37
Direction options, 37
Find button, 37
Find What field, 37
illustrated, 37
Mark Instances option, 38
Match Case option, 38
Match Whole Word Only option, 38
opening, 37
Search options, 37
See also searching
Find in Files option (Find dialog box), 37
Find in Project option (Find dialog box), 37
Find toolbar
Clear All Bookmarks button, 41
Next Bookmark button, 40 , 41
Previous Bookmark button, 40, 41
Repeat Search button, 38
Replace button, 38
Search button, 37
Toggle Bookmark button, 40
Find What field (Find dialog box), 37
findfile function, 289
finding. See searching
fixed_height (DCL attribute), 401
fixed_width (DCL attribute), 401
fixed_width_font (DCL attribute), 401
floating point numbers
REAL Inspect window, 97, 98
floating point numbers, distance to floating point
function, 280
forcing line breaks in strings , 237–238
foreach function, 86
foreign-language support, 261, 359–360
Format Code in Editor command (VLISP Tools
menu), 50
Format Date/Time option, 60
Format Options dialog box , 51 –57
Close Parenthesis Style options, 54
illustrated, 51–52
Insert Form-Closing Comment option, 55
Long List Format Style options , 56–57
More Options button, 51–52
opening, 51
Preserve Existing Line Breaks option, 55–56
Setting Case for Symbols options, 57
Split Comments option, 56
formatting AutoLISP code, 50–60 , 229 –230
blocks of text, 50
Close Parenthesis style, 54
Column style, 53
comment styles , 58

formatting AutoLISP code (continued)
Format Options dialog box , 51 –57
formatter restrictions, 59
in active editor window, 50–51
inserting form-closing comments , 55
long lists , 56–57
Narrow style, 53
options, 479 –482
overriding session settings, 59
Plane style, 52
preserving existing line breaks, 55–56
saving formatting options, 58 –59
selected text, 50
shortcut keys for, 59–60
Smart Indent feature, 50, 51
splitting long comments , 56
text editor feature, 19
Wide style, 53
Frame Binding window, 88–92
adding symbol to Watch window, 89
calling Inspect feature, 88
calling Symbol Service dialog box, 89
copying value to *obj* system variable, 89
described, 82
displaying for local variables , 88
displaying value in Console, 88
keyword frames, 89–91
printing value to Console window, 88
special function call frames, 91
freeing memory and releasing objects , 189
function call frames, 86
Function symbol command (Trace Stack window
shortcut menu), 88
:FUNCTION-ENTRY trace keyword frame, 90
function-handling functions , 245–254
252–254
defun-q function, 251 –252
synopsis of, 441
functions
ActiveX versus ename, 162
application-handling, 436
Apropos filter value, 44
arithmetic, 437–438
as AutoCAD commands, 247 –250
call stack, 68
callback functions for reactors , 205–207
collection manipulation, 458

Index

|

511

functions (continued)
menus , 264–268
overview, 264
conversion functions
angular values from radians or
degrees, 281 –282
286–289
measurement unit conversions,
283–286
synopsis of, 446
curve measurement, 461–462
device access and control
synopsis of, 447
291–293
accessing user input, 291
calibrating tablets , 291–293
dialog box function synopsis , 427–429
application-specific data-handling
functions , 429
dialog box opening and closing
functions , 427
image tile-handling functions , 429
list box and pop-up list-handling
functions , 428
tile- and attribute-handling functions,
428
dialog box management functions,
365–389
action expressions and callbacks,
368–372
sample block definition dialog box,
389
displaying definition for Symbol Service
dialog box, 94
displaying source text for, 88

512

|

Index

Drop directives and safe optimization, 158,
160
modifying entities, 314–315
obtaining entity information,
311–313
entity context and coordinate
transform data, 307–311
setting entity name to variable name,
306
equality and conditional, 439
error handling, 440
exporting, to document namespaces,
130–132
exposing. See functions, exporting
EXRXSUBR Inspect window, 97, 101
extended data functions, 323–330
attaching extended data to entities,
329
filtering selection sets for extended
data , 300
group codes for extended data,
323–324
handles in extended data, 330
organization of extended data,
324–326
retrieving extended data, 323,
327–328
synopsis of, 453
file-handling functions , 289–291
synopsis of, 449
function handling
synopsis of, 441
function-handling functions , 245–254
c:xxx functions, 247–250
252–254

249–250
274
274
274
overview, 274
synopsis of, 450
help for, 50
list handling
list-handling functions, 240–245
adding items to list beginning, 241,
241
substituting items, 241, 241
as lists, 247–250
local variables in, 251–252
making available
as AutoCAD commands, 247 –250
to documents, 130 –132
to ObjectARX applications, 95
to other VLX applications, 132
multiple namespaces affect on, 128
number handling in AutoLISP 233
,
object-handling functions
321–323
polylines, old-style and lightweight,
320–321
237–238

output windows for, 15
protected symbols and, 94
query and command functions
environment variables,
263–264
commands, 262–263
sending commands to AutoCAD
prompt, 260–261
synopsis of, 451
undoing commands issued with
command function, 263
querying reactors using function calls , 213
reactor callback functions, 205 –207
restrictions when dialog box is open,
367–368
selection set-handling functions
deleting entities, 303 –304
and ObjectARX
applications, 305
synopsis of, 455
304
string handling, 444–445
SUBR Inspect window, 97, 100
summary of
basic functions, 436–445
category summary, 434–436
namespace communication
functions , 468
selection set, object, and symbol table
symbol-handling functions , 445
Visual LISP extended functions ,
457–460
symbol table access functions, 332–333

Index

|

513

syntax conventions in AutoLISP, 223
trace stack and, 86
tracing user-defined functions , 94
7
controlling user-input conditions,
271–273
restrictions when dialog box is open,
367
synopsis of, 452
user-defined
defining with defun, 245–253
tracing, 94
using with ActiveX methods , 170–191
applying object's property to new
object, 181
converting AutoLISP data types to
ActiveX data types, 173 –180
determining function needed,
171–172
determining how to call functions,
172–173
determining if method or property
applies to object, 186–187
determining if object is available for
updating, 183
listing object properties and methods,
185–187
releasing objects and freeing memory,
189
using ActiveX methods that return
values in arguments,
184–185
vla-get functions, 170
working with collection objects,
187–189

514

|

Index

USUBR Inspect window, 97, 100
Visual LISP extensions , 22, 457–463
458
461–462
defined, 22
running, 22
vl-load-com and, 22
functions (Apropos filter value), 44
fundamental units, 284

G
geometric utilities , 274–279, 450
finding
angle between line and X axis , 274
distance between two points, 274
intersection of two lines , 274
polar coordinates of points , 274
overview, 274
synopsis of, 450
get_attr function, 374
getangle function, 269 –270
GetBoundingBox method, 184
getcorner function, 268–269
getdist function, 269
getenv function, 264
getfiled function, 289 –290
getint function, 268–269
getkword function, 269, 270
getorient function, 269–270
getpoint function, 268–269
getreal function, 268 , 269
getstring function, 268, 269

getvar function, 263
Global Declarations file for projects , 154
Go to Last Edited command (text editor shortcut
menu), 33
graphics screen and entity data functions,
319–320
graphscr function, 267
grdraw function, 267–268
group codes for regular and extended data,
323–324
grread function, 291
grtext function, 267–268
grvecs function , 267–268

H
handent function, 307, 330
handles
in extended data, 330
searching for ename associated with, 190
searching for object associated with, 191
searching for, associated with ename, 190
searching for, associated with object, 191
height (DCL attribute), 401 –402
Help command (Apropos results window shortcut
menu), 47
help feature
accessing Help files , 290–291
for ActiveX object methods , 164
described, 3
for Apropos results , 46
for AutoLISP functions, 50
providing dialog box help, 355
Symbol Service dialog box, 94
help function , 290
Help menu (VLISP), 17
.hh files, 140
hiding dialog boxes
canceling and, 377
design guidelines, 358
handling, 377–379
history of Console input
retrieving previous commands , 18, 26 –27
searching, 18 , 27
.hpp files , 140

I
IDE. See integrated development environment
(IDE)
image tiles. See tiles (dialog box)
image_button tile, 416–417
importing type libraries , 193–195
improper lists, 244
inches, converting to meters , 284

Indent Block option, 59
Indent to Current Level option, 59
indenting code
initget function, 270, 271–273
initial_focus (DCL attribute), 402
input history. See history of Console input
input, user. See dialog box design, user input;
getting user input
Inquire Extended Data command
Inspect window shortcut menu, 105
VLISP View menu, 107
Insert Date option, 60
Insert File option, 60
Insert Form-Closing Comment option (Format
Options dialog box), 55
Insert Time option, 60
inserting
files into text editor window, 60
form-closing comments, 55
symbols from Apropos results window, 46
using text editor overstrike mode, 34
Inspect command
error handling, 103
Inspect Drawing Objects Verbosely option, 104
Inspect feature
caption (title bar) of window, 96
closing all Inspect windows, 103
copying Inspect window contents to Trace
window and log, 102
copying objects to *obj* system variable,
103
described, 3 , 68, 82
element list content, 96
element list formats, 97–102
error handling, 103
expanding element list items, 97
Inspect window contents, 96–97
inspecting reactors , 212
invoking
for symbol in Apropos results window,
46
from Frame Binding window, 88
from Symbol Service dialog box, 94
from Trace Stack window, 88
from Watch window, 84
Symbol Service feature, 102
maximum element lines per window, 96
navigating multiple pages, 96

Index

|

515

Inspect feature (continued)
object line of window, 96
opening Inspect window, 29, 33, 95
opening text editor window containing
selected text, 103
overview, 95–96
passing element values as argument, 102
printing Inspect window object to Console
window, 102
shortcut menu commands , 102, 105
updating Inspect window, 102
viewing AutoCAD drawing entities ,
104–108
106–107
information, 104
104–105
105, 107–108
database, 105
viewing AutoCAD object properties,
166–169
Inspect Next Entity command (Inspect window
shortcut menu), 105
Inspect Raw Data command (Inspect window
shortcut menu), 105
Inspect Value command (Watch window shortcut
menu), 84
Inspect window. See Inspect feature
:INSPECT-EVAL trace keyword frame, 89
inspecting. See displaying; Inspect feature
inspection tools. See Frame Binding window;
Inspect feature; Symbol Service dialog
box; Trace Stack window
:INSPECT-VERBOSE trace keyword frame, 89
INT Inspect window, 98
integer data type
for DCL attribute values , 392
defined, 224
,
overflow handling by AutoLISP 224 –225
,
integrated development environment (IDE)
components , 2 –3
returning to, 12
starting Visual LISP, 12 , 22
Visual LISP as, 1
interactive programming in Console window, 25
intercepting program errors, 257–258
international language considerations, 261,
359–360
interrupting commands , 27
is_bold (DCL attribute), 402

516

|

Index

is_cancel (DCL attribute), 402
is_default (DCL attribute), 402–403
is_enabled (DCL attribute), 403
is_tab_stop (DCL attribute), 403
italic type in this manual, 7

K
:KBD-BREAK trace keyword frame, 90
key (DCL attribute), 403
keyboard input and dialog box design, 359
keyboard shortcuts. See shortcut keys
keyword frames (in trace stack)
overview, 86, 89
types at bottom of stack, 89
types at top of stack, 90–91

L
label (DCL attribute), 404
lambda forms , 86
lambda function, 86
language in dialog box design
avoiding abbreviations , 357
capitalization, 356–357
clarity, 353
international language considerations,
359–360
languages, supporting foreign, 261, 359–360
layout (DCL attribute), 404
layout of dialog boxes , 347–352
adjusting space at right side or bottom, 350
adjusting space between tiles, 349
example, 347–348
fixing spacing around boxed row or
column, 350 –351
life cycle of breakpoints, 81
lines (graphic)
finding angle between line and X axis, 274
old-style and lightweight polylines ,
320–321
processing curve-fit and spline-fit
polylines , 321
lines (text)
deleting from cursor to end of line, 60
forcing line breaks in strings , 237–238
Preserve Existing Line Breaks option, 55–56
starting new lines in text editor, 31
Link mode option (Build Options dialog box),
155
Linker reactors , 203

linking
choosing a link mode, 155, 157
function calls, 111, 116
safe optimization and, 158, 159
See also compiling and linking programs
LISP Files to Include dialog box , 119, 152
LISP, reasons for choosing, 2
list (DCL attribute), 404
list boxes. See tiles (dialog box)
list data type
defined, 225
overview, 225
list function
forming point lists , 242
list handling
adding items to list beginning, 241
association lists , 244
improper lists, 244
viewing, 97, 99
proper lists, 244
viewing, 97, 99
substituting items, 241
LIST Inspect window, 97, 99
list_box tile, 417
listing
breakpoints, 80
condition-function pairs for reactors, 213
functions exported by applications, 132
object properties and methods, 185–187
objects that fire notifications to reactors,
213
reactor callback events, 205
reactor types , 204
reactors of given type, 211–212
separate-namespace applications associated
with documents, 132
lists, AutoLISP. See list handling
Load Application command (VLISP Tools
menu), 124
Load command (Project window shortcut
menu), 146
Load File command (VLISP File menu), 114, 124
load function
loading compiled programs , 114
loading VLX applications , 124
Load Project FAS button (Project window), 145,
147

Load Source command (Project window shortcut
menu), 146
Load Source Files button (Project window), 147
Load Text command (VLISP Tools menu), 20
load_dialog function , 366, 387
loading
ActiveX support, 165
application in its own namespace, 128–129
AutoLISP programs from text editor, 20
compiled programs, 114
dialog boxes, 366, 387
order for application file loading, 120
order for project file loading, 144
project .fas files , 146–148
reactor support, 202, 205
selected lines of code, 21
VLX applications , 124
See also opening; running; starting
loading compiled programs , 114
loading VLX applications , 124
local variables , 251–252
Local Variables command (Trace Stack window
shortcut menu), 88
Localize directives and safe optimization, 158,
160
Localize Variables option (Build Options dialog
box), 155
Log command (Inspect window shortcut
menu), 102
logging Console window activity, 29–30
appending information to existing file, 30
creating log files , 30
quitting the logging process , 30
replacing existing file, 30
logging Trace activity
copying Apropos search results to log file,
46
turning on and off, 82
Long List Format Style options (Format Options
dialog box), 56–57
long lists
defined, 56
format style options, 56–57
lsa compiler mode parameter, 111
lsm compiler mode parameter, 111
.lsp files
described, 138–139
finding strings in, 151
loading from project, 145–146

M
Make Application command (VLISP File menu),
125
Make Application Wizard, 117–123, 152
application directory, 118
application options, 118

Index

|

517

Make Application Wizard (continued)
building the application, 123
compilation options , 122–123
including projects in applications, 152
LISP files to include, 119 , 152
naming applications , 118
order for loading application files, 120
resource files to include, 121, 152
Wizard mode, 117
making application modules
changing application options, 124 –125
creating new applications , 117
including projects, 151
loading and running VLISP applications ,
124
object directory for, 125
updating applications, 125
using Make Application Wizard. See Make
Application Wizard
managing dialog boxes. See dialog box
management
managing VLISP applications , 137–160
defining projects, 140–149
assigning project properties, 141–144
overview, 140
managing multiple LISP files, 138 –140
optimizing application code, 153–160
choosing a Compilation mode,
155–156
choosing a Link mode, 155, 157
safe optimization, 157–160
working with existing projects , 149–152
finding strings in project source files,
151
including projects in VLISP
applications, 151
opening projects, 149
332–334
mapchar function, 381
Match Backward command (VLISP Edit menu),
61–63
Match by Prefix option (Apropos dialog box), 43
Match Case option (Find dialog box), 38
Match Forward command (VLISP Edit menu),
61–63
Match Whole Word Only option (Find dialog
box), 38

518

|

Index

matching parentheses
in AutoLISP code, 19
matching parentheses in AutoLISP code, 61–63,
222–223
matching wild-cards in strings , 238–239
max_value (DCL attribute), 405
MDI (multiple document interface), and
AutoLISP, 126–134
AutoLISP limitations , 136
134–135
limitations, AutoLISP, 136
sharing data between namespaces , 133–134
measurement unit conversions, 283–286
memory
freeing, 305 , 457
garbage collection, 305, 457
managing extended data memory use, 329
releasing objects and freeing memory, 189
menucmd function, 264–268
menus (VLISP)
See also specific menus
menus (AutoCAD)
controlling, 264–268
customizing. See AutoCAD Customization
Guide
menus (VLISP)
issuing VLISP commands from, 15
overview, 13, 15–17
shortcut menus
Apropos results window, 46–47
Console window, 29
displaying, 29
Frame Binding window, 88
Inspect window, 102
Project window, 146
text editor, 32–33
Trace Stack window, 87–88
Watch window, 84
variable contents of, 15–16
Merge Files mode option (Build Options dialog
box), 154
Message mode option (Build Options dialog
box), 155
messages, safe optimization warning, 158
meters, converting inches to , 284
methods, ActiveX. See ActiveX, methods
min_value (DCL attribute), 405
mnemonic (DCL attribute), 405
mode codes for, 373
mode_tile function, 372–374

Modify command (Inspect window shortcut
menu), 105
monitoring
evaluation results of an expression, 73–74
variables during program execution, 73–74
monospace font conventions in this manual, 7
mouse
Console window shortcut menus, 29
displaying shortcut menus , 29
dragging text in text editor, 36
See also dialog box design, user input; getting
user input
moving around. See navigating
moving text
by dragging in text editor, 36
Clipboard support for, 36
undoing move actions, 37
using Console window shortcut menu, 29
using text editor shortcut menu, 32–33
multiple document environment
designing for. See designing for multiple
document environments
multiple documents. See MDI
multiple LISP files, managing, 138–140
multiple namespaces. See namespaces
Multiple Selection command (Project window
shortcut menu), 146
multiple_select (DCL attribute), 406

N
names/naming
DCL attributes , 367–369
input file for compiler, 111–112
output file from compiler, 113
setting entity name to variable name, 306
symbol naming restrictions , 227
symbol table entries that cannot be
renamed, 322–323
tiles (dialog box), 342, 343
7
variables, 228
namespaces
blackboard, 133
defined, 126
134–135
functions and multiple, 128–129
making functions available to documents,
130–132
making functions available to other VLX
applications, 132
overview, 126

namespaces (continued)
referencing variables in document
namespaces , 132–133
sharing data between, 133–134
variables and multiple, 126–128
Narrow formatting style, 53
navigating
going to position last edited, 35
Inspect window pages , 96
moving insertion point to parentheses,
61–63
using bookmarks , 40 –41
nentsel function, 305–306, 307–311
nentselp function , 307–308 , 310
nesting dialog boxes
canceling all dialog boxes , 368, 377, 378
managing, 376 –377
New Application Wizard command (VLISP File
menu), 110, 117–122 , 131 , 152
New File command (VLISP File menu), 31, 229
new_dialog function
default actions, 369, 372
error handling, 387
nested dialog boxes and, 376, 377
nil values and, 367
passing dialog name and ID, 366
Windows and, 367
newline character, 237
Next Bookmark command (VLISP Search
menu), 40, 41
nil variables
overview, 232
Nonull (Apropos filter value), 44
notifications, reactor, 204–205
nth function, 240–241
ntmod function, anonymous blocks and, 319
Null (Apropos filter value), 44
,

O
.ob files, 139
Object Coordinate System, 287
object directory, for applications, 125
Object ID, ARX, 190, 191
object model, AutoCAD. See AutoCAD object
model
Object reactors
attaching data to reactor objects, 210
defining callback functions, 207
overview, 203

Index

|

519

Object reactors (continued)
seeing how they work, 209–210
using, 208–210
Object Snap modes, 274–275
ObjectARX applications
called from AutoLISP programs, 156
making functions available to , 95
and, 305
ObjectARX Reference, 8
objects
accessing in ActiveX , 165–169
object, 168
overview, 165 , 168–169
165
ActiveX objects , 162
applying properties to new object, 181
ARX Object ID of, 190, 191
changing. See objects, modifying
collection objects
458
evaluating series of functions with each
object in, 187 –188
overview, 164
retrieving member objects, 188–189
converting between enames and
VLA-objects , 190
creating new instance of application
object, 195
determining availability for updating, 183
determining if method or property applies,
186–187
dictionary objects , 323
modifying entities , 314–315
obtaining entity information,
311–313

520

|

Index

objects (continued)
entity context and coordinate
transform data, 307–311
setting entity name to variable name,
306
identifying ARX Object ID of, 191
listing properties and methods, 185–187
332–334
methods , 164
modifying
with ActiveX, 180–183
collection objects , 187
with entmod, 314–315
object-handling functions, 305–323
321–323
polylines, old-style and lightweight,
320–321
obtaining one object identifier from
another, 190 –191
PICKSET Inspect window, 98, 101
properties of, in ActiveX and VBA
Reference, 164
changing with ActiveX, 181–183
defined, 164
getting, 180–181
listing, 185–187
modifying with ActiveX, 181 –183
reading, 180–181
updating with ActiveX, 181–183
viewing, 180 –181
searching for handle associated with, 191
searching for object associated with
handle, 191
selection set handling functions
deleting entities, 303 , 304
and ObjectARX
applications, 305

objects (continued)
synopsis of, 455
304
symbol table objects , 322–323
testing, availability for modification, 183
availability for reading, 183
availability for updating, 183
whether erased or not, 183, 183
whether method applies to, 186
whether property applies to, 186 –187
whether released or not, 189
translating from ARX Object ID to object,
191
VLA-object type specification, 165
obtaining entity information, 311 –313
obtaining user input. See getting user input
ok_cancel tile, 343 , 418
ok_cancel_help tile, 418
ok_cancel_help_errtile tile, 418–419
ok_cancel_help_info tile, 419
ok_only tile, 418
Open File command (VLISP File menu), 14
Open Project command (VLISP Project menu),
149, 153
opening
Apropos window, 29, 33
AutoLISP source files in text editor, 14
dialog box opening functions , 427
drawings containing persistent
files in text editor, 32
Format Options dialog box , 51
Inspect window, 29, 33, 94 , 95
new files in text editor, 31
Project Properties dialog box , 142, 145
projects, 149
selecting text before opening files, 32
source files in text editor, 14
Symbol Service dialog box, 29, 33, 46 , 89,
93, 102
Watch window, 29, 33
operators, relational, for selection set filter lists,
300–302
optimizing application code, 153–160
analyzing for optimization correctness, 156
bug introduction during, 156
choosing a compilation mode, 111, 154,
155
choosing a Link mode, 155, 157

optimizing application code (continued)
See also safe optimization
order for loading
application files, 120
program files , 114
project AutoLISP files , 144
osnap function, 274–275
237–238
overriding format settings, 59
overstrike mode in text editor, 34

P
Pa symbol flag, 94
Paper Space DCS, 287
paragraph tile, 419 –420
parentheses
checking balance, 19, 61–63
Close Parenthesis Style options, 54
matching in AutoLISP code, 19, 61–63 ,
222–223
moving insertion point to , 61–63
selecting text between cursor and, 62
selecting text in text editor and, 34
Smart Indent feature and, 51
unbalanced, found by formatter, 50
passing pick points to AutoCAD commands,
262–263
passing selection sets between AutoLISP and
ObjectARX applications, 305
password_char (DCL attribute), 379 , 406
passwords, requesting from users, 379
Paste command
pasting. See copying; moving text
paths
for project files , 143, 144
for source files, 111 –112
Support File Search Path, 112
PAUSE symbol, 232, 261–262
.pdb files, 139
persistent reactors
defined, 215
making, 215
opening drawings containing, 215–216
transient reactors versus, 215
PI variable, 232
pick points, passing to AutoCAD commands ,
262–263
PICKSET Inspect window, 98, 101

Index

|

521

placement of dialog boxes , 357
Plane style, 52
points
286–289
finding distance between, 274
finding polar coordinates of, 274
transformations, 289
polylines
old-style and lightweight, 320 –321
processing curve-fit and spline-fit
polylines , 321
populating safearrays with data, 175 –178
popup_list tile, 420–421
predefined attributes, synopsis of, 394–396
predefined tiles and clusters (dialog box design
guidelines), 360–364
buttons, 360
clusters, 361
edit boxes, 361
image buttons and image tiles , 361–362
list boxes, 362
radio buttons, radio rows
and radio columns , 360–362
sliders, 362
text, 363
toggles, 363
predefined variables, AutoLISP, 232–233
Prefix With option, 59
Preserve Existing Line Breaks option (Format
Options dialog box), 55 –56
Pretty Print command (Inspect window shortcut
menu), 102
Preview DCL in Editor command (VLISP Tools
menu), 345
Previous Bookmark command (VLISP Search
menu), 41
prin1 function, 236
princ function
output display from , 18, 236
Print command
print function, 18, 236
Print message option for protected symbols, 228
Print Value command (Watch window shortcut
menu), 85
printing
files , 16
Frame Binding window value to Console
window, 88
Inspect window object to Console window,
102

522

|

Index

printing (continued)
list of arguments to Trace window, 206
messages in AutoLISP, 236
stack element to Console window, 88
symbol name from Apropos in Console
window, 46
Watch window variable values in Console
window, 85
.prj files
closing, 149
described, 139
progn expressions, Narrow style for, 53
programs. See AutoLISP programs
Project menu (VLISP)
Open Project command, 149 , 153
overview, 17
Project Properties button (Project window), 145,
153
Project Properties dialog box
changing order for loading files, 144
compiler build options, 144 , 153 –155
identifying path name of files, 143–144
opening, 148, 153
selecting files to include in project,
141–143
Project window
adding files to project, 146
arranging files , 146
buttons, 145
checking syntax of source code, 146
closing projects , 149
compiling project files, 148
editing source code, 146, 148
loading compiled files , 146–148
loading source files, 146
recompiling project files, 148
removing members, 146
saving projects, 146, 149
selecting multiple members, 146–147
projects
adding files , 146
checking syntax of source code, 146
closing, 149
compiler build options, 144 , 153 –155
compiling source files, 145, 148
defining, 140–149
assigning project properties, 141–144
overview, 140
editing source code, 146, 148
file types , 138–140
finding strings in project source files, 151
global declarations file, 154
home directory, 141
including in VLISP applications , 151
loading compiled files , 145–148

projects (continued)
loading source files, 145 , 146
opening, 149
order for loading files, 144
overview, 138
path name of files, 143–144
recompiling source files, 145, 148
removing members, 146
saving, 146 , 149
selecting files to include, 141 –143
selecting multiple members, 146–147
source directory, 141
prompt function, 236
Prompt to enter break loop option for protected
symbols , 228
proper lists, 244
properties of objects. See objects, properties
Protect-Assign symbol flag, 94
:PROTECT-ASSIGN trace keyword frame, 90
protected symbols , 228–229
prototypes. See tiles (dialog box)

Q
query and command functions
environment variables, 263 –264
commands, 262–263
260–261
synopsis of, 451
function, 263
querying reactors
listing all reactors of given type, 211–212
using function calls, 213
using Inspect tool, 212
Quit Current Level command (VLISP Debug
menu), 77
quitting. See exiting
quotation marks (")
and parentheses in expressions, 223
quote function, forming point lists, 242
quoted lists
Column style for, 53
Long List Format Style options , 56–57
quoted strings
control characters in, 237–238, 392

R
radians
converting degrees to , 281–282
converting to degrees, 281–282
radio buttons, radio rows, and radio columns. See
tiles (dialog box)
radio_button tile, 421
radio_column tile, 422
radio_row tile, 422
random access memory (RAM). See memory
:REACTOR-CALLBACK trace keyword frame, 90
reactors
adding owner object, 214
beeping your PC, 206
callback events , 204–205
callback functions, defining, 205–207
changing application-specific data
associated with, 213
changing callback function link, 213
communicating with applications, 202
creating, 207–210
defined, 202
determining if active, 214
determining if persistent or transient, 215
disabling, 214–215
enabling, 215
events, 204–205
function reactors, summary, 464–466
function synopsis , 464–466
guidelines for using, 216–217
inspecting, 212
listing
all reactors of given type, 211–212
callback events , 205
condition-function pairs , 213
objects that fire notifications, 213
reactor types , 204
loading support for, 202, 205
making persistent, 215
modifying definitions , 213–214
notifications, 204 –205
opening drawings containing persistent
persistence, 215–216
printing list of arguments to Trace window,
206
querying
for application-specific data value, 213
listing all reactors of given type,
211–212
listing condition-function pairs , 213
listing objects that fire notifications,
213
for name of event triggering callback
function, 213

Index

|

523

reactors (continued)
for reactor type, 213
using function calls, 213
using Inspect tool, 212
removing, 214 –215
removing owner object, 214
transient versus persistent, 215
types , 202–204
Database reactors, 202
Document reactors, 202
Editor reactors , 203–204
Linker reactors , 203
listing all types, 204
Object reactors, 203
using Object reactors, 208 –210
read function, 382
read-char function, 291
:READ-ERROR trace keyword frame, 91
read-line function, 291
real data type
converting to string, 279–280
defined, 225
,
overview, 225
scientific notation for, 225
REAL Inspect window, 97, 98
Rebuild Application command (VLISP File
menu), 125
Rebuild Project FAS button (Project window),
145
recompiling project source files, 145, 148
Redo command
VLISP Edit menu, 31
redraw function, 267
referencing
DCL files , 340
tiles (dialog box), 343
variables in document namespaces,
132–133
refreshing Trace Stack window contents, 92
regapp function, 327–328
Registry functions for Windows, 469
relational operators for selection set filter lists
logical grouping of, 302–303
Remove File command (Project window shortcut
menu), 146
Remove from Watch command (Watch window
shortcut menu), 85

524

|

Index

removing. See deleting
repeat function, 86
repeating earlier searches, 39
Replace command (VLISP Search menu), 39
Replace dialog box, 39
replacing
list items, 241, 241
text using overstrike mode, 34
text using search-and-replace, 39
requesting passwords from users, 379
reserved words for DCL attribute values , 392
Reset to Top Level command (VLISP Debug
menu), 77, 92
Resource Files to Include dialog box, 121, 152
restoring from backup files in text editor, 32
restrictions
formatter, 59
open, 367 –368
restricted characters, 227
restricted DCL attributes , 393
symbol naming restrictions , 227
retrieving
commands in Console window
searching for specific commands , 18,
27
using TAB key, 18, 26–27
entity names , 305–306
extended data, 105, 108, 323, 327–328
items from lists, 240–241
member objects in collections, 188–189
variable values from document namespace,
132–133
return character in quoted strings, 238
returning to the VLISP IDE, 12
row tile, 423
rtos function, 279–280
Run toolbar
Activate AutoCAD button , 21
Load Active Edit Window button, 20
Load Selection button, 21
running
application in its own namespace, 129–130
applications, 114–115, 124
AutoCAD with Visual LISP, 3, 20
AutoLISP programs from Console prompt,
20–21
Check command, 65
compiled programs, 114–115
in Animate mode, 74
selected lines of code, 21
separate-namespace applications , 129–132
See also loading; opening; starting

S
build option, 155
compiler checking of conditions, 159
conditions bypassed by, 158
overview, 157
warning messages, 158
Safe Optimize option (Build Options dialog
box), 155
SAFEARRAY Inspect window, 98, 102
safearrays
converting to lists, 177
creating, 175–177
creating variant with an array of four
doubles, 179
displaying contents of, 177
populating with data , 175–177
using with variants , 178–179
sample files, AutoLISP, 14
Save Block As option, 36, 60
Save Project As command (Project window
shortcut menu), 146
Save Settings command (VLISP Tools menu), 58
saving
changes to code when exiting AutoCAD, 22
formatting options, 58–59
projects, 146, 149
scientific notation for reals, 225
Search menu (VLISP)
Bookmarks submenu
Clear All Bookmarks command, 41
Next Bookmark command, 40
Previous Bookmark command, 41
Complete Word by Apropos command,
48–49
Complete Word by Match command, 47
Find command, 37
overview, 16
Replace command, 39
search order, for loading program files, 114
searching
Console input history, 18, 27
Console window, 29
for ename associated with handle, 190
for file names , 289–290
for strings in project source files, 151
for symbols using Apropos feature, 43–47
inserting symbols from results
window, 46
overview, 43
by prefix, 45

searching (continued)
for handle associated with ename, 190
for handle associated with object, 191
in text editor, 37–39
overview, 19
repeating earlier searches, 39
replacing text, 39
shortcut menu command, 33
using Find dialog box, 37–39
for object associated with handle, 191
Select All command (Project window shortcut
menu), 146
Select Backward command (VLISP Edit menu),
62
Select Forward command (VLISP Edit menu), 62
selecting
copying selected text to new file, 36, 60
cursor location and, 34
entities, 305 , 307 –311
files to include in projects, 141–144
multiple members from Project window,
146–147
objects , 305, 307–311
searching highlighted text, 38
text before opening files, 34
text between cursor and, 62
using bookmarks , 41
using text editor shortcut keys, 34 –35
selection set data type
defined, 226
selection set handling functions , 296–305, 455
selection sets
adding entities to, 303–304
creating, 296–297
deleting entities from, 303 –304
filter lists, 298–304
examples, 298–299
logical grouping of filter tests ,
302–303
passing between AutoLISP and ObjectARX
applications, 305
synopsis of functions for handling, 455
testing whether an entity is a member, 304
semantic auditing of DCL files , 346–347,
387–388
semicolon (;) VLISP comment styles , 58

Index

|

525

260–261
set_tile function, 372
setfunhelp function, 290–291
setq function, 231
setting
breakpoints, 70–71
variable values in document namespace,
133
Setting Case for Symbols options (Format Options
dialog box), 57
setvar function, 263
sharing data between namespaces, 133 –134
shortcut keys
Complete Word by Apropos feature, 48
Complete Word by Match feature, 47
text editor
for code indentation, 36
for correcting text, 33
for formatting text, 59–60
for navigation, 35
for selecting text, 34–35
shortcut menus
Apropos results window, 45, 46–47
Console window, 29
displaying, 29
Frame Binding window, 88
Inspect window, 102, 104, 105
for object line, 105
Project window, 146
text editor, 32–33
Watch window, 84
single quotation mark ('), forming point lists ,
243
size of dialog boxes , 357
slashes (//) for DCL comments, 344
slide_image function, 383, 384–385
slider tile, 423
sliders. See tiles (dialog box)
small_increment (DCL attribute), 406
Smart Indent feature, 50, 51
Snap modes, 274 –275
Sort Block option, 60
sorting
blocks of text, 60
variables in Watch window, 84
Source Position command, Trace Stack window
shortcut menu, 88
spacer tiles (dialog box), 343, 426
spaces
AutoCAD command window versus VLISP
Console window, 26
in AutoLISP code, 229 –230
clearing in text editor, 36
deleting from cursor to first non-blank
character, 60

526

|

Index

spacing in dialog boxes
adjusting space at right side or bottom, 350
adjusting space between tiles, 349
column, 350 –351
special characters
control characters in DCL strings , 392
237–238
relational operators for selection set filter
lists , 300–302
spline-fit polylines, processing, 321
Split Comments option (Format Options dialog
box), 56
SQL, 472
.sql files, 140
ssadd function, 303 –304
ssdel function, 303 –305
ssget function
restrictions when dialog box is open, 368
sslength function, 304
ssmemb function, 304
ssname function, 304
st compiler mode parameter, 111
stack elements
calling Inspect feature for, 88
defined, 86
printing to Console window, 88
types of, 86
See also Trace Stack window
start_dialog function
functions restricted during, 367 –368
nested dialog boxes and, 376
passing dialog control to AutoCAD, 367
Windows and, 367
start_image function, 383
start_list function, 380–381
starting
Animate mode, 74
break loop mode, 75–77
debugging session, 76
See also loading; opening; running
Trace logging, 82
Visual LISP, 12, 22
status bar (VLISP)
asterisk next to file names, 14
menu command descriptions on , 14
overview, 14
toolbar button explanations on, 13

Step Indicator button, 71
Step Into command (VLISP Debug menu), 71, 78
Step Out command (VLISP Debug menu), 78
Step Over command (VLISP Debug menu), 72,
78
stepping through programs from breakpoints ,
71–72, 78
Stop Once command (VLISP Debug menu), 75,
76
storing arbitrary data, 331
strcase function, 234
strcat function , 234
string data type
defined, 225
overview, 225
STRING Inspect window, 97, 98
strings
AutoLISP output functions, 235–239
AutoLISP string-handling, 234–235
concatenating, 234
237–238
converting angles to , 280
converting case, 234
converting reals to , 279–280
DIESEL string expressions , 266–268
finding number of characters, 234
forcing line breaks in, 237–238
returning substrings , 234–235
string-handling functions, 444–445
strlen function, 234, 235
stylistic conventions in this manual, 7
subassemblies. See tiles (dialog box)
SUBR Inspect window, 97, 100
subst function, 241, 241
substituting list items, 241, 241
substr function, 234–235
Support File Search Path, 111 –112
Symbol command
Watch window shortcut menu, 85
symbol flags, 94
SYMBOL Inspect window, 99
Symbol Service command
Symbol Service dialog box
adding symbol to Watch window, 94
described, 82

Symbol Service dialog box (continued)
displaying function definition , 94
help feature, 94
opening, 29 , 33, 46, 89, 92, 102
opening Inspect window, 94
overview, 92–93
symbol flags, 94
toolbar, 94
updating symbols, 93
symbol table
names , 240
objects , 322–323
in the drawing database, 105
symbolic names for colors, 399 –400
symbols
AutoLISP data type, 227 –229
AutoLISP symbol-handling, 245
case setting by VLISP formatter, 57
case setting of, 227, 240
defined, 227
finding using Apropos feature, 43–47
inserting symbols from results
window, 46
overview, 43
with prefix, 45
flags, 94
inserting from Apropos results window, 46
naming restrictions , 227
PAUSE symbol, 261–262
protected, 228–229
restricted characters, 227
SYMBOL Inspect window, 97, 99
symbol table
access functions , 332–333
entries that cannot be modified, 322
entries that cannot be renamed,
322–323
and dictionary handling functions,
455–456
objects , 322–323
symbol-handling functions , 445
using Apropos search results, 45–47
syntax checking
balance of parentheses, 61 –63
from Project window, 146
in text editor, 19
using Check command, 64–65
using color coding, 63
Syntax Coloring command (VLISP Tools menu),
42, 43
:SYNTAX-ERROR trace keyword frame, 91

Index

|

527

system variables
ERRNO, 486
specifying values , 263
TABMODE , 292

T
T symbol, 232
TAB character in quoted strings, 238
TAB key
clearing TAB characters in text editor, 36
for Console window history, 26 –27
tab_truncate (DCL attribute), 407
tablet function, 291–293
tablets, calibrating, 291–293
TABMODE system variable, 292
tabs (DCL attribute), 406
tblnext function, 332–333
tblsearch function, 332–333
temporary file directory for projects , 154
term_dialog function, 368, 377, 378
terpri function, 238
text editor, Visual LISP, 31–41
backing up files automatically, 31–32
bookmarking text, 40–41
color coding of files, 19, 42–43, 345
converting code to comments, 60
converting comments to active text, 60
copying text, 36
described, 3
editing files , 31
editing project file source code, 146, 148
features , 19
formatting text in active window, 50–51
indenting or unindenting blocks of text, 59
loading AutoLISP programs from, 20
moving text, 36
need for, 31
opening
existing files , 32
LISP programs, 14
new files, 31
window containing text selected from
Inspect window, 103
overstrike mode, 34
overview, 14, 19, 31
replacing text, 39
restoring from backup files, 32
saving text to new file, 36 , 60
searching for text, 37–39
shortcut keys
for code indentation, 36
for correcting text, 33
for formatting text, 59–60
for navigation, 35
for selecting text, 34–35
shortcut menu commands , 32 –33

528

|

Index

text editor, Visual LISP (continued)
sorting text, 60
starting new lines , 31
undoing last edit, 31
window prototyping, 475
See also formatting text
text tile, 424
text_part tile, 424
textbox function, 275–279
textpage function, 267
textscr function, 267
tiles (dialog box)
example, 347–348
column, 350 –351
layout guidelines, 357
attributes
case-sensitivity, 393
data types for values , 392
naming, 393
numeric values and, 393
overview, 393
restricted attributes , 393
synopsis of predefined attributes,
394–396
syntax, 343–344
user-defined attributes , 393–394
attributes listed by function
action expression specification, 397
aligning horizontally or vertically in a
cluster, 397–426
aspect ratio specification, 398
background color of image, 399 –400
bold text specification, 402
button is selected with ESC key (or
not), 402
callback specification, 397
character used to mask user input, 406
character width units for edit box
input, 400
default alignment for all tiles in a
cluster, 398
default button specification , 402–403
default height for all tiles in a cluster,
398–399
default width for all tiles in a cluster,
399

tiles (continued)
fixed pitch font for list boxes or pop-up
lists, 401
initial availability of tile, 403
initial choices for list box or pop-up
list, 404
initial value of tile, 407
key of tile to receive initial keyboard
focus , 402
keyboard mnemonic character for tile,
405
maximum characters for edit box
input, 400
maximum value for slider, 405
minimum value for slider, 405
multiple selections allowed in list box
(or not), 406
slider incremental control value
specification, 398, 406
slider orientation specification, 404
specifying if tile is activated, 398
tab placement in character width
units, 406
text larger than tab stop truncated in
list box or pop-up list (or
not), 407
tile height allowed to fill space (or
not), 401
tile height specification, 401–402
tile name specification, 403
tile receives focus with TAB key (or
not), 403
tile text (label) specification , 404
tile width allowed to fill space (or not),
401
tile width specification , 407
attributes listed by name, 397–407
action, 397
alignment, 397 –426
allow_accept, 398
aspect_ratio, 398
big_increment, 398
children_alignment, 398
children_fixed_height, 398–399
children_fixed_width, 399
color, 399–400
edit_limit, 400
edit_width , 400
fixed_height, 401
fixed_width, 401
fixed_width_font, 401
height, 401–402
initial_focus, 402
is_bold, 402
is_cancel, 402
is_default, 402–403
is_enabled, 403

tiles (continued)
is_tab_stop, 403
key, 403
label, 404
layout, 404
list, 404
max_value, 405
min_value, 405
mnemonic, 405
multiple_select, 406
password_char, 406
small_increment, 406
tab_truncate, 407
tabs , 406
value, 407
width, 407
buttons
when Cancel and Default button are
the same, 352
centering, 347–348
default_button definition, 342
defining, 342
design guidelines, 360 –361, 362
radio buttons, 360–362
callback reason codes , 371
children tiles, 338
cluster design guidelines , 361
clusters, handling radio clusters, 374 –375
DCL syntax
attributes and attribute values ,
343–344
tile definitions, 342
tile references, 343
defined, 338
disabling, 358
edit boxes
callback reasons, 371
handling actions and callbacks, 376
error tiles, 363–364
functional groupings, 408–410
decorative and informative tiles, 409
dialog box exit buttons and error tile,
410
predefined active tiles, 408
restricted tiles, 410
text clusters , 409
tile clusters , 408
handling, 372–376
changing modes and values at callback
time, 373–374
edit boxes, 376
initializing modes and values ,
372–373
mode codes for mode_tile function,
373

Index

|

529

tiles (continued)
radio clusters, 374–375
sliders, 375–376
image buttons
callback reason code, 371
callback reasons, 372
design guidelines, 361 –362
handling, 385
image tiles
list boxes
appending list items, 381
changing list items, 381
deleting list items, 381
functions handling, 380, 428
handling, 380–382
inserting list items, 381
list operations, 380–381
operation codes for start_list function,
380
listed by name, 410–426
boxed_column, 410–411
boxed_radio_column, 411
boxed_radio_row, 412
boxed_row, 412
button, 413
column, 413 –414
concatenation , 414
dialog, 414
edit_box, 415
errtile, 415
image, 416
image_button, 416–417
list_box, 417
ok_cancel, 418
ok_cancel_help, 418
ok_cancel_help_errtile, 418–419
ok_cancel_help_info , 419
ok_only, 418
paragraph, 419–420
popup_list, 420–421
radio_button, 421
radio_column, 422
radio_row, 422
row, 423
slider, 423
spacer, 425

530

|

Index

tiles (continued)
spacer_0, 426
spacer_1, 426
text, 424
text_part, 424
toggle, 425
naming, 342, 343
ok_cancel tile, 343
predefined tiles and clusters , 360–364
buttons, 360
clusters, 361
edit boxes, 361
image buttons and image tiles ,
361–362
list boxes, 362
radio buttons, radio rows, and radio
columns , 360–362
sliders, 362
text, 363
toggles, 363
prototypes
naming, 342
overview, 339
tile definitions for, 341, 342
radio buttons, radio rows, and radio columns
handling actions and callbacks,
374–375
referencing tiles , 343
sliders
handling actions and callbacks,
375–376
spacer tiles, 343, 426
subassemblies
children tiles, 338
overview, 338
tile definitions for, 341
toggles, design guidelines, 363
typical tiles , 338
tiles listed by name
spacer_1, 426
time
changing format for, 60
inserting current, 60
Tmp Directory option (Build Options dialog
box), 154
Toggle Breakpoint command
toolbar button, 70
VLISP Debug menu, 70, 79
Toggle Console Log command
VLISP File menu, 30
toggle tile, 425

Toggle Trace Log command (VLISP File menu),
82
toggles (dialog box). See tiles (dialog box)
toolbars (VLISP)
Apropos results window, 46
Debug, 70–71
Edit, 31
Find, 37, 39
Project window, 145
Run, 20, 21
Symbol Service, 94
Tools , 50
Trace Stack window toolbar, 92
Watch, 84
See also specific toolbars
Tools menu (AutoCAD), AutoLISP submenu,
Visual LISP Editor command, 12
Tools menu (VLISP)
Check Selection command, 65
Check Text in Editor command, 65
Environment Options submenu
AutoLISP Format Options command,
51, 59
General Options command, 32, 75,
104
Format Code in Editor command, 50
Load Application command, 124
Load Text command, 20
overview, 17
Save Settings command, 58
Window Attributes submenu
Configure Current command, 42, 79
Syntax Coloring command, 42, 43
Tools menu (VLISP), Interface Tools submenu,
Preview DCL in Editor command, 345
Tools toolbar
Format Edit window button, 50
Format Selection button, 50
Help button , 50
top forms, 86
:TOP-COMMAND trace keyword frame, 89
Touch command (Project window shortcut
menu), 146
Tr symbol flag, 94
trace function. See AutoLISP Reference
Trace log file
copying Apropos search results to , 46
copying Inspect window contents to , 102
copying Watch window contents to , 84
turning Trace logging on and off, 82
Trace Stack command (VLISP View menu), 87
calling Inspect feature for stack elements,
88
calling Symbol Service feature for
functions , 88

Trace Stack window (continued)
copying stack elements to *obj* system
variable, 88
described, 68, 82
displaying Frame Binding window for local
variables, 88
displaying position of caller expression, 88
displaying source text for functions, 88
displaying stack element information ,
87–88
keyword frames, 89–91
printing stack elements to Console
window, 88
refreshing contents , 92
shortcut menu commands , 87 –88
stack element lists, 86
toolbar, 92
trace stack overview, 85–86
using the Frame Binding window, 88–92
viewing current trace stack, 87
viewing error trace stack, 92
See also Frame Binding window
Trace symbol flag, 94
Trace window
copying Apropos search results to , 46
copying Inspect window contents to , 102
copying Watch window contents to , 84
described, 69
messages during start-up, 14
turning Trace logging on and off, 82
Trace window, printing list of arguments to, 206
trans function, 286–289
transient reactors , 215
Transparent option for protected symbols, 228
turning on. See starting
type libraries
importing, 193–195
using ActiveX without importing, 198–199
typographical conventions in this manual, 7

U
unbalanced parentheses
checking in VLISP 61–63
,
text editor formatter and, 50
unbalanced parentheses, checking in AutoLISP,
222–223
Uncomment Block option, 60
underscore (_)
for foreign-language support, 261
for VLISP comments , 58
Undo command
VLISP Edit menu, 31

Index

|

531

undoing
commands issued with command
function, 263
copy actions, 37
in Console window, 29
in text editor, 31
move actions, 37
Unindent option, 59
unit conversions, 283–286
inches to meters, 284
overview, 283
defining new units, 284
derived units, 285–286
fundamental units, 284
user comments, 286
valid name definitions, 284
unload_dialog function, 367
[Un]Select All command (Project window
shortcut menu), 146
Up option (Find dialog box), 37
Upcase option, 60
Update command (Inspect window shortcut
menu), 102
updating
ActiveX property with vlax-put-property,
199
applications, 125
determining if objects available for
updating, 183
entities, 314 –315
object properties, 181–183
symbols in Symbol Service dialog box, 93
Use WCMATCH option (Apropos dialog box), 44
user comments, 286
User Coordinate System, 286
User function (Apropos filter value), 44
controlling user-input conditions, 271–273
restrictions when dialog box is open, 367
synopsis of, 452
user-defined DCL attributes , 393–394
user-defined functions
defining with defun function, 245–253

532

|

Index

user-defined functions (continued)
compatibility with AutoCAD versions,
246–247
249–250
with arguments, 252–254
tracing, 94
:USER-INPUT trace keyword frame, 89
USUBR Inspect window, 97, 100

V
valid name definitions, 284
value (DCL attribute), 407
variables
action expression variables, 369–370
adding to Watch window, 84
assigning values , 227–228 , 231
AutoLISP, 231–233
AutoLISP data type, 227 –229
blackboard variables, 133 –134
case sensitivity of, 227
clearing from Watch window, 84, 85
defined, 227
displaying values, 231–232
environment variables, inspecting and
changing, 264
localizing, 155, 159, 160
monitoring during program execution,
73–74
multiple namespaces affect on, 127–128
names, case and, 227
naming, 228
nil variables , 232
predefined, 232–233
printing values from Watch window, 85
referencing in document namespaces,
132–133
sorting in Watch window, 84
system variables
specifying values , 263
TABMODE , 292
7
viewing current value of, 18, 25
VARIANT Inspect window, 98, 101
variants
changing data type of, 174
creating, 174, 174–175
creating with an array of four doubles, 179
returning data type of, 174
returning value of, 174
using safearrays with, 178–179
vector_image function, 383

vertical bar (|) for VLISP comments, 58
View menu (VLISP)
Apropos Window command, 43
Browse Drawing Database submenu
Browse All Entities command, 104
Browse Blocks command, 106
Browse Selection command, 107
Browse Tables command, 105
Inquire Extended Data command, 107
overview, 16
Trace Stack command, 87
View Source command (Inspect window shortcut
menu), 103
viewing. See displaying; Inspect feature
Visual LISP
closing, 22
DCL file references, 344
exiting, 22
extended functions , 22, 457–463
458
461–462
IDE components , 2 –3
issuing commands from Console window,
14
overview, 1–3
relationship to AutoCAD, 3
relationship to AutoLISP, 1, 3
running AutoCAD with , 3, 20
starting, 12 , 22
user interface, 13 –15
Visual LISP Developer’s Guide
additional publications , 4 , 8
experience requirements , 4
guidelines for using, 4–5
organization of, 4 –5
sections of, 4
typographical conventions , 7
Visual LISP Editor command, AutoCAD Tools
menu, 12
Visual LISP extended functions , 22, 457–463
defined, 22

Visual LISP extended functions (continued)
running, 22
vl-load-com and, 22
Visual LISP Tutorial, 4
vla-get functions, 170, 180
vla-get-center function, 180, 181
VLA-objects
ActiveX and, 165–169
converting between enames and
VLA-objects , 190
data type, 226
defined, 226
vlax-3d-point function, 178–179
vlax-create-object function, 195
vlax-dump-object function, 185 –186
vlax-ename->vla-object function, 190
vlax-erased-p function, 183
vlax-for function, 187–188
vlax-get-acad-object function, 165
vlax-get-object function, 195
vlax-get-property function, 199
vlax-import-type-library function , 194–195
vlax-invoke-method function, 198–199
vlax-make-safearray function, 175–177
vlax-make-variant function, 174 , 174 –175
vlax-map-collection function, 187
vlax-method-applicable-p function, 186
vlax-object-released-p function, 189
vlax-property-available-p function, 186–187
vlax-put-property function, 199
vlax-read-enabled-p function, 183
vlax-release-object function, 189
vlax-safearray-fill function, 175, 177
vlax-safearray-put-element function, 177–178
vlax-variant-change-type function , 174
vlax-variant-type function, 174
vlax-variant-value function, 174
vlax-write-enabled-p function, 183
vl-bb-ref function, 133
vl-bb-set function, 133–134
vl-catch-all-apply, 257
vl-doc-export function, 130–131, 132, 135
vl-doc-import function, 132
vl-doc-ref function, 132, 134
vl-doc-set function, 132–134
vl-exit-with-error function, 135
vl-exit-with-value function, 135
vlide command, 12
vlisp command, 12
VLISP text editor. See text editor
VLISP. See Visual LISP
vlisp-compile function, 110–113, 116
compiler modes, 111

Index

|

533

vlisp-compile function (continued)
example using, 113–114
identifying the input file, 112
naming an output file, 113
overview, 110
syntax, 111
vl-list-exported-function, 131
vl-list-loaded-vlx function , 131
vl-load-all function, 129
vl-load-com function, 165
vl-load-reactors function, 202, 205
vl-propagate function, 133
vlr-add function, 215
vlr-added-p function, 215
vlr-beep-reaction function, 206
vlr-current-reaction-name function, 213
vlr-data function, 213
vlr-data-set function, 213
vlr-owner-add function, 214
vlr-owner-remove function, 214
vlr-owners function, 213
vlr-pers function, 215
vlr-pers-p function, 215
vlr-pers-release function, 215
vlr-reaction-names function, 204–205
vlr-reactions function, 213
vlr-reaction-set function, 213
vlr-reactors function, 211–212
vlr-remove function, 214
vlr-remove-all function, 215
vlr-trace-reaction function, 206
vlr-type function, 213
vlr-types function, 204
vl-unload-vlx function, 129, 131
.vlx files , 114–117, 118, 123, 125, 139
See also building applications

W
warning messages for safe optimization, 158
Watch window, 83–85
Add Watch button, 73
adding symbol from Apropos results
window, 47
adding symbol from Frame Binding
window, 89
adding symbol from Symbol Service dialog
box, 94
adding variables , 84
calling Apropos feature, 85
calling Symbol Service dialog box, 85
clearing all variables, 84
copying contents to Trace window, 84

534

|

Index

Watch window (continued)
copying variable value to *obj* system
variable, 84
described, 3 , 68, 82
invoking Inspect feature, 84
monitoring variables during program
execution, 73–74
opening, 29 , 33
overview, 83–84
printing variable values, 85
removing variables, 85
sorting variables , 84
toolbar, 84
:WATCH-EVAL trace keyword frame, 89
wcmatch function, 238–239
Web site for Autodesk, 8
Wide style, 53
width (DCL attribute), 407
wild-card characters
in filter lists for selection sets, 300
in Apropos searches, 44
matching in strings, 238–239
Window menu (VLISP), 17
windows
Console, 14 , 18–19
controlling AutoCAD graphics and text
windows, 267
copying text from output windows, 15
for VLISP function output, 15
menu content variations and, 15–16
Trace, 14
Wizard Mode dialog box , 117
word completion
working with existing projects , 149–152
finding strings in project source files, 151
including projects in VLISP applications,
151
opening projects, 149
World Coordinate System, 286
World Wide Web site for Autodesk, 8

X
X axis of circle, changing, 181–183
xdata. See extended data
xdroom function, 329
xdsize function, 329

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