Inside Android's UI / ABS 2013
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The input layer in Android uses the standard Linux input layer in the kernel to handle raw input from devices like touchscreens and keyboards, it then processes this input through a native library and the Input Manager Service which is started and tied to the Window Manager to dispatch input events to apps. Specific device configuration files and the soft keyboard and input method frameworks handle app-specific input handling and text entry.
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Inside Android's UI / ABS 2013
- 1. Inside Android's UI Android Builders Summit 2013 Karim Yaghmour @karimyaghmour karim.yaghmour@opersys.com 1
- 2. These slides are made available to you under a Creative Commons Share- Delivered and/or customized by Alike 3.0 license. The full terms of this license are here: https://creativecommons.org/licenses/by-sa/3.0/ Attribution requirements and misc., PLEASE READ: ● This slide must remain as-is in this specific location (slide #2), everything else you are free to change; including the logo :-) ● Use of figures in other documents must feature the below “Originals at” URL immediately under that figure and the below copyright notice where appropriate. ● You are free to fill in the “Delivered and/or customized by” space on the right as you see fit. ● You are FORBIDEN from using the default “About” slide as-is or any of its contents. ● You are FORBIDEN from using any content provided by 3rd parties without the EXPLICIT consent from those parties. (C) Copyright 2013, Opersys inc. These slides created by: Karim Yaghmour Originals at: www.opersys.com/community/docs 2
- 3. About ● Author of: ● Introduced Linux Trace Toolkit in 1999 ● Originated Adeos and relayfs (kernel/relay.c) ● Training, Custom Dev, Consulting, ... 3
- 4. Agenda ● Android's UI, what's that? ● Architecture Basics ● Display Core ● OpenGL ● Input Layer ● Relevant Apps and Services ● System Startup ● References and Pointers 4
- 5. 1. Android's UI, what's that? ●SoC / GPU ??? ●Touch input ●LCD ●Keyboard 5
- 6. 1.1. What I'm NOT covering ● Media layer ● StageFright ● Video playback ● Camera ● DRM ● Etc. 6
- 7. 2. Architecture Basics ● Hardware used to run Android ● AOSP ● Binder ● System Services ● HAL 7
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- 13. /frameworks/base/core/... /frameworks/base/services/java/... AOSP-provided ASL /frameworks/base/services/jni/ /hardware/libhardware/ /device/[MANUF.]/[DEVICE] Manuf.-provided /sdk/emulator/ Manuf. license Kernel or module Manuf.-provided GPL-license 13
- 14. 3. Display Core ● Display Hardware ● Classic Linux display stack ● Display stack in Android ● Kernel driver ● HAL definition ● HAL module ● Surface Flinger ● Window Manager ● Walkthrough 14
- 15. 3.1. Display Hardware MMU IOMMU 15
- 16. 3.2. Classic Linux display stack 16
- 17. 3.3. Display stack in Android 17
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- 19. 3.4. Kernel driver ● Video memory management ● Mode setting ● Checking of parameters ● Motorola Xoom: ● /dev/nvhdcp1 ● /dev/nvhost-ctrl ● /dev/nvhost-display ● /dev/nvhost-dsi ● /dev/nvhost-gr2d ● /dev/nvhost-gr3d ● /dev/nvhost-isp ● /dev/nvhost-mpe ● /dev/nvhost-vi ● /dev/nvmap ● /dev/tegra-crypto ● /dev/tegra_avp ● /dev/tegra_camera ● /dev/tegra_fuse ● /dev/tegra_rpc ● /dev/tegra_sema ● ... whatever hides in hwcomposer HAL module 19
- 20. 3.5. HAL Definition ● /hardware/libhardware/include/hardware/hwcomposer.h ● struct hwc_procs: ● invalidate() ● vsync() ● struct hwc_composer_device: ● prepare() ● set() ● dump() ● registerProcs() ● query() ● *() 20
- 21. 3.6. HAL module ● Skeleton /hardware/libhardware/modules/hwcomposer.cpp ● /system/lib/hw/hwcomposer.BOARD.so ● /system/lib/hw/gralloc.BOARD.so ● Ex. - Mot Xoom: ● hwcomposer.tegra.so ● gralloc.tegra.so ● Surface Flinger hook: ● /frameworks/native/services/surfaceflinger/DisplayHardware – HWComposer.cpp – Provides fake vsync if none is provided in HW 21
- 22. 3.7. Surface Flinger ● Actual server: ● /frameworks/native/services/surfaceflinger ● Client side: ● /frameworks/native/libs/gui ● Client / Server interface: ● ISurfaceComposerClient.cpp ● ISurfaceComposer.cpp ● This is NOT an aidl'ed service ● All communication is manually marshalled/unmarshalled 22
- 23. 3.8. Window Manager ● Server side: ● /frameworks/base/services/java/com/android/server/wm/ – WindowManagerService.java – Session.java ● Client side: ● /frameworks/base/core/java/android/view/ – WindowManager.java – WindowManagerImpl.java – ViewRootImpl.java ● Interfaces: ● IWindowManager.aidl ● IWindowSession.aidl ● Parameters (incl. z-order): ● See WindowManager.java 23
- 24. 3.9. Walkthrough ● Activity Manager relies on Activity Thread ● AT calls on attach() and makeVisible() ● makeVisible does wm.addView() ● wm.addView() - this also called by StatusBar to display itself ● Creates a new ViewRootImpl ● Call on its setView() ● setView() calls on mWindowSession.addToDisplay(...) ● This results in call to WM's addWindow() ● ViewRootImpl's performTraversals() ● Calls on relayoutWindow() ● Calls to WM session's relayout() ● Call to WM's relayoutWindow() ● Call to createSurfaceLocked() ● new Surface(...) 24
- 25. frameworks/base/core/java/android/*/* LocalActivityManager.java: startActivity() - moveToState() - startActivityNow() ActivityThread.java: startActivityNow() - performLaunchActivity() - attach() -- gets AM handle and ties to it - handleResumeActivity() - makeVisible() Activity.java: makeVisible() - wm.addView() WindowManagerGlobal.java: addView() - root = new ViewRootImpl() - root.setView() ViewRootImpl.java: setView() - mWindowSession.addToDisplay() IWindowSession.aidl: addToDisplay() 25
- 26. frameworks/base/services/java/com/android/server/wm/* Session.java: addToDisplay() - mService.addWindow() WindowManagerService.java: addWindow() ... frameworks/base/core/java/android/*/* ViewRootImpl.java: performTraversals() - relayoutWindow() - mWindowSession.relayout() frameworks/base/services/java/com/android/server/wm/* Session.java: relayoutWindow() - mService.relayoutWindow() WindowManagerService.java: relayoutWindow() - surface = winAnimator.createSurfaceLocked(); WindowStateAnimator.java: createSurfaceLocked() - new Surface(); 26
- 27. 4. OpenGL ● What's OpenGL? ● What's in a modern-day GPU? ● Software layers involved ● Kernel driver ● EGL libs ● Native interface ● Java interface ● Software GL implementation 27
- 28. 4.1. What's OpenGL? ● It's just an API ... nothing but an API ... ● Check out Wikipedia ● Multiple versions out ● “ES” versions for embedded use ● Up to ES 3.0 ● Android support up to ES 2.0 28
- 29. 4.2. What's in a modern-day GPU? ● A tremendous amount of parallel processing units ● “SIMD”-like instruction set ● Video decoding/encoding capabilities ● ... 29
- 30. 4.3. Software layers involved ● Kernel driver ● GL libraries ● Native GL API ● Java GL API 30
- 31. 4.4. Kernel driver Y AR ET RI OP PR 31
- 32. 4.5. EGL libs ● /frameworks/base/native/opengl/libs ● Entry point: /system/lib/libEGL.so ● Looks for /system/lib/egl/egl.cfg ● /system/lib/egl - Mot Xoom: ● egl.cfg ● libEGL_perfhud.so ● libEGL_tegra.so ● libGLES_android.so ● libGLESv1_CM_perfhud.so ● libGLESv1_CM_tegra.so ● libGLESv2_perfhud.so ● libGLESv2_tegra.so ● elg.cfg: 0 0 tegra 32
- 33. 4.6. Native interface ● /frameworks/native/opengl/include ● EGL ● ETC1 ● GLES ● GLES2 ● KHR 33
- 34. 4.7. Java interface ● GL libs required by libandroid_runtime.so ● /frameworks/base/opengl/java/android/opengl: ● ... 34
- 35. 4.8. Software GL implementation ● /frameworks/native/opengl/libagl 35
- 36. 5. Input Layer ● Kernel side - “std” Linux input layer: ● /dev/input/* ● No HAL use ● Native lib: ● libinput ● /frameworks/base/services/input ● Input Manager Service: ● /frameworks/base/services/java/com/android/server/input ● Started and directly tied to Window Manager ● Specific config files (see source.android.com) ● Soft keyboard: ● /frameworks/base/core/java/android/inputmethodservice ● Input methods: ● /packages/inputmehods ● http://developer.android.com/guide/topics/text/creating-input-method.html 36
- 37. 6. Relevant Apps and Services ● Launcher ● StatusBar ● Wallpaper Manager Service ● Notification Service ● App Widgets 37
- 38. 6.1. Launcher ● An app like any other ● See /packages/app/Launcher2 38
- 39. 6.2. StatusBar ● A unique app ● See /frameworks/base/packages/SystemUI ● Connects to Status Bar Manager and gives an interface it can use to call back into Status Bar ● Can use setIcon() to display icons on the right ● Provides a CPU usage add-on that renders straight on rest of display using higher z-order 39
- 40. 6.3. Wallpaper Manager Service ● See /frameworks/base/services/java/com/android/se rver/WallpaperManagerService.java 40
- 41. 6.4. Notification Service ● Toasts ● Status bar notifications ● Gets handle to Status Bar Service at instantiation ● Uses handle to communicate with Status Bar 41
- 42. 6.5. App Widgets ● See /frameworks/base/services/java/com/android/se rver/AppWidgetService.java 42
- 43. 7. System Startup ● Kernel ● Init ● Boot animation ● Launcher 43
- 44. 7.1. Boot animation ● Started by Surface Flinger ● “bootanim” binary ● /frameworks/base/cmds/bootanimation ● Relies on bootanimation.zip w/ PNGs (nothing but) ● See https://github.com/CyanogenMod/android_vendor_cm/tree/jellybean/pre built/common/bootanimatino ● Must contain a desc.txt: <width> <height> <fps> p <count> <pause> <path> p <count> <pause> <path> 44
- 45. 8. References and Pointers ● “Use the source, Luke” ● Jim Huang's “Android Graphics” ● Benjamin Zores' “Linux Magazine / France” articles ● MIPS article on graphics internals: http://developer.mips.com/2012/04/11/learning-about- android-graphics-subsystem/ ● Stéphane Marchesin's “Linux Graphics Drivers: an Introduction” http://source.android.com/tech/input/index.html 45