The Ring programming language version 1.5.1 book - Part 46 of 180
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The document discusses using RingLibSDL to create 2D games in Ring. It describes how RingLibSDL allows Ring code to interface with the SDL libraries for graphics, audio, input etc. It provides examples of creating windows, displaying images, playing sounds, and handling events like mouse and keyboard input. The document then outlines a game engine project structure in Ring for 2D games, separating it into a games layer, engine classes layer, graphics interface layer, and graphics library bindings layer.
The Ring programming language version 1.5.1 book - Part 46 of 180
- 1. CHAPTER FIFTYONE USING RINGLIBSDL In this chapter we will learn about using RingLibSDL to create games based on the LibSDL, SDLImage, SDLTTF and SDLMixer libraries. Tip: RingLibSDL is not distributed with the binary releases for desktop which uses RingAllegro Note: To use RingLibSDL, Check ring/android/ringlibsdl folder. 51.1 Create Window Example: Load "libsdl.ring" SDL_Init(SDL_INIT_EVERYTHING) win = SDL_CreateWindow("Hello World!", 100, 100, 640, 480, SDL_WINDOW_SHOWN) SDL_Delay(2000) SDL_DestroyWindow(win) SDL_Quit() 51.2 Display Image Example: Load "libsdl.ring" SDL_Init(SDL_INIT_EVERYTHING) win = SDL_CreateWindow("Hello World!", 100, 100, 640, 480, SDL_WINDOW_SHOWN) ren = SDL_CreateRenderer(win, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC ) bmp = SDL_LoadBMP("hello.bmp") tex = SDL_CreateTextureFromSurface(ren,bmp) SDL_FreeSurface(bmp) SDL_RenderClear(ren) SDL_RenderCopy2(ren,tex) SDL_RenderPresent(ren) SDL_Delay(2000) SDL_DestroyTexture(tex) SDL_DestroyRenderer(ren) SDL_DestroyWindow(win) SDL_Quit() 425
- 2. Ring Documentation, Release 1.5.1 51.3 Switch between two images Example: Load "libsdl.ring" SDL_Init(SDL_INIT_EVERYTHING) win = SDL_CreateWindow("Hello World!", 100, 100, 640, 480, SDL_WINDOW_SHOWN) ren = SDL_CreateRenderer(win, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC ) bmp = SDL_LoadBMP("hello.bmp") tex = SDL_CreateTextureFromSurface(ren,bmp) SDL_FreeSurface(bmp) bmp = SDL_LoadBMP("hello2.bmp") tex2 = SDL_CreateTextureFromSurface(ren,bmp) SDL_FreeSurface(bmp) for x = 1 to 10 showtex(tex) showtex(tex2) next SDL_DestroyTexture(tex) SDL_DestroyTexture(tex2) SDL_DestroyRenderer(ren) SDL_DestroyWindow(win) SDL_Quit() func showtex oTex SDL_RenderClear(ren) SDL_RenderCopy2(ren,oTex) SDL_RenderPresent(ren) SDL_Delay(200) 51.4 Draw Rectangle Example: Load "libsdl.ring" SDL_Init(SDL_INIT_EVERYTHING) win = SDL_CreateWindow("Hello World!", 100, 100, 640, 480, SDL_WINDOW_SHOWN) ren = SDL_CreateRenderer(win, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC ) SDL_RenderClear(ren) rect = sdl_new_sdl_rect() sdl_set_sdl_rect_x(rect,10) sdl_set_sdl_rect_y(rect,10) sdl_set_sdl_rect_w(rect,100) sdl_set_sdl_rect_h(rect,100) SDL_SetRenderDrawColor(ren,255,255,255,255) SDL_RenderDrawRect(ren,rect) sdl_destroy_sdl_rect(rect) SDL_RenderPresent(ren) SDL_Delay(2000) SDL_DestroyRenderer(ren) SDL_DestroyWindow(win) SDL_Quit() 51.3. Switch between two images 426
- 3. Ring Documentation, Release 1.5.1 51.5 Display PNG Images Example: Load "libsdl.ring" SDL_Init(SDL_INIT_EVERYTHING) win = SDL_CreateWindow("Hello World!", 100, 100, 640, 480, SDL_WINDOW_SHOWN) ren = SDL_CreateRenderer(win, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC ) bmp = IMG_Load("hello3.png") tex = SDL_CreateTextureFromSurface(ren,bmp) SDL_FreeSurface(bmp) SDL_RenderClear(ren) SDL_RenderCopy2(ren,tex) SDL_RenderPresent(ren) SDL_Delay(2000) SDL_DestroyTexture(tex) SDL_DestroyRenderer(ren) SDL_DestroyWindow(win) SDL_Quit() 51.6 Use TTF Fonts Example: Load "libsdl.ring" SDL_Init(SDL_INIT_EVERYTHING) win = SDL_CreateWindow("Hello World!", 100, 100, 640, 480, SDL_WINDOW_SHOWN) ren = SDL_CreateRenderer(win, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC ) SDL_RenderClear(ren) TTF_Init() font = TTF_OpenFont("pirulen.ttf", 16) color = sdl_new_sdl_color() sdl_set_sdl_color_r(color,0) sdl_set_sdl_color_g(color,255) sdl_set_sdl_color_b(color,0) text = TTF_RenderText_Solid(font,"Welcome to the Ring language",color) surface = SDL_GetWindowSurface(win) SDL_BlitSurface(text, nullpointer(), surface, nullpointer()) SDL_UpdateWindowSurface(win) SDL_Delay(2000) SDL_Destroy_SDL_Color(color) SDL_FreeSurface(text) TTF_CloseFont(font) SDL_DestroyRenderer(ren) SDL_DestroyWindow(win) SDL_Quit() 51.7 Display Transparent Images Example: 51.5. Display PNG Images 427
- 4. Ring Documentation, Release 1.5.1 Load "libsdl.ring" SDL_Init(SDL_INIT_EVERYTHING) flags = IMG_INIT_JPG | IMG_INIT_PNG IMG_Init(flags) win = SDL_CreateWindow("Hello World!", 100, 100, 800, 600, SDL_WINDOW_SHOWN) ren = SDL_CreateRenderer(win, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC ) bmp = IMG_Load("stars.jpg") tex = SDL_CreateTextureFromSurface(ren,bmp) SDL_FreeSurface(bmp) SDL_RenderClear(ren) SDL_RenderCopy(ren,tex,nullpointer(),nullpointer()) SDL_DestroyTexture(tex) bmp = IMG_Load("player.png") # Image - Set Transparent color (white) myformat = sdl_get_sdl_surface_format(bmp) white = SDL_MapRGB(myformat, 255, 255, 255) SDL_SetColorKey(bmp, SDL_True, white) tex = SDL_CreateTextureFromSurface(ren,bmp) SDL_FreeSurface(bmp) rect = sdl_new_sdl_rect() sdl_set_sdl_rect_x(rect,0) sdl_set_sdl_rect_y(rect,0) sdl_set_sdl_rect_w(rect,100) sdl_set_sdl_rect_h(rect,100) SDL_RenderCopy(ren,tex,nullpointer(),rect) SDL_SetTextureBlendMode(tex,2) SDL_SetTextureAlphaMod(tex,255) sdl_set_sdl_rect_x(rect,200) sdl_set_sdl_rect_y(rect,200) sdl_set_sdl_rect_w(rect,100) sdl_set_sdl_rect_h(rect,100) SDL_RenderCopy(ren,tex,nullpointer(),rect) SDL_DestroyTexture(tex) SDL_Destroy_SDL_Rect(rect) SDL_RenderPresent(ren) SDL_Delay(2000) SDL_DestroyRenderer(ren) SDL_DestroyWindow(win) SDL_Quit() 51.8 Close Window Event Example: Load "libsdl.ring" SDL_Init(SDL_INIT_EVERYTHING) 51.8. Close Window Event 428
- 5. Ring Documentation, Release 1.5.1 win = SDL_CreateWindow("Hello World!", 100, 100, 640, 480, SDL_WINDOW_SHOWN) myevent = sdl_new_sdl_event() while true thevent = sdl_pollevent(myevent) switch sdl_get_sdl_event_type(myevent) on sdl_get_sdl_quit() exit on sdl_get_sdl_keydown() Key = SDL_GET_SDL_Event_key_keysym_sym(myevent) if key = 27 exit ok off end SDL_DestroyWindow(win) SDL_Quit() 51.9 Mouse Events Example: Load "libsdl.ring" SDL_Init(SDL_INIT_EVERYTHING) win = SDL_CreateWindow("Mouse Events ", 100, 100, 640, 480, SDL_WINDOW_SHOWN) TTF_Init() font = TTF_OpenFont("pirulen.ttf", 16) color = sdl_new_sdl_color() sdl_set_sdl_color_r(color,0) sdl_set_sdl_color_g(color,255) sdl_set_sdl_color_b(color,0) surface = SDL_GetWindowSurface(win) myevent = sdl_new_sdl_event() while true cMsg = "" sdl_pollevent(myevent) switch sdl_get_sdl_event_type(myevent) on SDL_QUIT exit on SDL_KEYDOWN Key = SDL_GET_SDL_Event_key_keysym_sym(myevent) if key = 27 exit ok on SDL_MOUSEBUTTONDOWN if sdl_get_Sdl_Event_button_button(myevent) = SDL_BUTTON_LEFT SDL_SETWINDOWTITLE(win, " Button_Left_Down " ) but sdl_get_Sdl_Event_button_button(myevent) = SDL_BUTTON_MIDDLE SDL_SETWINDOWTITLE(win, " Button_Middle_Down " ) but sdl_get_Sdl_Event_button_button(myevent) = SDL_BUTTON_RIGHT SDL_SETWINDOWTITLE(win, " Button_Right_Down " ) ok on SDL_MOUSEMOTION 51.9. Mouse Events 429
- 6. Ring Documentation, Release 1.5.1 sdl_fillrect(surface,nullpointer(),0) if sdl_get_sdl_event_motion_xrel(myevent) < 0 cMsg += " Left " else cMsg += " Right " ok if sdl_get_sdl_event_motion_yrel(myevent) < 0 cMsg += " Up " else cMsg += " Down " ok cMsg += " x = " + sdl_get_sdl_event_motion_x(myevent) cMsg += " y = " + sdl_get_sdl_event_motion_y(myevent) showmsg(cMsg) off end SDL_Destroy_SDL_Color(Color) TTF_CloseFont(font) SDL_DestroyWindow(win) SDL_Quit() func showmsg mymsg text = TTF_RenderText_Solid(font,mymsg,color) SDL_BlitSurface(text, nullpointer(), surface, nullpointer()) SDL_UpdateWindowSurface(win) SDL_FreeSurface(text) 51.10 Play Sound Example: Load "libsdl.ring" SDL_Init(SDL_INIT_EVERYTHING) win = SDL_CreateWindow("Hello World!", 100, 100, 640, 480, SDL_WINDOW_SHOWN) Mix_OpenAudio( 44100, MIX_DEFAULT_FORMAT , 2, 10000) Mix_AllocateChannels(4) sound = Mix_LoadWav( "sound.wav" ) Mix_VolumeChunk(sound,1) Mix_PlayChannel(1,sound,0) myevent = sdl_new_sdl_event() while true thevent = sdl_pollevent(myevent) switch sdl_get_sdl_event_type(myevent) on sdl_get_sdl_quit() exit on sdl_get_sdl_keydown() Key = SDL_GET_SDL_Event_key_keysym_sym(myevent) if key = 27 exit ok off end Mix_FreeChunk( sound ) Mix_CloseAudio() 51.10. Play Sound 430
- 7. Ring Documentation, Release 1.5.1 Mix_Quit() SDL_DestroyWindow(win) SDL_Quit() 51.10. Play Sound 431
- 8. CHAPTER FIFTYTWO DEMO PROJECT - GAME ENGINE FOR 2D GAMES In this chapter we will learn about using the different programming paradigms in the same project. We will create a simple Game Engine for 2D Games. You can use the Engine directly to create 2D Games for Desktop or Mobile. 52.1 Project Layers The project contains the next layers • Games Layer (Here we will use declarative programming) • Game Engine Classes (Here we will use the Object-Oriented Programming paradigm) • Interface to graphics library (Here we will use procedural programming) • Graphics Library bindings (Here we have RingAllegro and RingLibSDL) 52.2 Graphics Library bindings We already have RingAllegro to use the Allegro game programming library and we have RingLibSDL to use the LibSDL game programming library. Both of RingAllegro and RingLibSDL are created using the C language with the help of the Ring code generator for extensions. Each of them is over 10,000 lines of C code which is generated after writing simple configuration files (That are processed by the code generator). Each configuration file determines the functions names, structures information and constants then the generator process this configuration file to produce the C code and the library that can be loaded from Ring code. Using RingAllegro and RingLibSDL is very similar to using Allegro and LibSDL from C code where you have the same functions but we can build on that using the Ring language features • RingAllegro Source Code : https://github.com/ring-lang/ring/tree/master/extensions/ringallegro • RingLibSDL Source Code : https://github.com/ring-lang/ring/tree/master/extensions/ringsdl 432
- 9. Ring Documentation, Release 1.5.1 52.3 Interface to graphics library In this layer we have gl_allegro.ring and gl_libsdl.ring Each library provides the same functions to be used with interacting with the Graphics Library. This layer hides the details and the difference between RingAllegro and RingLibSDL. You have the same functions, Just use it and you can switch between Allegro and LibSDL at anytime. Why ? Allegro is very simple, we can use it to quickly create 2D games for Windows, Linux and MacOS X. In Ring 1.0 we started by supporting Allegro. Also LibSDL is very powerful and popular, very easy to use for Mobile Development. Ring 1.1 comes with support for LibSDL so we can quickly create games for Mobile. Note: We can use just one library for Desktop and Mobile development. • gl_allegro.ring source code : https://github.com/ring-lang/ring/blob/master/ringlibs/gameengine/gl_allegro.ring • gl_libsdl.ring source code : https://github.com/ring-lang/ring/blob/master/ringlibs/gameengine/gl_libsdl.ring 52.4 Game Engine Classes The Engine comes with the next classes • GameBase class • Resources class • Game class • GameObject class • Sprite class • Text class • Animate class • Sound class • Map class • Source Code : https://github.com/ring-lang/ring/blob/master/ringlibs/gameengine/gameengine.ring 52.5 Games Layer In this layer we create our games using the Game Engine classes The classes are designed to be used through Declarative Programming. In our games we will use the next classes • Game class • Sprite class 52.3. Interface to graphics library 433
- 10. Ring Documentation, Release 1.5.1 • Text class • Animate class • Sound class • Map class Note: Other classes in the engine are for internal use by the engine. We will introduce some examples and three simple games :- • Stars Fighter Game • Flappy Bird 3000 Game • Super Man 2016 Game 52.6 Game Class The next table present the class attributes. Attributes Description FPS Number determines how many times the draw() method will be called per second. FixedFPS Number determines how many times the animate() method will be called per second. Title String determines the window title of the game. aObjects List contains all objects in the game shutdown True/False value to end the game loop The next table present the class methods. Method Description refresh() Delete objects. settitle(cTitle) Set the window title using a string parameter. shutdown() Close the application. The next table present a group of keywords defined by the class. Keyword Description sprite Create new Sprite object and add it to the game objects. text Create new Text object and add it to the game objects. animate Create new Animate object and add it to the game objects. sound Create new Sound object and add it to the game objects. map Create new Map object and add it ot the game objects. 52.7 GameObject Class The next table present the class attributes. 52.6. Game Class 434