The Ring programming language version 1.5.4 book - Part 48 of 185
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This chapter discusses creating a game engine for 2D games in Ring. The project has several layers: a games layer that uses declarative programming to create games, game engine classes that use object-oriented programming, an interface layer that hides the details of the graphics libraries, and graphics library bindings that were created using procedural programming. The game engine includes classes like Game, Sprite, Text, and Sound that can be used to easily create 2D games. Examples are provided of simple games created using the engine.
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The Ring programming language version 1.5.4 book - Part 48 of 185
- 1. Ring Documentation, Release 1.5.4 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 445
- 2. Ring Documentation, Release 1.5.4 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 446
- 3. Ring Documentation, Release 1.5.4 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 447
- 4. Ring Documentation, Release 1.5.4 Mix_Quit() SDL_DestroyWindow(win) SDL_Quit() 51.10. Play Sound 448
- 5. 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 449
- 6. Ring Documentation, Release 1.5.4 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 450
- 7. Ring Documentation, Release 1.5.4 • 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 451
- 8. Ring Documentation, Release 1.5.4 Attributes Description enabled True/False determine the state of the object (Active/Not Active) x Number determine the x position of the object. y Number determine the y position of the object. width Number determine the width of the object. height Number determine the height of the object. nIndex Number determine the index of the object in objects list. animate True/False to animate the object or not. move True/False to move the object using the keyboard or not. Scaled True/False to scale the object image or not. draw Function to be called when drawing the object. state Function to be called for object animation. keypress Function to be called when a key is pressed. mouse Function to be called when a mouse event happens. The next table present the class methods. Method Description keyboard(oGame,nkey) Check Keyboard Events mouse(oGame,nType,aMouseList) Check Mouse Events rgb(r,g,b) Return new color using the RGB (Red, Green and Blue) Values. 52.8 Sprite Class Parent Class : GameObject Class The next table present the class attributes. Attributes Description image String determine the image file name. point Number determine the limit of automatic movement of the object. direction Number determine the direction of movement. nstep Number determine the increment/decrement during movement. type Number determine the object type in the game (Optional). transparent True/False value determine if the image is transparent. The next table present the class methods. Method Description Draw(oGame) Draw the object 52.9 Text Class Parent Class : Sprite Class The next table present the class attributes. Attributes Description size Number determine the font size font String determine the font file name text String determine the text to be displayed color Number determine the color The next table present the class methods. 52.8. Sprite Class 452
- 9. Ring Documentation, Release 1.5.4 Method Description Draw(oGame) Draw the object 52.10 Animate Class Parent Class : Sprite Class The next table present the class attributes. Attributes Description frames Number determine the number of frames frame Number determine the active frame framewidth Number determine the frame width. animate True/False determine using animate or not. scaled True/False determine scaling image or not. The next table present the class methods. Method Description Draw(oGame) Draw the object 52.11 Sound Class Parent Class : GameObject Class The next table present the class attributes. Attributes Description file String determine the sound file name. once True/False determine to play the file one time or not (loop). The next table present the class methods. Method Description playsound() Play the sound file 52.12 Map Class Parent Class : Sprite Class The next table present the class attributes. Attributes Description aMap List determine the map content using numbers. aImages List determine the image used for each number in the map. BlockWidth Number determine the block width (default = 32). BlockHeight Number determine the block height (default = 32). Animate True/False determine the animation status. The next table present the class methods. Method Description getvalue(x,y) Return the item value in the Map according to the visible part 52.10. Animate Class 453
- 10. Ring Documentation, Release 1.5.4 52.13 Using the Game Engine - Creating the Game Window Load "gameengine.ring" # Give Control to the Game Engine func main # Called by the Game Engine oGame = New Game # Create the Game Object { title = "My First Game" } # Start the Events Loop Note: if you want to define global variables, this must be before load “gameengine.ring” because this instruction will give the control to the game engine. Screen Shot: 52.14 Using the Game Engine - Drawing Text Load "gameengine.ring" # Give Control to the Game Engine func main # Called by the Game Engine 52.13. Using the Game Engine - Creating the Game Window 454