The Ring programming language version 1.5.2 book - Part 47 of 181

1. Ring Documentation, Release 1.5.2
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()
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2. Ring Documentation, Release 1.5.2
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 436

3. Ring Documentation, Release 1.5.2
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 437

4. Ring Documentation, Release 1.5.2
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
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5. Ring Documentation, Release 1.5.2
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 439

6. Ring Documentation, Release 1.5.2
Mix_Quit()
SDL_DestroyWindow(win)
SDL_Quit()
51.10. Play Sound 440

7. 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
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8. Ring Documentation, Release 1.5.2
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
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9. Ring Documentation, Release 1.5.2
• 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.
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10. Ring Documentation, Release 1.5.2
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 444