Subscribe to GameFromScratch on YouTube Support GameFromScratch on Patreon


19. November 2015

 

I remember using Allegro wayyyyyy back in the day in the early 1990s.  It was one of few graphics libraries available for DOS based machines (even though it started life as an Atari library) and certainly one of the only free game libraries available.  Amazingly enough Allegro is still under active development.  Anyways enough reminiscing…  today Allegro.js was released, an HTML5 library inspired by Allegro.  For a brand new library there is already an impressive amount of documentation and reference material available.  One of the hallmarks of the Allegro library was it was brutally simple to use and Allegro.js seems to have carried on that tradition.  Here is an example Allegro app:

 

// bitmap oobjects
var logo,ball;

// sample object
var bounce;

// size and speed of the ball
var size=64,speed=5;

// positon of the ball
var cx=100,cy=100;

// velocity of the ball
var vx=speed,vy=speed;

// drawing function
function draw()
{
   // draw allegro logo background
   stretch_blit(logo,canvas,0,0,logo.w,logo.h,0,0,SCREEN_W,SCREEN_H);
   
   // draws the ball resized to size*size, centered
   // stretch it a bit vertically according to velocity
   stretch_sprite(canvas,ball,cx-size/2,cy-size/2,size,size+abs(vy));
}

// update game logic
function update()
{
   // did the ball bounce off the wall this turn?
   var bounced=false;

   
   // if the ball is going to collide with screen bounds
   // after applying velocity, if so, reverse velocity
   // and remember that it bonced
   if (cx+vx>SCREEN_W-size/2) {vx=-speed;bounced=true;}
   if (cy+vy>SCREEN_H-size/2) {vy=-speed*3;bounced=true;}
   if (cx+vx<size/2) {vx=speed;bounced=true;}
   if (cy+vy<size/2) {vy=speed;bounced=true;}
      
   // move the ball
   cx+=vx;
   cy+=vy;
   
   // if it bounced, play a sound
   if (bounced) play_sample(bounce);
   
   // add gravity
   vy+=.3;
}

// entry point of our example
function main()
{
   // enable debugging to console element
   enable_debug("debug");
   
   // init all subsystems, put allegro in canvas with id="canvas_id"
   // make the dimesnions 640x480
   allegro_init_all("canvas_id", 640, 480);
   
   // load ball image
   ball = load_bmp("data/planet.png");
   
   // load background image
   logo = load_bmp("data/allegro.png");
   
   // load the bounce sound
   bounce = load_sample("data/bounce.mp3");

   // make sure everything has loaded
   ready(function(){
      
      // repeat this game loop
      loop(function(){
         
         // clear screen
         clear_to_color(canvas, makecol(255, 255, 255));

         // update game logic
         update();

         // render everything
         draw();
   
      // all this happens 60 times per second
      }, BPS_TO_TIMER(60));
   });
   
   // the end
   return 0;
}
// make sure that main() gets called as soon as the wesbite has loaded
END_OF_MAIN();

 

If this looks interesting to you be sure to check out Allegro.js.  It looks like a cool library, based on another cool library, just waiting for a community to form around it.

GameDev News, Programming ,

blog comments powered by Disqus

Month List

Popular Comments