问Javascript画布游戏引擎

EN

var GameCanvas = {
    // GameCanvas Variables
    animation: {
        requestAnimationFrame: null,
        halt: false
    },
    canvas: {
        element: null,
        context: null,
        width: 500,
        height: 500,
        backgroundColor: '#000000'
    },

    objects: [

    ],

    baseObject: function(){
        return {
            // Custom internal name of object (Mostly for debugging)
            name: '',
            position: {
                width: 0,
                height: 0,
                x: 0,
                y: 0
            },
            // Any custom data for this object
            data: {
            },
            // the draw method

            draw: function(GameCanvas){

            },
            criticalObj: true
        };
    },

    addObject: function(obj){
        this.objects.unshift(obj);
    },


    init: function(CanvasID){
        // Get Canvas by ID
        this.canvas.element = document.getElementById(CanvasID);
        if(this.canvas.element===null){
            this.console.error("No valid canvas with ID \""+CanvasID+"\" found.");
            return false;
        }

        // Get Canvas dimensions
        this.canvas.width = this.canvas.element.width || this.canvas.width;
        this.canvas.height = this.canvas.element.height || this.canvas.height;

        // Get the context
        this.canvas.context = this.canvas.element.getContext('2d');
        if(this.canvas.context===null){
            this.console.error("Failed to get context.");
            return false;
        }

        // Setup Request Animation Frame
        // RequestAnimationFrame Shim
    this.animation.requestAnimationFrame = (function(){
      return  window.requestAnimationFrame       ||
        window.webkitRequestAnimationFrame ||
        window.mozRequestAnimationFrame    ||
        function(callback){
                  //hack for RequestAnimationFrame not being there
                  this.console.log('No support for RequestAnimationFrame.');
          window.setTimeout(callback, 1000 / 60);
        };
     })();

        this.console.log("Initialized Successfully.");
        return true;
    },

    console: {
        data: '',
        // Allows for custom error output
        error: function(data){
          if(console.error!==undefined){
              console.error('GameCanvas: '+String(data));
          }
            this.data += data+"\n";
      },
        log: function(data){
          if(console.log!==undefined){
              console.log('GameCanvas: '+String(data));
          }
            this.data += data+"\n";
      }
    },

    run:function(){
        this.console.log("Starting mainLoop().");
        this.mainLoop();
  },

    mainLoop: function(){
        // Fill Background
        this.canvas.context.fillStyle = this.canvas.backgroundColor;
        this.canvas.context.fillRect(0,0,this.canvas.width,this.canvas.height);

        //Loop through objects
        for(var obj in this.objects){
            try{
                this.objects[obj].draw(this);
            }
            catch(err){
                this.console.log("Object "+this.objects[obj].name+":"+obj+" throws error:\n"+err);
                if(this.objects[obj].criticalObj){
                    this.console.error("Critical Object "+this.objects[obj].name+":"+obj+" not drawn. Halting mainLoop().");
                    this.animation.halt = true;
                }
            }
        }

        // Looping call
        if(!this.animation.halt){
          this.animation.requestAnimationFrame.call(
            window, // Call function in context of window

            // Call the mainLoop() function in the context of the current object
              this.mainLoop.bind(this)
          );
        }
        else{
            this.console.log("mainLoop() halted.");
            this.animation.halt = false;
        }
    }
};

GameCanvas.init("canvas");

var box = GameCanvas.baseObject();
box.name = "Box";
box.draw = function(GameCanvas){
    GameCanvas.canvas.context.fillStyle = "#00FF00";
    GameCanvas.canvas.context.fillRect(this.position.x,this.position.y,this.position.width,this.position.height);
};
box.position.width = 50;
box.position.height = 50;
box.position.x = 10;
box.position.y = 10;

GameCanvas.addObject(box);
GameCanvas.run();