function Display(canvas) {
   var self = this;
   
	self.canvas     = canvas;
	self.context    = undefined;
	self.framerate  = 100;
	self.numFrames  = 0;
	self.paused     = true;
	self.nextRedraw = 0;
	self.scale      = 1;
	self.listeners  = {};
	self.draw = {
   	continuous : false,
	   info   : false
	};

	self.info      = {
	   fps               : 0,
	   lastFrameTime     : 0,
	   runningFrameTime  : 0
   };
	
	self.init = function(){
		if(!self.canvas.getContext){
         self.error("No Context");
			return;
		}

		self.context = self.canvas.getContext( "2d" );
		self.context.scale(self.scale,self.scale);
		
		self.width = canvas.width / self.scale;
		self.height = canvas.height / self.scale;
		
      self.canvas.onmousedown = function(evt) {self.fireEvent('mouseDown',evt);return false;};
      self.canvas.onmouseup   = function(evt) {self.fireEvent('mouseUp',evt);return false;};
      self.canvas.onmouseover = function(evt) {self.fireEvent('mouseOver',evt)};
      self.canvas.onmousemove = function(evt) {self.fireEvent('mouseMove',evt)};
      
      window.requestAnimFrame = window.requestAnimationFrame       || 
         window.webkitRequestAnimationFrame || 
         window.mozRequestAnimationFrame    || 
         window.oRequestAnimationFrame      || 
         window.msRequestAnimationFrame;

      self.addListener('draw', self);
      self.addListener('afterDraw', self);
      self.addListener('newFrame', self);
		self.main();
	};
	
	self.addListener = function(eventName, object) {
	   if (!self.listeners[eventName]) {
	      self.listeners[eventName] = [];
	   }
	   self.listeners[eventName].push(object);
	}
	self.fireEvent = function(eventName,evt) {
	   if (self.listeners[eventName] && self.listeners[eventName].length > 0) {
         var eventMethod = "on" + eventName.substr(0,1).toUpperCase() + eventName.substr(1);
	      for (var i = 0; i < self.listeners[eventName].length; i++) {
	         if (self.listeners[eventName][i][eventMethod]) {
	            self.listeners[eventName][i][eventMethod].call(self.listeners[eventName][i],evt,self);
	         }
	      }
	   }
	}

	self.main = function(){
	   if (!self.paused) {
   		self.nextFrame();
	   }
	   if (window.requestAnimFrame) {
         window.requestAnimFrame(function(){ self.main(); });
      } else {
         self.nextRedraw = setTimeout( function(){ self.main(); }, 1000/self.framerate );
      }
	};
	
	self.nextFrame = function() {
	   self.fireEvent('newFrame');
	   self.fireEvent('beforeUpdate');
	   self.fireEvent('update');
	   self.fireEvent('afterUpdate');
	   self.fireEvent('beforeDraw');
	   self.fireEvent('draw');
	   self.fireEvent('afterDraw');
	}
	
	self.error = function (msg) {
	   self.fireEvent('error', { text : msg });
   };
	
	self.getFps = function() {
	   return (1000/self.info.runningFrameTime).toFixed(1);
	};
	
	self.onDraw = function(){
      self.tick();
	};
	self.onAfterDraw = function() {
	   if (self.draw.info) {
	      self.drawStats();
	   }
	}
   self.drawStats = function() {
      self.fillStyle("white");
      self.drawText("FPS : " + self.getFps(), new Point(10, self.height-10),80);  
   };
   self.onNewFrame = function() {
	   if (!self.draw.continuous) {
         self.clear();
      }
   }

   self.drawLine = function(startPoint, endPoint) {
		self.context.beginPath();
		self.context.moveTo(startPoint.x,startPoint.y);
		self.context.lineTo(endPoint.x, endPoint.y);
		self.context.stroke();
   }
   
   self.drawText = function(txt,point,width){
      self.context.fillText(txt, point.x, point.y, width);
   }
   
   self.drawCircle = function(point, radius) {
      self.context.beginPath();
      self.context.arc(point.x, point.y, radius, 0, Math.PI*2); 
      self.context.closePath();
      self.context.fill();
   }
   self.fillStyle = function(fill) { self.context.fillStyle = fill; }
   self.strokeStyle = function(fill) { self.context.strokeStyle = fill; }
   
	self.tick = function() {
	   self.numFrames++;
	   if (!self.info.lastFrameTime) {
	      self.info.lastFrameTime = new Date().getTime();
	   } else {
	      var now = new Date().getTime();
	      var timeToDraw = now - self.info.lastFrameTime;
	      self.info.runningFrameTime = self.info.runningFrameTime * .8 + timeToDraw * .2;
	      self.info.lastFrameTime = now;
	   }
	};
	
	self.clear = function() {
      self.context.clearRect( 0, 0, self.width, self.height);
	};
	self.start        = function() { self.paused = false;       };
	self.stop         = function() { self.paused = true;        };
	self.togglePause  = function() { self.paused = !self.paused;};
	self.unpause      = self.start;
	self.pause        = self.stop;
	self.step         = function() { self.stop(); self.nextFrame(); };
};