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canvas模拟hover事件

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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Untitled Document</title>
<style>
html,body{ margin:0; padding:0;}
</style>
</head>

<body>
<canvas id="cvs" width="300" height="300" style="border:1px solid #333;">你的浏览器不支持canvas，狗日的IE。</canvas>
<div id="log"></div>
<script>
var cvs = document.getElementById("cvs");
var ctx = cvs.getContext('2d');
if(ctx){
	var objs = [];
	var CCircle = function(){
		this.type = 'circle';
		this.x = 0;
		this.y = 0;
		this.radius = 0;
		this.isHover = false;
		this.color = '#000';
	};
	var Draw = function(){
		ctx.clearRect(0,0,cvs.width,cvs.height);
		for(var i=0;i<objs.length;i++){
			if(objs[i].type='circle'){
				ctx.beginPath();
				ctx.lineWidth = 2;
				ctx.strokeStyle = objs[i].color;
				ctx.arc(objs[i].x,objs[i].y,objs[i].radius,0,Math.PI*2,false);
				ctx.stroke();
				ctx.closePath();
			}
		}
	}// end function
	
	for(var i=0;i<100;i++){
		var c = new CCircle();
		c.x = (Math.random()*300)|0;
		c.y = (Math.random()*300)|0;
		c.radius = 10;
		c.hover = function(){
			this.color = "#f00";
			Draw();	
		}
		c.out = function(){
			this.color = "#000";
			Draw();	
		}
		objs.push(c);
	}// end for
	Draw();
	cvs.onmousemove = function(e){
		var hasHover = false;
		for(var i=objs.length-1;i>-1;i--){
			var c = objs[i];
			if(((e.clientX-c.x)*(e.clientX-c.x)+(e.clientY-c.y)*(e.clientY-c.y)<=c.radius*c.radius) && (!hasHover)){
				c.isHover = true;
				hasHover = true;
				c.hover && c.hover();
			}else{
				if(c.isHover){
					c.isHover = false;
					c.out && c.out();
				}
			}//end if
		}// end for
	}// end function
}
</script>
</body>
</html>
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