// by zhangxinxu welcome to visit my personal website http://www.zhangxinxu.com/

// zxx.drag v1.0 2010-03-23 å…ƒç´ çš„æ‹–æ‹½å®žçŽ°

var params = {

	left: 0,

	top: 0,

	currentX: 0,

	currentY: 0,

	flag: false

};

//获取相关CSS属性

var getCss = function(o,key){

	return o.currentStyle? o.currentStyle[key] : document.defaultView.getComputedStyle(o,false)[key];

};

//拖拽的实现

var startDrag = function(bar, target, callback){

	if(getCss(target, "left") !== "auto"){

		params.left = getCss(target, "left");

	}

	if(getCss(target, "top") !== "auto"){

		params.top = getCss(target, "top");

	}

	//o是移动对象

	bar.onmousedown = function(event){

		params.flag = true;

		if(!event){

			event = window.event;

			//防止IE文字选中

			bar.onselectstart = function(){

				return false;

			}

		}

		var e = event;

		params.currentX = e.clientX;

		params.currentY = e.clientY;

	};

	document.onmouseup = function(){

		params.flag = false;

		if(getCss(target, "left") !== "auto"){

			params.left = getCss(target, "left");

		}

		if(getCss(target, "top") !== "auto"){

			params.top = getCss(target, "top");

		}

	};

	document.onmousemove = function(event){

		var e = event ? event: window.event;

		if(params.flag){

			var nowX = e.clientX, nowY = e.clientY;

			var disX = nowX - params.currentX, disY = nowY - params.currentY;

			target.style.left = parseInt(params.left) + disX + "px";

			target.style.top = parseInt(params.top) + disY + "px";

		}

		if (typeof callback == "function") {

			callback(parseInt(params.left) + disX, parseInt(params.top) + disY);

		}

	}

};