javascript控件开发之可见控件(2)
   经过上一篇，我们开始了可见控件的实现，考虑控件会用到键盘及鼠标，因此在上一篇控件com.ui.window基础上，我们再添加事件的处理，添加函数_sysEvent及_clearEvent

	    /**
	     * 系统事件.
	     */
        _sysEvent:function(){
        	var _this = this;
        	/**
        	 * 事件列表
        	 */
        	this._eventList = {
                mouseup:function(ev) {
                	var ev = ev || window.event;
        		    _this._docMouseUp(ev);
        	    },
        	    mousedown:function(ev) {
        	    	var ev = ev || window.event;
        	    	_this._docMouseDown(ev);
        	    },
        	    mousemove:function(ev) {
        	    	var ev = ev || window.event;
        	    	_this._docMouseMove(ev);
        	    },
        	    keyup:function(ev) {
        	    	var ev = ev || window.event;
        	    	return _this._docKeyUp(ev);
        	    },
        	    keydown:function(ev) {
        	    	var ev = ev || window.event;
        	    	return _this._docKeyDown(ev);
        	    },
        	    mousewheel:function(ev) {
        	    	var ev = ev || window.event;
        	    	var re = _this._docMouseWheel(ev);
        	    	if(re) {
          	    		evt = ev || window.event;     
        	    		if(evt.preventDefault) {     
        	    			// Firefox       
        	    		    evt.preventDefault();       
        	    		    evt.stopPropagation();     
        	    		} else {       
        	    			// IE       
        	    		    evt.cancelBubble=true;       
        	    		    evt.returnValue = false;
        	    		}
        	    		return false
        	    	}
        	    	return true;
        	    }
        	};
	    	if (window.addEventListener) {
                // 其它浏览器的事件代码: Mozilla, Netscape, Firefox
                // 添加的事件的顺序即执行顺序
                // 注意用 addEventListener 添加带on的事件，不用加on
                document.addEventListener("mousedown", 
                    this._eventList.mousedown, false);
                document.addEventListener("mouseup", 
                    this._eventList.mouseup, false);
                document.addEventListener("mousemove", 
                    this._eventList.mousemove, false);
                document.addEventListener("keydown", 
                    this._eventList.keydown, false);
                document.addEventListener("keyup", 
                    this._eventList.keyup, false);
                document.addEventListener('DOMMouseScroll',
                    this._eventList.mousewheel,false);
                //chrome
                document.addEventListener('mousewheel',
                    this._eventList.mousewheel,false); 
            } else {
                // IE 的事件代码 在原先事件上添加 add 方法
                document.attachEvent("onmousedown", this._eventList.mousedown); 
                document.attachEvent("onmouseup", this._eventList.mouseup);
                document.attachEvent("onmousemove", this._eventList.mousemove);
                document.attachEvent("onkeydown", this._eventList.keydown);
                document.attachEvent("onkeyup", this._eventList.keyup);
                document.attachEvent("onmousewheel", this._eventList.mousewheel);
            }     	
        },
        /**
         * 清除系统事件.
         */		 
	    clearEvent:function() {
	    	if (window.removeEventListener) {
                // 其它浏览器的事件代码: Mozilla, Netscape, Firefox
                // 添加的事件的顺序即执行顺序
                // 注意用 addEventListener 添加带on的事件，不用加on
                document.removeEventListener("mousedown",
                    this._eventList.mousedown, false);
                document.removeEventListener("mouseup", 
                    this._eventList.mouseup, false);
                document.removeEventListener("mousemove", 
                    this._eventList.mousemove, false);
                document.removeEventListener("keydown", 
                    this._eventList.keydown, false);
                document.removeEventListener("keyup", 
                    this._even