function Mask()
{
	this._bgMask;
	this._maskDiv;	
	
	//+----------------------------------------------------------------------------
	//	Functions:		getoffset
	//	Description:	计算当前对象的位置
	//-----------------------------------------------------------------------------				
	this.getoffset = function(e)
	{	 		 
		var t=0;
		var l=0;
		var isRight = 0;
		try{
			t=e.offsetTop;
			l=e.offsetLeft;									
		 	while(e=e.offsetParent)
		 	{
		  		t+=e.offsetTop;
		  		l+=e.offsetLeft;
		 	}
			isRight = 1;
		}catch(e)
		{
			
		}
	 	var rec = {};
	 	rec["top"]  = t;
	 	rec["left"] = l;
	 	return rec
	}
	
//+----------------------------------------------------------------------------
//	Functions:		initMask
//	Description:	初始化蒙层
//-----------------------------------------------------------------------------	
	this.initMask  = function()
	{
		var obj = $("body");
		var _offset = obj.offset();
		this._bgMask = $("<iframe marginheight='0px' marginwidth='0px' scrolling='no' frameborder='0' style='position:absolute;'></iframe>");
		$("body").append(this._bgMask);
		this._maskDiv = $("<div style='position:absolute;display:none;width:100%;opacity:0.8;" +
		"height:100%;z-index:-1;left:0;top:0;filter:progid:DXImageTransform.Microsoft.Alpha(style=0,opacity=0);" +
		"background:#FFFFFF'><div>");
		$("body").append(this._maskDiv);
		
		this._bgMask.css({"position":"absolute","visibility":"inherit","filter":"progid:DXImageTransform.Microsoft.Alpha(style=0,opacity=0)","z-Index":"0","top":_offset["top"],"left":_offset["left"],"width":obj.width(),"height":obj.height(),"opacity":0.1});
		this._bgMask.hide();		
		this._maskDiv.css({"position":"absolute","z-index":-1,"filter":"progid:DXImageTransform.Microsoft.Alpha(style=0,opacity=0)","top":_offset["top"],"left":_offset["left"],"width":obj.width(),"height":obj.height(),"opacity":0.1});
		this._maskDiv.hide();		
	}	
//+----------------------------------------------------------------------------
//	Functions:		showMask
//	Description:	显示蒙层
//-----------------------------------------------------------------------------	
	this.showMask = function(_left,_top,_width,_height)
	{		
		if(this._bgMask == null)
			this.initMask();		
		this._bgMask.css({"z-index":1});
		this._bgMask.css({"top":_top,"left":_left,"width":_width,"height":_height});
	    this._bgMask.show();
		this._maskDiv.css({"z-index":2});
	    this._maskDiv.show();	    
	}

//+----------------------------------------------------------------------------
//	Functions:		showAllMask
//	Description:	显示所有蒙层
//-----------------------------------------------------------------------------	
	this.showAllMask = function()
	{		
		this.showMask(0,0,$("body").width(),$("body").height());	    
	}
//+----------------------------------------------------------------------------
//	Functions:		hideMask
//	Description:	隐藏蒙层
//-----------------------------------------------------------------------------	
	this.hideMask = function()
	{
		if(this._bgMask == null)
			this.initMask();
		this._bgMask.css({"z-index":-2});
	    this._bgMask.hide();
		this._maskDiv.css({"z-index":-1});
	    this._maskDiv.hide();	   
	}
}