var sch=0;
var ref_x=0;
var ref_y=0;
var c_y=0;

function mousedown(event) {
	//alert("mousedown");
	var e = window.event;
	sch=1;
	ref_x=e.pageX;
	ref_y=e.pageY;
	/*
	var a1=document.getElementById("abc1");
	a1.innerText="event.pageX="+ e.pageX+" "+"event.pageY="+e.pageY+" "+"event.clientX="+e.clientX+" "+"event.clientY="+e.clientY;
	a1.style.color = 'yellow';

	var a2=document.getElementById("abc2");
	a2.style.color = 'black';
	*/
}

function mouseup(event) {
	//alert("mouseup");
	var e = window.event;
	sch=0;
	c_y=0;
	
	/*
	var a1=document.getElementById("abc1");
	a1.style.color = 'black';


	var a2=document.getElementById("abc2");
	a2.innerText="event.pageX="+ e.pageX+" "+"event.pageY="+e.pageY+" "+"event.clientX="+e.clientX+" "+"event.clientY="+e.clientY;
	a2.style.color = 'red';
	*/
}

function mousemove(event){

	var e = window.event;
	
	//var a3=document.getElementById("abc3");
	//a3.style.color = 'blue';
	
	var mx = e.pageX || e.clientX + document.body.scrollLeft;
	// 计算鼠标指针的x轴距离
	var my = e.pageY || e.clientY + document.body.scrollTop;
	
	if(sch==1){
		if(e.pageY>ref_y){
			c_y = c_y + 1 //每次改变top
		}
		else{
			c_y = c_y - 1 //每次改变top
		}
		window.scrollTo(0, window.pageYOffset + c_y) //滚动到需要到位置
	}
	/*
	a3.innerText="c_y="+c_y+" "+"event.pageX="+ e.pageX+" "+"event.pageY="+e.pageY+" "+"event.clientX="+e.clientX+" "+"event.clientY="+e.clientY+" "+"event.mx="+mx+" "+"event.my="+my;
	*/
	// 计算鼠标指针的y轴距离
}
document.addEventListener("mousedown", mousedown);
document.addEventListener("mouseup", mouseup);
document.addEventListener("mousemove", mousemove);