//跟within差不多，不过考虑到滚动条，也许是在元素上面，但不是直接在上面，因为滚动条也许已经使元素不可见了
withinIncludingScrolloffsets: function(element, x, y) {
var offsetcache = this.realOffset(element);
this.xcomp = x + offsetcache[0] - this.deltaX;
this.ycomp = y + offsetcache[1] - this.deltaY;
this.offset = this.cumulativeOffset(element);
return (this.ycomp >= this.offset[1] &&
this.ycomp < this.offset[1] + element.offsetHeight &&
this.xcomp >= this.offset[0] &&
this.xcomp < this.offset[0] + element.offsetWidth);
},
// within must be called directly before
//在调用这个方法前，必须先调用within，返回在with指定的位置在水平或者垂直方向上占用的百分比
overlap: function(mode, element) {
if (!mode) return 0;
if (mode == 'vertical')
return ((this.offset[1] + element.offsetHeight) - this.ycomp) /
element.offsetHeight;
if (mode == 'horizontal')
return ((this.offset[0] + element.offsetWidth) - this.xcomp) /
element.offsetWidth;
},
//返回元素相对页面的真实位置
page: function(forElement) {
var valueT = 0, valueL = 0;
var element = forElement;
do {
valueT += element.offsetTop || 0;
valueL += element.offsetLeft || 0;
// Safari fix
if (element.offsetParent==document.body)
if (Element.getStyle(element,'position')=='absolute') break;
} while (element = element.offsetParent);
element = forElement;
do {
if (!window.opera || element.tagName=='BODY') {
valueT -= element.scrollTop || 0;
valueL -= element.scrollLeft || 0;
}
} while (element = element.parentNode);
return [valueL, valueT];
},
//设置target为source的位置，大小
clone: function(source, target) {
var options = Object.extend({
setLeft: true,
setTop: true,
setWidth: true,
setHeight: true,
offsetTop: 0,
offsetLeft: 0
}, arguments[2] || {})
// find page position of source
source = $(source);
var p = Position.page(source);
// find coordinate system to use
target = $(target);
var delta = [0, 0];
var parent = null;
// delta [0,0] will do fine with position: fixed elements,
// position:absolute needs offsetParent deltas
if (Element.getStyle(target,'position') == 'absolute') {
parent = Position.offsetParent(target);
delta = Position.page(parent);
}
// correct by body offsets (fixes Safari)
if (parent == document.body) {
delta[0] -= document.body.offsetLeft;
delta[1] -= document.body.offsetTop;
}
// set position
if(options.setLeft) target.style.left = (p[0] - delta[0] + options.offsetLeft) + 'px';
if(options.setTop) target.style.top = (p[1] - delta[1] + options.offsetTop) + 'px';
if(options.setWidth) target.style.width = source.offsetWidth + 'px';
if(options.setHeight) target.style.height = source.offsetHeight + 'px';
},
//将element的position设置为absolute的模式
absolutize: function(element) {
element = $(element);
if (element.style.position == 'absolute') return;
Position.prepare();