jquery/src/offset.js

if ( "getBoundingClientRect" in document.documentElement )
	jQuery.fn.offset = function() {
		var elem = this[0];
		if ( !elem || !elem.ownerDocument ) return null;
		if ( elem === elem.ownerDocument.body ) return jQuery.offset.bodyOffset( elem );
		var box = elem.getBoundingClientRect(), doc = elem.ownerDocument, body = doc.body, docElem = doc.documentElement,
			clientTop = docElem.clientTop || body.clientTop || 0, clientLeft = docElem.clientLeft || body.clientLeft || 0,
			top  = box.top  + (self.pageYOffset || jQuery.support.boxModel && docElem.scrollTop  || body.scrollTop ) - clientTop,
			left = box.left + (self.pageXOffset || jQuery.support.boxModel && docElem.scrollLeft || body.scrollLeft) - clientLeft;
		return { top: top, left: left };
	};
else
	jQuery.fn.offset = function() {
		var elem = this[0];
		if ( !elem || !elem.ownerDocument ) return null;
		if ( elem === elem.ownerDocument.body ) return jQuery.offset.bodyOffset( elem );
		jQuery.offset.initialize();

		var offsetParent = elem.offsetParent, prevOffsetParent = elem,
			doc = elem.ownerDocument, computedStyle, docElem = doc.documentElement,
			body = doc.body, defaultView = doc.defaultView,
			prevComputedStyle = defaultView.getComputedStyle(elem, null),
			top = elem.offsetTop, left = elem.offsetLeft;

		while ( (elem = elem.parentNode) && elem !== body && elem !== docElem ) {
			if ( jQuery.offset.supportsFixedPosition && prevComputedStyle.position === "fixed" ) break;
			computedStyle = defaultView.getComputedStyle(elem, null);
			top -= elem.scrollTop, left -= elem.scrollLeft;
			if ( elem === offsetParent ) {
				top += elem.offsetTop, left += elem.offsetLeft;
				if ( jQuery.offset.doesNotAddBorder && !(jQuery.offset.doesAddBorderForTableAndCells && /^t(able|d|h)$/i.test(elem.tagName)) )
					top  += parseFloat( computedStyle.borderTopWidth  ) || 0,
					left += parseFloat( computedStyle.borderLeftWidth ) || 0;
				prevOffsetParent = offsetParent, offsetParent = elem.offsetParent;
			}
			if ( jQuery.offset.subtractsBorderForOverflowNotVisible && computedStyle.overflow !== "visible" )
				top  += parseFloat( computedStyle.borderTopWidth  ) || 0,
				left += parseFloat( computedStyle.borderLeftWidth ) || 0;
			prevComputedStyle = computedStyle;
		}

		if ( prevComputedStyle.position === "relative" || prevComputedStyle.position === "static" )
			top  += body.offsetTop,
			left += body.offsetLeft;

		if ( jQuery.offset.supportsFixedPosition && prevComputedStyle.position === "fixed" )
			top  += Math.max( docElem.scrollTop, body.scrollTop ),
			left += Math.max( docElem.scrollLeft, body.scrollLeft );

		return { top: top, left: left };
	};

jQuery.offset = {
	initialize: function() {
		var body = document.body, container = document.createElement('div'), innerDiv, checkDiv, table, td, bodyMarginTop = parseFloat( jQuery.curCSS(body, 'marginTop', true) ) || 0,
			html = '<div style="position:absolute;top:0;left:0;margin:0;border:5px solid #000;padding:0;width:1px;height:1px;"><div></div></div><table style="position:absolute;top:0;left:0;margin:0;border:5px solid #000;padding:0;width:1px;height:1px;" cellpadding="0" cellspacing="0"><tr><td></td></tr></table>';

		jQuery.extend( container.style, { position: 'absolute', top: 0, left: 0, margin: 0, border: 0, width: '1px', height: '1px', visibility: 'hidden' } );

		container.innerHTML = html;
		body.insertBefore( container, body.firstChild );
		innerDiv = container.firstChild, checkDiv = innerDiv.firstChild, td = innerDiv.nextSibling.firstChild.firstChild;

		this.doesNotAddBorder = (checkDiv.offsetTop !== 5);
		this.doesAddBorderForTableAndCells = (td.offsetTop === 5);

		checkDiv.style.position = 'fixed', checkDiv.style.top = '20px';
		this.supportsFixedPosition = (checkDiv.offsetTop === 20 || checkDiv.offsetTop === 15); // safari subtracts parent border width here which is 5px
		checkDiv.style.position = '', checkDiv.style.top = '';

		innerDiv.style.overflow = 'hidden', innerDiv.style.position = 'relative';
		this.subtractsBorderForOverflowNotVisible = (checkDiv.offsetTop === -5);

		this.doesNotIncludeMarginInBodyOffset = (body.offsetTop !== bodyMarginTop);

		body.removeChild( container );
		jQuery.offset.initialize = function(){};

		body = container = innerDiv = checkDiv = table = td = null;
	},

	bodyOffset: function(body) {
		jQuery.offset.initialize();
		var top = body.offsetTop, left = body.offsetLeft;
		if ( jQuery.offset.doesNotIncludeMarginInBodyOffset )
			top  += parseFloat( jQuery.curCSS(body, 'marginTop',  true) ) || 0,
			left += parseFloat( jQuery.curCSS(body, 'marginLeft', true) ) || 0;
		return { top: top, left: left };
	}
};


jQuery.fn.extend({
	position: function() {
		if ( !this[0] ) return null;

		var elem = this[0],

		// Get *real* offsetParent
		offsetParent = this.offsetParent(),

		// Get correct offsets
		offset       = this.offset(),
		parentOffset = /^body|html$/i.test(offsetParent[0].tagName) ? { top: 0, left: 0 } : offsetParent.offset();

		// Subtract element margins
		// note: when an element has margin: auto the offsetLeft and marginLeft
		// are the same in Safari causing offset.left to incorrectly be 0
		offset.top  -= parseFloat( jQuery.curCSS(elem, 'marginTop',  true) ) || 0;
		offset.left -= parseFloat( jQuery.curCSS(elem, 'marginLeft', true) ) || 0;

		// Add offsetParent borders
		parentOffset.top  += parseFloat( jQuery.curCSS(offsetParent[0], 'borderTopWidth',  true) ) || 0;
		parentOffset.left += parseFloat( jQuery.curCSS(offsetParent[0], 'borderLeftWidth', true) ) || 0;

		// Subtract the two offsets
		return {
			top:  offset.top  - parentOffset.top,
			left: offset.left - parentOffset.left
		};
	},

	offsetParent: function() {
		var offsetParent = this[0].offsetParent || document.body;
		while ( offsetParent && (!/^body|html$/i.test(offsetParent.tagName) && jQuery.css(offsetParent, 'position') === 'static') )
			offsetParent = offsetParent.offsetParent;
		return jQuery( offsetParent );
	}
});


// Create scrollLeft and scrollTop methods
jQuery.each( ['Left', 'Top'], function(i, name) {
	var method = 'scroll' + name;

	jQuery.fn[ method ] = function(val) {
		if ( !this[0] ) return null;

		if ( val !== undefined ) {
			// Set the scroll offset
			return this.each(function() {
				win = getWindow( this );

				win ?
					win.scrollTo(
						!i ? val : jQuery(win).scrollLeft(),
						 i ? val : jQuery(win).scrollTop()
					) :
					this[ method ] = val;
			});
		} else {
			var elem = this[0],
				win  = getWindow( elem );

			// Return the scroll offset
			return win && 'pageXOffset' in win ?
				win[ i ? 'pageYOffset' : 'pageXOffset' ] ||
					jQuery.support.boxModel && win.document.documentElement[ method ] ||
					win.document.body[ method ] :
				elem[ method ];
		}
	};

	function getWindow( elem ) {
		return ("scrollTo" in elem && elem.document) ? elem :
			(elem.nodeName === "#document") ? elem.defaultView || elem.parentWindow :
				false;
	}
});