Offset setter for fixed position elements in Webkit. Fixes #8316.

src/offset.js

@@ -181,10 +181,10 @@ jQuery.offset = {
 			curOffset = curElem.offset(),
 			curCSSTop = jQuery.css( elem, "top" ),
 			curCSSLeft = jQuery.css( elem, "left" ),
-			calculatePosition = (position === "absolute" && jQuery.inArray('auto', [curCSSTop, curCSSLeft]) > -1),
+			calculatePosition = ((position === "absolute" || position === "fixed") && jQuery.inArray('auto', [curCSSTop, curCSSLeft]) > -1),
 			props = {}, curPosition = {}, curTop, curLeft;
 
-		// need to be able to calculate position if either top or left is auto and position is absolute
+		// need to be able to calculate position if either top or left is auto and position is either absolute or fixed
 		if ( calculatePosition ) {
 			curPosition = curElem.position();
 		}

test/unit/offset.js

@@ -422,6 +422,21 @@ test("offsetParent", function(){
 	equals( div[1], jQuery("#nothiddendiv")[0], "The div is the offsetParent." );
 });
 
+testoffset("bug_8316", function( jQuery ){
+  expect(2);
+
+  var tests = [
+    { id:'#elem', top: 100, left: 100 }
+  ];
+
+  jQuery.each(tests, function(){
+    var el = jQuery(this.id);
+    el.offset({ top: this.top, left: this.left});
+    equals(Math.round(el.offset().top), this.top);
+    equals(Math.round(el.offset().left), this.left);
+  });
+});
+
 function testoffset(name, fn) {
 
 	test(name, function() {
@@ -447,7 +462,7 @@ function testoffset(name, fn) {
 	function loadFixture() {
 		var src = './data/offset/' + name + '.html?' + parseInt( Math.random()*1000, 10 ),
 			iframe = jQuery('<iframe />').css({
-				width: 500, height: 500, position: 'absolute', top: -600, left: -600, visiblity: 'hidden'
+				width: 500, height: 500, position: 'absolute', top: -600, left: -600, visibility: 'hidden'
 			}).appendTo('body')[0];
 		iframe.contentWindow.location = src;
 		return iframe;