jQuery: test for CSS position: fixed support

support-posfixed.js

/* jQuery-based feature test for CSS position: fixed support.
Modified from Kangax's test (http://kangax.github.com/cft/#IS_POSITION_FIXED_SUPPORTED) in two ways: 1) uses jQuery API, 2) remove document.body dependency.
Method changes aside, the required workaround for dropping document.body use was to set scroll using window.scrollTo instead of body.scrollTop.

//Testing notes:
iOS4.3: false (expected)
iOS5: true (expected)
Chrome latest: true  (expected)
...more soon
*/

$.support.positionFixed = (function (){
	var contain = $( document.documentElement ),
		el = $( "<div style='position:fixed;top:100px;'>x</div>" ).appendTo( contain ),
		originalHeight = contain[ 0 ].style.height,
		w = window,
		result;
	
	contain.height( screen.height * 2 + "px" );

	w.scrollTo( 0, 100 );

	result = el[ 0 ].getBoundingClientRect().top === 100;

	contain.height( originalHeight );

	el.remove();

	w.scrollTo( 0, 0 );

	return result;
})();