>> Perhaps it just needs a bit of minor refactoring?
>>
>> Still keep offset, but simplify it to use other plugins (that you
>> could use separately if you only wanted the left position of an
>> element for instance):
>>
>> jQuery.fn.offset = function(refElem) {
>> var elem = this[0];
>> return {
>> left: this.realLeft() - jQuery(refElem).realLeft(),
>> top: this.realTop() - jQuery(refElem).realTop(), ....etc
>> }
>> }
>
> With an approach like this it would be even slower since it
> would have to query the DOM all over again just to get the
> left and then the top.
> Perhaps separating out the scroll offsets into its own method
> would be worth while. Getting the scroll offsets is very expensive
> since it can't just rely on offsetParent.
Requests for these properties definitely need to be "batched"; it's too
expensive to make successive calls for the same element. Yesterday I was
thinking the best approach was to just grab it all and return a single
object with all the properties the way dimensions .offset() does now, but
that could be wasteful when some of them are expensive and unneeded. Luke
Lutman suggested passing an array into .attr() in the "How to get $.css"
thread, that might be a tactic worth exploring because you could get just
the stuff the user wanted but have the economy of doing the expensive
operations once.
The approach I proposed a while back was to first see if the standard style
interfaces returned measures with "px"; if so use them. If not (mostly the
IE case I think) use the jQuery.swap trick to zero out the stuff you're not
interested in and measure what's left. That's the trick already used for
height and width in .attr(). Margins are a bit tougher, it may be possible
to find them by wrapping the measured element in a div and getting the
clientWidth of the wrapper.
At the time I desperately needed a solution the dimensions plugin wasn't
around, and I haven't had the need for it since then so I haven't put it
through any testing. It seems like the problem comes up frequently enough
and a bulletproof solution is tough, so it definitely makes sense to have
the plugin. This might even go in the core once it's all shaken out.
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