Image2: EventsBuffer integration

[Olek Nowodziński]

The plugin should integrate CKEDITOR.tools.eventsBuffer to improve the performance of mousemove callback (Firefox, IE).

[Olek Nowodziński]

Created branch ​t/10837 with eventsBuffer while resizing.

The basic problem is that to keep UX at the high level, the maximum buffer interval for mousemove can be ~30ms. Otherwise the experience becomes choppy.

Such interval, however, makes eventsBuffer integration pointless because benefits (expressed by CPU load) are questionable and the code gets complicated. For example:

In Chrome a slight improvement can be observed:

In IE9 there's no improvement:

In IE8 there's a measurable drop of the load:

I'm leaving this ticket as something to be discussed.

[Piotrek Koszuliński]

I don't see a significant improvement too and, moreover, resizing works now smoothly even on IE9 on VM. Actually... it works there better than on Firefox running on my main OS.

Anyway, AFAIR it didn't work so well when I reported this issue. The current performance is good, so I'm removing a milestone, but we can keep this ticket if users will report us that something is wrong.

BTW. Avoid this kind of cache:

+        var $ = evt.data.$;
+
+        screenX = $.screenX;
+        screenY = $.screenY;

You use the variable twice, so you may lost more time on defining it than on accessing.