[Webkit-unassigned] [Bug 99669] hover, layout and scrolling super slow

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=99669





--- Comment #6 from Allan Sandfeld Jensen <allan.jensen at digia.com>  2012-10-21 11:57:35 PST ---
I don't know what you consider a quad tree, but I have been working on designing an interval tree solution, and simply search and order the interval tree based on the longest dimension (usually height). Since a typical layout will have close to full width elements, making x-ordering much less useful.

An interval tree has O(log(n)+k) run-time, where k is the number of results, and it only uses O(n) memory. The problem with it though is that it takes at least O(n*log(n)^2) to build, and probably will take O(n^2) to build in a low overhead fashion. So part of such solution will be a heuristic for when to build the tree, so it doesn't get build when it isn't needed or when the content is changing fast.

Of course before we do that, please make sure you are throttleing mouse-events, there is no reason to do more than 60 per second, but a mouse often send 300 updates each second. And the idea about only doing a mouse over at the end sounds like a good idea, or alternatively, only send them at a lower pace.

All this shouldn't be that big a problem though. Browsers has been doing these hit tests forever on every single mouse move event. If it gets that slow now, something else is likely to be wrong.

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