[Webkit-unassigned] [Bug 39582] [Gtk] very slow page scrolling on big -webkit-box-shadow areas

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=39582


Alejandro G. Castro <alex at igalia.com> changed:

           What    |Removed                     |Added
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                 CC|                            |alex at igalia.com




--- Comment #1 from Alejandro G. Castro <alex at igalia.com>  2010-05-24 02:03:40 PST ---
(In reply to comment #0)
>
> [...]
>
> It is neccessary to check sideeffects for inset shadows.
> 
> I don't have the time to implement it atm :-( and hope that someone else could try it.

Hi krit, very nice analysis, I've spent sometime checking the problem after the bug 38915 appeared,  I'm not very experienced about this topics but my conclusions after checking it a little bit are:

   - Avoid getters/setters and use arrays directly, I measured 20% win easy patch, but not much real difference in the scrolling
   - Add a skip region, we do not want to blur all the image when we want a shadow, not sure if this is happening now
   - Use alpha-only for shadows instead of all the channels?

I have time checking if we can fix this, so I can try it, do you think last point make senses? I've checked the information in the filters page (http://www.w3.org/TR/SVG/filters.html#feGaussianBlur) and if I understand correctly in most cases alpha only is enough.

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