[Webkit-unassigned] [Bug 50869] [cairo] Rendering a lot of arcs on top of each other causes time outs in some tests

bugzilla-daemon at webkit.org bugzilla-daemon at webkit.org
Fri Jan 7 04:24:25 PST 2011


https://bugs.webkit.org/show_bug.cgi?id=50869





--- Comment #5 from Alejandro G. Castro <alex at igalia.com>  2011-01-07 04:24:25 PST ---
(In reply to comment #4)
> (In reply to comment #3)
> > Are we guaranteed that this will produce the proper rendering? What if the stroke is partially opaque? Is this hitting some weird slow path in Cairo?
> 
> Hrm, good point, it would not be accurate with oppacity, we will have to sum it. I think chrome is doing actually something similar I assume it is very costly to render a lot (like millions) of huge arcs (18s just to render one arc) that are exactly the same one, it is true that cairo could do this instead of us.
> 

I've just checked that it does not matter the amount of arcs you add to the path one over the other for the opacity, I guess the opacity of the tint is just applied when stroking so you will have the same result if you draw one or 100, at least in cairo. I've also checked that other ports like skia or qt are applying similar solutions.

I like skia solution (it avoids the modff) but it seems slower for cairo, I'll try to check it.

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