[cairo-bugs] [Bug 81699] Segfault sweep_line_delete on video playback (2)

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=81699

--- Comment #6 from Massimo <sixtysix at inwind.it> ---
(In reply to comment #5)
> Hi Massimo. Looks like you last patch with only 3 lines of code solved the
> problem!
> I applied here and no more segfault.
> How i don't understand and i know nothing about cairo, i don't know if what
> this patch do is the right thing or if is safe use it. All i know it is that
> it solved, i think.
>

To me it seems correct and safe, it only drops empty
boxes from the list of boxes to be tessellated. 

Empty boxes do not alter the insideness of any pixel
because if a ray from the pixel intersects the top edge
it also intersects the bottom edge, one from the left
and the other from the right, so it should be correct
for both (EVEN_ODD, WINDING) fill rules that cairo implements. 

OTOH these empty boxes are problematic as they possibly
lead to a segfault.

It is possible that there are better places to discard
these boxes.

> Should i mark as solved?

I'm not a cairo developer, but I'd say not until a fix
has been included in the official source tree. So people
experiencing the same problem can find a solution and report
shortcomings. 

There are already many duplicates in many 
distribution/application/library bugzilla

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