[cairo-bugs] [Bug 43397] EXTEND_NONE is used instead of EXTEND_PAD when src sample area is entirely within the surface

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Tue Dec 13 08:59:18 PST 2011


--- Comment #11 from Michel Dänzer <michel at daenzer.net> 2011-12-13 08:59:18 PST ---
(In reply to comment #10)
> There might be 3D hardware that has to jump through a lot more hoops to
> implement render semantics for REPEAT_PAD compared to REPEAT_NONE.

Do you have any evidence to substantiate that?

> I already pointed out that it's the job of render to figure out a feature that
> makes Cairo say EXTEND_ANY or fix it their way. Which is the crux for why this
> is not a bug in Cairo. Cairo cannot know which is the extend mode it should use
> if the extend mode doesn't matter.

But this bug is isn't about EXTEND_ANY. It's about the app asking for
EXTEND_PAD but Cairo using something else.

> And the Xrender spec is very clear that the default value is None. See
> http://www.x.org/releases/current/doc/renderproto/renderproto.txt for details.

Yes, this is one unfortunate result of the RENDER extension being designed with
little consideration for how 3D hardware works.

> I can understand that it makes your life as an X server or driver developer
> more complicated,

As I pointed out in comment #5, it also incurs unnecessary overhead, both in
Cairo and in the X server.

> Or feel free to propose a solution inside Cairo that does not break backwards
> compatibility with systems where NONE is faster than PAD.

Such systems must be using old / buggy X servers / drivers, so it should be
possible to only enable this overhead when it's really necessary.

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