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

Tue Dec 13 18:14:57 PST 2011

https://bugs.freedesktop.org/show_bug.cgi?id=43397

--- Comment #18 from Bill Spitzak <spitzak at gmail.com> 2011-12-13 18:14:57 PST ---
I believe the proposed EXTEND_ANY is the same as "WHATEVER_IS_FASTEST".

Like several others, I do believe Cairo is doing the wrong thing. You are
assuming that EXTEND_NONE is fastest, which is false for everything except
XRender.

This means that whatever work Cairo did to figure out that "extend does not
matter" is wasted, because the backend has to re-run these tests whenever it
gets EXTEND_NONE in order to realize it can switch to a faster one.

Adding EXTEND_ANY will fix this, because the information that the front end
figured out that extend did not matter is preserved.

But it might make a lot more sense to leave extend unchanged and have the
backends figure out if it matters. In many cases (especially when EXTEND_PAD is
used on modern 3D hardware) it is actually pointless to do the test, because it
cannot be made faster by switching in any way, so the time spent doing the test
is wasted. Only a backend can know this answer.

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