[cairo] broken pixman bilinear filtering?

[Vladimir Vukicevic]

On 2/13/06, Bill Spitzak <spitzak at d2.com> wrote:
>
> Is this going to change XRender? That may be a bad idea. I have worked
> around this bug, and I assumme many other people have, in XRender, by
> adjusting the transformation before doing any scaling of images. If this
> is fixed in XRender it will actually break these fixed programs. Another
> alternative would be a test to tell if the implementation is the old or
> new one.
>
> Fixing Cairo or any other API that is not in common use yet is entirely
> appropriate, however.

So this is an interesting question.. I realize that fixing XRender
would cause breakage in the apps that work around this, but there
aren't that many apps that would be hit by this yet, either.  The
danger with not fixing it is that it will eventually make XRender
basically unusable by apps, and we'll be back to the same situation
where we were before XRender -- everyone using software fallbacks for
everything, because they can't trust XRender.  There was already one
such issue (the memory corruption caused by using a repeating picture)
that was fixed in the server.

In this particular case, one option is to keep the old code in, and
rename the bilinear filter #define to BILINEAR_BROKEN_DEPRECATED or
something, and add a new identifier for the "correct" bilinear
processing.  But again, I don't know what the situation is with
XRender development in the server, and what the potential would be to
get this fix out in a release in the short term.

  - Vlad