[Bug 28670] some 2D apps way too slow, fast with noaccel (regression)

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=28670

--- Comment #6 from Alex Deucher <agd5f at yahoo.com> 2010-06-22 13:20:50 PDT ---
(In reply to comment #5)
> Thanks for the reference. I would never have figured that out. When setting
> CAIRO_EXTEND_PAD, things are fast even with the latest git driver.
> 

Firefox should use the same fix.

> I don't actually care about the behaviour at the border, since it always is
> outside the screen. Would you reccommend to render the image to RGBA instead of
> RGB, to increase the chance to get an accelerated transformation also from
> other hardware?

Most 3D hardware has the same limitation; however, I'm not sure all hw drivers
check for the case properly.  Ideally the render spec would not have required
alpha=0 when sampling outside the source region.

> 
> We really don't want to hit such a slower-than-software fallback. It makes
> MyPaint unusable, while pure software rendering would still be very fast.

Software fallbacks are almost always slower then pure software rendering since
you end up ping-ponging between hw and sw rendering.  To be fast you need
either all hw or all sw.

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