[cairo] Road to 1.10

[Emmanuele Bassi]

On Mon, 2009-02-16 at 10:06 +0000, Chris Wilson wrote:

> On a more wider topic, having played with wayland and creating a
> cairo-based compositor, we sorely lack the ability to use a
> non-premultiplied source (such as an OpenGL window, or SDL surface as
> above). CAIRO_FORMAT_ARGB32_NON_PREMULTIPLIED_SOURCE - hideous, but
> fairly trivial to handle in a shader. (Slightly more work to add the
> extra code paths to pixman though!)

one of the hits we get when using Cairo in Clutter comes from the
unpremultiplication of the alpha channel when uploading an image surface
into a GL texture. it's a one-off operation, but done for a lot of
textures, and if the textures are changing their size (e.g. during an
animation involving width/height properties) then it causes performance
issues -- on top of the usual performance implications of using an image
surface.

we tried using shaders as well:

  http://bugzilla.openedhand.com/show_bug.cgi?id=1184

and the results are not entirely encouraging. just a FYI.

ciao,
 Emmanuele.

-- 
Emmanuele Bassi, Intel Open Source Technology Center