text and compositing

[Keith Packard]

Around 11 o'clock on Apr 23, Jon Smirl wrote:

> Suppose xserver is transforming my app window into a trapezoid or some
> other odd shape. Does my app paint into the pbuffer and then xserver
> applies the transform, or does xserver apply the transform while my app is
> painting into the pbuffer? The second case would yield a non-rectangluar
> image which would be framed by a transparent area.

X protocol semantics require that the pbuffer be drawn with an identity 
transform; the results of core rendering are exactly specified and visible 
(through GetImage).

> This makes a different in font generation. In the first case the app puts the
> bitmap of the font into the pbuffer and then the pbuffer is transformed. This
> distorts the font. In the second case the font could be generated with the
> correct aliasing for the transformed buffer.

Yup.  Transformed applications using X rendering requests are going to 
look sloppy on the screen.  We'll obviously want to build some migration 
mechanism to move rendering to a system which isn't tied to the X pixel 
coordinate space.  I'm hoping that we'll be able to push the 
transformation into the application through cairo/GL and make things look 
sharp and clean.

-keith


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