text and compositing

[Jon Smirl]

xserver implemented on top of OpenGL doesn't have the identity transform
requirement. Does the Cairo architecture for text allow text generation for a
transformed destination buffer? Does freetype support a 3D projection martix or
is it contrained to 2D? But now thinking about your answer that Cairo has no
wire protocol this would have to be implemented for text on the xlib protocol.

The font caching system will need to track the transformation matrix too.
Although non-distorted transformed glyphs could be reused at different scaling
factors (points).

--- Keith Packard <keithp at keithp.com> wrote:
> 
> 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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=====
Jon Smirl
jonsmirl at yahoo.com


	
		
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