Compositing issues with 30-bit RGB visuals

Kai-Uwe Behrmann ku.b at
Mon Oct 17 23:41:45 PDT 2011

I am not sure where to start and seek for input on a problem with KWin and 
Compiz. They show very similiar wrong rendering of borders, shadows and 
the logout screens.

In compiz is a RGBA buffer used to contruct window borders and shadows:
/* all pixmaps are ARGB32 */
     format = XRenderFindStandardFormat (xdisplay, PictStandardARGB32);

A sreenshot suggests that the 8-bit buffers are blended as is into the 
30-bit visuals. What is the correct way to blend in the final frame buffer 
image with XRenderComposite()?

As a side note, the window contents are almost fine with the exception of 
FF and GTK2 drawing areas.

kind regards
Kai-Uwe Behrmann
developing for colour management +

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