Effects currently modify the matrices by reading back the uniform
values from the shader they assume will be used to paint the window,
set new values for the uniforms, call paintWindow(), and then restore
the uniforms to their previous values.
This is both slow and unreliable, and will not work with dynamically
generated shaders.
This patch solves the problem by putting the matrices in
WindowPaintData and making it the responsibility of the paintWindow()
implementation to set the uniforms.
d2cb9f9bf6