When the crtc transformation changes, the entire crtc must be repainted.
This was being done by clearing the shadow and then painting the rectangle
containing the screen image; the clear being required as the screen image
may not fill the crtc. When changing the transform rapidly, this leads to
flashing. Eliminate the clear by painting the entire crtc instead of just
the screen rectangle.
(cherry picked fom commit 5394b7e662)
Signed-off-by: Keith Packard <keithp@keithp.com>
a86dd529e9