Driver may change screen pixmaps after page flipping that would then
make damage lose track of the root pixmap.
Using root window for shadow damages fixes the problem because
SetWindowPixmap is implemented in shadow code.
Signed-off-by: Pauli Nieminen <pauli.nieminen@linux.intel.com>
Reviewed-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Keith Packard <keithp@keithp.com>