The MSC offset used by a window is adjusted as the window moves
between screens, and between shown/unshown. The value shouldn't
matter, but it's helpful for debugging to have window MSC values be
the same as the CRTC MSC at first.
This patch introduces a unique CRTC value so that Present can detect
the first time a window is a PresentPixmap destination and set the MSC
offset to zero, rather than using the fake MSC value as the previous
window MSC.
Signed-off-by: Keith Packard <keithp@keithp.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
627bce8089