sna: Always readback shadow damage after replacing the buffer

Instead track what we explicitly want to discard for the next operation,
so that we don't have to copy back the whole buffer if we have to
replace the shadow and intend to overwrite it all.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 1 insertions, 0 deletions

diff --git a/src/sna/sna.h b/src/sna/sna.h
index 76869444..1985ad84 100644
--- a/src/sna/sna.h
+++ b/src/sna/sna.h
@@ -290,6 +290,7 @@ struct sna {
 
 		int max_crtc_width, max_crtc_height;
 		RegionRec shadow_region;
+		RegionRec shadow_cancel;
 		struct list shadow_crtc;
 		bool shadow_dirty;