Don't commit same buffer multiple times

In Qt we call flush() when we think the window might need to be
updated. It is also possible to trigger a flush while painting.

Two fixes:

1) If there are attempted flushes between beginPaint() and endPaint,
queue them up, and do them in endPaint().

2) Make sure we only commit the buffer once: after that the
compositor owns the buffer, and it can repaint on its own.

Change-Id: Ibf61068fa95760eb67dbc0b1d0534854114ea528
Reviewed-by: Johan Helsing <johan.helsing@qt.io>

1 files changed, 2 insertions, 0 deletions

diff --git a/src/client/qwaylandshmbackingstore_p.h b/src/client/qwaylandshmbackingstore_p.h
index cb66288fc..88ecfc5ec 100644
--- a/src/client/qwaylandshmbackingstore_p.h
+++ b/src/client/qwaylandshmbackingstore_p.h
@@ -120,6 +120,8 @@ private:
     QWaylandShmBuffer *mFrontBuffer = nullptr;
     QWaylandShmBuffer *mBackBuffer = nullptr;
     bool mPainting = false;
+    bool mPendingFlush = false;
+    QRegion mPendingRegion;
     QMutex mMutex;
 
     QSize mRequestedSize;