Make it possible to discard currentBuffer of a view

This will be convenient if there is a view which copies the
currentBuffer to a cache and then wants to release the ref to the buffer

Change-Id: I0b7bbb4bc22c420fdf0d1af4bb1bbf0a4f888bc8

3 files changed, 13 insertions, 1 deletions

diff --git a/src/compositor/compositor_api/qwaylandview.cpp b/src/compositor/compositor_api/qwaylandview.cpp
index 90f182c5d..fa1371925 100644
--- a/src/compositor/compositor_api/qwaylandview.cpp
+++ b/src/compositor/compositor_api/qwaylandview.cpp
@@ -200,18 +200,27 @@ void QWaylandView::attach(const QWaylandBufferRef &ref, const QRegion &damage)
 bool QWaylandView::advance()
 {
     Q_D(QWaylandView);
-    if (d->currentBuffer == d->nextBuffer)
+    if (d->currentBuffer == d->nextBuffer && !d->forceAdvanceSucceed)
         return false;
 
     if (d->bufferLock)
         return false;
 
     QMutexLocker locker(&d->bufferMutex);
+    d->forceAdvanceSucceed = false;
     d->currentBuffer = d->nextBuffer;
     d->currentDamage = d->nextDamage;
     return true;
 }
 
+void QWaylandView::discardCurrentBuffer()
+{
+    Q_D(QWaylandView);
+    QMutexLocker locker(&d->bufferMutex);
+    d->currentBuffer = QWaylandBufferRef();
+    d->forceAdvanceSucceed = true;
+}
+
 QWaylandBufferRef QWaylandView::currentBuffer()
 {
     Q_D(QWaylandView);
diff --git a/src/compositor/compositor_api/qwaylandview.h b/src/compositor/compositor_api/qwaylandview.h
index eddcdea49..bc7eea764 100644
--- a/src/compositor/compositor_api/qwaylandview.h
+++ b/src/compositor/compositor_api/qwaylandview.h
@@ -81,6 +81,7 @@ public:
 
     virtual void attach(const QWaylandBufferRef &ref, const QRegion &damage);
     virtual bool advance();
+    virtual void discardCurrentBuffer();
     virtual QWaylandBufferRef currentBuffer();
     virtual QRegion currentDamage();
 
diff --git a/src/compositor/compositor_api/qwaylandview_p.h b/src/compositor/compositor_api/qwaylandview_p.h
index c37cd6b71..b31c37112 100644
--- a/src/compositor/compositor_api/qwaylandview_p.h
+++ b/src/compositor/compositor_api/qwaylandview_p.h
@@ -60,6 +60,7 @@ public:
         , output(Q_NULLPTR)
         , bufferLock(false)
         , broadcastRequestedPositionChanged(false)
+        , forceAdvanceSucceed(false)
     { }
 
     void markSurfaceAsDestroyed(QWaylandSurface *surface);
@@ -75,6 +76,7 @@ public:
     QRegion nextDamage;
     bool bufferLock;
     bool broadcastRequestedPositionChanged;
+    bool forceAdvanceSucceed;
 };
 
 QT_END_NAMESPACE