Merge remote-tracking branch 'origin/5.8' into dev

Conflicts:
	src/qml/compiler/qv4isel_moth_p.h

Change-Id: I8e86a649d1ef8ad27dc66cc8c290093b2faabc69

1 files changed, 11 insertions, 2 deletions

diff --git a/src/quick/scenegraph/adaptations/software/qsgsoftwarerenderer.cpp b/src/quick/scenegraph/adaptations/software/qsgsoftwarerenderer.cpp
index ae89ed7d8a..cad826fb27 100644
--- a/src/quick/scenegraph/adaptations/software/qsgsoftwarerenderer.cpp
+++ b/src/quick/scenegraph/adaptations/software/qsgsoftwarerenderer.cpp
@@ -101,8 +101,13 @@ void QSGSoftwareRenderer::render()
         return;
 
     // If there is a backingstore, set the current paint device
-    if (m_backingStore)
+    if (m_backingStore) {
+        // For HiDPI QBackingStores, the paint device is not valid
+        // until begin() has been called. See: QTBUG-55875
+        m_backingStore->beginPaint(QRegion());
         m_paintDevice = m_backingStore->paintDevice();
+        m_backingStore->endPaint();
+    }
 
     QElapsedTimer renderTimer;
 
@@ -133,8 +138,12 @@ void QSGSoftwareRenderer::render()
     qint64 optimizeRenderListTime = renderTimer.restart();
 
     // If Rendering to a backingstore, prepare it to be updated
-    if (m_backingStore != nullptr)
+    if (m_backingStore != nullptr) {
         m_backingStore->beginPaint(updateRegion);
+        // It is possible that a QBackingStore's paintDevice() will change
+        // when begin() is called.
+        m_paintDevice = m_backingStore->paintDevice();
+    }
 
     QPainter painter(m_paintDevice);
     painter.setRenderHint(QPainter::Antialiasing);