2 files changed, 16 insertions, 6 deletions
diff --git a/src/platformsupport/graphics/qrasterbackingstore.cpp b/src/platformsupport/graphics/qrasterbackingstore.cpp
index 58e811dff1..325c98b93d 100644
--- a/src/platformsupport/graphics/qrasterbackingstore.cpp
+++ b/src/platformsupport/graphics/qrasterbackingstore.cpp
@@ -62,13 +62,20 @@ void QRasterBackingStore::resize(const QSize &size, const QRegion &staticContent
     if (m_image.size() == effectiveBufferSize)
         return;
 
-    QImage::Format format = window()->format().hasAlpha() ? QImage::Format_ARGB32_Premultiplied : QImage::Format_RGB32;
-    m_image = QImage(effectiveBufferSize, format);
+    m_image = QImage(effectiveBufferSize, format());
     m_image.setDevicePixelRatio(windowDevicePixelRatio);
-    if (format == QImage::Format_ARGB32_Premultiplied)
+    if (m_image.format() == QImage::Format_ARGB32_Premultiplied)
         m_image.fill(Qt::transparent);
 }
 
+QImage::Format QRasterBackingStore::format() const
+{
+    if (window()->format().hasAlpha())
+        return QImage::Format_ARGB32_Premultiplied;
+    else
+        return QImage::Format_RGB32;
+}
+
 QPaintDevice *QRasterBackingStore::paintDevice()
 {
     return &m_image;
diff --git a/src/platformsupport/graphics/qrasterbackingstore_p.h b/src/platformsupport/graphics/qrasterbackingstore_p.h
index de96c99b5a..55976d2ceb 100644
--- a/src/platformsupport/graphics/qrasterbackingstore_p.h
+++ b/src/platformsupport/graphics/qrasterbackingstore_p.h
@@ -62,13 +62,16 @@ public:
     QRasterBackingStore(QWindow *window);
     ~QRasterBackingStore();
 
-    QPaintDevice *paintDevice() Q_DECL_OVERRIDE;
-    QImage toImage() const Q_DECL_OVERRIDE;
-    void resize (const QSize &size, const QRegion &) Q_DECL_OVERRIDE;
+    void resize(const QSize &size, const QRegion &staticContents) Q_DECL_OVERRIDE;
     bool scroll(const QRegion &area, int dx, int dy) Q_DECL_OVERRIDE;
     void beginPaint(const QRegion &region) Q_DECL_OVERRIDE;
 
+    QPaintDevice *paintDevice() Q_DECL_OVERRIDE;
+    QImage toImage() const Q_DECL_OVERRIDE;
+
 protected:
+    virtual QImage::Format format() const;
+
     QImage m_image;
 };