Avoid deep copy when updating BitmapTextureGL

Since we use a ImageBuffer to paint into a BitmapTextureGL, and
ImageBuffer's always have an active painter, the convertion from QPixmap
to QImage causes a deep copy of the content before it is uploaded to
OpenGL. This copy is unnecessary and can be avoided by temporarily
redirecting the QPaintDevice.

Change-Id: I0106c0f6dfb9cc3fbbee943411fc8f6853df4f98
Reviewed-by: Jocelyn Turcotte <jocelyn.turcotte@digia.com>

1 files changed, 12 insertions, 1 deletions

diff --git a/Source/WebCore/platform/graphics/texmap/TextureMapperGL.cpp b/Source/WebCore/platform/graphics/texmap/TextureMapperGL.cpp
index 55c0b6aca..4469fde58 100644
--- a/Source/WebCore/platform/graphics/texmap/TextureMapperGL.cpp
+++ b/Source/WebCore/platform/graphics/texmap/TextureMapperGL.cpp
@@ -38,6 +38,7 @@
 #include <wtf/TemporaryChange.h>
 
 #if PLATFORM(QT)
+#include <QPaintEngine>
 #include "NativeImageQt.h"
 #endif
 
@@ -908,7 +909,17 @@ void BitmapTextureGL::updateContents(Image* image, const IntRect& targetRect, co
     const char* imageData;
 
 #if PLATFORM(QT)
-    QImage qImage = frameImage->toImage();
+    QImage qImage;
+    QPaintEngine* paintEngine = frameImage->paintEngine();
+    if (paintEngine && paintEngine->type() == QPaintEngine::Raster) {
+        // QRasterPixmapData::toImage() will deep-copy the backing QImage if there's an active QPainter on it.
+        // For performance reasons, we don't want that here, so we temporarily redirect the paint engine.
+        QPaintDevice* currentPaintDevice = paintEngine->paintDevice();
+        paintEngine->setPaintDevice(0);
+        qImage = frameImage->toImage();
+        paintEngine->setPaintDevice(currentPaintDevice);
+    } else
+        qImage = frameImage->toImage();
     imageData = reinterpret_cast<const char*>(qImage.constBits());
     bytesPerLine = qImage.bytesPerLine();
 #elif USE(CAIRO)