Apply device pixel ratio to transparency layers

The transparency layers are currently created with taking hiDPI into
account. This means that any CSS opacity causes a shift in rendering
quality.

This patch forwards the device pixelratio for any QPaintDevice to
transparency layers created for that device.

Change-Id: Ie65f76771a4cc59bc714a9b89511cab1f7617abc
Reviewed-by: Michael Bruning <michael.bruning@digia.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/Source/WebCore/platform/graphics/qt/TransparencyLayer.h b/Source/WebCore/platform/graphics/qt/TransparencyLayer.h
index f13deb03b..0312690e0 100644
--- a/Source/WebCore/platform/graphics/qt/TransparencyLayer.h
+++ b/Source/WebCore/platform/graphics/qt/TransparencyLayer.h
@@ -46,11 +46,13 @@ struct TransparencyLayer {
     WTF_MAKE_FAST_ALLOCATED;
 public:
     TransparencyLayer(const QPainter* p, const QRect &rect, qreal opacity, QPixmap& alphaMask)
-        : pixmap(rect.width(), rect.height())
-        , opacity(opacity)
+        : opacity(opacity)
         , alphaMask(alphaMask)
         , saveCounter(1) // see the comment for saveCounter
     {
+        int devicePixelRatio = p->device()->devicePixelRatio();
+        pixmap = QPixmap(rect.width() * devicePixelRatio, rect.height() * devicePixelRatio);
+        pixmap.setDevicePixelRatio(devicePixelRatio);
         offset = rect.topLeft();
         pixmap.fill(Qt::transparent);
         painter.begin(&pixmap);