[Qt][WK2] Fix painting on Mac with retina display

https://bugs.webkit.org/show_bug.cgi?id=104574

Reviewed by Kenneth Rohde Christiansen.

Since HiDPI support has been added and enabled in Qt we ended up
painting incorrectly scaled content on high-resolution screens.
Because the intrinsic device pixel ratio is always taken into
account by Qt when painting to high-resolution screens we should
automatically obtain the scale ratio from the window in which the
item is rendered instead of setting it in QML.

Qt does not make it possible to override the device pixel ratio
of the native window, therefore our experimental QML API for setting
a custom value is of no use any more and should be removed.

This patch fixes the scaling issue on Mac retina display by querying
the underlying window for the device scale factor and applying it to
the backing store and the scene-graph rendering of the content node.
Additionally removes the experimental API and related API tests.

Change-Id: I04f23059147773ca279a89ae8976ccd3d9bef292
git-svn-id: http://svn.webkit.org/repository/webkit/trunk@137597 268f45cc-cd09-0410-ab3c-d52691b4dbfc
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>

2 files changed, 13 insertions, 5 deletions

diff --git a/Source/WebKit2/UIProcess/CoordinatedGraphics/LayerTreeCoordinatorProxy.cpp b/Source/WebKit2/UIProcess/CoordinatedGraphics/LayerTreeCoordinatorProxy.cpp
index 8fb12b902..9cb2c1bc5 100644
--- a/Source/WebKit2/UIProcess/CoordinatedGraphics/LayerTreeCoordinatorProxy.cpp
+++ b/Source/WebKit2/UIProcess/CoordinatedGraphics/LayerTreeCoordinatorProxy.cpp
@@ -56,6 +56,11 @@ void LayerTreeCoordinatorProxy::updateViewport()
     m_drawingAreaProxy->updateViewport();
 }
 
+float LayerTreeCoordinatorProxy::deviceScaleFactor() const
+{
+    return m_drawingAreaProxy->page()->deviceScaleFactor();
+}
+
 void LayerTreeCoordinatorProxy::dispatchUpdate(const Function<void()>& function)
 {
     m_renderer->appendUpdate(function);
@@ -178,19 +183,20 @@ void LayerTreeCoordinatorProxy::setAnimationsLocked(bool locked)
     dispatchUpdate(bind(&LayerTreeRenderer::setAnimationsLocked, m_renderer.get(), locked));
 }
 
-void LayerTreeCoordinatorProxy::setVisibleContentsRect(const FloatRect& rect, float scale, const FloatPoint& trajectoryVector)
+void LayerTreeCoordinatorProxy::setVisibleContentsRect(const FloatRect& rect, float pageScaleFactor, const FloatPoint& trajectoryVector)
 {
     // Inform the renderer to adjust viewport-fixed layers.
     dispatchUpdate(bind(&LayerTreeRenderer::setVisibleContentsRect, m_renderer.get(), rect));
 
     // Round the rect instead of enclosing it to make sure that its size stays the same while panning. This can have nasty effects on layout.
     IntRect roundedRect = roundedIntRect(rect);
-    if (roundedRect == m_lastSentVisibleRect && scale == m_lastSentScale && trajectoryVector == m_lastSentTrajectoryVector)
+    const float effectiveScale = deviceScaleFactor() * pageScaleFactor;
+    if (roundedRect == m_lastSentVisibleRect && effectiveScale == m_lastSentScale && trajectoryVector == m_lastSentTrajectoryVector)
         return;
 
-    m_drawingAreaProxy->page()->process()->send(Messages::LayerTreeCoordinator::SetVisibleContentsRect(roundedRect, scale, trajectoryVector), m_drawingAreaProxy->page()->pageID());
+    m_drawingAreaProxy->page()->process()->send(Messages::LayerTreeCoordinator::SetVisibleContentsRect(roundedRect, effectiveScale, trajectoryVector), m_drawingAreaProxy->page()->pageID());
     m_lastSentVisibleRect = roundedRect;
-    m_lastSentScale = scale;
+    m_lastSentScale = effectiveScale;
     m_lastSentTrajectoryVector = trajectoryVector;
 }
 
diff --git a/Source/WebKit2/UIProcess/CoordinatedGraphics/LayerTreeCoordinatorProxy.h b/Source/WebKit2/UIProcess/CoordinatedGraphics/LayerTreeCoordinatorProxy.h
index fb58b1ae7..a3961ffef 100644
--- a/Source/WebKit2/UIProcess/CoordinatedGraphics/LayerTreeCoordinatorProxy.h
+++ b/Source/WebKit2/UIProcess/CoordinatedGraphics/LayerTreeCoordinatorProxy.h
@@ -64,7 +64,7 @@ public:
     void deleteCompositingLayer(WebLayerID);
     void setRootCompositingLayer(WebLayerID);
     void setContentsSize(const WebCore::FloatSize&);
-    void setVisibleContentsRect(const WebCore::FloatRect&, float scale, const WebCore::FloatPoint& trajectoryVector);
+    void setVisibleContentsRect(const WebCore::FloatRect&, float pageScaleFactor, const WebCore::FloatPoint& trajectoryVector);
     void didRenderFrame(const WebCore::IntSize& contentsSize, const WebCore::IntRect& coveredRect);
     void createTileForLayer(int layerID, int tileID, const WebCore::IntRect&, const SurfaceUpdateInfo&);
     void updateTileForLayer(int layerID, int tileID, const WebCore::IntRect&, const SurfaceUpdateInfo&);
@@ -94,6 +94,8 @@ public:
 #endif
     void setBackgroundColor(const WebCore::Color&);
 
+    float deviceScaleFactor() const;
+
 protected:
     void dispatchUpdate(const Function<void()>&);