Bug 883646 - Apply the mDevPixelsPerCSSPixel scaling factor in a few places. r=kentuckyfriedtakahe

gfx/layers/client/ClientLayerManager.cpp

@@ -408,8 +408,8 @@ ClientLayerManager::ProgressiveUpdateCallback(bool aHasPendingNewThebesContent,
     // This is derived from the code in
     // gfx/layers/ipc/CompositorParent.cpp::TransformShadowTree.
     const gfx3DMatrix& rootTransform = GetRoot()->GetTransform();
-    CSSToLayerScale paintScale = LayerToCSSScale(rootTransform.GetXScale(),
-                                                 rootTransform.GetYScale()).Inverse();
+    CSSToLayerScale paintScale(metrics.mDevPixelsPerCSSPixel / rootTransform.GetXScale(),
+                               metrics.mDevPixelsPerCSSPixel / rootTransform.GetYScale());
     const CSSRect& metricsDisplayPort =
       (aDrawingCritical && !metrics.mCriticalDisplayPort.IsEmpty()) ?
         metrics.mCriticalDisplayPort : metrics.mDisplayPort;

gfx/layers/composite/AsyncCompositionManager.cpp

@@ -351,12 +351,13 @@ AsyncCompositionManager::ApplyAsyncContentTransformToTree(TimeStamp aCurrentFram
 
     const gfx3DMatrix& rootTransform = mLayerManager->GetRoot()->GetTransform();
     const FrameMetrics& metrics = container->GetFrameMetrics();
+    float paintScale = metrics.mDevPixelsPerCSSPixel / rootTransform.GetXScale();
     CSSRect displayPort(metrics.mCriticalDisplayPort.IsEmpty() ?
                         metrics.mDisplayPort : metrics.mCriticalDisplayPort);
     gfx::Margin fixedLayerMargins(0, 0, 0, 0);
     ScreenPoint offset(0, 0);
     SyncFrameMetrics(scrollOffset, treeTransform.mScale.scale, metrics.mScrollableRect,
-                     mLayersUpdated, displayPort, 1 / rootTransform.GetXScale(),
+                     mLayersUpdated, displayPort, paintScale,
                      mIsFirstPaint, fixedLayerMargins, offset);
 
     mIsFirstPaint = false;
@@ -404,8 +405,8 @@ AsyncCompositionManager::TransformScrollableLayer(Layer* aLayer, const gfx3DMatr
 
   gfx3DMatrix treeTransform;
 
-  CSSToLayerScale geckoZoom = LayerToCSSScale(aRootTransform.GetXScale(),
-                                              aRootTransform.GetYScale()).Inverse();
+  CSSToLayerScale geckoZoom(metrics.mDevPixelsPerCSSPixel / aRootTransform.GetXScale(),
+                            metrics.mDevPixelsPerCSSPixel / aRootTransform.GetYScale());
 
   LayerIntPoint scrollOffsetLayerPixels = RoundedToInt(metrics.mScrollOffset * geckoZoom);
 

gfx/layers/ipc/AsyncPanZoomController.cpp

@@ -1085,12 +1085,6 @@ bool AsyncPanZoomController::SampleContentTransformForFrame(const TimeStamp& aSa
   // responsibility to schedule a composite.
   bool requestAnimationFrame = false;
 
-  const gfx3DMatrix& currentTransform = aLayer->GetTransform();
-
-  // Scales on the root layer, on what's currently painted.
-  LayerToCSSScale rootScale(currentTransform.GetXScale(),
-                            currentTransform.GetYScale());
-
   LayerPoint metricsScrollOffset;
   CSSPoint scrollOffset;
   CSSToScreenScale localScale;
@@ -1184,6 +1178,11 @@ bool AsyncPanZoomController::SampleContentTransformForFrame(const TimeStamp& aSa
                                             mAsyncScrollTimeout);
   }
 
+  // Scales on the root layer, on what's currently painted.
+  const gfx3DMatrix& currentTransform = aLayer->GetTransform();
+  LayerToCSSScale rootScale(currentTransform.GetXScale() / frame.mDevPixelsPerCSSPixel,
+                            currentTransform.GetYScale() / frame.mDevPixelsPerCSSPixel);
+
   LayerPoint translation = (scrollOffset / rootScale) - metricsScrollOffset;
   *aNewTransform = ViewTransform(-translation, localScale);
   aScrollOffset = scrollOffset * localScale;