cc: When the transform's scale is unknown, draw render surfaces at the resolution of the screen.

cc/layer_tree_host_common.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/layer_tree_host_common.h"
 
 #include <algorithm>
 
 #include "base/debug/trace_event.h"
 #include "cc/layer.h"
@@ skipping 372 matching lines @@
 {
 }
 
 static inline void updateLayerContentsScale(Layer* layer, const gfx::Transform& combinedTransform, float deviceScaleFactor, float pageScaleFactor, bool animatingTransformToScreen)
 {
     float rasterScale = layer->rasterScale();
     if (!rasterScale) {
         rasterScale = 1;
 
         if (!animatingTransformToScreen && layer->automaticallyComputeRasterScale()) {
-            gfx::Vector2dF transformScale = MathUtil::computeTransform2dScaleComponents(combinedTransform);
+            gfx::Vector2dF transformScale = MathUtil::computeTransform2dScaleComponents(combinedTransform, 0.f);

[danakj, 2012/12/20 23:27:12]

Now switch to 0.f so we don't save it when we don't know the scale. Thanks :)

             float combinedScale = std::max(transformScale.x(), transformScale.y());
             rasterScale = combinedScale / deviceScaleFactor;
             if (!layer->boundsContainPageScale())
                 rasterScale /= pageScaleFactor;
             // Prevent scale factors below 1 from being used or saved.
             if (rasterScale < 1)
                 rasterScale = 1;
             else
                 layer->setRasterScale(rasterScale);
         }
@@ skipping 249 matching lines @@
                               (accumulatedDrawOpacity == 1.0) &&
                               layerDrawProperties.target_space_transform.IsIdentityOrIntegerTranslation();
 
     gfx::RectF contentRect(gfx::PointF(), layer->contentBounds());
 
     // fullHierarchyMatrix is the matrix that transforms objects between screen space (except projection matrix) and the most recent RenderSurfaceImpl's space.
     // nextHierarchyMatrix will only change if this layer uses a new RenderSurfaceImpl, otherwise remains the same.
     gfx::Transform nextHierarchyMatrix = fullHierarchyMatrix;
     gfx::Transform sublayerMatrix;
 
-    gfx::Vector2dF renderSurfaceSublayerScale = MathUtil::computeTransform2dScaleComponents(combinedTransform);
+    gfx::Vector2dF renderSurfaceSublayerScale = MathUtil::computeTransform2dScaleComponents(combinedTransform, deviceScaleFactor * pageScaleFactor);
 
     if (subtreeShouldRenderToSeparateSurface(layer, combinedTransform.IsScaleOrTranslation())) {
         // Check back-face visibility before continuing with this surface and its subtree
         if (!layer->doubleSided() && transformToParentIsKnown(layer) && isSurfaceBackFaceVisible(layer, combinedTransform))
             return;
 
         if (!layer->renderSurface())
             layer->createRenderSurface();
 
         RenderSurfaceType* renderSurface = layer->renderSurface();
@@ skipping 444 matching lines @@
 
   // At this point, we think the point does hit the touch event handler region on the layer, but we need to walk up
   // the parents to ensure that the layer was not clipped in such a way that the
   // hit point actually should not hit the layer.
   if (pointIsClippedBySurfaceOrClipRect(screenSpacePoint, layerImpl))
      return false;
 
   return true;
 }
 }  // namespace cc