Changes subtreeShouldRenderToSeparateSurface logic to account for explicit clipping

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 249 matching lines @@
 
     // If the layer has a reflection.
     if (layer->replicaLayer())
         return true;
 
     // If the layer uses a CSS filter.
     if (!layer->filters().isEmpty() || !layer->backgroundFilters().isEmpty() || layer->filter())
         return true;
 
     int numDescendantsThatDrawContent = layer->drawProperties().num_descendants_that_draw_content;
+    int numDescendantsThatDrawContentAndCantClipThemselves = layer->drawProperties().num_descendants_that_draw_content_and_cant_clip_themselves;
 
     // If the layer flattens its subtree (i.e. the layer doesn't preserve-3d), but it is
     // treated as a 3D object by its parent (i.e. parent does preserve-3d).
     if (layerIsInExisting3DRenderingContext(layer) && !layer->preserves3D() && numDescendantsThatDrawContent > 0)
         return true;
 
     // If the layer clips its descendants but it is not axis-aligned with respect to its parent.
-    if (layerClipsSubtree(layer) && !axisAlignedWithRespectToParent && numDescendantsThatDrawContent > 0)
+    if (layerClipsSubtree(layer) && !axisAlignedWithRespectToParent && numDescendantsThatDrawContentAndCantClipThemselves > 0)
         return true;
 
     // If the layer has some translucency and does not have a preserves-3d transform style.
     // This condition only needs a render surface if two or more layers in the
     // subtree overlap. But checking layer overlaps is unnecessarily costly so
     // instead we conservatively create a surface whenever at least two layers
     // draw content for this subtree.
     bool atLeastTwoLayersInSubtreeDrawContent = layer->hasDelegatedContent() ||
         (numDescendantsThatDrawContent > 0 && (layer->drawsContent() || numDescendantsThatDrawContent > 1));
 
@@ skipping 134 matching lines @@
     // layers from the end of the list.
     while (renderSurfaceLayerList.back() != layerToRemove) {
         renderSurfaceLayerList.back()->clearRenderSurface();
         renderSurfaceLayerList.pop_back();
     }
     DCHECK(renderSurfaceLayerList.back() == layerToRemove);
     renderSurfaceLayerList.pop_back();
     layerToRemove->clearRenderSurface();
 }
 
+inline bool isPositiveScaleOrTranslation(const gfx::Transform& xform)

[jamesr, 2012/12/14 21:48:54]

is there a caller to this function? I can't find it.

Can we share the logic that's common between this function and
TextureDrawQuad::PerformClipping() ? the two need to have the same return values
for correctness, and I suspect we'll want to make the clipping more general over
time, so if we can factor this into a shared function we'll only have one thing
to update rather than two things that we have to keep in sync with each other

[whunt, 2012/12/14 22:12:20]

This function is no longer used due to the reliance of
axisAlignedWithRespectToParent in the recursive call.  I'll remove it.

On 2012/12/14 21:48:54, jamesr wrote:

+{
+    if (!xform.IsScaleOrTranslation())
+        return false;
+
+    // Grab our scale and make sure it's positive.
+    double x_scale = xform.matrix().getDouble(0,0);

[jamesr, 2012/12/14 21:48:54]

nit: space after the comma

+    double y_scale = xform.matrix().getDouble(1,1);
+    if (x_scale <= 0.0f || y_scale <= 0.0f)

[jamesr, 2012/12/14 21:48:54]

nit: "0.0", not "0.0f" since it's a double-double comparison

+        return false;
+
+    return true;
+}
+
 // Recursively walks the layer tree to compute any information that is needed
 // before doing the main recursion.
 template<typename LayerType>
 static void preCalculateMetaInformation(LayerType* layer)
 {
     int numDescendantsThatDrawContent = 0;
+    int numDescendantsThatDrawContentAndCantClipThemsleves = 0;
 
     for (size_t i = 0; i < layer->children().size(); ++i) {
         LayerType* childLayer = layer->children()[i];
         preCalculateMetaInformation<LayerType>(childLayer);
+
         numDescendantsThatDrawContent += childLayer->drawsContent() ? 1 : 0;
         numDescendantsThatDrawContent += childLayer->drawProperties().num_descendants_that_draw_content;
+
+        numDescendantsThatDrawContentAndCantClipThemsleves += childLayer->drawsContent() && !childLayer->CanClipSelf() ? 1 : 0;
+        numDescendantsThatDrawContentAndCantClipThemsleves += childLayer->drawProperties().num_descendants_that_draw_content_and_cant_clip_themselves;
     }
 
     layer->drawProperties().num_descendants_that_draw_content = numDescendantsThatDrawContent;
+    layer->drawProperties().num_descendants_that_draw_content_and_cant_clip_themselves = numDescendantsThatDrawContentAndCantClipThemsleves;
 }
 
 // Recursively walks the layer tree starting at the given node and computes all the
 // necessary transformations, clipRects, render surfaces, etc.
 template<typename LayerType, typename LayerList, typename RenderSurfaceType>
 static void calculateDrawPropertiesInternal(LayerType* layer, const gfx::Transform& parentMatrix,
     const gfx::Transform& fullHierarchyMatrix, const gfx::Transform& currentScrollCompensationMatrix,
     const gfx::Rect& clipRectFromAncestor, const gfx::Rect& clipRectFromAncestorInDescendantSpace, bool ancestorClipsSubtree,
     RenderSurfaceType* nearestAncestorThatMovesPixels, LayerList& renderSurfaceLayerList, LayerList& layerList,
     LayerSorter* layerSorter, int maxTextureSize, float deviceScaleFactor, float pageScaleFactor, bool subtreeCanUseLCDText,
@@ skipping 638 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