Implement PaintArtifactCompositor::mightOverlap.

third_party/WebKit/Source/platform/graphics/compositing/PaintArtifactCompositor.cpp

 // Copyright 2015 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 "platform/graphics/compositing/PaintArtifactCompositor.h"
 
 #include "cc/layers/content_layer_client.h"
 #include "cc/layers/layer.h"
 #include "cc/layers/picture_layer.h"
 #include "cc/playback/compositing_display_item.h"
@@ skipping 1023 matching lines @@
     if (*currentState == candidatePendingLayer.propertyTreeState)
       return true;
   }
   return false;
 }
 
 bool PaintArtifactCompositor::mightOverlap(
     const PaintChunk& paintChunk,
     const PendingLayer& candidatePendingLayer,
     GeometryMapper& geometryMapper) {
-  // TODO(chrishtr): implement
-  return true;
+  PropertyTreeState rootPropertyTreeState(

[wkorman, 2016/12/29 19:49:40]

nit: could be worth adding a static instance for this, following what we do for
the root nodes themselves. We use this in a few other places already though
they're all tests until this case. Could replace those with this if we had it,
but mainly, might make overlap tests a bit faster since we wouldn't need to
construct each time. Premature optimization, etc.

[chrishtr, 2016/12/29 19:52:29]

Good idea. I have a cleanup CL for PaintArtifactCompositorTest queued up that is
sort of related to this, will this change to it.

+      TransformPaintPropertyNode::root(), ClipPaintPropertyNode::root(),
+      EffectPaintPropertyNode::root(), ScrollPaintPropertyNode::root());
+
+  bool success = false;
+  FloatRect paintChunkScreenVisualRect =
+      geometryMapper.localToVisualRectInAncestorSpace(
+          paintChunk.bounds, paintChunk.properties.propertyTreeState,
+          rootPropertyTreeState, success);
+  DCHECK(success);
+
+  success = false;
+  FloatRect pendingLayerScreenVisualRect =
+      geometryMapper.localToVisualRectInAncestorSpace(
+          candidatePendingLayer.bounds, candidatePendingLayer.propertyTreeState,
+          rootPropertyTreeState, success);
+  DCHECK(success);
+
+  return paintChunkScreenVisualRect.intersects(pendingLayerScreenVisualRect);
 }
 
 PaintArtifactCompositor::PendingLayer::PendingLayer(
     const PaintChunk& firstPaintChunk)
     : bounds(firstPaintChunk.bounds),
       knownToBeOpaque(firstPaintChunk.knownToBeOpaque),
       backfaceHidden(firstPaintChunk.properties.backfaceHidden),
       propertyTreeState(firstPaintChunk.properties.propertyTreeState) {
   paintChunks.append(&firstPaintChunk);
 }
@@ skipping 127 matching lines @@
 #ifndef NDEBUG
 void PaintArtifactCompositor::showDebugData() {
   LOG(ERROR) << layersAsJSON(LayerTreeIncludesDebugInfo)
                     ->toPrettyJSONString()
                     .utf8()
                     .data();
 }
 #endif
 
 }  // namespace blink