Calculate and track display item opaqueness

third_party/WebKit/Source/platform/graphics/paint/PaintArtifact.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/paint/PaintArtifact.h"
 
 #include "platform/TraceEvent.h"
 #include "platform/geometry/IntRect.h"
 #include "platform/graphics/paint/DrawingDisplayItem.h"
+#include "third_party/skia/include/core/SkRegion.h"
 
 namespace blink {
 
 namespace {
 
-void computeChunkBounds(const DisplayItemList& displayItems, Vector<PaintChunk>& paintChunks)
+void computeChunkBoundsAndOpaqueness(const DisplayItemList& displayItems, Vector<PaintChunk>& paintChunks)
 {
     for (PaintChunk& chunk : paintChunks) {
         FloatRect bounds;
+        SkRegion knownToBeOpaqueRegion;
         for (const DisplayItem& item : displayItems.itemsInPaintChunk(chunk)) {
             if (!item.isDrawing())
                 continue;
             const auto& drawing = static_cast<const DrawingDisplayItem&>(item);
-            if (const SkPicture* picture = drawing.picture())
-                bounds.unite(picture->cullRect());
+            if (const SkPicture* picture = drawing.picture()) {
+                const SkRect& pictureRect = picture->cullRect();
+                bounds.unite(pictureRect);
+                if (drawing.knownToBeOpaque()) {
+                    // TODO(pdr): This may be too conservative and fail due to
+                    // floating point precision issues.
+                    SkIRect conservativelyRoundedPictureRect;
+                    pictureRect.roundIn(&conservativelyRoundedPictureRect);
+                    knownToBeOpaqueRegion.op(conservativelyRoundedPictureRect, SkRegion::kUnion_Op);
+                }
+            }
         }
         chunk.bounds = bounds;
+        if (knownToBeOpaqueRegion.contains(enclosingIntRect(bounds)))
+            chunk.knownToBeOpaque = true;
     }
 }
 
 } // namespace
 
 PaintArtifact::PaintArtifact()
     : m_displayItemList(0)
 {
 }
 
 PaintArtifact::PaintArtifact(DisplayItemList displayItems, Vector<PaintChunk> paintChunks)
     : m_displayItemList(std::move(displayItems))
     , m_paintChunks(std::move(paintChunks))
 {
-    computeChunkBounds(m_displayItemList, m_paintChunks);
+    computeChunkBoundsAndOpaqueness(m_displayItemList, m_paintChunks);
 }
 
 PaintArtifact::PaintArtifact(PaintArtifact&& source)
     : m_displayItemList(std::move(source.m_displayItemList))
     , m_paintChunks(std::move(source.m_paintChunks))
 {
 }
 
 PaintArtifact::~PaintArtifact()
 {
@@ skipping 31 matching lines @@
 #if ENABLE(ASSERT)
     m_displayItemList.assertDisplayItemClientsAreAlive();
 #endif
     for (const DisplayItem& displayItem : m_displayItemList) {
         // TODO(wkorman): Pass the actual visual rect for the display item.
         displayItem.appendToWebDisplayItemList(IntRect(), list);
     }
 }
 
 } // namespace blink