Subtree caching implementation in blink-core

Source/core/paint/DeprecatedPaintLayerPainter.cpp

 // Copyright 2014 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 "config.h"
 #include "core/paint/DeprecatedPaintLayerPainter.h"
 
 #include "core/frame/Settings.h"
 #include "core/layout/ClipPathOperation.h"
 #include "core/layout/LayoutBlock.h"
 #include "core/layout/LayoutView.h"
 #include "core/layout/svg/LayoutSVGResourceClipper.h"
 #include "core/page/Page.h"
 #include "core/paint/CompositingRecorder.h"
 #include "core/paint/DeprecatedPaintLayer.h"
 #include "core/paint/FilterPainter.h"
 #include "core/paint/LayerClipRecorder.h"
 #include "core/paint/LayerFixedPositionRecorder.h"
 #include "core/paint/PaintInfo.h"
 #include "core/paint/SVGClipPainter.h"
 #include "core/paint/ScopeRecorder.h"
 #include "core/paint/ScrollRecorder.h"
 #include "core/paint/ScrollableAreaPainter.h"
 #include "core/paint/Transform3DRecorder.h"
 #include "platform/graphics/GraphicsLayer.h"
 #include "platform/graphics/paint/ClipPathRecorder.h"
 #include "platform/graphics/paint/ClipRecorder.h"
 #include "platform/graphics/paint/CompositingDisplayItem.h"
+#include "platform/graphics/paint/SubsequenceRecorder.h"
 #include "platform/graphics/paint/Transform3DDisplayItem.h"
 #include "wtf/Optional.h"
 
 namespace blink {
 
 static inline bool shouldSuppressPaintingLayer(DeprecatedPaintLayer* layer)
 {
     // Avoid painting descendants of the root layer when stylesheets haven't loaded. This eliminates FOUC.
     // It's ok not to draw, because later on, when all the stylesheets do load, updateStyleSelector on the Document
     // will do a full paintInvalidationForWholeLayoutObject().
@@ skipping 22 matching lines @@
 
     if (m_paintLayer.compositingState() != NotComposited) {
         if (paintingInfo.globalPaintFlags() & GlobalPaintFlattenCompositingLayers) {
             // FIXME: ok, but what about GlobalPaintFlattenCompositingLayers? That's for printing and drag-image.
             // FIXME: why isn't the code here global, as opposed to being set on each paintLayer() call?
             paintFlags |= PaintLayerUncachedClipRects;
         }
     }
 
     // Non self-painting leaf layers don't need to be painted as their layoutObject() should properly paint itself.
-    if (!m_paintLayer.isSelfPaintingLayer() && !m_paintLayer.hasSelfPaintingLayerDescendant())
+    if (!m_paintLayer.isSelfPaintingLayer() && !m_paintLayer.hasSelfPaintingLayerDescendant()) {
+        ASSERT(!m_paintLayer.needsRepaint());
         return;
+    }
+
+    bool needsRepaint = m_paintLayer.needsRepaint();
+    m_paintLayer.clearNeedsRepaint();
 
     if (shouldSuppressPaintingLayer(&m_paintLayer))
         return;
 
     // If this layer is totally invisible then there is nothing to paint.
     if (!m_paintLayer.layoutObject()->opacity())
         return;
 
+    if (!needsRepaint && SubsequenceRecorder::useCachedSubsequenceIfPossible(*context, *m_paintLayer.layoutObject()))

[chrishtr, 2015/08/27 04:29:48]

Why aren't you checking for being a stacking context?

[Xianzhu, 2015/08/27 16:38:02]

Adding condition for stacking context seems just to complicate and cause missing
of some chances of relatively independently painted subsequences e.g for
non-stacking-context overflow:scroll divs.

+        return;
+    SubsequenceRecorder subsequenceRecorder(*context, *m_paintLayer.layoutObject());
+
     if (m_paintLayer.paintsWithTransparency(paintingInfo.globalPaintFlags()))
         paintFlags |= PaintLayerHaveTransparency;
 
     LayerFixedPositionRecorder fixedPositionRecorder(*context, *m_paintLayer.layoutObject());
 
     // PaintLayerAppliedTransform is used in LayoutReplica, to avoid applying the transform twice.
     if (m_paintLayer.paintsWithTransform(paintingInfo.globalPaintFlags()) && !(paintFlags & PaintLayerAppliedTransform)) {
         paintLayerWithTransform(context, paintingInfo, paintFlags);
         return;
     }
@@ skipping 509 matching lines @@
     if (!m_paintLayer.containsDirtyOverlayScrollbars())
         return;
 
     DeprecatedPaintLayerPaintingInfo paintingInfo(&m_paintLayer, LayoutRect(enclosingIntRect(damageRect)), paintFlags, LayoutSize(), paintingRoot);
     paintLayer(context, paintingInfo, PaintLayerPaintingOverlayScrollbars);
 
     m_paintLayer.setContainsDirtyOverlayScrollbars(false);
 }
 
 } // namespace blink