compositor-worker: plumb element id and mutable properties

third_party/WebKit/Source/core/layout/compositing/PaintLayerCompositor.cpp

 /*
  * Copyright (C) 2009, 2010 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 45 matching lines @@
 #include "core/paint/TransformRecorder.h"
 #include "platform/RuntimeEnabledFeatures.h"
 #include "platform/ScriptForbiddenScope.h"
 #include "platform/TraceEvent.h"
 #include "platform/graphics/GraphicsLayer.h"
 #include "platform/graphics/paint/CullRect.h"
 #include "platform/graphics/paint/DrawingRecorder.h"
 #include "platform/graphics/paint/PaintController.h"
 #include "platform/graphics/paint/TransformDisplayItem.h"
 #include "public/platform/Platform.h"
+#include "public/platform/WebCompositorMutableProperties.h"
 
 namespace blink {
 
 PaintLayerCompositor::PaintLayerCompositor(LayoutView& layoutView)
     : m_layoutView(layoutView)
     , m_compositingReasonFinder(layoutView)
     , m_pendingUpdateType(CompositingUpdateNone)
     , m_hasAcceleratedCompositing(true)
     , m_compositing(false)
     , m_rootShouldAlwaysCompositeDirty(true)
@@ skipping 308 matching lines @@
                 for (ScrollableArea* scrollableArea : *scrollableAreas)
                     layersChanged |= scrollableArea->updateAfterCompositingChange();
             }
         }
 
         if (layersChanged)
             updateType = std::max(updateType, CompositingUpdateRebuildTree);
     }
 
     if (updateType != CompositingUpdateNone) {
+        if (RuntimeEnabledFeatures::compositorWorkerEnabled() && m_scrollLayer) {

[chrishtr, 2015/12/01 23:17:03]

Is there a testcase for the code here?

[Ian Vollick, 2015/12/02 00:39:33]

Yes. In CompositorWorkerTest, I test three types of CompositorProxy.
 1. A proxy of a typical div (for opacity and transform).
 2. A proxy of an overflow:scrolling div (for scrollLeft and scrollTop), and
 3. A proxy of document.scrollingElement (for scrollLeft and scrollTop).

This code sets up the elementId and mutableProperties for the scrolling element
(#3 above) and the tests check that we're getting the right values. If you
search for rootScrollLayer in CompositorWorkerTest.cpp you'll see the relevant
lines.

+            if (Element* scrollingElement = m_layoutView.document().scrollingElement()) {
+                uint64_t elementId = 0;
+                uint32_t mutableProperties = WebCompositorMutablePropertyNone;
+                if (scrollingElement->hasCompositorProxy()) {
+                    elementId = DOMNodeIds::idForNode(scrollingElement);
+                    mutableProperties = (WebCompositorMutablePropertyScrollLeft | WebCompositorMutablePropertyScrollTop) & scrollingElement->compositorMutableProperties();
+                }
+                m_scrollLayer->setElementId(elementId);
+                m_scrollLayer->setCompositorMutableProperties(mutableProperties);
+            }
+        }
+
         GraphicsLayerUpdater updater;
         updater.update(*updateRoot, layersNeedingPaintInvalidation);
 
         if (updater.needsRebuildTree())
             updateType = std::max(updateType, CompositingUpdateRebuildTree);
 
 #if ENABLE(ASSERT)
         // FIXME: Move this check to the end of the compositing update.
         GraphicsLayerUpdater::assertNeedsToUpdateGraphicsLayerBitsCleared(*updateRoot);
 #endif
@@ skipping 791 matching lines @@
     } else if (graphicsLayer == m_scrollLayer.get()) {
         name = "Frame Scrolling Layer";
     } else {
         ASSERT_NOT_REACHED();
     }
 
     return name;
 }
 
 } // namespace blink