Land layer squashing behind a flag

Source/core/rendering/RenderLayerCompositor.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 460 matching lines @@
                 childList.clear();
                 childList.append(video->compositedLayerMapping()->mainGraphicsLayer());
             }
         }
 
         if (childList.isEmpty())
             destroyRootLayer();
         else
             m_rootContentLayer->setChildren(childList);
     } else if (needGeometryUpdate) {
+
         // We just need to do a geometry update. This is only used for position:fixed scrolling;
         // most of the time, geometry is updated via RenderLayer::styleChanged().
         updateLayerTreeGeometry(updateRoot);
     }
 
     ASSERT(updateRoot || !m_compositingLayersNeedRebuild);
 
     if (!hasAcceleratedCompositing())
         enableCompositingMode(false);
 
     // The scrolling coordinator may realize that it needs updating while compositing was being updated in this function.
     needsToUpdateScrollingCoordinator |= scrollingCoordinator() ? scrollingCoordinator()->needsToUpdateAfterCompositingChange() : false;
     if (needsToUpdateScrollingCoordinator && isMainFrame() && scrollingCoordinator() && inCompositingMode())
         scrollingCoordinator()->updateAfterCompositingChange();
 
     // Inform the inspector that the layer tree has changed.
     if (isMainFrame())
         InspectorInstrumentation::layerTreeDidChange(page());
 }
 
 static bool requiresCompositing(CompositingReasons reasons)
 {
+    // Any reasons other than overlap or assumed overlap will require the layer to be separately compositing.
+    return reasons & ~CompositingReasonComboAllOverlapReasons;
+}
+
+static bool requiresSquashing(CompositingReasons reasons)
+{
+    // If the layer has overlap or assumed overlap, but no other reasons, then it should be squashed.
+    return !requiresCompositing(reasons) && (reasons & CompositingReasonComboAllOverlapReasons);
+}
+
+static bool requiresCompositingOrSquashing(CompositingReasons reasons)
+{
+#ifndef NDEBUG
+    bool fastAnswer = reasons != CompositingReasonNone;
+    bool slowAnswer = requiresCompositing(reasons) || requiresSquashing(reasons);
+    ASSERT(fastAnswer == slowAnswer);
+#endif
     return reasons != CompositingReasonNone;
 }
 
 void RenderLayerCompositor::addOutOfFlowPositionedLayer(RenderLayer* layer)
 {
     m_outOfFlowPositionedLayers.add(layer);
 }
 
 void RenderLayerCompositor::removeOutOfFlowPositionedLayer(RenderLayer* layer)
 {
@@ skipping 18 matching lines @@
 
             layer->ensureCompositedLayerMapping();
             compositedLayerMappingChanged = true;
 
             // At this time, the ScrollingCooridnator only supports the top-level frame.
             if (layer->isRootLayer() && isMainFrame()) {
                 if (ScrollingCoordinator* scrollingCoordinator = this->scrollingCoordinator())
                     scrollingCoordinator->frameViewRootLayerDidChange(m_renderView->frameView());
             }
 
+            // If this layer was previously squashed, we need to remove its reference to a groupedMapping right away, so
+            // that computing repaint rects will know the layer's correct compositingState.
+            // FIXME: do we need to also remove the layer from it's location in the squashing list of its groupedMapping?
+            // Need to create a test where a squashed layer pops into compositing. And also to cover all other
+            // sorts of compositingState transitions.
+            layer->setGroupedMapping(0);
+
+            // FIXME: it seems premature to compute this before all compositing state has been updated?
             // This layer and all of its descendants have cached repaints rects that are relative to
             // the repaint container, so change when compositing changes; we need to update them here.
             if (layer->parent())
                 layer->repainter().computeRepaintRectsIncludingDescendants();
         }
 
         if (layer->compositedLayerMapping()->updateRequiresOwnBackingStoreForIntrinsicReasons())
             compositedLayerMappingChanged = true;
     } else {
         if (layer->hasCompositedLayerMapping()) {
@@ skipping 46 matching lines @@
     }
 
     return compositedLayerMappingChanged || nonCompositedReasonChanged;
 }
 
 bool RenderLayerCompositor::updateLayerCompositingState(RenderLayer* layer)
 {
     updateDirectCompositingReasons(layer);
     bool layerChanged = allocateOrClearCompositedLayerMapping(layer);
 
+    if (isLayerSquashingEnabled()) {
+        // FIXME: this is not correct... info may be out of date and squashing returning true doesn't indicate that the layer changed
+        layerChanged = requiresSquashing(layer->compositingReasons());
+    }
+
     // See if we need content or clipping layers. Methods called here should assume
     // that the compositing state of descendant layers has not been updated yet.
     if (layer->hasCompositedLayerMapping() && layer->compositedLayerMapping()->updateGraphicsLayerConfiguration())
         layerChanged = true;
 
     return layerChanged;
 }
 
 void RenderLayerCompositor::repaintOnCompositingChange(RenderLayer* layer)
 {
     // If the renderer is not attached yet, no need to repaint.
     if (layer->renderer() != m_renderView && !layer->renderer()->parent())
         return;
 
     RenderLayerModelObject* repaintContainer = layer->renderer()->containerForRepaint();
     if (!repaintContainer)
         repaintContainer = m_renderView;
 
     layer->repainter().repaintIncludingNonCompositingDescendants(repaintContainer);
 }
 
 // This method assumes that layout is up-to-date, unlike repaintOnCompositingChange().
 void RenderLayerCompositor::repaintInCompositedAncestor(RenderLayer* layer, const LayoutRect& rect)
 {
     RenderLayer* compositedAncestor = layer->enclosingCompositingLayerForRepaint(false /*exclude self*/);
     if (compositedAncestor) {
-        ASSERT(compositedAncestor->compositingState() == PaintsIntoOwnBacking);
-
+        // FIXME: make sure repaintRect is computed correctly for squashed scenario
         LayoutPoint offset;
         layer->convertToLayerCoords(compositedAncestor, offset);
 
         LayoutRect repaintRect = rect;
         repaintRect.moveBy(offset);
 
-        compositedAncestor->repainter().setBackingNeedsRepaintInRect(repaintRect);
+        if (compositedAncestor->compositingState() == PaintsIntoOwnBacking) {
+            compositedAncestor->repainter().setBackingNeedsRepaintInRect(repaintRect);
+        } else if (compositedAncestor->compositingState() == PaintsIntoGroupedBacking) {
+            // FIXME: Need to perform the correct coordinate conversion for repaintRect here, including transforms
+            compositedAncestor->groupedMapping()->squashingLayer()->setNeedsDisplayInRect(repaintRect);
+        } else {
+            ASSERT_NOT_REACHED();
+        }
     }
 }
 
 // The bounds of the GraphicsLayer created for a compositing layer is the union of the bounds of all the descendant
 // RenderLayers that are rendered by the composited RenderLayer.
 IntRect RenderLayerCompositor::calculateCompositedBounds(const RenderLayer* layer, const RenderLayer* ancestorLayer) const
 {
     if (!canBeComposited(layer))
         return IntRect();
 
@@ skipping 142 matching lines @@
         for (size_t i = 0; i < unclippedDescendantsToRemove.size(); i++)
             unclippedDescendants.remove(unclippedDescendantsToRemove.at(unclippedDescendantsToRemove.size() - i - 1));
 
         if (reasonsToComposite & CompositingReasonOutOfFlowClipping)
             unclippedDescendants.append(layer);
     }
 
     bool haveComputedBounds = false;
     IntRect absBounds;
     // If we know for sure the layer is going to be composited, don't bother looking it up in the overlap map.
-    if (overlapMap && !overlapMap->isEmpty() && currentRecursionData.m_testingOverlap && !requiresCompositing(directReasons)) {
+    if (overlapMap && !overlapMap->isEmpty() && currentRecursionData.m_testingOverlap && !requiresCompositingOrSquashing(directReasons)) {
         // If we're testing for overlap, we only need to composite if we overlap something that is already composited.
         absBounds = enclosingIntRect(overlapMap->geometryMap().absoluteRect(layer->overlapBounds()));
 
         // Empty rects never intersect, but we need them to for the purposes of overlap testing.
         if (absBounds.isEmpty())
             absBounds.setSize(IntSize(1, 1));
         haveComputedBounds = true;
         overlapCompositingReason = overlapMap->overlapsLayers(absBounds) ? CompositingReasonOverlap : CompositingReasonNone;
     }
 
     reasonsToComposite |= overlapCompositingReason;
 
     // The children of this layer don't need to composite, unless there is
     // a compositing layer among them, so start by inheriting the compositing
     // ancestor with m_subtreeIsCompositing set to false.
     CompositingRecursionData childRecursionData(currentRecursionData);
     childRecursionData.m_subtreeIsCompositing = false;
 
-    bool willBeComposited = canBeComposited(layer) && requiresCompositing(reasonsToComposite);
+    bool willBeComposited = canBeComposited(layer) && requiresCompositingOrSquashing(reasonsToComposite);
     if (willBeComposited) {
         // Tell the parent it has compositing descendants.
         currentRecursionData.m_subtreeIsCompositing = true;
         // This layer now acts as the ancestor for kids.
         childRecursionData.m_compositingAncestor = layer;
 
         // Here we know that all children and the layer's own contents can blindly paint into
         // this layer's backing, until a descendant is composited. So, we don't need to check
         // for overlap with anything behind this layer.
         if (overlapMap)
@@ skipping 78 matching lines @@
     if (layer->stackingNode()->isStackingContext()) {
         layer->setShouldIsolateCompositedDescendants(childRecursionData.m_hasUnisolatedCompositedBlendingDescendant);
     } else {
         layer->setShouldIsolateCompositedDescendants(false);
         currentRecursionData.m_hasUnisolatedCompositedBlendingDescendant = childRecursionData.m_hasUnisolatedCompositedBlendingDescendant;
     }
 
     // Now check for reasons to become composited that depend on the state of descendant layers.
     CompositingReasons subtreeCompositingReasons = subtreeReasonsForCompositing(layer->renderer(), childRecursionData.m_subtreeIsCompositing, anyDescendantHas3DTransform);
     reasonsToComposite |= subtreeCompositingReasons;
-    if (!willBeComposited && canBeComposited(layer) && requiresCompositing(subtreeCompositingReasons)) {
+    if (!willBeComposited && canBeComposited(layer) && requiresCompositingOrSquashing(subtreeCompositingReasons)) {
         childRecursionData.m_compositingAncestor = layer;
         if (overlapMap) {
             // FIXME: this context push is effectively a no-op but needs to exist for
             // now, because the code is designed to push overlap information to the
             // second-from-top context of the stack.
             overlapMap->beginNewOverlapTestingContext();
             addToOverlapMapRecursive(*overlapMap, layer);
         }
         willBeComposited = true;
     }
@@ skipping 21 matching lines @@
     bool isCompositedClippingLayer = canBeComposited(layer) && (reasonsToComposite & CompositingReasonClipsCompositingDescendants);
     if ((!childRecursionData.m_testingOverlap && !isCompositedClippingLayer) || isRunningAcceleratedTransformAnimation(layer->renderer()))
         currentRecursionData.m_testingOverlap = false;
 
     if (overlapMap && childRecursionData.m_compositingAncestor == layer && !layer->isRootLayer())
         overlapMap->finishCurrentOverlapTestingContext();
 
     if (layer->isRootLayer()) {
         // The root layer needs to be composited if anything else in the tree is composited.
         // Otherwise, we can disable compositing entirely.
-        if (childRecursionData.m_subtreeIsCompositing || requiresCompositing(reasonsToComposite) || m_forceCompositingMode) {
+        if (childRecursionData.m_subtreeIsCompositing || requiresCompositingOrSquashing(reasonsToComposite) || m_forceCompositingMode) {
             willBeComposited = true;
             reasonsToComposite |= CompositingReasonRoot;
         } else {
             enableCompositingMode(false);
             willBeComposited = false;
             reasonsToComposite = CompositingReasonNone;
         }
     }
 
     // At this point we have finished collecting all reasons to composite this layer.
     layer->setCompositingReasons(reasonsToComposite);
 
     if (!willBeComposited && layer->parent())
         layer->parent()->setHasNonCompositedChild(true);
 
     descendantHas3DTransform |= anyDescendantHas3DTransform || layer->has3DTransform();
 
     if (overlapMap)
         overlapMap->geometryMap().popMappingsToAncestor(ancestorLayer);
 }
 
-void RenderLayerCompositor::assignLayersToBackings(RenderLayer* layer, bool& layersChanged)
+void RenderLayerCompositor::SquashingState::updateSquashingStateForNewMapping(CompositedLayerMappingPtr newCompositedLayerMapping, bool hasNewCompositedLayerMapping, IntPoint newOffsetFromAbsolute)
 {
-    // FIXME: squashing state will be added internally here.
-    assignLayersToBackingsInternal(layer, layersChanged);
+    // The most recent backing is done accumulating any more squashing layers.
+    if (hasMostRecentMapping)
+        mostRecentMapping->finishAccumulatingSquashingLayers(nextSquashedLayerIndex);
+
+    nextSquashedLayerIndex = 0;
+    mostRecentMapping = newCompositedLayerMapping;
+    hasMostRecentMapping = hasNewCompositedLayerMapping;
+    offsetFromAbsolute = newOffsetFromAbsolute;
 }
 
-void RenderLayerCompositor::assignLayersToBackingsInternal(RenderLayer* layer, bool& layersChanged)
+static IntPoint computeOffsetFromAbsolute(RenderLayer* layer)

[Ian Vollick, 2013/12/11 16:45:18]

why was this moved?

[shawnsingh, 2013/12/11 18:50:34]

Nothing was moved?  Or maybe i'm misunderstanding what you're asking.   The diff
itself is a little unclean, but it is what I intended...  This is a new helper
function to make it smoother to get the correct painting offsets plumbed into
the paint task for squashing layers.   assignLayersToBackings still exists as it
did before, but it's in the diff only because of the new SquashingState arg.

[Ian Vollick, 2013/12/11 19:47:22]

This was my mistake. I misinterpreted the patch to patch diff :)

+{
+    TransformState transformState(TransformState::ApplyTransformDirection, FloatPoint());
+    layer->renderer()->mapLocalToContainer(0, transformState, ApplyContainerFlip);
+    transformState.flatten();
+    return roundedIntPoint(transformState.lastPlanarPoint());
+}
+
+void RenderLayerCompositor::assignLayersToBackings(RenderLayer* updateRoot, bool& layersChanged)
+{
+    SquashingState squashingState;
+    assignLayersToBackingsInternal(updateRoot, squashingState, layersChanged);
+    if (squashingState.hasMostRecentMapping)
+        squashingState.mostRecentMapping->finishAccumulatingSquashingLayers(squashingState.nextSquashedLayerIndex);
+}
+
+void RenderLayerCompositor::assignLayersToBackingsInternal(RenderLayer* layer, SquashingState& squashingState, bool& layersChanged)
 {
     if (allocateOrClearCompositedLayerMapping(layer))
         layersChanged = true;
 
     if (layer->reflectionInfo() && updateLayerCompositingState(layer->reflectionInfo()->reflectionLayer()))
         layersChanged = true;
 
-    // FIXME: squashing code here: if a layer requiresSquashing(), then assign this layer to the most recent
-    // squashing layer and update recursion state of this function.
+    // Add this layer to a squashing backing if needed.
+    if (isLayerSquashingEnabled()) {
+        // NOTE: In the future as we generalize this, the background of this layer may need to be assigned to a different backing than
+        // the layer's own primary contents. This would happen when we have a composited negative z-index element that needs to
+        // paint on top of the background, but below the layer's main contents. For now, because we always composite layers
+        // when they have a composited negative z-index child, such layers will never need squashing so it is not yet an issue.
+        if (requiresSquashing(layer->compositingReasons())) {
+            // A layer that is squashed with other layers cannot have its own CompositedLayerMapping.
+            ASSERT(!layer->hasCompositedLayerMapping());
+            ASSERT(squashingState.hasMostRecentMapping);
+
+            IntPoint offsetFromAbsolute = computeOffsetFromAbsolute(layer);
+
+            // FIXME: see if we can refactor this to be clearer
+            IntSize offsetFromTargetBacking(offsetFromAbsolute.x() - squashingState.offsetFromAbsolute.x(),
+                offsetFromAbsolute.y() - squashingState.offsetFromAbsolute.y());
+
+            squashingState.mostRecentMapping->addRenderLayerToSquashingGraphicsLayer(layer, offsetFromTargetBacking, squashingState.nextSquashedLayerIndex);
+            squashingState.nextSquashedLayerIndex++;
+
+            // FIXME: does this need to be true here? Do we need more logic to decide when it should be true?
+            layersChanged = true;
+
+            // FIXME: this should be conditioned on whether this layer actually changed status
+            layer->clipper().clearClipRectsIncludingDescendants();
+        }
+    }
 
     if (layer->stackingNode()->isStackingContainer()) {
         RenderLayerStackingNodeIterator iterator(*layer->stackingNode(), NegativeZOrderChildren);
         while (RenderLayerStackingNode* curNode = iterator.next())
-            assignLayersToBackings(curNode->layer(), layersChanged);
+            assignLayersToBackingsInternal(curNode->layer(), squashingState, layersChanged);
     }
 
-    // FIXME: squashing code here: if this layer actually becomes separately composited, then we need to update the
-    // squashing layer that subsequent overlapping layers will contribute to.
+    if (isLayerSquashingEnabled()) {
+        // At this point, if the layer is to be "separately" composited, then its backing becomes the most recent in paint-order.
+        if (layer->compositingState() == PaintsIntoOwnBacking || layer->compositingState() == HasOwnBackingButPaintsIntoAncestor) {
+            ASSERT(!requiresSquashing(layer->compositingReasons()));
+            IntPoint offsetFromAbsolute = computeOffsetFromAbsolute(layer);
+            squashingState.updateSquashingStateForNewMapping(layer->compositedLayerMapping(), layer->hasCompositedLayerMapping(), offsetFromAbsolute);
+        }
+    }
 
     RenderLayerStackingNodeIterator iterator(*layer->stackingNode(), NormalFlowChildren | PositiveZOrderChildren);
     while (RenderLayerStackingNode* curNode = iterator.next())
-        assignLayersToBackings(curNode->layer(), layersChanged);
+        assignLayersToBackingsInternal(curNode->layer(), squashingState, layersChanged);
 }
 
 void RenderLayerCompositor::setCompositingParent(RenderLayer* childLayer, RenderLayer* parentLayer)
 {
     ASSERT(!parentLayer || childLayer->ancestorCompositingLayer() == parentLayer);
     ASSERT(childLayer->hasCompositedLayerMapping());
 
     // It's possible to be called with a parent that isn't yet composited when we're doing
     // partial updates as required by painting or hit testing. Just bail in that case;
     // we'll do a full layer update soon.
@@ skipping 478 matching lines @@
     layerReasons &= ~CompositingReasonComboAllDirectReasons;
     layerReasons |= directReasonsForCompositing(layer);
     layer->setCompositingReasons(layerReasons);
 }
 
 bool RenderLayerCompositor::needsOwnBacking(const RenderLayer* layer) const
 {
     if (!canBeComposited(layer))
         return false;
 
-    return requiresCompositing(layer->compositingReasons()) || (inCompositingMode() && layer->isRootLayer());
+    // If squashing is disabled, then layers that would have been squashed should just be separately composited.
+    bool needsOwnBackingDueToOverlap = !isLayerSquashingEnabled() && requiresSquashing(layer->compositingReasons());
+
+    return requiresCompositing(layer->compositingReasons()) || needsOwnBackingDueToOverlap || (inCompositingMode() && layer->isRootLayer());
 }
 
 bool RenderLayerCompositor::canBeComposited(const RenderLayer* layer) const
 {
     // FIXME: We disable accelerated compositing for elements in a RenderFlowThread as it doesn't work properly.
     // See http://webkit.org/b/84900 to re-enable it.
     return m_hasAcceleratedCompositing && layer->isSelfPaintingLayer() && layer->renderer()->flowThreadState() == RenderObject::NotInsideFlowThread;
 }
 
 CompositingReasons RenderLayerCompositor::directReasonsForCompositing(const RenderLayer* layer) const
@@ skipping 44 matching lines @@
 // Return true if the given layer has some ancestor in the RenderLayer hierarchy that clips,
 // up to the enclosing compositing ancestor. This is required because compositing layers are parented
 // according to the z-order hierarchy, yet clipping goes down the renderer hierarchy.
 // Thus, a RenderLayer can be clipped by a RenderLayer that is an ancestor in the renderer hierarchy,
 // but a sibling in the z-order hierarchy.
 bool RenderLayerCompositor::clippedByAncestor(const RenderLayer* layer) const
 {
     if (!layer->hasCompositedLayerMapping() || !layer->parent())
         return false;
 
+    // FIXME: need to double-check if semantics of ancestorCompositingLayer() work correctly here?
     const RenderLayer* compositingAncestor = layer->ancestorCompositingLayer();
     if (!compositingAncestor)
         return false;
 
     // If the compositingAncestor clips, that will be taken care of by clipsCompositingDescendants(),
     // so we only care about clipping between its first child that is our ancestor (the computeClipRoot),
     // and layer.
     const RenderLayer* computeClipRoot = 0;
     const RenderLayer* curr = layer;
     while (curr) {
@@ skipping 909 matching lines @@
     } else if (graphicsLayer == m_scrollLayer.get()) {
         name = "Frame Scrolling Layer";
     } else {
         ASSERT_NOT_REACHED();
     }
 
     return name;
 }
 
 } // namespace WebCore