WIP: Construct SPV2's scroll paint property tree

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

Index: third_party/WebKit/Source/platform/graphics/compositing/PaintArtifactCompositor.cpp
diff --git a/third_party/WebKit/Source/platform/graphics/compositing/PaintArtifactCompositor.cpp b/third_party/WebKit/Source/platform/graphics/compositing/PaintArtifactCompositor.cpp
index 8e811bf0f93badfb6929d77332b80e14d94905fa..3ff0fcb4748b1ee10fc081f18cf670978638ddab 100644
--- a/third_party/WebKit/Source/platform/graphics/compositing/PaintArtifactCompositor.cpp
+++ b/third_party/WebKit/Source/platform/graphics/compositing/PaintArtifactCompositor.cpp
@@ -15,6 +15,7 @@
 #include "cc/trees/effect_node.h"
 #include "cc/trees/layer_tree_host.h"
 #include "cc/trees/property_tree.h"
+#include "cc/trees/scroll_node.h"
 #include "cc/trees/transform_node.h"
 #include "platform/RuntimeEnabledFeatures.h"
 #include "platform/graphics/paint/ClipPaintPropertyNode.h"
@@ -23,6 +24,7 @@
 #include "platform/graphics/paint/ForeignLayerDisplayItem.h"
 #include "platform/graphics/paint/PaintArtifact.h"
 #include "platform/graphics/paint/PropertyTreeState.h"
+#include "platform/graphics/paint/ScrollPaintPropertyNode.h"
 #include "platform/graphics/paint/TransformPaintPropertyNode.h"
 #include "public/platform/Platform.h"
 #include "public/platform/WebCompositorSupport.h"
@@ -175,6 +177,10 @@ void setMinimalPropertyTrees(cc::PropertyTrees* propertyTrees, int ownerId)
 
     cc::ScrollTree& scrollTree = propertyTrees->scroll_tree;
     scrollTree.clear();
+    cc::ScrollNode& scrollNode = *scrollTree.Node(scrollTree.Insert(cc::ScrollNode(), kRealRootNodeId));
+    DCHECK_EQ(scrollNode.id, kSecondaryRootNodeId);
+    scrollNode.owner_id = ownerId;
+    scrollNode.transform_id = kRealRootNodeId;
 }
 
 } // namespace
@@ -222,6 +228,16 @@ public:
     int compositorIdForClipNode(const ClipPaintPropertyNode*);
     int switchToEffectNode(const EffectPaintPropertyNode& nextEffect);
     int compositorIdForCurrentEffectNode() const { return m_effectStack.last().id; }
+    int compositorIdForScrollNode(const ScrollPaintPropertyNode*);
+    bool compositorIdExistsForScrollNode(const ScrollPaintPropertyNode* scrollNode)
+    {
+        return m_scrollNodeMap.contains(scrollNode);
+    }
+
+    // Scroll offset has special treatment in the compositor and needs an
+    // adjustment to the transform node (to switch from a transform to a scroll
+    // offset) as well as an update to the ScrollTree scroll offset.
+    void updateScrollOffset(int layerId, int scrollId);
 
 private:
     void buildEffectNodesRecursively(const EffectPaintPropertyNode* nextEffect);
@@ -229,6 +245,7 @@ private:
     cc::TransformTree& transformTree() { return m_propertyTrees.transform_tree; }
     cc::ClipTree& clipTree() { return m_propertyTrees.clip_tree; }
     cc::EffectTree& effectTree() { return m_propertyTrees.effect_tree; }
+    cc::ScrollTree& scrollTree() { return m_propertyTrees.scroll_tree; }
 
     const EffectPaintPropertyNode* currentEffectNode() const { return m_effectStack.last().effect; }
 
@@ -242,6 +259,7 @@ private:
     // Maps from Blink-side property tree nodes to cc property node indices.
     HashMap<const TransformPaintPropertyNode*, int> m_transformNodeMap;
     HashMap<const ClipPaintPropertyNode*, int> m_clipNodeMap;
+    HashMap<const ScrollPaintPropertyNode*, int> m_scrollNodeMap;
 
     struct BlinkEffectAndCcIdPair {
         const EffectPaintPropertyNode* effect;
@@ -333,6 +351,63 @@ int PropertyTreeManager::compositorIdForClipNode(const ClipPaintPropertyNode* cl
     return id;
 }
 
+int PropertyTreeManager::compositorIdForScrollNode(const ScrollPaintPropertyNode* scrollNode)
+{
+    if (!scrollNode)
+        return kSecondaryRootNodeId;
+
+    auto it = m_scrollNodeMap.find(scrollNode);
+    if (it != m_scrollNodeMap.end())
+        return it->value;
+
+    int parentId = compositorIdForScrollNode(scrollNode->parent());
+    int id = scrollTree().Insert(cc::ScrollNode(), parentId);
+
+    cc::ScrollNode& compositorNode = *scrollTree().Node(id);
+    compositorNode.owner_id = parentId;
+
+    // TODO(pdr): Set scrollable properly.
+    compositorNode.scrollable = true;
+
+    // TODO(pdr): Set main thread scrolling reasons.
+    IntSize snappedClip = roundedIntSize(scrollNode->clip());
+    compositorNode.scroll_clip_layer_bounds.SetSize(snappedClip.width(), snappedClip.height());
+    IntSize snappedBounds = roundedIntSize(scrollNode->bounds());
+    compositorNode.scroll_clip_layer_bounds.SetSize(snappedBounds.width(), snappedBounds.height());
+    compositorNode.user_scrollable_horizontal = scrollNode->userScrollableHorizontal();
+    compositorNode.user_scrollable_vertical = scrollNode->userScrollableVertical();
+    compositorNode.transform_id = compositorIdForTransformNode(scrollNode->scrollOffsetTranslation());
+
+    auto result = m_scrollNodeMap.set(scrollNode, id);
+    DCHECK(result.isNewEntry);
+    scrollTree().set_needs_update(true);
+
+    return id;
+}
+
+void PropertyTreeManager::updateScrollOffset(int layerId, int scrollId)
+{
+    cc::ScrollNode& scrollNode = *scrollTree().Node(scrollId);
+    cc::TransformNode& transformNode = *transformTree().Node(scrollNode.transform_id);
+
+    // The transform associated with a scroll should only contain a 2d scroll offset.
+    DCHECK(transformNode.local.IsIdentityOr2DTranslation());
+
+    // TODO(pdr): Set the transform node's scrollable bit from scrollNode.
+
+    auto scrollOffsetVector = transformNode.local.To2dTranslation();
+
+    // Remove the 2d scroll translation set from blink's transform paint property
+    // node.
+    transformNode.local.MakeIdentity();
+
+    gfx::ScrollOffset scrollOffset(scrollOffsetVector.x(), -scrollOffsetVector.y());
+    scrollTree().SetScrollOffset(layerId, scrollOffset);
+
+    // TODO(pdr): Is this needed or can we rely on SetScrollOffset handling it?
+    transformNode.scroll_offset = scrollOffset;
+}
+
 unsigned depth(const EffectPaintPropertyNode* node)
 {
     unsigned result = 0;
@@ -449,9 +524,12 @@ void PaintArtifactCompositor::update(const PaintArtifact& paintArtifact)
         scoped_refptr<cc::Layer> layer = layerForPaintChunk(paintArtifact, paintChunk, layerOffset);
 
         int transformId = propertyTreeManager.compositorIdForTransformNode(paintChunk.properties.transform.get());
+        int scrollId = propertyTreeManager.compositorIdForScrollNode(paintChunk.properties.scroll.get());
         int clipId = propertyTreeManager.compositorIdForClipNode(paintChunk.properties.clip.get());
         int effectId = propertyTreeManager.switchToEffectNode(*paintChunk.properties.effect.get());
 
+        propertyTreeManager.updateScrollOffset(layer->id(), scrollId);
+
         layer->set_offset_to_transform_parent(layerOffset);
 
         m_rootLayer->AddChild(layer);
@@ -459,7 +537,7 @@ void PaintArtifactCompositor::update(const PaintArtifact& paintArtifact)
         layer->SetTransformTreeIndex(transformId);
         layer->SetClipTreeIndex(clipId);
         layer->SetEffectTreeIndex(effectId);
-        layer->SetScrollTreeIndex(kRealRootNodeId);
+        layer->SetScrollTreeIndex(scrollId);
 
         // TODO(jbroman): This probably shouldn't be necessary, but it is still
         // queried by RenderSurfaceImpl.