[BGPT] Ensure cc::TransformNode::in_subtree_of_page_scale_layer is set

cc::TransformNode::in_subtree_of_page_scale_layer is important for
avoiding raster during pinch-zoom (see ideal_page_scale calculation
in PictureLayerImpl::UpdateIdealScales) and was not being set at the
blink->cc boundary when BlinkGenPropertyTrees was enabled.

This patch adds in_subtree_of_page_scale to TransformPaintPropertyNode
and sets it when building the VisualViewport property nodes. This is
then used to update cc::TransformNode::in_subtree_of_page_scale_layer
in PaintPropertyTreeManager.

Bug: 951861
Change-Id: Ic3bd0f48fb3a383825503b04b4f42d7db51bd651
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1586996Reviewed-by: Xianzhu Wang <wangxianzhu@chromium.org>
Auto-Submit: Philip Rogers <pdr@chromium.org>
Commit-Queue: Xianzhu Wang <wangxianzhu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#654866}

third_party/blink/renderer/core/frame/visual_viewport.cc

@@ -130,6 +130,7 @@ PaintPropertyChangeType VisualViewport::UpdatePaintPropertyNodesIfNeeded(
         GetChromeClient()->GetDeviceEmulationTransform();
     if (!device_emulation_transform.IsIdentity()) {
       TransformPaintPropertyNode::State state{device_emulation_transform};
+      state.in_subtree_of_page_scale = false;
       if (!device_emulation_transform_node_) {
         device_emulation_transform_node_ = TransformPaintPropertyNode::Create(
             *transform_parent, std::move(state));
@@ -152,7 +153,10 @@ PaintPropertyChangeType VisualViewport::UpdatePaintPropertyNodesIfNeeded(
   }
 
   {
+    DCHECK(!transform_parent->IsInSubtreeOfPageScale());
+
     TransformPaintPropertyNode::State state;
+    state.in_subtree_of_page_scale = false;
     state.compositor_element_id = GetCompositorOverscrollElasticityElementId();
     // TODO(crbug.com/877794) Should create overscroll elasticity transform node
     // based on settings.
@@ -170,6 +174,7 @@ PaintPropertyChangeType VisualViewport::UpdatePaintPropertyNodesIfNeeded(
   {
     TransformPaintPropertyNode::State state{
         TransformationMatrix().Scale(Scale())};
+    state.in_subtree_of_page_scale = false;
     state.compositor_element_id = GetCompositorElementId();
 
     if (!scale_transform_node_) {

third_party/blink/renderer/core/frame/visual_viewport_test.cc

@@ -2594,5 +2594,36 @@ TEST_P(VisualViewportTest, DirectPinchZoomPropertyUpdate) {
   EXPECT_EQ(3.f, visual_viewport.Scale());
 }
 
+// |TransformPaintPropertyNode::in_subtree_of_page_scale| should be false for
+// the page scale transform node and all ancestors, and should be true for
+// descendants of the page scale transform node.
+TEST_P(VisualViewportTest, InSubtreeOfPageScale) {
+  InitializeWithAndroidSettings();
+  RegisterMockedHttpURLLoad("200-by-800-viewport.html");
+  NavigateTo(base_url_ + "200-by-800-viewport.html");
+
+  UpdateAllLifecyclePhases();
+
+  VisualViewport& visual_viewport = GetFrame()->GetPage()->GetVisualViewport();
+  const auto* page_scale = visual_viewport.GetPageScaleNode();
+  // The page scale is not in its own subtree.
+  EXPECT_FALSE(page_scale->IsInSubtreeOfPageScale());
+  // Ancestors of the page scale are not in the page scale's subtree.
+  for (const auto* ancestor = page_scale->Parent(); ancestor;
+       ancestor = ancestor->Parent()) {
+    EXPECT_FALSE(ancestor->IsInSubtreeOfPageScale());
+  }
+
+  const auto* view = GetFrame()->View()->GetLayoutView();
+  const auto& view_contents_transform =
+      view->FirstFragment().ContentsProperties().Transform();
+  // Descendants of the page scale node should have |IsInSubtreeOfPageScale|.
+  EXPECT_TRUE(view_contents_transform.IsInSubtreeOfPageScale());
+  for (const auto* ancestor = view_contents_transform.Parent();
+       ancestor != page_scale; ancestor = ancestor->Parent()) {
+    EXPECT_TRUE(ancestor->IsInSubtreeOfPageScale());
+  }
+}
+
 }  // namespace
 }  // namespace blink

third_party/blink/renderer/platform/graphics/compositing/paint_artifact_compositor_test.cc

@@ -3398,6 +3398,7 @@ TEST_P(PaintArtifactCompositorTest, CreatesViewportNodes) {
   TransformationMatrix matrix;
   matrix.Scale(2);
   TransformPaintPropertyNode::State transform_state{matrix};
+  transform_state.in_subtree_of_page_scale = false;
   transform_state.compositor_element_id =
       CompositorElementIdFromUniqueObjectId(1);
 
@@ -3420,6 +3421,58 @@ TEST_P(PaintArtifactCompositorTest, CreatesViewportNodes) {
   EXPECT_TRUE(cc_transform_node->pre_local.IsIdentity());
 }
 
+// Test that |cc::TransformNode::in_subtree_of_page_scale_layer| is not set on
+// the page scale transform node or ancestors, and is set on descendants.
+TEST_P(PaintArtifactCompositorTest, InSubtreeOfPageScale) {
+  TransformPaintPropertyNode::State ancestor_transform_state;
+  ancestor_transform_state.in_subtree_of_page_scale = false;
+  auto ancestor_transform = TransformPaintPropertyNode::Create(
+      TransformPaintPropertyNode::Root(), std::move(ancestor_transform_state));
+
+  TransformPaintPropertyNode::State page_scale_transform_state;
+  page_scale_transform_state.in_subtree_of_page_scale = false;
+  page_scale_transform_state.compositor_element_id =
+      CompositorElementIdFromUniqueObjectId(1);
+  auto page_scale_transform = TransformPaintPropertyNode::Create(
+      *ancestor_transform, std::move(page_scale_transform_state));
+
+  TransformPaintPropertyNode::State descendant_transform_state;
+  descendant_transform_state.compositor_element_id =
+      CompositorElementIdFromUniqueObjectId(2);
+  descendant_transform_state.in_subtree_of_page_scale = true;
+  descendant_transform_state.direct_compositing_reasons =
+      CompositingReason::kWillChangeTransform;
+  auto descendant_transform = TransformPaintPropertyNode::Create(
+      *page_scale_transform, std::move(descendant_transform_state));
+
+  TestPaintArtifact artifact;
+  artifact.Chunk(*descendant_transform, c0(), e0())
+      .RectDrawing(FloatRect(0, 0, 10, 10), Color::kBlack);
+  ViewportProperties viewport_properties;
+  viewport_properties.page_scale = page_scale_transform.get();
+  CompositorElementIdSet element_ids;
+  Update(artifact.Build(), element_ids, viewport_properties);
+
+  cc::TransformTree& transform_tree = GetPropertyTrees().transform_tree;
+  const auto* cc_page_scale_transform = transform_tree.FindNodeFromElementId(
+      page_scale_transform_state.compositor_element_id);
+  // The page scale node is not in a subtree of the page scale layer.
+  EXPECT_FALSE(cc_page_scale_transform->in_subtree_of_page_scale_layer);
+
+  // Ancestors of the page scale node are not in a page scale subtree.
+  auto cc_ancestor_id = cc_page_scale_transform->parent_id;
+  while (cc_ancestor_id != cc::TransformTree::kInvalidNodeId) {
+    const auto* ancestor = transform_tree.Node(cc_ancestor_id);
+    EXPECT_FALSE(ancestor->in_subtree_of_page_scale_layer);
+    cc_ancestor_id = ancestor->parent_id;
+  }
+
+  // Descendants of the page scale node should be in the page scale subtree.
+  const auto* cc_descendant_transform = transform_tree.FindNodeFromElementId(
+      descendant_transform_state.compositor_element_id);
+  EXPECT_TRUE(cc_descendant_transform->in_subtree_of_page_scale_layer);
+}
+
 enum {
   kNoRenderSurface = 0,
   kHasRenderSurface = 1 << 0,

third_party/blink/renderer/platform/graphics/compositing/property_tree_manager.cc

@@ -365,6 +365,9 @@ int PropertyTreeManager::EnsureCompositorTransformNode(
     GetTransformTree().AddNodeAffectedByOuterViewportBoundsDelta(id);
   }
 
+  compositor_node.in_subtree_of_page_scale_layer =
+      transform_node.IsInSubtreeOfPageScale();
+
   if (const auto* sticky_constraint = transform_node.GetStickyConstraint()) {
     DCHECK(sticky_constraint->is_sticky);
     cc::StickyPositionNodeData* sticky_data =
@@ -467,6 +470,7 @@ void PropertyTreeManager::SetCcTransformNodeScrollToTransformTranslation(
 
 int PropertyTreeManager::EnsureCompositorPageScaleTransformNode(
     const TransformPaintPropertyNode& node) {
+  DCHECK(!node.IsInSubtreeOfPageScale());
   int id = EnsureCompositorTransformNode(node);
   DCHECK(GetTransformTree().Node(id));
   cc::TransformNode& compositor_node = *GetTransformTree().Node(id);

third_party/blink/renderer/platform/graphics/paint/transform_paint_property_node.cc

@@ -12,7 +12,11 @@ const TransformPaintPropertyNode& TransformPaintPropertyNode::Root() {
   DEFINE_STATIC_REF(
       TransformPaintPropertyNode, root,
       base::AdoptRef(new TransformPaintPropertyNode(
-          nullptr, State{FloatSize(), &ScrollPaintPropertyNode::Root()},
+          nullptr,
+          State{FloatSize(), &ScrollPaintPropertyNode::Root(),
+                false /* flattens_inherited_transform */,
+                false /* affected_by_outer_viewport_bounds_delta */,
+                false /* in_subtree_of_page_scale */},
           true /* is_parent_alias */)));
   return *root;
 }
@@ -59,6 +63,8 @@ std::unique_ptr<JSONObject> TransformPaintPropertyNode::ToJSON() const {
   }
   if (!state_.flattens_inherited_transform)
     json->SetBoolean("flattensInheritedTransform", false);
+  if (!state_.in_subtree_of_page_scale)
+    json->SetBoolean("in_subtree_of_page_scale", false);
   if (state_.backface_visibility != BackfaceVisibility::kInherited) {
     json->SetString("backface",
                     state_.backface_visibility == BackfaceVisibility::kVisible

third_party/blink/renderer/platform/graphics/paint/transform_paint_property_node.h

@@ -116,6 +116,7 @@ class PLATFORM_EXPORT TransformPaintPropertyNode
     scoped_refptr<const ScrollPaintPropertyNode> scroll;
     bool flattens_inherited_transform = false;
     bool affected_by_outer_viewport_bounds_delta = false;
+    bool in_subtree_of_page_scale = true;
     BackfaceVisibility backface_visibility = BackfaceVisibility::kInherited;
     unsigned rendering_context_id = 0;
     CompositingReasons direct_compositing_reasons = CompositingReason::kNone;
@@ -128,6 +129,7 @@ class PLATFORM_EXPORT TransformPaintPropertyNode
       if (flattens_inherited_transform != other.flattens_inherited_transform ||
           affected_by_outer_viewport_bounds_delta !=
               other.affected_by_outer_viewport_bounds_delta ||
+          in_subtree_of_page_scale != other.in_subtree_of_page_scale ||
           backface_visibility != other.backface_visibility ||
           rendering_context_id != other.rendering_context_id ||
           compositor_element_id != other.compositor_element_id ||
@@ -275,6 +277,12 @@ class PLATFORM_EXPORT TransformPaintPropertyNode
     return state_.affected_by_outer_viewport_bounds_delta;
   }
 
+  // If true, this node is a descendant of the page scale transform. This is
+  // important for avoiding raster during pinch-zoom (see: crbug.com/951861).
+  bool IsInSubtreeOfPageScale() const {
+    return state_.in_subtree_of_page_scale;
+  }
+
   const cc::LayerStickyPositionConstraint* GetStickyConstraint() const {
     return state_.sticky_constraint.get();
   }