cc: Additional comments and cleanup of cc::Layer APIs.

The GetTransformNode() method is removed, as it is only safe to use
in certain cases, and just wraps a call to get the node from the
property tree, just do it directly in the callers.

R=weiliangc@chromium.org

Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I6f242f60209c6d9e3d603cfcf60f59ecafc8f523
Reviewed-on: https://chromium-review.googlesource.com/1099765Reviewed-by: weiliangc <weiliangc@chromium.org>
Commit-Queue: danakj <danakj@chromium.org>
Cr-Commit-Position: refs/heads/master@{#567386}

cc/layers/layer.cc

@@ -629,8 +629,10 @@ void Layer::SetPosition(const gfx::PointF& position) {
     return;
 
   SetSubtreePropertyChanged();
-  TransformNode* transform_node = GetTransformNode();
-  if (transform_node) {
+  if (has_transform_node_) {
+    TransformNode* transform_node =
+        layer_tree_host_->property_trees()->transform_tree.Node(
+            transform_tree_index_);
     transform_node->update_post_local_transform(position, transform_origin());
     transform_node->needs_local_transform_update = true;
     transform_node->transform_changed = true;
@@ -669,23 +671,21 @@ void Layer::SetTransform(const gfx::Transform& transform) {
   SetSubtreePropertyChanged();
   if (layer_tree_host_) {
     if (has_transform_node_) {
-      PropertyTrees* property_trees = layer_tree_host_->property_trees();
-      if (TransformNode* transform_node =
-              property_trees->transform_tree.Node(transform_tree_index())) {
-        // We need to trigger a rebuild if we could have affected 2d axis
-        // alignment. We'll check to see if transform and inputs_.transform are
-        // axis align with respect to one another.
-        DCHECK_EQ(transform_tree_index(), transform_node->id);
-        bool preserves_2d_axis_alignment =
-            Are2dAxisAligned(inputs_.transform, transform);
-        transform_node->local = transform;
-        transform_node->needs_local_transform_update = true;
-        transform_node->transform_changed = true;
-        layer_tree_host_->property_trees()->transform_tree.set_needs_update(
-            true);
-        if (!preserves_2d_axis_alignment)
-          SetPropertyTreesNeedRebuild();
-      }
+      TransformNode* transform_node =
+          layer_tree_host_->property_trees()->transform_tree.Node(
+              transform_tree_index_);
+      // We need to trigger a rebuild if we could have affected 2d axis
+      // alignment. We'll check to see if transform and inputs_.transform are
+      // axis align with respect to one another.
+      DCHECK_EQ(transform_tree_index(), transform_node->id);
+      bool preserves_2d_axis_alignment =
+          Are2dAxisAligned(inputs_.transform, transform);
+      transform_node->local = transform;
+      transform_node->needs_local_transform_update = true;
+      transform_node->transform_changed = true;
+      layer_tree_host_->property_trees()->transform_tree.set_needs_update(true);
+      if (!preserves_2d_axis_alignment)
+        SetPropertyTreesNeedRebuild();
     } else {
       SetPropertyTreesNeedRebuild();
     }
@@ -705,8 +705,10 @@ void Layer::SetTransformOrigin(const gfx::Point3F& transform_origin) {
     return;
 
   SetSubtreePropertyChanged();
-  TransformNode* transform_node = GetTransformNode();
-  if (transform_node) {
+  if (has_transform_node_) {
+    TransformNode* transform_node =
+        layer_tree_host_->property_trees()->transform_tree.Node(
+            transform_tree_index_);
     DCHECK_EQ(transform_tree_index(), transform_node->id);
     transform_node->update_pre_local_transform(transform_origin);
     transform_node->update_post_local_transform(position(), transform_origin);
@@ -1349,13 +1351,6 @@ void Layer::OnOpacityAnimated(float opacity) {
   inputs_.opacity = opacity;
 }
 
-TransformNode* Layer::GetTransformNode() const {
-  return has_transform_node_
-             ? layer_tree_host_->property_trees()->transform_tree.Node(
-                   transform_tree_index_)
-             : nullptr;
-}
-
 void Layer::OnTransformAnimated(const gfx::Transform& transform) {
   inputs_.transform = transform;
 }

cc/layers/layer.h

@@ -251,6 +251,14 @@ class CC_EXPORT Layer : public base::RefCounted<Layer> {
   void SetFilters(const FilterOperations& filters);
   const FilterOperations& filters() const { return inputs_.filters; }
 
+  // Set or get the origin to be used when applying the filters given to
+  // SetFilters(). By default the origin is at the origin of this layer, but
+  // may be moved positively or negatively relative to that. The origin effects
+  // any filters which do not apply uniformly to the entire layer and its
+  // subtree.
+  void SetFiltersOrigin(const gfx::PointF& origin);
+  gfx::PointF filters_origin() const { return inputs_.filters_origin; }
+
   // Set or get the list of filters that should be applied to the content this
   // layer and its subtree will be drawn into. The effect is clipped to only
   // apply directly behind this layer and its subtree.
@@ -459,8 +467,6 @@ class CC_EXPORT Layer : public base::RefCounted<Layer> {
     return inputs_.should_flatten_transform;
   }
 
-  bool Is3dSorted() const { return inputs_.sorting_context_id != 0; }
-
   void SetUseParentBackfaceVisibility(bool use);
   bool use_parent_backface_visibility() const {
     return inputs_.use_parent_backface_visibility;
@@ -485,14 +491,19 @@ class CC_EXPORT Layer : public base::RefCounted<Layer> {
   // given SetIsDrawable(true).
   bool DrawsContent() const;
 
+  // Returns the number of layers in this layers subtree (excluding itself) for
+  // which DrawsContent() is true.
+  int NumDescendantsThatDrawContent() const;
+
+  // Set or get if this layer and its subtree should be part of the compositor's
+  // output to the screen. When set to true, the layer's subtree does not appear
+  // to the user, but still remains part of the tree with all its normal drawing
+  // properties. This can be used to execute a CopyOutputRequest on this layer
+  // or another in its subtree, since the layers are still able to be drawn by
+  // the compositor, while not being composed into the result shown to the user.
   void SetHideLayerAndSubtree(bool hide);
   bool hide_layer_and_subtree() const { return inputs_.hide_layer_and_subtree; }
 
-  void SetFiltersOrigin(const gfx::PointF& origin);
-  gfx::PointF filters_origin() const { return inputs_.filters_origin; }
-
-  int NumDescendantsThatDrawContent() const;
-
   void UpdateDebugInfo();
 
   void SetLayerClient(base::WeakPtr<LayerClient> client);
@@ -521,6 +532,11 @@ class CC_EXPORT Layer : public base::RefCounted<Layer> {
   int effect_tree_index() const;
   int scroll_tree_index() const;
 
+  // While all layers have an index into the transform tree, this value
+  // indicates whether the transform tree node was created for this layer.
+  void SetHasTransformNode(bool val) { has_transform_node_ = val; }
+  bool has_transform_node() { return has_transform_node_; }
+
   void SetOffsetToTransformParent(gfx::Vector2dF offset);
   gfx::Vector2dF offset_to_transform_parent() const {
     return offset_to_transform_parent_;
@@ -561,10 +577,6 @@ class CC_EXPORT Layer : public base::RefCounted<Layer> {
   // Called on the scroll layer to trigger showing the overlay scrollbars.
   void ShowScrollbars() { needs_show_scrollbars_ = true; }
 
-  bool has_transform_node() { return has_transform_node_; }
-  void SetHasTransformNode(bool val) { has_transform_node_ = val; }
-  TransformNode* GetTransformNode() const;
-
   // Internal method to create the compositor thread type for this Layer.
   // Subclasses should override this method if they want to return their own
   // subclass of LayerImpl instead.
@@ -852,9 +864,6 @@ class CC_EXPORT Layer : public base::RefCounted<Layer> {
   bool subtree_property_changed_ : 1;
   bool may_contain_video_ : 1;
   bool needs_show_scrollbars_ : 1;
-  // Whether the nodes referred to by *_tree_index_ "belong" to this
-  // layer. Only applicable if LayerTreeSettings.use_layer_lists is
-  // false.
   bool has_transform_node_ : 1;
   // This value is valid only when LayerTreeHost::has_copy_request() is true
   bool subtree_has_copy_request_ : 1;

cc/trees/layer_tree_host.cc

@@ -1524,7 +1524,9 @@ void LayerTreeHost::SetElementTransformMutated(
   DCHECK(layer);
   layer->OnTransformAnimated(transform);
 
-  if (TransformNode* node = layer->GetTransformNode()) {
+  if (layer->has_transform_node()) {
+    TransformNode* node =
+        property_trees_.transform_tree.Node(layer->transform_tree_index());
     if (node->local == transform)
       return;
 

cc/trees/property_tree_builder.cc

@@ -296,7 +296,7 @@ static inline int SortingContextId(LayerImpl* layer) {
 }
 
 static inline bool Is3dSorted(Layer* layer) {
-  return layer->Is3dSorted();
+  return layer->sorting_context_id() != 0;
 }
 
 static inline bool Is3dSorted(LayerImpl* layer) {