cc : Create effect nodes for non axis aligned clips

cc/trees/property_tree_builder.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/trees/property_tree_builder.h"
 
 #include <stddef.h>
 
 #include <map>
 #include <set>
@@ skipping 37 matching lines @@
   bool in_subtree_of_page_scale_layer;
   bool affected_by_inner_viewport_bounds_delta;
   bool affected_by_outer_viewport_bounds_delta;
   bool should_flatten;
   bool is_hidden;
   uint32_t main_thread_scrolling_reasons;
   bool scroll_tree_parent_created_by_uninheritable_criteria;
   const gfx::Transform* device_transform;
   gfx::Transform compound_transform_since_render_target;
   bool animation_axis_aligned_since_render_target;
+  bool not_axis_aligned_since_last_clip;
   SkColor safe_opaque_background_color;
 };
 
 static LayerPositionConstraint PositionConstraint(Layer* layer) {
   return layer->position_constraint();
 }
 
 static LayerPositionConstraint PositionConstraint(LayerImpl* layer) {
   return layer->test_properties()->position_constraint;
 }
@@ skipping 807 matching lines @@
   const bool has_proxied_opacity =
       !!(layer->mutable_properties() & MutableProperty::kOpacity);
 
   data_for_children->animation_axis_aligned_since_render_target &=
       AnimationsPreserveAxisAlignment(layer);
   data_for_children->compound_transform_since_render_target *= Transform(layer);
   const bool should_create_render_surface = ShouldCreateRenderSurface(
       layer, data_for_children->compound_transform_since_render_target,
       data_for_children->animation_axis_aligned_since_render_target);
 
+  bool not_axis_aligned_since_last_clip =
+      data_from_ancestor.not_axis_aligned_since_last_clip
+          ? true
+          : !AnimationsPreserveAxisAlignment(layer) ||
+                !Transform(layer).Preserves2dAxisAlignment();
+  // A non-axis aligned clip may need a render surface. So, we create an effect
+  // node.
+  bool has_non_axis_aligned_clip =
+      not_axis_aligned_since_last_clip && LayerClipsSubtree(layer);
+
   bool requires_node = is_root || has_transparency ||
                        has_potential_opacity_animation || has_proxied_opacity ||
+                       has_non_axis_aligned_clip ||
                        should_create_render_surface;
 
   int parent_id = data_from_ancestor.effect_tree_parent;
 
   if (!requires_node) {
     layer->SetEffectTreeIndex(parent_id);
     data_for_children->effect_tree_parent = parent_id;
     return false;
   }
 
@@ skipping 245 matching lines @@
   bool created_transform_node = AddTransformNodeIfNeeded(
       data_from_parent, layer, created_render_surface, &data_for_children);
   AddClipNodeIfNeeded(data_from_parent, layer, created_transform_node,
                       &data_for_children);
 
   AddScrollNodeIfNeeded(data_from_parent, layer, &data_for_children);
 
   SetBackfaceVisibilityTransform(layer, created_transform_node);
   SetSafeOpaqueBackgroundColor(data_from_parent, layer, &data_for_children);
 
+  bool not_axis_aligned_since_last_clip =
+      data_from_parent.not_axis_aligned_since_last_clip
+          ? true
+          : !AnimationsPreserveAxisAlignment(layer) ||
+                !Transform(layer).Preserves2dAxisAlignment();
+  bool has_non_axis_aligned_clip =
+      not_axis_aligned_since_last_clip && LayerClipsSubtree(layer);
+  data_for_children.not_axis_aligned_since_last_clip =
+      !has_non_axis_aligned_clip;
+
   for (size_t i = 0; i < Children(layer).size(); ++i) {
     LayerType* current_child = ChildAt(layer, i);
     SetLayerPropertyChangedForChild(layer, current_child);
     if (!ScrollParent(current_child)) {
       BuildPropertyTreesInternal(current_child, data_for_children);
     } else {
       // The child should be included in its scroll parent's list of scroll
       // children.
       DCHECK(ScrollChildren(ScrollParent(current_child))->count(current_child));
     }
@@ skipping 90 matching lines @@
   data_for_recursion.is_hidden = false;
   data_for_recursion.main_thread_scrolling_reasons =
       MainThreadScrollingReason::kNotScrollingOnMain;
   data_for_recursion.scroll_tree_parent_created_by_uninheritable_criteria =
       true;
   data_for_recursion.device_transform = &device_transform;
 
   data_for_recursion.property_trees->clear();
   data_for_recursion.compound_transform_since_render_target = gfx::Transform();
   data_for_recursion.animation_axis_aligned_since_render_target = true;
+  data_for_recursion.not_axis_aligned_since_last_clip = false;
   data_for_recursion.property_trees->transform_tree.set_device_scale_factor(
       device_scale_factor);
   data_for_recursion.safe_opaque_background_color = color;
 
   ClipNode root_clip;
   root_clip.clip_type = ClipNode::ClipType::APPLIES_LOCAL_CLIP;
   root_clip.clip = gfx::RectF(viewport);
   root_clip.transform_id = TransformTree::kRootNodeId;
   data_for_recursion.clip_tree_parent =
       data_for_recursion.property_trees->clip_tree.Insert(
@@ skipping 93 matching lines @@
       root_layer, page_scale_layer, inner_viewport_scroll_layer,
       outer_viewport_scroll_layer, overscroll_elasticity_layer,
       elastic_overscroll, page_scale_factor, device_scale_factor, viewport,
       device_transform, property_trees, color);
   property_trees->effect_tree.CreateOrReuseRenderSurfaces(
       &render_surfaces, root_layer->layer_tree_impl());
   property_trees->ResetCachedData();
 }
 
 }  // namespace cc