Add ClipNode when Render Surface Inherits Clip

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 <map>
 #include <set>
 
 #include "cc/base/math_util.h"
@@ skipping 61 matching lines @@
   const bool render_surface_may_grow_due_to_clip_children =
       layer->render_surface() && layer->num_unclipped_descendants() > 0;
 
   if (layer->masks_to_bounds() || layer->mask_layer() ||
       render_surface_may_grow_due_to_clip_children)
     return true;
 
   if (!render_surface_applies_clip)
     return false;
 
+  if (!layer->transform().IsFlat())

[ajuma, 2015/08/04 15:37:19]

What if the transform is animated, and becomes non-flat on the compositor thread
(after tree creation)? How about just unconditionally creating a node if we
reach this point (and then we can get rid of the axis-alignment logic below)?

[jaydasika, 2015/08/04 15:38:53]

That breaks a lot of unit tests.

[ajuma, 2015/08/04 15:40:26]

It'd be good to understand why (since if there's something incorrect about that,
there might also be something incorrect about the non-flat case too, but we
maybe we just don't have that many unit tests with non-flat transforms).

+    return true;
+
   bool axis_aligned_with_respect_to_parent =
       data.transform_tree->Are2DAxisAligned(layer->transform_tree_index(),
                                             parent_transform_id);
 
   return !axis_aligned_with_respect_to_parent;
 }
 
 template <typename LayerType>
 static bool LayerClipsSubtree(LayerType* layer) {
   return layer->masks_to_bounds() || layer->mask_layer();
@@ skipping 23 matching lines @@
     data_for_children->ancestor_clips_subtree = ancestor_clips_subtree;
   }
 
   if (LayerClipsSubtree(layer))
     data_for_children->ancestor_clips_subtree = true;
 
   if (has_unclipped_surface)
     parent_id = 0;
 
   if (!RequiresClipNode(layer, data_from_ancestor, parent->data.transform_id,
-                        data_for_children->ancestor_clips_subtree)) {
+                        ancestor_clips_subtree)) {
     // Unclipped surfaces reset the clip rect.
     data_for_children->clip_tree_parent = parent_id;
   } else {
     LayerType* transform_parent = data_for_children->transform_tree_parent;
     if (layer->position_constraint().is_fixed_position() &&
         !created_transform_node) {
       transform_parent = data_for_children->transform_fixed_parent;
     }
     ClipNode node;
     node.data.clip = gfx::RectF(
         gfx::PointF() + layer->offset_to_transform_parent(), layer->bounds());
     node.data.transform_id = transform_parent->transform_tree_index();
     node.data.target_id =
         data_for_children->render_target->transform_tree_index();
     node.owner_id = layer->id();
+    node.data.inherit_parent_target_space_clip =
+        !data_for_children->ancestor_clips_subtree &&
+        layer->has_render_surface() && ancestor_clips_subtree;
 
     data_for_children->clip_tree_parent =
         data_for_children->clip_tree->Insert(node, parent_id);
   }
 
   layer->SetClipTreeIndex(
       has_unclipped_surface ? 0 : data_for_children->clip_tree_parent);
 
   layer->set_is_clipped(data_for_children->ancestor_clips_subtree);
 
@@ skipping 349 matching lines @@
     const gfx::Rect& viewport,
     const gfx::Transform& device_transform,
     PropertyTrees* property_trees) {
   BuildPropertyTreesTopLevelInternal(
       root_layer, page_scale_layer, inner_viewport_scroll_layer,
       outer_viewport_scroll_layer, page_scale_factor, device_scale_factor,
       viewport, device_transform, property_trees);
 }
 
 }  // namespace cc