Handle nested position:sticky elements correctly (compositor)

cc/layers/layer.cc

 // Copyright 2010 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/layers/layer.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 11 matching lines @@
 #include "cc/layers/layer_impl.h"
 #include "cc/layers/scrollbar_layer_interface.h"
 #include "cc/output/copy_output_request.h"
 #include "cc/output/copy_output_result.h"
 #include "cc/trees/draw_property_utils.h"
 #include "cc/trees/effect_node.h"
 #include "cc/trees/layer_tree_host.h"
 #include "cc/trees/layer_tree_impl.h"
 #include "cc/trees/mutable_properties.h"
 #include "cc/trees/mutator_host.h"
+#include "cc/trees/scroll_node.h"

[flackr, 2017/03/17 15:01:55]

Obsolete?

[smcgruer, 2017/03/17 17:36:51]

Done.

 #include "cc/trees/transform_node.h"
 #include "third_party/skia/include/core/SkImageFilter.h"
 #include "ui/gfx/geometry/rect_conversions.h"
 #include "ui/gfx/geometry/vector2d_conversions.h"
 
 namespace cc {
 
 base::StaticAtomicSequenceNumber g_next_layer_id;
 
 Layer::Inputs::Inputs(int layer_id)
@@ skipping 540 matching lines @@
                                        id())) {
     DCHECK_EQ(transform_tree_index(),
               property_trees->layer_id_to_transform_node_index[id()]);
     TransformNode* transform_node =
         property_trees->transform_tree.Node(transform_tree_index());
     transform_node->update_post_local_transform(position, transform_origin());
     if (transform_node->sticky_position_constraint_id >= 0) {
       StickyPositionNodeData* sticky_data =
           property_trees->transform_tree.StickyPositionData(
               transform_tree_index());
+      // This calculation will be incorrect if we have an ancestor sticky
+      // element that is not composited: http://crbug.com/702229

[flackr, 2017/03/17 15:01:55]

Can you change this to a TODO to either pass the main thread sticky shifting
offset of the non composited element or promote the ancestor sticky element?
i.e. suggests this will be fixed soon.

[smcgruer, 2017/03/17 17:36:51]

Done.

       sticky_data->main_thread_offset =
           position.OffsetFromOrigin() -
           sticky_data->constraints.parent_relative_sticky_box_offset
               .OffsetFromOrigin();
     }
     transform_node->needs_local_transform_update = true;
     transform_node->transform_changed = true;
     layer_tree_host_->property_trees()->transform_tree.set_needs_update(true);
     SetNeedsCommitNoRebuild();
     return;
@@ skipping 905 matching lines @@
       ->num_copy_requests_in_subtree;
 }
 
 gfx::Transform Layer::screen_space_transform() const {
   DCHECK_NE(transform_tree_index_, TransformTree::kInvalidNodeId);
   return draw_property_utils::ScreenSpaceTransform(
       this, layer_tree_host_->property_trees()->transform_tree);
 }
 
 }  // namespace cc