Implement CSS: scroll-boundary-behavior

cc/layers/layer_impl.cc

 // Copyright 2012 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_impl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 62 matching lines @@
       draw_blend_mode_(SkBlendMode::kSrcOver),
       transform_tree_index_(TransformTree::kInvalidNodeId),
       effect_tree_index_(EffectTree::kInvalidNodeId),
       clip_tree_index_(ClipTree::kInvalidNodeId),
       scroll_tree_index_(ScrollTree::kInvalidNodeId),
       current_draw_mode_(DRAW_MODE_NONE),
       mutable_properties_(MutableProperty::kNone),
       debug_info_(nullptr),
       has_will_change_transform_hint_(false),
       needs_push_properties_(false),
-      scrollbars_hidden_(false) {
+      scrollbars_hidden_(false),
+      scroll_boundary_behavior_(SCROLL_BOUNDARY_BEHAVIOR_PROPAGATE) {

[bokan, 2017/03/23 13:18:26]

How does a LayerImpl get scroll_boundary_behavior_ set? I think you need to add
a line in Layer::PushPropertiesTo(LayerImpl*)

[sunyunjia, 2017/03/23 20:16:54]

Yeah, that's added.

[bokan, 2017/03/23 21:52:19]

Sorry, actually, now that you're storing the bit in ScrollNode, you don't
actually need to propagate this to LayerImpl. I think we can just return the
default value here and not worry about it, maybe DCHECK that it's not called?
+ajuma@, this value is only needed (and non-default from Blink) on cc::Layer to
build the scroll tree but the BuildPropertyTree functions demand both kinds of
layers have the same interface. What's the right way to handle this?

   DCHECK_GT(layer_id_, 0);
 
   DCHECK(layer_tree_impl_);
   layer_tree_impl_->RegisterLayer(this);
   layer_tree_impl_->AddToElementMap(this);
 
   SetNeedsPushProperties();
 }
 
 LayerImpl::~LayerImpl() {
@@ skipping 247 matching lines @@
 
   if (layer_property_changed_) {
     layer->layer_tree_impl()->set_needs_update_draw_properties();
     layer->layer_property_changed_ = true;
   }
 
   layer->SetBounds(bounds_);
   layer->SetScrollClipLayer(scroll_clip_layer_id_);
   layer->SetElementId(element_id_);
   layer->SetMutableProperties(mutable_properties_);
+  layer->SetScrollBoundaryBehavior(scroll_boundary_behavior_);
 
   // If the main thread commits multiple times before the impl thread actually
   // draws, then damage tracking will become incorrect if we simply clobber the
   // update_rect here. The LayerImpl's update_rect needs to accumulate (i.e.
   // union) any update changes that have occurred on the main thread.
   update_rect_.Union(layer->update_rect());
   layer->SetUpdateRect(update_rect_);
 
   if (owned_debug_info_)
     layer->SetDebugInfo(std::move(owned_debug_info_));
@@ skipping 466 matching lines @@
 
 gfx::Vector2dF LayerImpl::ClampScrollToMaxScrollOffset() {
   gfx::ScrollOffset old_offset = CurrentScrollOffset();
   gfx::ScrollOffset clamped_offset = ClampScrollOffsetToLimits(old_offset);
   gfx::Vector2dF delta = clamped_offset.DeltaFrom(old_offset);
   if (!delta.IsZero())
     ScrollBy(delta);
   return delta;
 }
 
+void LayerImpl::SetScrollBoundaryBehavior(ScrollBoundaryBehavior behavior) {
+  if (scroll_boundary_behavior_ == behavior)
+    return;
+  scroll_boundary_behavior_ = behavior;
+  layer_tree_impl()->DidUpdateScrollState(id());
+  NoteLayerPropertyChanged();
+}
+
 void LayerImpl::SetNeedsPushProperties() {
   if (layer_tree_impl_ && !needs_push_properties_) {
     needs_push_properties_ = true;
     layer_tree_impl()->AddLayerShouldPushProperties(this);
   }
 }
 
 void LayerImpl::GetAllPrioritizedTilesForTracing(
     std::vector<PrioritizedTile>* prioritized_tiles) const {
 }
@@ skipping 203 matching lines @@
 
 ScrollTree& LayerImpl::GetScrollTree() const {
   return GetPropertyTrees()->scroll_tree;
 }
 
 TransformTree& LayerImpl::GetTransformTree() const {
   return GetPropertyTrees()->transform_tree;
 }
 
 }  // namespace cc