cc/layers/layer.h - chromium/src - Git at Google

 // 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.

 #ifndef CC_LAYERS_LAYER_H_
 #define CC_LAYERS_LAYER_H_

 #include <stddef.h>
 #include <stdint.h>

 #include <set>
 #include <string>
 #include <unordered_map>
 #include <vector>

 #include "base/callback.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/observer_list.h"
 #include "cc/animation/layer_animation_controller.h"
 #include "cc/animation/layer_animation_value_observer.h"
 #include "cc/animation/layer_animation_value_provider.h"
 #include "cc/base/cc_export.h"
 #include "cc/base/region.h"
 #include "cc/debug/frame_timing_request.h"
 #include "cc/debug/micro_benchmark.h"
 #include "cc/input/input_handler.h"
 #include "cc/layers/layer_lists.h"
 #include "cc/layers/layer_position_constraint.h"
 #include "cc/layers/paint_properties.h"
 #include "cc/output/filter_operations.h"
 #include "cc/trees/property_tree.h"
 #include "skia/ext/refptr.h"
 #include "third_party/skia/include/core/SkColor.h"
 #include "third_party/skia/include/core/SkImageFilter.h"
 #include "third_party/skia/include/core/SkPicture.h"
 #include "third_party/skia/include/core/SkXfermode.h"
 #include "ui/gfx/geometry/point3_f.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/geometry/rect_f.h"
 #include "ui/gfx/geometry/scroll_offset.h"
 #include "ui/gfx/transform.h"

 namespace gfx {
 class BoxF;
 }

 namespace base {
 namespace trace_event {
 class ConvertableToTraceFormat;
 }
 }

 namespace cc {

 class Animation;
 class AnimationDelegate;
 struct AnimationEvent;
 class CopyOutputRequest;
 class LayerAnimationEventObserver;
 class LayerClient;
 class LayerImpl;
 class LayerSettings;
 class LayerTreeHost;
 class LayerTreeHostCommon;
 class LayerTreeImpl;
 class LayerTreeSettings;
 class RenderingStatsInstrumentation;
 class ResourceUpdateQueue;
 class ScrollbarLayerInterface;
 class SimpleEnclosedRegion;
 struct AnimationEvent;

 namespace proto {
 class LayerNode;
 class LayerProperties;
 class LayerUpdate;
 }  // namespace proto

 // Base class for composited layers. Special layer types are derived from
 // this class.
 class CC_EXPORT Layer : public base::RefCounted<Layer>,
                         public LayerAnimationValueObserver,
                         public LayerAnimationValueProvider {
  public:
   using LayerListType = LayerList;
   using LayerIdMap = std::unordered_map<int, scoped_refptr<Layer>>;

   enum LayerIdLabels {
     INVALID_ID = -1,
   };

   static scoped_refptr<Layer> Create(const LayerSettings& settings);

   int id() const { return layer_id_; }

   Layer* RootLayer();
   Layer* parent() { return parent_; }
   const Layer* parent() const { return parent_; }
   void AddChild(scoped_refptr<Layer> child);
   void InsertChild(scoped_refptr<Layer> child, size_t index);
   void ReplaceChild(Layer* reference, scoped_refptr<Layer> new_layer);
   void RemoveFromParent();
   void RemoveAllChildren();
   void SetChildren(const LayerList& children);
   bool HasAncestor(const Layer* ancestor) const;

   const LayerList& children() const { return children_; }
   Layer* child_at(size_t index) { return children_[index].get(); }

   // This requests the layer and its subtree be rendered and given to the
   // callback. If the copy is unable to be produced (the layer is destroyed
   // first), then the callback is called with a nullptr/empty result. If the
   // request's source property is set, any prior uncommitted requests having the
   // same source will be aborted.
   void RequestCopyOfOutput(scoped_ptr<CopyOutputRequest> request);
   bool HasCopyRequest() const {
     return !copy_requests_.empty();
   }

   virtual void SetBackgroundColor(SkColor background_color);
   SkColor background_color() const { return background_color_; }
   // If contents_opaque(), return an opaque color else return a
   // non-opaque color.  Tries to return background_color(), if possible.
   SkColor SafeOpaqueBackgroundColor() const;

   // A layer's bounds are in logical, non-page-scaled pixels (however, the
   // root layer's bounds are in physical pixels).
   void SetBounds(const gfx::Size& bounds);
   gfx::Size bounds() const { return bounds_; }

   void SetMasksToBounds(bool masks_to_bounds);
   bool masks_to_bounds() const { return masks_to_bounds_; }

   void SetMaskLayer(Layer* mask_layer);
   Layer* mask_layer() { return mask_layer_.get(); }
   const Layer* mask_layer() const { return mask_layer_.get(); }

   virtual void SetNeedsDisplayRect(const gfx::Rect& dirty_rect);
   void SetNeedsDisplay() { SetNeedsDisplayRect(gfx::Rect(bounds())); }

   void SetOpacity(float opacity);
   float opacity() const { return opacity_; }
   float EffectiveOpacity() const;
   bool OpacityIsAnimating() const;
   bool HasPotentiallyRunningOpacityAnimation() const;
   virtual bool OpacityCanAnimateOnImplThread() const;

   void SetBlendMode(SkXfermode::Mode blend_mode);
   SkXfermode::Mode blend_mode() const { return blend_mode_; }

   void set_draw_blend_mode(SkXfermode::Mode blend_mode) {
     if (draw_blend_mode_ == blend_mode)
       return;
     draw_blend_mode_ = blend_mode;
     SetNeedsPushProperties();
   }
   SkXfermode::Mode draw_blend_mode() const { return draw_blend_mode_; }

   bool uses_default_blend_mode() const {
     return blend_mode_ == SkXfermode::kSrcOver_Mode;
   }

   // A layer is root for an isolated group when it and all its descendants are
   // drawn over a black and fully transparent background, creating an isolated
   // group. It should be used along with SetBlendMode(), in order to restrict
   // layers within the group to blend with layers outside this group.
   void SetIsRootForIsolatedGroup(bool root);
   bool is_root_for_isolated_group() const {
     return is_root_for_isolated_group_;
   }

   void SetFilters(const FilterOperations& filters);
   const FilterOperations& filters() const { return filters_; }
   bool FilterIsAnimating() const;
   bool HasPotentiallyRunningFilterAnimation() const;

   // Background filters are filters applied to what is behind this layer, when
   // they are viewed through non-opaque regions in this layer. They are used
   // through the WebLayer interface, and are not exposed to HTML.
   void SetBackgroundFilters(const FilterOperations& filters);
   const FilterOperations& background_filters() const {
     return background_filters_;
   }

   virtual void SetContentsOpaque(bool opaque);
   bool contents_opaque() const { return contents_opaque_; }

   void SetPosition(const gfx::PointF& position);
   gfx::PointF position() const { return position_; }

   // A layer that is a container for fixed position layers cannot be both
   // scrollable and have a non-identity transform.
   void SetIsContainerForFixedPositionLayers(bool container);
   bool IsContainerForFixedPositionLayers() const;

   gfx::Vector2dF FixedContainerSizeDelta() const {
     return gfx::Vector2dF();
   }

   void SetPositionConstraint(const LayerPositionConstraint& constraint);
   const LayerPositionConstraint& position_constraint() const {
     return position_constraint_;
   }

   void SetTransform(const gfx::Transform& transform);
   const gfx::Transform& transform() const { return transform_; }
   bool TransformIsAnimating() const;
   bool HasPotentiallyRunningTransformAnimation() const;
   bool HasOnlyTranslationTransforms() const;
   bool AnimationsPreserveAxisAlignment() const;
   bool transform_is_invertible() const { return transform_is_invertible_; }

   bool MaximumTargetScale(float* max_scale) const;
   bool AnimationStartScale(float* start_scale) const;

   void SetTransformOrigin(const gfx::Point3F&);
   gfx::Point3F transform_origin() const { return transform_origin_; }

   bool HasAnyAnimationTargetingProperty(TargetProperty::Type property) const;

   bool ScrollOffsetAnimationWasInterrupted() const;

   void SetScrollParent(Layer* parent);

   Layer* scroll_parent() { return scroll_parent_; }
   const Layer* scroll_parent() const { return scroll_parent_; }

   void AddScrollChild(Layer* child);
   void RemoveScrollChild(Layer* child);

   std::set<Layer*>* scroll_children() { return scroll_children_.get(); }
   const std::set<Layer*>* scroll_children() const {
     return scroll_children_.get();
   }

   void SetClipParent(Layer* ancestor);

   Layer* clip_parent() { return clip_parent_; }
   const Layer* clip_parent() const {
     return clip_parent_;
   }

   void AddClipChild(Layer* child);
   void RemoveClipChild(Layer* child);

   std::set<Layer*>* clip_children() { return clip_children_.get(); }
   const std::set<Layer*>* clip_children() const {
     return clip_children_.get();
   }

   // TODO(enne): Fix style here (and everywhere) once LayerImpl does the same.
   gfx::Transform draw_transform() const;
   gfx::Transform screen_space_transform() const;

   void set_num_unclipped_descendants(size_t descendants) {
     num_unclipped_descendants_ = descendants;
   }
   size_t num_unclipped_descendants() const {
     return num_unclipped_descendants_;
   }

   void SetScrollOffset(const gfx::ScrollOffset& scroll_offset);
   void SetScrollCompensationAdjustment(
       const gfx::Vector2dF& scroll_compensation_adjustment);
   gfx::Vector2dF ScrollCompensationAdjustment() const;

   gfx::ScrollOffset scroll_offset() const { return scroll_offset_; }
   void SetScrollOffsetFromImplSide(const gfx::ScrollOffset& scroll_offset);

   void SetScrollClipLayerId(int clip_layer_id);
   bool scrollable() const { return scroll_clip_layer_id_ != INVALID_ID; }
   Layer* scroll_clip_layer() const;

   void SetUserScrollable(bool horizontal, bool vertical);
   bool user_scrollable_horizontal() const {
     return user_scrollable_horizontal_;
   }
   bool user_scrollable_vertical() const { return user_scrollable_vertical_; }

   void AddMainThreadScrollingReasons(uint32_t main_thread_scrolling_reasons);
   void ClearMainThreadScrollingReasons(
       uint32_t main_thread_scrolling_reasons_to_clear);
   uint32_t main_thread_scrolling_reasons() const {
     return main_thread_scrolling_reasons_;
   }
   bool should_scroll_on_main_thread() const {
     return !!main_thread_scrolling_reasons_;
   }

   void SetNonFastScrollableRegion(const Region& non_fast_scrollable_region);
   const Region& non_fast_scrollable_region() const {
     return non_fast_scrollable_region_;
   }

   void SetTouchEventHandlerRegion(const Region& touch_event_handler_region);
   const Region& touch_event_handler_region() const {
     return touch_event_handler_region_;
   }

   void set_did_scroll_callback(const base::Closure& callback) {
     did_scroll_callback_ = callback;
   }

   void SetForceRenderSurface(bool force_render_surface);
   bool force_render_surface() const { return force_render_surface_; }

   gfx::Vector2dF ScrollDelta() const { return gfx::Vector2dF(); }
   gfx::ScrollOffset CurrentScrollOffset() const { return scroll_offset_; }

   void SetDoubleSided(bool double_sided);
   bool double_sided() const { return double_sided_; }

   void SetShouldFlattenTransform(bool flatten);
   bool should_flatten_transform() const { return should_flatten_transform_; }

   bool Is3dSorted() const { return sorting_context_id_ != 0; }

   void SetUseParentBackfaceVisibility(bool use);
   bool use_parent_backface_visibility() const {
     return use_parent_backface_visibility_;
   }

   void SetUseLocalTransformForBackfaceVisibility(bool use_local);
   bool use_local_transform_for_backface_visibility() const {
     return use_local_transform_for_backface_visibility_;
   }

   void SetShouldCheckBackfaceVisibility(bool should_check_backface_visibility);
   bool should_check_backface_visibility() const {
     return should_check_backface_visibility_;
   }

   virtual void SetLayerTreeHost(LayerTreeHost* host);

   void SetIsDrawable(bool is_drawable);

   void SetHideLayerAndSubtree(bool hide);
   bool hide_layer_and_subtree() const { return hide_layer_and_subtree_; }

   void SetReplicaLayer(Layer* layer);
   Layer* replica_layer() { return replica_layer_.get(); }
   const Layer* replica_layer() const { return replica_layer_.get(); }

   bool has_mask() const { return !!mask_layer_.get(); }
   bool has_replica() const { return !!replica_layer_.get(); }
   bool replica_has_mask() const {
     return replica_layer_.get() &&
            (mask_layer_.get() || replica_layer_->mask_layer_.get());
   }

   int NumDescendantsThatDrawContent() const;

   // This is only virtual for tests.
   // TODO(awoloszyn): Remove this once we no longer need it for tests
   virtual bool DrawsContent() const;

   // This methods typically need to be overwritten by derived classes.
   // TODO(chrishtr): Blink no longer resizes anything during paint. We can
   // remove this.
   virtual void SavePaintProperties();
   // Returns true iff anything was updated that needs to be committed.
   virtual bool Update();
   virtual void SetIsMask(bool is_mask) {}
   virtual bool IsSuitableForGpuRasterization() const;

   virtual scoped_refptr<base::trace_event::ConvertableToTraceFormat>
   TakeDebugInfo();

   void SetLayerClient(LayerClient* client) { client_ = client; }

   virtual void PushPropertiesTo(LayerImpl* layer);

   // Sets the type proto::LayerType that should be used for serialization
   // of the current layer by calling LayerNode::set_type(proto::LayerType).
   // TODO(nyquist): Start using a forward declared enum class when
   // https://github.com/google/protobuf/issues/67 has been fixed and rolled in.
   // This function would preferably instead return a proto::LayerType, but
   // since that is an enum (the protobuf library does not generate enum
   // classes), it can't be forward declared. We don't want to include
   // //cc/proto/layer.pb.h in this header file, as it requires that all
   // dependent targets would have to be given the config for how to include it.
   virtual void SetTypeForProtoSerialization(proto::LayerNode* proto) const;

   // Recursively iterate over this layer and all children and write the
   // hierarchical structure to the given LayerNode proto. In addition to the
   // structure itself, the Layer id and type is also written to facilitate
   // construction of the correct layer on the client.
   void ToLayerNodeProto(proto::LayerNode* proto) const;

   // Recursively iterate over the given LayerNode proto and read the structure
   // into this node and its children. The |layer_map| should be used to look
   // for previously existing Layers, since they should be re-used between each
   // hierarchy update.
   void FromLayerNodeProto(const proto::LayerNode& proto,
                           const LayerIdMap& layer_map);

   // This method is similar to PushPropertiesTo, but instead of pushing to
   // a LayerImpl, it pushes the properties to proto::LayerProperties. It adds
   // this layer to the proto::LayerUpdate if it or any of its descendants
   // have changed properties. If this layer contains changed properties, the
   // properties themselves will also be pushed the proto::LayerProperties.
   // Similarly to PushPropertiesTo, this method also resets
   // |needs_push_properties_| and |num_dependents_need_push_properties_|.
   // Returns whether any of the descendants have changed properties.
   bool ToLayerPropertiesProto(proto::LayerUpdate* layer_update);

   // Read all property values from the given LayerProperties object and update
   // the current layer. The values for |needs_push_properties_| and
   // |num_dependents_need_push_properties_| are always updated, but the rest
   // of |proto| is only read if |needs_push_properties_| is set.
   void FromLayerPropertiesProto(const proto::LayerProperties& proto);

   LayerTreeHost* layer_tree_host() { return layer_tree_host_; }
   const LayerTreeHost* layer_tree_host() const { return layer_tree_host_; }

   bool AddAnimation(scoped_ptr<Animation> animation);
   void PauseAnimation(int animation_id, double time_offset);
   void RemoveAnimation(int animation_id);
   void AbortAnimation(int animation_id);
   LayerAnimationController* layer_animation_controller() const {
     return layer_animation_controller_.get();
   }
   void SetLayerAnimationControllerForTest(
       scoped_refptr<LayerAnimationController> controller);

   void set_layer_animation_delegate(AnimationDelegate* delegate) {
     DCHECK(layer_animation_controller_);
     layer_animation_controller_->set_layer_animation_delegate(delegate);
   }

   bool HasActiveAnimation() const;
   void RegisterForAnimations(AnimationRegistrar* registrar);

   void AddLayerAnimationEventObserver(
       LayerAnimationEventObserver* animation_observer);
   void RemoveLayerAnimationEventObserver(
       LayerAnimationEventObserver* animation_observer);

   virtual ScrollbarLayerInterface* ToScrollbarLayer();

   virtual skia::RefPtr<SkPicture> GetPicture() const;

   // Constructs a LayerImpl of the correct runtime type for this Layer type.
   virtual scoped_ptr<LayerImpl> CreateLayerImpl(LayerTreeImpl* tree_impl);

   bool NeedsDisplayForTesting() const { return !update_rect_.IsEmpty(); }
   void ResetNeedsDisplayForTesting() { update_rect_ = gfx::Rect(); }

   RenderingStatsInstrumentation* rendering_stats_instrumentation() const;

   const PaintProperties& paint_properties() const {
     return paint_properties_;
   }

   void SetNeedsPushProperties();
   bool needs_push_properties() const { return needs_push_properties_; }
   bool descendant_needs_push_properties() const {
     return num_dependents_need_push_properties_ > 0;
   }
   void reset_needs_push_properties_for_testing() {
     needs_push_properties_ = false;
   }

   virtual void RunMicroBenchmark(MicroBenchmark* benchmark);

   void Set3dSortingContextId(int id);
   int sorting_context_id() const { return sorting_context_id_; }

   void set_property_tree_sequence_number(int sequence_number) {
     property_tree_sequence_number_ = sequence_number;
   }
   int property_tree_sequence_number() { return property_tree_sequence_number_; }

   void SetTransformTreeIndex(int index);
   int transform_tree_index() const;

   void SetClipTreeIndex(int index);
   int clip_tree_index() const;

   void SetEffectTreeIndex(int index);
   int effect_tree_index() const;

   void SetScrollTreeIndex(int index);
   int scroll_tree_index() const;

   void set_offset_to_transform_parent(gfx::Vector2dF offset) {
     if (offset_to_transform_parent_ == offset)
       return;
     offset_to_transform_parent_ = offset;
     SetNeedsPushProperties();
   }
   gfx::Vector2dF offset_to_transform_parent() const {
     return offset_to_transform_parent_;
   }

   // TODO(enne): Once LayerImpl only uses property trees, remove these
   // functions.
   const gfx::Rect& visible_rect_from_property_trees() const {
     return visible_layer_rect();
   }
   void set_visible_rect_from_property_trees(const gfx::Rect& rect) {
     set_visible_layer_rect(rect);
   }
   const gfx::Rect& clip_rect_in_target_space_from_property_trees() const {
     return clip_rect();
   }
   void set_clip_rect_in_target_space_from_property_trees(
       const gfx::Rect& rect) {
     set_clip_rect(rect);
   }
   // TODO(enne): This needs a different name.  It is a calculated value
   // from the property tree builder and not a synonym for "should
   // flatten transform".
   void set_should_flatten_transform_from_property_tree(bool should_flatten) {
     if (should_flatten_transform_from_property_tree_ == should_flatten)
       return;
     should_flatten_transform_from_property_tree_ = should_flatten;
     SetNeedsPushProperties();
   }
   bool should_flatten_transform_from_property_tree() const {
     return should_flatten_transform_from_property_tree_;
   }

   const gfx::Rect& visible_layer_rect() const { return visible_layer_rect_; }
   void set_visible_layer_rect(const gfx::Rect& rect) {
     visible_layer_rect_ = rect;
   }

   const gfx::Rect& clip_rect() const { return clip_rect_; }
   void set_clip_rect(const gfx::Rect& rect) { clip_rect_ = rect; }

   // This should only be called during BeginMainFrame since it does not trigger
   // a Commit. This is called right after property tree being built and should
   // not trigger property tree rebuild.
   void SetHasRenderSurface(bool has_render_surface);
   bool has_render_surface() const {
     return has_render_surface_;
   }

   void SetSubtreePropertyChanged();
   bool subtree_property_changed() const { return subtree_property_changed_; }

   // Sets new frame timing requests for this layer.
   void SetFrameTimingRequests(const std::vector<FrameTimingRequest>& requests);

   // Accessor for unit tests
   const std::vector<FrameTimingRequest>& FrameTimingRequests() const {
     return frame_timing_requests_;
   }

   void DidBeginTracing();

   int num_copy_requests_in_target_subtree();

   void SetElementId(uint64_t id);
   uint64_t element_id() const { return element_id_; }

   void SetMutableProperties(uint32_t properties);
   uint32_t mutable_properties() const { return mutable_properties_; }

   void set_visited(bool visited);
   bool visited();
   void set_layer_or_descendant_is_drawn(bool layer_or_descendant_is_drawn);
   bool layer_or_descendant_is_drawn();
   void set_sorted_for_recursion(bool sorted_for_recursion);
   bool sorted_for_recursion();

   // LayerAnimationValueProvider implementation.
   gfx::ScrollOffset ScrollOffsetForAnimation() const override;

   // LayerAnimationValueObserver implementation.
   void OnFilterAnimated(const FilterOperations& filters) override;
   void OnOpacityAnimated(float opacity) override;
   void OnTransformAnimated(const gfx::Transform& transform) override;
   void OnScrollOffsetAnimated(const gfx::ScrollOffset& scroll_offset) override;
   void OnAnimationWaitingForDeletion() override;
   void OnTransformIsPotentiallyAnimatingChanged(bool is_animating) override;
   bool IsActive() const override;

  protected:
   friend class LayerImpl;
   friend class TreeSynchronizer;
   ~Layer() override;

   explicit Layer(const LayerSettings& settings);

   // These SetNeeds functions are in order of severity of update:
   //
   // Called when this layer has been modified in some way, but isn't sure
   // that it needs a commit yet.  It needs CalcDrawProperties and UpdateLayers
   // before it knows whether or not a commit is required.
   void SetNeedsUpdate();
   // Called when a property has been modified in a way that the layer
   // knows immediately that a commit is required.  This implies SetNeedsUpdate
   // as well as SetNeedsPushProperties to push that property.
   void SetNeedsCommit();
   // This is identical to SetNeedsCommit, but the former requests a rebuild of
   // the property trees.
   void SetNeedsCommitNoRebuild();
   // Called when there's been a change in layer structure.  Implies both
   // SetNeedsUpdate and SetNeedsCommit, but not SetNeedsPushProperties.
   void SetNeedsFullTreeSync();

   // Called when the next commit should wait until the pending tree is activated
   // before finishing the commit and unblocking the main thread. Used to ensure
   // unused resources on the impl thread are returned before commit completes.
   void SetNextCommitWaitsForActivation();

   // Will recalculate whether the layer draws content and set draws_content_
   // appropriately.
   void UpdateDrawsContent(bool has_drawable_content);
   virtual bool HasDrawableContent() const;

   // Called when the layer's number of drawable descendants changes.
   void AddDrawableDescendants(int num);

   void AddDependentNeedsPushProperties();
   void RemoveDependentNeedsPushProperties();
   bool parent_should_know_need_push_properties() const {
     return needs_push_properties() || descendant_needs_push_properties();
   }

   bool IsPropertyChangeAllowed() const;

   // Serialize all the necessary properties to be able to reconstruct this Layer
   // into proto::LayerProperties. This function must not set values for
   // |needs_push_properties_| or |num_dependents_need_push_properties_| as they
   // are dealt with at a higher level. This is only called if
   // |needs_push_properties_| is set. For descendants of Layer, implementations
   // must first call their parent class. This method is not marked as const
   // as some implementations need reset member fields, similarly to
   // PushPropertiesTo().
   virtual void LayerSpecificPropertiesToProto(proto::LayerProperties* proto);

   // Deserialize all the necessary properties from proto::LayerProperties into
   // this Layer. This function must not set values for |needs_push_properties_|
   // or |num_dependents_need_push_properties_| as they are dealt with at a
   // higher level. This is only called if |needs_push_properties_| is set. For
   // descendants of Layer, implementations must first call their parent class.
   virtual void FromLayerSpecificPropertiesProto(
       const proto::LayerProperties& proto);

   // This flag is set when the layer needs to push properties to the impl
   // side.
   bool needs_push_properties_;

   // The number of direct children or dependent layers that need to be recursed
   // to in order for them or a descendent of them to push properties to the impl
   // side.
   int num_dependents_need_push_properties_;

   // The update rect is the region of the compositor resource that was
   // actually updated by the compositor. For layers that may do updating
   // outside the compositor's control (i.e. plugin layers), this information
   // is not available and the update rect will remain empty.
   // Note this rect is in layer space (not content space).
   gfx::Rect update_rect_;

   scoped_refptr<Layer> mask_layer_;

   int layer_id_;

   // When true, the layer is about to perform an update. Any commit requests
   // will be handled implicitly after the update completes.
   bool ignore_set_needs_commit_;

   // Layers that share a sorting context id will be sorted together in 3d
   // space.  0 is a special value that means this layer will not be sorted and
   // will be drawn in paint order.
   int sorting_context_id_;

  private:
   friend class base::RefCounted<Layer>;
   friend class LayerSerializationTest;
   friend class LayerTreeHostCommon;

   void SetParent(Layer* layer);
   bool DescendantIsFixedToContainerLayer() const;

   // This should only be called from RemoveFromParent().
   void RemoveChildOrDependent(Layer* child);

   // If this layer has a scroll parent, it removes |this| from its list of
   // scroll children.
   void RemoveFromScrollTree();

   // If this layer has a clip parent, it removes |this| from its list of clip
   // children.
   void RemoveFromClipTree();

   // When we detach or attach layer to new LayerTreeHost, all property trees'
   // indices becomes invalid.
   void InvalidatePropertyTreesIndices();

   LayerList children_;
   Layer* parent_;

   // Layer instances have a weak pointer to their LayerTreeHost.
   // This pointer value is nil when a Layer is not in a tree and is
   // updated via SetLayerTreeHost() if a layer moves between trees.
   LayerTreeHost* layer_tree_host_;

   scoped_refptr<LayerAnimationController> layer_animation_controller_;

   // Layer properties.
   gfx::Size bounds_;

   gfx::ScrollOffset scroll_offset_;
   gfx::Vector2dF scroll_compensation_adjustment_;
   // This variable indicates which ancestor layer (if any) whose size,
   // transformed relative to this layer, defines the maximum scroll offset for
   // this layer.
   int scroll_clip_layer_id_;
   int num_descendants_that_draw_content_;
   int transform_tree_index_;
   int effect_tree_index_;
   int clip_tree_index_;
   int scroll_tree_index_;
   int property_tree_sequence_number_;
   uint64_t element_id_;
   uint32_t mutable_properties_;
   gfx::Vector2dF offset_to_transform_parent_;
   uint32_t main_thread_scrolling_reasons_;
   bool should_flatten_transform_from_property_tree_ : 1;
   bool user_scrollable_horizontal_ : 1;
   bool user_scrollable_vertical_ : 1;
   bool is_root_for_isolated_group_ : 1;
   bool is_container_for_fixed_position_layers_ : 1;
   bool is_drawable_ : 1;
   bool draws_content_ : 1;
   bool hide_layer_and_subtree_ : 1;
   bool masks_to_bounds_ : 1;
   bool contents_opaque_ : 1;
   bool double_sided_ : 1;
   bool should_flatten_transform_ : 1;
   bool use_parent_backface_visibility_ : 1;
   bool use_local_transform_for_backface_visibility_ : 1;
   bool should_check_backface_visibility_ : 1;
   bool force_render_surface_ : 1;
   bool transform_is_invertible_ : 1;
   bool has_render_surface_ : 1;
   bool subtree_property_changed_ : 1;
   Region non_fast_scrollable_region_;
   Region touch_event_handler_region_;
   gfx::PointF position_;
   SkColor background_color_;
   float opacity_;
   SkXfermode::Mode blend_mode_;
   // draw_blend_mode may be different than blend_mode_,
   // when a RenderSurface re-parents the layer's blend_mode.
   SkXfermode::Mode draw_blend_mode_;
   FilterOperations filters_;
   FilterOperations background_filters_;
   LayerPositionConstraint position_constraint_;
   Layer* scroll_parent_;
   scoped_ptr<std::set<Layer*>> scroll_children_;

   // The following three variables are tracker variables. They are bools
   // wrapped inside an integer variable. If true, their value equals the
   // LayerTreeHost's meta_information_sequence_number. This wrapping of bools
   // inside ints is done to avoid a layer tree treewalk to reset their values.
   int layer_or_descendant_is_drawn_tracker_;
   int sorted_for_recursion_tracker_;
   int visited_tracker_;

   Layer* clip_parent_;
   scoped_ptr<std::set<Layer*>> clip_children_;

   gfx::Transform transform_;
   gfx::Point3F transform_origin_;

   // Replica layer used for reflections.
   scoped_refptr<Layer> replica_layer_;

   LayerClient* client_;

   std::vector<scoped_ptr<CopyOutputRequest>> copy_requests_;

   base::Closure did_scroll_callback_;

   PaintProperties paint_properties_;

   // These all act like draw properties, so don't need push properties.
   gfx::Rect visible_layer_rect_;
   gfx::Rect clip_rect_;
   size_t num_unclipped_descendants_;

   std::vector<FrameTimingRequest> frame_timing_requests_;
   bool frame_timing_requests_dirty_;

   DISALLOW_COPY_AND_ASSIGN(Layer);
 };

 }  // namespace cc

 #endif  // CC_LAYERS_LAYER_H_