// 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>

#include "cc/base/math_util.h"
#include "cc/layers/layer.h"
#include "cc/layers/layer_impl.h"
#include "cc/layers/picture_layer.h"
#include "cc/trees/clip_node.h"
#include "cc/trees/draw_property_utils.h"
#include "cc/trees/effect_node.h"
#include "cc/trees/layer_tree_impl.h"
#include "cc/trees/layer_tree_settings.h"
#include "cc/trees/mutator_host.h"
#include "cc/trees/scroll_node.h"
#include "cc/trees/transform_node.h"
#include "components/viz/common/frame_sinks/copy_output_request.h"
#include "ui/gfx/geometry/point_f.h"
#include "ui/gfx/geometry/vector2d_conversions.h"

namespace cc {

namespace {

template <typename LayerType>
struct DataForRecursion {
  int transform_tree_parent;
  int transform_tree_parent_fixed;
  int clip_tree_parent;
  int effect_tree_parent;
  int scroll_tree_parent;
  int closest_ancestor_with_cached_render_surface;
  int closest_ancestor_with_copy_request;
  uint32_t main_thread_scrolling_reasons;
  SkColor safe_opaque_background_color;
  bool in_subtree_of_page_scale_layer;
  bool affected_by_outer_viewport_bounds_delta;
  bool should_flatten;
  bool scroll_tree_parent_created_by_uninheritable_criteria;
  bool animation_axis_aligned_since_render_target;
  bool not_axis_aligned_since_last_clip;
  gfx::Transform compound_transform_since_render_target;
};

template <typename LayerType>
class PropertyTreeBuilderContext {
 public:
  PropertyTreeBuilderContext(LayerType* root_layer,
                             const LayerType* page_scale_layer,
                             const LayerType* inner_viewport_scroll_layer,
                             const LayerType* outer_viewport_scroll_layer,
                             const ElementId overscroll_elasticity_element_id,
                             const gfx::Vector2dF& elastic_overscroll,
                             float page_scale_factor,
                             const gfx::Transform& device_transform,
                             MutatorHost* mutator_host,
                             PropertyTrees* property_trees)
      : root_layer_(root_layer),
        page_scale_layer_(page_scale_layer),
        inner_viewport_scroll_layer_(inner_viewport_scroll_layer),
        outer_viewport_scroll_layer_(outer_viewport_scroll_layer),
        overscroll_elasticity_element_id_(overscroll_elasticity_element_id),
        elastic_overscroll_(elastic_overscroll),
        page_scale_factor_(page_scale_factor),
        device_transform_(device_transform),
        mutator_host_(*mutator_host),
        property_trees_(*property_trees),
        transform_tree_(property_trees->transform_tree),
        clip_tree_(property_trees->clip_tree),
        effect_tree_(property_trees->effect_tree),
        scroll_tree_(property_trees->scroll_tree) {
    InitializeScrollChildrenMap();
  }

  void InitializeScrollChildrenMap();

  void BuildPropertyTrees(float device_scale_factor,
                          const gfx::Rect& viewport,
                          SkColor root_background_color) const;

 private:
  void BuildPropertyTreesInternal(
      LayerType* layer,
      const DataForRecursion<LayerType>& data_from_parent) const;

  bool AddTransformNodeIfNeeded(
      const DataForRecursion<LayerType>& data_from_ancestor,
      LayerType* layer,
      bool created_render_surface,
      DataForRecursion<LayerType>* data_for_children) const;

  void AddClipNodeIfNeeded(
      const DataForRecursion<LayerType>& data_from_ancestor,
      LayerType* layer,
      bool created_transform_node,
      DataForRecursion<LayerType>* data_for_children) const;

  bool AddEffectNodeIfNeeded(
      const DataForRecursion<LayerType>& data_from_ancestor,
      LayerType* layer,
      DataForRecursion<LayerType>* data_for_children) const;

  void AddScrollNodeIfNeeded(
      const DataForRecursion<LayerType>& data_from_ancestor,
      LayerType* layer,
      DataForRecursion<LayerType>* data_for_children) const;

  LayerType* root_layer_;
  const LayerType* page_scale_layer_;
  const LayerType* inner_viewport_scroll_layer_;
  const LayerType* outer_viewport_scroll_layer_;
  const ElementId overscroll_elasticity_element_id_;
  const gfx::Vector2dF elastic_overscroll_;
  float page_scale_factor_;
  const gfx::Transform& device_transform_;
  MutatorHost& mutator_host_;
  PropertyTrees& property_trees_;
  TransformTree& transform_tree_;
  ClipTree& clip_tree_;
  EffectTree& effect_tree_;
  ScrollTree& scroll_tree_;
  std::multimap<const LayerType*, LayerType*> scroll_children_map_;
};

static LayerPositionConstraint PositionConstraint(Layer* layer) {
  return layer->position_constraint();
}

static LayerPositionConstraint PositionConstraint(LayerImpl* layer) {
  return layer->test_properties()->position_constraint;
}

static LayerStickyPositionConstraint StickyPositionConstraint(Layer* layer) {
  return layer->sticky_position_constraint();
}

static LayerStickyPositionConstraint StickyPositionConstraint(
    LayerImpl* layer) {
  return layer->test_properties()->sticky_position_constraint;
}

static LayerImplList& LayerChildren(LayerImpl* layer) {
  return layer->test_properties()->children;
}

static const LayerList& LayerChildren(Layer* layer) {
  return layer->children();
}

static LayerImpl* LayerChildAt(LayerImpl* layer, int index) {
  return layer->test_properties()->children[index];
}

static Layer* LayerChildAt(Layer* layer, int index) {
  return layer->children()[index].get();
}

static Layer* ScrollParent(Layer* layer) {
  return layer->scroll_parent();
}

static LayerImpl* ScrollParent(LayerImpl* layer) {
  return layer->test_properties()->scroll_parent;
}

static Layer* ClipParent(Layer* layer) {
  return layer->clip_parent();
}

static LayerImpl* ClipParent(LayerImpl* layer) {
  return layer->test_properties()->clip_parent;
}

static inline const FilterOperations& Filters(Layer* layer) {
  return layer->filters();
}

static inline const FilterOperations& Filters(LayerImpl* layer) {
  return layer->test_properties()->filters;
}

static PictureLayer* MaskLayer(Layer* layer) {
  return layer->mask_layer();
}

static LayerImpl* MaskLayer(LayerImpl* layer) {
  return layer->test_properties()->mask_layer;
}

static const gfx::Transform& Transform(Layer* layer) {
  return layer->transform();
}

static const gfx::Transform& Transform(LayerImpl* layer) {
  return layer->test_properties()->transform;
}

static const gfx::PointF& Position(Layer* layer) {
  return layer->position();
}

static const gfx::PointF& Position(LayerImpl* layer) {
  return layer->test_properties()->position;
}

// Methods to query state from the AnimationHost ----------------------
template <typename LayerType>
bool OpacityIsAnimating(const MutatorHost& host, LayerType* layer) {
  return host.IsAnimatingOpacityProperty(layer->element_id(),
                                         layer->GetElementTypeForAnimation());
}

template <typename LayerType>
bool HasPotentiallyRunningOpacityAnimation(const MutatorHost& host,
                                           LayerType* layer) {
  return host.HasPotentiallyRunningOpacityAnimation(
      layer->element_id(), layer->GetElementTypeForAnimation());
}

template <typename LayerType>
bool FilterIsAnimating(const MutatorHost& host, LayerType* layer) {
  return host.IsAnimatingFilterProperty(layer->element_id(),
                                        layer->GetElementTypeForAnimation());
}

template <typename LayerType>
bool HasPotentiallyRunningFilterAnimation(const MutatorHost& host,
                                          LayerType* layer) {
  return host.HasPotentiallyRunningFilterAnimation(
      layer->element_id(), layer->GetElementTypeForAnimation());
}

template <typename LayerType>
bool TransformIsAnimating(const MutatorHost& host, LayerType* layer) {
  return host.IsAnimatingTransformProperty(layer->element_id(),
                                           layer->GetElementTypeForAnimation());
}

template <typename LayerType>
bool HasPotentiallyRunningTransformAnimation(const MutatorHost& host,
                                             LayerType* layer) {
  return host.HasPotentiallyRunningTransformAnimation(
      layer->element_id(), layer->GetElementTypeForAnimation());
}

template <typename LayerType>
bool HasOnlyTranslationTransforms(const MutatorHost& host, LayerType* layer) {
  return host.HasOnlyTranslationTransforms(layer->element_id(),
                                           layer->GetElementTypeForAnimation());
}

template <typename LayerType>
bool AnimationsPreserveAxisAlignment(const MutatorHost& host,
                                     LayerType* layer) {
  return host.AnimationsPreserveAxisAlignment(layer->element_id());
}

template <typename LayerType>
bool HasAnyAnimationTargetingProperty(const MutatorHost& host,
                                      LayerType* layer,
                                      TargetProperty::Type property) {
  return host.HasAnyAnimationTargetingProperty(layer->element_id(), property);
}

// -------------------------------------------------------------------

template <typename LayerType>
static int GetTransformParent(const DataForRecursion<LayerType>& data,
                              LayerType* layer) {
  return PositionConstraint(layer).is_fixed_position()
             ? data.transform_tree_parent_fixed
             : data.transform_tree_parent;
}

template <typename LayerType>
static bool LayerClipsSubtree(LayerType* layer) {
  return layer->masks_to_bounds() || MaskLayer(layer);
}

template <typename LayerType>
static int GetScrollParentId(const DataForRecursion<LayerType>& data,
                             LayerType* layer) {
  const bool inherits_scroll = !ScrollParent(layer);
  const int id = inherits_scroll ? data.scroll_tree_parent
                                 : ScrollParent(layer)->scroll_tree_index();
  return id;
}

static Layer* LayerParent(Layer* layer) {
  return layer->parent();
}

static LayerImpl* LayerParent(LayerImpl* layer) {
  return layer->test_properties()->parent;
}

static inline int SortingContextId(Layer* layer) {
  return layer->sorting_context_id();
}

static inline int SortingContextId(LayerImpl* layer) {
  return layer->test_properties()->sorting_context_id;
}

static inline bool Is3dSorted(Layer* layer) {
  return layer->sorting_context_id() != 0;
}

static inline bool Is3dSorted(LayerImpl* layer) {
  return layer->test_properties()->sorting_context_id != 0;
}

static inline bool HasLatestSequenceNumber(const Layer* layer, int number) {
  return layer->property_tree_sequence_number() == number;
}

static inline bool HasLatestSequenceNumber(const LayerImpl*, int) {
  return true;
}

template <typename LayerType>
void PropertyTreeBuilderContext<LayerType>::AddClipNodeIfNeeded(
    const DataForRecursion<LayerType>& data_from_ancestor,
    LayerType* layer,
    bool created_transform_node,
    DataForRecursion<LayerType>* data_for_children) const {
  const bool inherits_clip = !ClipParent(layer);
  // Sanity check the clip parent already built clip node before us.
  DCHECK(inherits_clip ||
         HasLatestSequenceNumber(ClipParent(layer),
                                 property_trees_.sequence_number));
  const int parent_id = inherits_clip ? data_from_ancestor.clip_tree_parent
                                      : ClipParent(layer)->clip_tree_index();

  bool layer_clips_subtree = LayerClipsSubtree(layer);
  bool requires_node =
      layer_clips_subtree || Filters(layer).HasFilterThatMovesPixels();
  if (!requires_node) {
    data_for_children->clip_tree_parent = parent_id;
  } else {
    ClipNode node;
    node.clip = gfx::RectF(gfx::PointF() + layer->offset_to_transform_parent(),
                           gfx::SizeF(layer->bounds()));
    node.transform_id = created_transform_node
                            ? data_for_children->transform_tree_parent
                            : GetTransformParent(data_from_ancestor, layer);
    if (layer_clips_subtree) {
      node.clip_type = ClipNode::ClipType::APPLIES_LOCAL_CLIP;
    } else {
      DCHECK(Filters(layer).HasFilterThatMovesPixels());
      node.clip_type = ClipNode::ClipType::EXPANDS_CLIP;
      node.clip_expander = ClipExpander(layer->effect_tree_index());
    }
    data_for_children->clip_tree_parent = clip_tree_.Insert(node, parent_id);
  }

  layer->SetClipTreeIndex(data_for_children->clip_tree_parent);
}

template <typename LayerType>
static inline bool IsAtBoundaryOf3dRenderingContext(LayerType* layer) {
  return LayerParent(layer)
             ? SortingContextId(LayerParent(layer)) != SortingContextId(layer)
             : Is3dSorted(layer);
}

static inline gfx::Point3F TransformOrigin(Layer* layer) {
  return layer->transform_origin();
}

static inline gfx::Point3F TransformOrigin(LayerImpl* layer) {
  return layer->test_properties()->transform_origin;
}

static inline bool IsContainerForFixedPositionLayers(Layer* layer) {
  return layer->IsContainerForFixedPositionLayers();
}

static inline bool IsContainerForFixedPositionLayers(LayerImpl* layer) {
  return layer->test_properties()->is_container_for_fixed_position_layers;
}

static inline bool ShouldFlattenTransform(Layer* layer) {
  return layer->should_flatten_transform();
}

static inline bool ShouldFlattenTransform(LayerImpl* layer) {
  return layer->test_properties()->should_flatten_transform;
}

template <typename LayerType>
bool PropertyTreeBuilderContext<LayerType>::AddTransformNodeIfNeeded(
    const DataForRecursion<LayerType>& data_from_ancestor,
    LayerType* layer,
    bool created_render_surface,
    DataForRecursion<LayerType>* data_for_children) const {
  const bool is_root = !LayerParent(layer);
  const bool is_page_scale_layer = layer == page_scale_layer_;
  const bool is_overscroll_elasticity_layer =
      overscroll_elasticity_element_id_ &&
      layer->element_id() == overscroll_elasticity_element_id_;
  const bool is_scrollable = layer->scrollable();
  const bool is_fixed = PositionConstraint(layer).is_fixed_position();
  const bool is_sticky = StickyPositionConstraint(layer).is_sticky;
  // Scrolling a layer should not move it from being pixel-aligned to moving off
  // the pixel grid and becoming fuzzy. So always snap scrollable things to the
  // pixel grid. Layers may also request to be snapped as such.
  const bool is_snapped =
      is_scrollable || layer->IsSnappedToPixelGridInTarget();

  const bool has_significant_transform =
      !Transform(layer).IsIdentityOr2DTranslation();

  const bool has_potentially_animated_transform =
      HasPotentiallyRunningTransformAnimation(mutator_host_, layer);

  // A transform node is needed even for a finished animation, since differences
  // in the timing of animation state updates can mean that an animation that's
  // in the Finished state at tree-building time on the main thread is still in
  // the Running state right after commit on the compositor thread.
  const bool has_any_transform_animation = HasAnyAnimationTargetingProperty(
      mutator_host_, layer, TargetProperty::TRANSFORM);

  const bool has_surface = created_render_surface;

  const bool is_at_boundary_of_3d_rendering_context =
      IsAtBoundaryOf3dRenderingContext(layer);

  DCHECK(!is_scrollable || is_snapped);
  bool requires_node = is_root || is_snapped || has_significant_transform ||
                       has_any_transform_animation || has_surface || is_fixed ||
                       is_page_scale_layer || is_overscroll_elasticity_layer ||
                       is_sticky || is_at_boundary_of_3d_rendering_context;

  int parent_index = TransformTree::kRootNodeId;
  int source_index = TransformTree::kRootNodeId;
  gfx::Vector2dF source_offset;

  if (!is_root) {
    parent_index = GetTransformParent(data_from_ancestor, layer);
    // Because Blink still provides positions with respect to the parent layer,
    // we track both a parent TransformNode (which is the parent in the
    // TransformTree) and a 'source' TransformNode (which is the TransformNode
    // for the parent in the Layer tree).
    source_index = LayerParent(layer)->transform_tree_index();
    source_offset = LayerParent(layer)->offset_to_transform_parent();
  }

  // For a container of fixed position descendants, define for them their
  // fixed-position transform parent as being this layer's transform node, or
  // its transform parent's node if this layer won't have a node of its own.
  //
  // But if this layer is scrollable, then we point fixed position descendants
  // to not be affected by this layer as it changes its scroll offset during
  // a compositor thread scroll. We do this by pointing them to the direct
  // parent of this layer, which acts as a proxy for this layer, without
  // including scrolling, based on the assumption this layer has no transform
  // itself when scrollable.
  if (IsContainerForFixedPositionLayers(layer) || is_root) {
    data_for_children->affected_by_outer_viewport_bounds_delta =
        layer->IsResizedByBrowserControls();
    if (is_scrollable) {
      DCHECK(Transform(layer).IsIdentity());
      if (!is_root) {
        data_for_children->transform_tree_parent_fixed =
            LayerParent(layer)->transform_tree_index();
      }
    } else {
      data_for_children->transform_tree_parent_fixed =
          requires_node ? transform_tree_.next_available_id() : parent_index;
    }
  }

  if (!requires_node) {
    data_for_children->should_flatten |= ShouldFlattenTransform(layer);
    gfx::Vector2dF local_offset =
        Position(layer).OffsetFromOrigin() + Transform(layer).To2dTranslation();
    gfx::Vector2dF source_to_parent;
    if (source_index != parent_index) {
      gfx::Transform to_parent;
      transform_tree_.ComputeTranslation(source_index, parent_index,
                                         &to_parent);
      source_to_parent = to_parent.To2dTranslation();
    }
    layer->SetOffsetToTransformParent(source_offset + source_to_parent +
                                      local_offset);
    layer->SetShouldFlattenScreenSpaceTransformFromPropertyTree(
        data_from_ancestor.should_flatten);
    layer->SetTransformTreeIndex(parent_index);
    return false;
  }

  transform_tree_.Insert(TransformNode(), parent_index);
  TransformNode* node = transform_tree_.back();
  layer->SetTransformTreeIndex(node->id);
  data_for_children->transform_tree_parent = node->id;

  // For animation subsystem purposes, if this layer has a compositor element
  // id, we build a map from that id to this transform node.
  if (layer->element_id()) {
    property_trees_.element_id_to_transform_node_index[layer->element_id()] =
        node->id;
    node->element_id = layer->element_id();
  }

  node->scrolls = is_scrollable;
  node->should_be_snapped = is_snapped;
  node->flattens_inherited_transform = data_for_children->should_flatten;

  node->sorting_context_id = SortingContextId(layer);

  if (layer == page_scale_layer_)
    data_for_children->in_subtree_of_page_scale_layer = true;
  node->in_subtree_of_page_scale_layer =
      data_for_children->in_subtree_of_page_scale_layer;

  // Surfaces inherently flatten transforms.
  data_for_children->should_flatten =
      ShouldFlattenTransform(layer) || has_surface;

  node->has_potential_animation = has_potentially_animated_transform;
  node->is_currently_animating = TransformIsAnimating(mutator_host_, layer);
  if (has_potentially_animated_transform) {
    node->has_only_translation_animations =
        HasOnlyTranslationTransforms(mutator_host_, layer);
  }

  float post_local_scale_factor = 1.0f;

  if (is_page_scale_layer) {
    if (!is_root)
      post_local_scale_factor *= page_scale_factor_;
    transform_tree_.set_page_scale_factor(page_scale_factor_);
  }

  node->source_node_id = source_index;
  node->post_local_scale_factor = post_local_scale_factor;
  if (is_root) {
    float page_scale_factor_for_root =
        is_page_scale_layer ? page_scale_factor_ : 1.f;
    // SetRootTransformsAndScales will be incorrect if the root layer has
    // non-zero position, so ensure it is zero.
    DCHECK(Position(layer).IsOrigin());
    transform_tree_.SetRootTransformsAndScales(
        transform_tree_.device_scale_factor(), page_scale_factor_for_root,
        device_transform_);
  } else {
    node->source_offset = source_offset;
    node->update_post_local_transform(Position(layer), TransformOrigin(layer));
  }

  if (is_overscroll_elasticity_layer) {
    DCHECK(!is_scrollable);
    node->scroll_offset = gfx::ScrollOffset(elastic_overscroll_);
  } else if (!ScrollParent(layer)) {
    node->scroll_offset = layer->CurrentScrollOffset();
  }

  if (is_fixed) {
    if (data_from_ancestor.affected_by_outer_viewport_bounds_delta) {
      node->moved_by_outer_viewport_bounds_delta_x =
          PositionConstraint(layer).is_fixed_to_right_edge();
      node->moved_by_outer_viewport_bounds_delta_y =
          PositionConstraint(layer).is_fixed_to_bottom_edge();
      if (node->moved_by_outer_viewport_bounds_delta_x ||
          node->moved_by_outer_viewport_bounds_delta_y) {
        transform_tree_.AddNodeAffectedByOuterViewportBoundsDelta(node->id);
      }
    }
  }

  node->local = Transform(layer);
  node->update_pre_local_transform(TransformOrigin(layer));

  if (StickyPositionConstraint(layer).is_sticky) {
    StickyPositionNodeData* sticky_data =
        transform_tree_.StickyPositionData(node->id);
    sticky_data->constraints = StickyPositionConstraint(layer);
    sticky_data->scroll_ancestor = GetScrollParentId(data_from_ancestor, layer);
    ScrollNode* scroll_ancestor =
        scroll_tree_.Node(sticky_data->scroll_ancestor);

    // Position sticky should never attach to the inner viewport since it
    // shouldn't be affected by pinch-zoom. If we did then we'd need setting
    // the inner viewport bounds delta to cause a TransformTree update, which
    // it currently doesn't.
    DCHECK(!scroll_ancestor->scrolls_inner_viewport);

    if (sticky_data->constraints.is_anchored_right ||
        sticky_data->constraints.is_anchored_bottom) {
      // Sticky nodes whose ancestor scroller is the inner / outer viewport
      // need to have their local transform updated when the inner / outer
      // viewport bounds change, but do not unconditionally move by that delta
      // like fixed position nodes.
      if (scroll_ancestor->scrolls_outer_viewport)
        transform_tree_.AddNodeAffectedByOuterViewportBoundsDelta(node->id);
    }
    // Copy the ancestor nodes for later use. These elements are guaranteed to
    // have transform nodes at this point because they are our ancestors (so
    // have already been processed) and are sticky (so have transform nodes).
    ElementId shifting_sticky_box_element_id =
        sticky_data->constraints.nearest_element_shifting_sticky_box;
    if (shifting_sticky_box_element_id) {
      sticky_data->nearest_node_shifting_sticky_box =
          transform_tree_.FindNodeFromElementId(shifting_sticky_box_element_id)
              ->id;
    }
    ElementId shifting_containing_block_element_id =
        sticky_data->constraints.nearest_element_shifting_containing_block;
    if (shifting_containing_block_element_id) {
      sticky_data->nearest_node_shifting_containing_block =
          transform_tree_
              .FindNodeFromElementId(shifting_containing_block_element_id)
              ->id;
    }
  }

  node->needs_local_transform_update = true;
  transform_tree_.UpdateTransforms(node->id);

  layer->SetOffsetToTransformParent(gfx::Vector2dF());

  // Flattening (if needed) will be handled by |node|.
  layer->SetShouldFlattenScreenSpaceTransformFromPropertyTree(false);

  return true;
}

static inline bool HasPotentialOpacityAnimation(const MutatorHost& host,
                                                Layer* layer) {
  return HasPotentiallyRunningOpacityAnimation(host, layer) ||
         layer->OpacityCanAnimateOnImplThread();
}

static inline bool HasPotentialOpacityAnimation(const MutatorHost& host,
                                                LayerImpl* layer) {
  return HasPotentiallyRunningOpacityAnimation(host, layer) ||
         layer->test_properties()->opacity_can_animate;
}

static inline bool DoubleSided(Layer* layer) {
  return layer->double_sided();
}

static inline bool DoubleSided(LayerImpl* layer) {
  return layer->test_properties()->double_sided;
}

static inline bool TrilinearFiltering(Layer* layer) {
  return layer->trilinear_filtering();
}

static inline bool TrilinearFiltering(LayerImpl* layer) {
  return layer->test_properties()->trilinear_filtering;
}

static inline bool CacheRenderSurface(Layer* layer) {
  return layer->cache_render_surface();
}

static inline bool CacheRenderSurface(LayerImpl* layer) {
  return layer->test_properties()->cache_render_surface;
}

static inline bool ForceRenderSurface(Layer* layer) {
  return layer->force_render_surface_for_testing();
}

static inline bool ForceRenderSurface(LayerImpl* layer) {
  return layer->test_properties()->force_render_surface;
}

template <typename LayerType>
static inline bool LayerIsInExisting3DRenderingContext(LayerType* layer) {
  return Is3dSorted(layer) && LayerParent(layer) &&
         Is3dSorted(LayerParent(layer)) &&
         (SortingContextId(LayerParent(layer)) == SortingContextId(layer));
}

static inline bool IsRootForIsolatedGroup(Layer* layer) {
  return layer->is_root_for_isolated_group();
}

static inline bool IsRootForIsolatedGroup(LayerImpl* layer) {
  return false;
}

static inline int NumDescendantsThatDrawContent(Layer* layer) {
  return layer->NumDescendantsThatDrawContent();
}

static inline int NumLayerOrDescendantsThatDrawContentRecursive(
    LayerImpl* layer) {
  int num = layer->DrawsContent() ? 1 : 0;
  for (size_t i = 0; i < layer->test_properties()->children.size(); ++i) {
    LayerImpl* child_layer = layer->test_properties()->children[i];
    num += NumLayerOrDescendantsThatDrawContentRecursive(child_layer);
  }
  return num;
}

static inline int NumDescendantsThatDrawContent(LayerImpl* layer) {
  int num_descendants_that_draw_content = 0;
  for (size_t i = 0; i < layer->test_properties()->children.size(); ++i) {
    LayerImpl* child_layer = layer->test_properties()->children[i];
    num_descendants_that_draw_content +=
        NumLayerOrDescendantsThatDrawContentRecursive(child_layer);
  }
  return num_descendants_that_draw_content;
}

static inline float EffectiveOpacity(Layer* layer) {
  return layer->EffectiveOpacity();
}

static inline float EffectiveOpacity(LayerImpl* layer) {
  return layer->test_properties()->hide_layer_and_subtree
             ? 0.f
             : layer->test_properties()->opacity;
}

static inline float Opacity(Layer* layer) {
  return layer->opacity();
}

static inline float Opacity(LayerImpl* layer) {
  return layer->test_properties()->opacity;
}

static inline SkBlendMode BlendMode(Layer* layer) {
  return layer->blend_mode();
}

static inline SkBlendMode BlendMode(LayerImpl* layer) {
  return layer->test_properties()->blend_mode;
}

static inline const gfx::PointF FiltersOrigin(Layer* layer) {
  return layer->filters_origin();
}

static inline const gfx::PointF FiltersOrigin(LayerImpl* layer) {
  return layer->test_properties()->filters_origin;
}

static inline const FilterOperations& BackdropFilters(Layer* layer) {
  return layer->backdrop_filters();
}

static inline const FilterOperations& BackdropFilters(LayerImpl* layer) {
  return layer->test_properties()->backdrop_filters;
}

static inline const gfx::RRectF& BackdropFilterBounds(Layer* layer) {
  return layer->backdrop_filter_bounds();
}

static inline const gfx::RRectF& BackdropFilterBounds(LayerImpl* layer) {
  return layer->test_properties()->backdrop_filter_bounds;
}

static inline float BackdropFilterQuality(Layer* layer) {
  return layer->backdrop_filter_quality();
}

static inline float BackdropFilterQuality(LayerImpl* layer) {
  return layer->test_properties()->backdrop_filter_quality;
}

static inline bool HideLayerAndSubtree(Layer* layer) {
  return layer->hide_layer_and_subtree();
}

static inline bool HideLayerAndSubtree(LayerImpl* layer) {
  return layer->test_properties()->hide_layer_and_subtree;
}

static inline bool HasCopyRequest(Layer* layer) {
  return layer->HasCopyRequest();
}

static inline bool HasCopyRequest(LayerImpl* layer) {
  return !layer->test_properties()->copy_requests.empty();
}

static inline bool PropertyChanged(Layer* layer) {
  return layer->subtree_property_changed();
}

static inline bool PropertyChanged(LayerImpl* layer) {
  return false;
}

template <typename LayerType>
bool ShouldCreateRenderSurface(const MutatorHost& mutator_host,
                               LayerType* layer,
                               gfx::Transform current_transform,
                               bool animation_axis_aligned) {
  const bool preserves_2d_axis_alignment =
      current_transform.Preserves2dAxisAlignment() && animation_axis_aligned;
  const bool is_root = !LayerParent(layer);
  if (is_root)
    return true;

  // If the layer uses a mask.
  if (MaskLayer(layer)) {
    return true;
  }

  // If the layer uses trilinear filtering.
  if (TrilinearFiltering(layer)) {
    return true;
  }

  // If the layer uses a CSS filter.
  if (!Filters(layer).IsEmpty()) {
    return true;
  }

  // If the layer uses a CSS backdrop-filter.
  if (!BackdropFilters(layer).IsEmpty()) {
    return true;
  }

  // If the layer will use a CSS filter.  In this case, the animation
  // will start and add a filter to this layer, so it needs a surface.
  if (HasPotentiallyRunningFilterAnimation(mutator_host, layer)) {
    return true;
  }

  int num_descendants_that_draw_content = NumDescendantsThatDrawContent(layer);

  // If the layer flattens its subtree, but it is treated as a 3D object by its
  // parent (i.e. parent participates in a 3D rendering context).
  if (LayerIsInExisting3DRenderingContext(layer) &&
      ShouldFlattenTransform(layer) && num_descendants_that_draw_content > 0) {
    TRACE_EVENT_INSTANT0(
        "cc", "PropertyTreeBuilder::ShouldCreateRenderSurface flattening",
        TRACE_EVENT_SCOPE_THREAD);
    return true;
  }

  // If the layer has blending.
  // TODO(rosca): this is temporary, until blending is implemented for other
  // types of quads than viz::RenderPassDrawQuad. Layers having descendants that
  // draw content will still create a separate rendering surface.
  if (BlendMode(layer) != SkBlendMode::kSrcOver) {
    TRACE_EVENT_INSTANT0(
        "cc", "PropertyTreeBuilder::ShouldCreateRenderSurface blending",
        TRACE_EVENT_SCOPE_THREAD);
    return true;
  }
  // If the layer clips its descendants but it is not axis-aligned with respect
  // to its parent.
  bool layer_clips_external_content = LayerClipsSubtree(layer);
  if (layer_clips_external_content && !preserves_2d_axis_alignment &&
      num_descendants_that_draw_content > 0) {
    TRACE_EVENT_INSTANT0(
        "cc", "PropertyTreeBuilder::ShouldCreateRenderSurface clipping",
        TRACE_EVENT_SCOPE_THREAD);
    return true;
  }

  // If the layer has some translucency and does not have a preserves-3d
  // transform style.  This condition only needs a render surface if two or more
  // layers in the subtree overlap. But checking layer overlaps is unnecessarily
  // costly so instead we conservatively create a surface whenever at least two
  // layers draw content for this subtree.
  bool at_least_two_layers_in_subtree_draw_content =
      num_descendants_that_draw_content > 0 &&
      (layer->DrawsContent() || num_descendants_that_draw_content > 1);

  bool may_have_transparency =
      EffectiveOpacity(layer) != 1.f ||
      HasPotentiallyRunningOpacityAnimation(mutator_host, layer);
  if (may_have_transparency && ShouldFlattenTransform(layer) &&
      at_least_two_layers_in_subtree_draw_content) {
    TRACE_EVENT_INSTANT0(
        "cc", "PropertyTreeBuilder::ShouldCreateRenderSurface opacity",
        TRACE_EVENT_SCOPE_THREAD);
    DCHECK(!is_root);
    return true;
  }
  // If the layer has isolation.
  // TODO(rosca): to be optimized - create separate rendering surface only when
  // the blending descendants might have access to the content behind this layer
  // (layer has transparent background or descendants overflow).
  // https://code.google.com/p/chromium/issues/detail?id=301738
  if (IsRootForIsolatedGroup(layer)) {
    TRACE_EVENT_INSTANT0(
        "cc", "PropertyTreeBuilder::ShouldCreateRenderSurface isolation",
        TRACE_EVENT_SCOPE_THREAD);
    return true;
  }

  // If we force it.
  if (ForceRenderSurface(layer))
    return true;

  // If we cache it.
  if (CacheRenderSurface(layer))
    return true;

  // If we'll make a copy of the layer's contents.
  if (HasCopyRequest(layer))
    return true;

  return false;
}

static void TakeCopyRequests(
    Layer* layer,
    std::vector<std::unique_ptr<viz::CopyOutputRequest>>* copy_requests) {
  layer->TakeCopyRequests(copy_requests);
}

static void TakeCopyRequests(
    LayerImpl* layer,
    std::vector<std::unique_ptr<viz::CopyOutputRequest>>* copy_requests) {
  for (auto& request : layer->test_properties()->copy_requests)
    copy_requests->push_back(std::move(request));
  layer->test_properties()->copy_requests.clear();
}

static void SetSubtreeHasCopyRequest(Layer* layer,
                                     bool subtree_has_copy_request) {
  layer->SetSubtreeHasCopyRequest(subtree_has_copy_request);
}

static void SetSubtreeHasCopyRequest(LayerImpl* layer,
                                     bool subtree_has_copy_request) {
  layer->test_properties()->subtree_has_copy_request = subtree_has_copy_request;
}

static bool SubtreeHasCopyRequest(Layer* layer) {
  return layer->SubtreeHasCopyRequest();
}

static bool SubtreeHasCopyRequest(LayerImpl* layer) {
  return layer->test_properties()->subtree_has_copy_request;
}

template <typename LayerType>
bool UpdateSubtreeHasCopyRequestRecursive(LayerType* layer) {
  bool subtree_has_copy_request = false;
  if (HasCopyRequest(layer))
    subtree_has_copy_request = true;
  for (size_t i = 0; i < LayerChildren(layer).size(); ++i) {
    LayerType* current_child = LayerChildAt(layer, i);
    subtree_has_copy_request |=
        UpdateSubtreeHasCopyRequestRecursive(current_child);
  }
  SetSubtreeHasCopyRequest(layer, subtree_has_copy_request);
  return subtree_has_copy_request;
}

template <typename LayerType>
bool PropertyTreeBuilderContext<LayerType>::AddEffectNodeIfNeeded(
    const DataForRecursion<LayerType>& data_from_ancestor,
    LayerType* layer,
    DataForRecursion<LayerType>* data_for_children) const {
  const bool is_root = !LayerParent(layer);
  const bool has_transparency = EffectiveOpacity(layer) != 1.f;
  const bool has_potential_opacity_animation =
      HasPotentialOpacityAnimation(mutator_host_, layer);
  const bool has_potential_filter_animation =
      HasPotentiallyRunningFilterAnimation(mutator_host_, layer);

  data_for_children->animation_axis_aligned_since_render_target &=
      AnimationsPreserveAxisAlignment(mutator_host_, layer);
  data_for_children->compound_transform_since_render_target *= Transform(layer);
  const bool should_create_render_surface = ShouldCreateRenderSurface(
      mutator_host_, 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(mutator_host_, 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_potential_filter_animation || 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;
  }

  int node_id = effect_tree_.Insert(EffectNode(), parent_id);
  EffectNode* node = effect_tree_.back();

  node->stable_id = layer->id();
  node->opacity = Opacity(layer);
  node->blend_mode = BlendMode(layer);
  node->unscaled_mask_target_size = layer->bounds();
  node->has_render_surface = should_create_render_surface;
  node->cache_render_surface = CacheRenderSurface(layer);
  node->has_copy_request = HasCopyRequest(layer);
  node->filters = Filters(layer);
  node->backdrop_filters = BackdropFilters(layer);
  node->backdrop_filter_bounds = BackdropFilterBounds(layer);
  node->backdrop_filter_quality = BackdropFilterQuality(layer);
  node->filters_origin = FiltersOrigin(layer);
  node->trilinear_filtering = TrilinearFiltering(layer);
  node->has_potential_opacity_animation = has_potential_opacity_animation;
  node->has_potential_filter_animation = has_potential_filter_animation;
  node->double_sided = DoubleSided(layer);
  node->subtree_hidden = HideLayerAndSubtree(layer);
  node->is_currently_animating_opacity =
      OpacityIsAnimating(mutator_host_, layer);
  node->is_currently_animating_filter = FilterIsAnimating(mutator_host_, layer);
  node->effect_changed = PropertyChanged(layer);
  node->subtree_has_copy_request = SubtreeHasCopyRequest(layer);
  node->closest_ancestor_with_cached_render_surface_id =
      CacheRenderSurface(layer)
          ? node_id
          : data_from_ancestor.closest_ancestor_with_cached_render_surface;
  node->closest_ancestor_with_copy_request_id =
      HasCopyRequest(layer)
          ? node_id
          : data_from_ancestor.closest_ancestor_with_copy_request;

  if (MaskLayer(layer)) {
    node->mask_layer_id = MaskLayer(layer)->id();
    effect_tree_.AddMaskLayerId(node->mask_layer_id);
  }

  if (!is_root) {
    // The effect node's transform id is used only when we create a render
    // surface. So, we can leave the default value when we don't create a render
    // surface.
    if (should_create_render_surface) {
      // In this case, we will create a transform node, so it's safe to use the
      // next available id from the transform tree as this effect node's
      // transform id.
      node->transform_id = transform_tree_.next_available_id();
    }
    node->clip_id = data_from_ancestor.clip_tree_parent;
  } else {
    // The root render surface acts as the unbounded and untransformed
    // surface into which content is drawn. The transform node created
    // from the root layer (which includes device scale factor) and
    // the clip node created from the root layer (which includes
    // viewports) apply to the root render surface's content, but not
    // to the root render surface itself.
    node->transform_id = TransformTree::kRootNodeId;
    node->clip_id = ClipTree::kViewportNodeId;
  }

  data_for_children->closest_ancestor_with_cached_render_surface =
      node->closest_ancestor_with_cached_render_surface_id;
  data_for_children->closest_ancestor_with_copy_request =
      node->closest_ancestor_with_copy_request_id;
  data_for_children->effect_tree_parent = node_id;
  layer->SetEffectTreeIndex(node_id);

  // For animation subsystem purposes, if this layer has a compositor element
  // id, we build a map from that id to this effect node.
  if (layer->element_id()) {
    property_trees_.element_id_to_effect_node_index[layer->element_id()] =
        node_id;
  }

  std::vector<std::unique_ptr<viz::CopyOutputRequest>> layer_copy_requests;
  TakeCopyRequests(layer, &layer_copy_requests);
  for (auto& it : layer_copy_requests) {
    effect_tree_.AddCopyRequest(node_id, std::move(it));
  }
  layer_copy_requests.clear();

  if (should_create_render_surface) {
    data_for_children->compound_transform_since_render_target =
        gfx::Transform();
    data_for_children->animation_axis_aligned_since_render_target = true;
  }
  return should_create_render_surface;
}

static inline bool UserScrollableHorizontal(Layer* layer) {
  return layer->GetUserScrollableHorizontal();
}

static inline bool UserScrollableHorizontal(LayerImpl* layer) {
  return layer->test_properties()->user_scrollable_horizontal;
}

static inline bool UserScrollableVertical(Layer* layer) {
  return layer->GetUserScrollableVertical();
}

static inline bool UserScrollableVertical(LayerImpl* layer) {
  return layer->test_properties()->user_scrollable_vertical;
}

static inline OverscrollBehavior GetOverscrollBehavior(Layer* layer) {
  return layer->overscroll_behavior();
}

static inline OverscrollBehavior GetOverscrollBehavior(LayerImpl* layer) {
  return layer->test_properties()->overscroll_behavior;
}

static inline const base::Optional<SnapContainerData>& GetSnapContainerData(
    Layer* layer) {
  return layer->snap_container_data();
}

static inline const base::Optional<SnapContainerData>& GetSnapContainerData(
    LayerImpl* layer) {
  return layer->test_properties()->snap_container_data;
}

static inline uint32_t MainThreadScrollingReasons(Layer* layer) {
  return layer->GetMainThreadScrollingReasons();
}

static inline uint32_t MainThreadScrollingReasons(LayerImpl* layer) {
  return layer->test_properties()->main_thread_scrolling_reasons;
}

template <typename LayerType>
void SetHasTransformNode(LayerType* layer, bool val) {
  layer->SetHasTransformNode(val);
}

template <typename LayerType>
void PropertyTreeBuilderContext<LayerType>::AddScrollNodeIfNeeded(
    const DataForRecursion<LayerType>& data_from_ancestor,
    LayerType* layer,
    DataForRecursion<LayerType>* data_for_children) const {
  int parent_id = GetScrollParentId(data_from_ancestor, layer);

  bool is_root = !LayerParent(layer);
  bool scrollable = layer->scrollable();
  bool contains_non_fast_scrollable_region =
      !layer->non_fast_scrollable_region().IsEmpty();
  uint32_t main_thread_scrolling_reasons = MainThreadScrollingReasons(layer);

  bool scroll_node_uninheritable_criteria =
      is_root || scrollable || contains_non_fast_scrollable_region;
  bool has_different_main_thread_scrolling_reasons =
      main_thread_scrolling_reasons !=
      data_from_ancestor.main_thread_scrolling_reasons;
  bool requires_node =
      scroll_node_uninheritable_criteria ||
      (main_thread_scrolling_reasons !=
           MainThreadScrollingReason::kNotScrollingOnMain &&
       (has_different_main_thread_scrolling_reasons ||
        data_from_ancestor
            .scroll_tree_parent_created_by_uninheritable_criteria));

  int node_id;
  if (!requires_node) {
    node_id = parent_id;
    data_for_children->scroll_tree_parent = node_id;
  } else {
    ScrollNode node;
    node.scrollable = scrollable;
    node.main_thread_scrolling_reasons = main_thread_scrolling_reasons;
    node.scrolls_inner_viewport = layer == inner_viewport_scroll_layer_;
    node.scrolls_outer_viewport = layer == outer_viewport_scroll_layer_;

    if (node.scrolls_inner_viewport &&
        data_from_ancestor.in_subtree_of_page_scale_layer) {
      node.max_scroll_offset_affected_by_page_scale = true;
    }

    node.bounds = layer->bounds();
    node.container_bounds = layer->scroll_container_bounds();
    node.offset_to_transform_parent = layer->offset_to_transform_parent();
    node.should_flatten =
        layer->should_flatten_screen_space_transform_from_property_tree();
    node.user_scrollable_horizontal = UserScrollableHorizontal(layer);
    node.user_scrollable_vertical = UserScrollableVertical(layer);
    node.element_id = layer->element_id();
    node.transform_id = data_for_children->transform_tree_parent;
    node.overscroll_behavior = GetOverscrollBehavior(layer);
    node.snap_container_data = GetSnapContainerData(layer);

    node_id = scroll_tree_.Insert(node, parent_id);
    data_for_children->scroll_tree_parent = node_id;
    data_for_children->main_thread_scrolling_reasons =
        node.main_thread_scrolling_reasons;
    data_for_children->scroll_tree_parent_created_by_uninheritable_criteria =
        scroll_node_uninheritable_criteria;
    // For animation subsystem purposes, if this layer has a compositor element
    // id, we build a map from that id to this scroll node.
    if (layer->element_id()) {
      property_trees_.element_id_to_scroll_node_index[layer->element_id()] =
          node_id;
    }

    if (node.scrollable) {
      scroll_tree_.SetBaseScrollOffset(layer->element_id(),
                                       layer->CurrentScrollOffset());
    }
  }

  layer->SetScrollTreeIndex(node_id);
}

template <typename LayerType>
void SetBackfaceVisibilityTransform(LayerType* layer,
                                    bool created_transform_node) {
  if (layer->use_parent_backface_visibility()) {
    DCHECK(LayerParent(layer));
    DCHECK(!LayerParent(layer)->use_parent_backface_visibility());
    layer->SetShouldCheckBackfaceVisibility(
        LayerParent(layer)->should_check_backface_visibility());
  } else {
    // A double-sided layer's backface can been shown when its visible.
    // In addition, we need to check if (1) there might be a local 3D transform
    // on the layer that might turn it to the backface, or (2) it is not drawn
    // into a flattened space.
    layer->SetShouldCheckBackfaceVisibility(
        !DoubleSided(layer) && (created_transform_node ||
                                !ShouldFlattenTransform(LayerParent(layer))));
  }
}

template <typename LayerType>
void SetSafeOpaqueBackgroundColor(
    const DataForRecursion<LayerType>& data_from_ancestor,
    LayerType* layer,
    DataForRecursion<LayerType>* data_for_children) {
  SkColor background_color = layer->background_color();
  data_for_children->safe_opaque_background_color =
      SkColorGetA(background_color) == 255
          ? background_color
          : data_from_ancestor.safe_opaque_background_color;
  layer->SetSafeOpaqueBackgroundColor(
      data_for_children->safe_opaque_background_color);
}

static void SetLayerPropertyChangedForChild(Layer* parent, Layer* child) {
  if (parent->subtree_property_changed())
    child->SetSubtreePropertyChanged();
}

static void SetLayerPropertyChangedForChild(LayerImpl* parent,
                                            LayerImpl* child) {}

template <typename LayerType>
void PropertyTreeBuilderContext<LayerType>::BuildPropertyTreesInternal(
    LayerType* layer,
    const DataForRecursion<LayerType>& data_from_parent) const {
  layer->set_property_tree_sequence_number(property_trees_.sequence_number);

  DataForRecursion<LayerType> data_for_children(data_from_parent);

  bool created_render_surface =
      AddEffectNodeIfNeeded(data_from_parent, layer, &data_for_children);

  bool created_transform_node = AddTransformNodeIfNeeded(
      data_from_parent, layer, created_render_surface, &data_for_children);
  SetHasTransformNode(layer, created_transform_node);
  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(mutator_host_, 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 < LayerChildren(layer).size(); ++i) {
    LayerType* current_child = LayerChildAt(layer, i);
    SetLayerPropertyChangedForChild(layer, current_child);
    if (!ScrollParent(current_child)) {
      BuildPropertyTreesInternal(current_child, data_for_children);
    }
  }

  auto scroll_children_range = scroll_children_map_.equal_range(layer);
  for (auto it = scroll_children_range.first;
       it != scroll_children_range.second; ++it) {
    LayerType* scroll_child = it->second;
    DCHECK_EQ(ScrollParent(scroll_child), layer);
    DCHECK(LayerParent(scroll_child));
    data_for_children.effect_tree_parent =
        LayerParent(scroll_child)->effect_tree_index();
    BuildPropertyTreesInternal(scroll_child, data_for_children);
  }

  if (MaskLayer(layer)) {
    MaskLayer(layer)->set_property_tree_sequence_number(
        property_trees_.sequence_number);
    MaskLayer(layer)->SetOffsetToTransformParent(
        layer->offset_to_transform_parent());
    MaskLayer(layer)->SetTransformTreeIndex(layer->transform_tree_index());
    MaskLayer(layer)->SetClipTreeIndex(layer->clip_tree_index());
    MaskLayer(layer)->SetEffectTreeIndex(layer->effect_tree_index());
    MaskLayer(layer)->SetScrollTreeIndex(layer->scroll_tree_index());
  }
}

const LayerTreeHost& AllLayerRange(const Layer* root_layer) {
  return *root_layer->layer_tree_host();
}
const LayerTreeImpl& AllLayerRange(const LayerImpl* root_layer) {
  return *root_layer->layer_tree_impl();
}

}  // namespace

Layer* PropertyTreeBuilder::FindFirstScrollableLayer(Layer* layer) {
  if (!layer)
    return nullptr;

  if (layer->scrollable())
    return layer;

  for (size_t i = 0; i < layer->children().size(); ++i) {
    Layer* found = FindFirstScrollableLayer(layer->children()[i].get());
    if (found)
      return found;
  }

  return nullptr;
}

template <typename LayerType>
void PropertyTreeBuilderContext<LayerType>::BuildPropertyTrees(
    float device_scale_factor,
    const gfx::Rect& viewport,
    SkColor root_background_color) const {
  if (!property_trees_.needs_rebuild) {
    bool page_scale_is_root_layer = page_scale_layer_ == root_layer_;
    if (page_scale_layer_) {
      DCHECK_GE(page_scale_layer_->transform_tree_index(),
                TransformTree::kRootNodeId);
      TransformNode* node = property_trees_.transform_tree.Node(
          page_scale_layer_->transform_tree_index());

      // When the page scale layer is also the root layer, the node should also
      // store the combined scale factor and not just the page scale factor.
      float device_scale_factor_for_page_scale_node = 1.f;
      gfx::Transform device_transform_for_page_scale_node;
      if (page_scale_is_root_layer) {
        device_transform_for_page_scale_node = device_transform_;
        device_scale_factor_for_page_scale_node = device_scale_factor;
      }

      draw_property_utils::UpdatePageScaleFactor(
          &property_trees_, node, page_scale_factor_,
          device_scale_factor_for_page_scale_node,
          device_transform_for_page_scale_node);
    }
    draw_property_utils::UpdateElasticOverscroll(
        &property_trees_, overscroll_elasticity_element_id_,
        elastic_overscroll_);
    clip_tree_.SetViewportClip(gfx::RectF(viewport));
    float page_scale_factor_for_root =
        page_scale_is_root_layer ? page_scale_factor_ : 1.f;
    // SetRootTransformsAndScales will be incorrect if the root layer has
    // non-zero position, so ensure it is zero.
    DCHECK(Position(root_layer_).IsOrigin());
    transform_tree_.SetRootTransformsAndScales(
        device_scale_factor, page_scale_factor_for_root, device_transform_);
    return;
  }

  DataForRecursion<LayerType> data_for_recursion;
  data_for_recursion.transform_tree_parent = TransformTree::kInvalidNodeId;
  data_for_recursion.transform_tree_parent_fixed =
      TransformTree::kInvalidNodeId;
  data_for_recursion.clip_tree_parent = ClipTree::kRootNodeId;
  data_for_recursion.effect_tree_parent = EffectTree::kInvalidNodeId;
  data_for_recursion.scroll_tree_parent = ScrollTree::kRootNodeId;
  data_for_recursion.closest_ancestor_with_cached_render_surface =
      EffectTree::kInvalidNodeId;
  data_for_recursion.closest_ancestor_with_copy_request =
      EffectTree::kInvalidNodeId;
  data_for_recursion.in_subtree_of_page_scale_layer = false;
  data_for_recursion.affected_by_outer_viewport_bounds_delta = false;
  data_for_recursion.should_flatten = false;
  data_for_recursion.main_thread_scrolling_reasons =
      MainThreadScrollingReason::kNotScrollingOnMain;
  data_for_recursion.scroll_tree_parent_created_by_uninheritable_criteria =
      true;
  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.safe_opaque_background_color = root_background_color;

  property_trees_.clear();
  transform_tree_.set_device_scale_factor(device_scale_factor);
  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 =
      clip_tree_.Insert(root_clip, ClipTree::kRootNodeId);

  BuildPropertyTreesInternal(root_layer_, data_for_recursion);
  property_trees_.needs_rebuild = false;

  // The transform tree is kept up to date as it is built, but the
  // combined_clips stored in the clip tree and the screen_space_opacity and
  // is_drawn in the effect tree aren't computed during tree building.
  transform_tree_.set_needs_update(false);
  clip_tree_.set_needs_update(true);
  effect_tree_.set_needs_update(true);
  scroll_tree_.set_needs_update(false);
}

#if DCHECK_IS_ON()
template <typename LayerType>
static void CheckDanglingScrollParent(LayerType* root_layer) {
  std::unordered_set<const LayerType*> layers;
  for (const auto* layer : AllLayerRange(root_layer))
    layers.insert(layer);
  for (auto* layer : AllLayerRange(root_layer))
    DCHECK(!ScrollParent(layer) ||
           layers.find(ScrollParent(layer)) != layers.end());
}

static void CheckClipPointersForLayer(Layer* layer) {
  if (!layer)
    return;

  if (layer->clip_children()) {
    for (auto it = layer->clip_children()->begin();
         it != layer->clip_children()->end(); ++it) {
      DCHECK_EQ((*it)->clip_parent(), layer);
    }
  }
}
#endif

template <typename LayerType>
void PropertyTreeBuilderContext<LayerType>::InitializeScrollChildrenMap() {
#if DCHECK_IS_ON()
  CheckDanglingScrollParent(root_layer_);
#endif
  for (auto* layer : AllLayerRange(root_layer_)) {
    if (ScrollParent(layer))
      scroll_children_map_.emplace(ScrollParent(layer), layer);
  }
}

void PropertyTreeBuilder::BuildPropertyTrees(
    Layer* root_layer,
    const Layer* page_scale_layer,
    const Layer* inner_viewport_scroll_layer,
    const Layer* outer_viewport_scroll_layer,
    const ElementId overscroll_elasticity_element_id,
    const gfx::Vector2dF& elastic_overscroll,
    float page_scale_factor,
    float device_scale_factor,
    const gfx::Rect& viewport,
    const gfx::Transform& device_transform,
    PropertyTrees* property_trees) {
  property_trees->is_main_thread = true;
  property_trees->is_active = false;
  SkColor color = root_layer->layer_tree_host()->background_color();
  if (SkColorGetA(color) != 255)
    color = SkColorSetA(color, 255);
  if (root_layer->layer_tree_host()->has_copy_request())
    UpdateSubtreeHasCopyRequestRecursive(root_layer);
  PropertyTreeBuilderContext<Layer>(
      root_layer, page_scale_layer, inner_viewport_scroll_layer,
      outer_viewport_scroll_layer, overscroll_elasticity_element_id,
      elastic_overscroll, page_scale_factor, device_transform,
      root_layer->layer_tree_host()->mutator_host(), property_trees)
      .BuildPropertyTrees(device_scale_factor, viewport, color);
#if DCHECK_IS_ON()
  for (auto* layer : AllLayerRange(root_layer))
    CheckClipPointersForLayer(layer);
#endif
  property_trees->ResetCachedData();
  // During building property trees, all copy requests are moved from layers to
  // effect tree, which are then pushed at commit to compositor thread and
  // handled there. LayerTreeHost::has_copy_request is only required to
  // decide if we want to create a effect node. So, it can be reset now.
  root_layer->layer_tree_host()->SetHasCopyRequest(false);
}

void PropertyTreeBuilder::BuildPropertyTrees(
    LayerImpl* root_layer,
    const LayerImpl* page_scale_layer,
    const LayerImpl* inner_viewport_scroll_layer,
    const LayerImpl* outer_viewport_scroll_layer,
    const ElementId overscroll_elasticity_element_id,
    const gfx::Vector2dF& elastic_overscroll,
    float page_scale_factor,
    float device_scale_factor,
    const gfx::Rect& viewport,
    const gfx::Transform& device_transform,
    PropertyTrees* property_trees) {
  // Preserve render surfaces when rebuilding.
  std::vector<std::unique_ptr<RenderSurfaceImpl>> render_surfaces;
  property_trees->effect_tree.TakeRenderSurfaces(&render_surfaces);
  property_trees->is_main_thread = false;
  property_trees->is_active = root_layer->IsActive();
  SkColor color = root_layer->layer_tree_impl()->background_color();
  if (SkColorGetA(color) != 255)
    color = SkColorSetA(color, 255);
  UpdateSubtreeHasCopyRequestRecursive(root_layer);

  PropertyTreeBuilderContext<LayerImpl>(
      root_layer, page_scale_layer, inner_viewport_scroll_layer,
      outer_viewport_scroll_layer, overscroll_elasticity_element_id,
      elastic_overscroll, page_scale_factor, device_transform,
      root_layer->layer_tree_impl()->mutator_host(), property_trees)
      .BuildPropertyTrees(device_scale_factor, viewport, color);
  property_trees->effect_tree.CreateOrReuseRenderSurfaces(
      &render_surfaces, root_layer->layer_tree_impl());
  property_trees->ResetCachedData();
}

}  // namespace cc