property_tree.h

// 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.

#ifndef CC_TREES_PROPERTY_TREE_H_
#define CC_TREES_PROPERTY_TREE_H_

#include <vector>

#include "base/basictypes.h"
#include "cc/base/cc_export.h"
#include "ui/gfx/geometry/rect.h"
#include "ui/gfx/geometry/scroll_offset.h"
#include "ui/gfx/transform.h"

namespace cc {

template <typename T>
struct CC_EXPORT TreeNode {
  TreeNode() : id(-1), parent_id(-1), owner_id(-1), data() {}
  int id;
  int parent_id;
  int owner_id;
  T data;
};

struct CC_EXPORT TransformNodeData {
  TransformNodeData();
  ~TransformNodeData();

  // The local transform information is combined to form to_parent (ignoring
  // snapping) as follows:
  //
  //   to_parent = M_post_local * T_scroll * M_local * M_pre_local.
  //
  // The pre/post may seem odd when read LTR, but we multiply our points from
  // the right, so the pre_local matrix affects the result "first". This lines
  // up with the notions of pre/post used in skia and gfx::Transform.
  //
  // TODO(vollick): The values labeled with "will be moved..." take up a lot of
  // space, but are only necessary for animated or scrolled nodes (otherwise
  // we'll just use the baked to_parent). These values will be ultimately stored
  // directly on the transform/scroll display list items when that's possible,
  // or potentially in a scroll tree.
  //
  // TODO(vollick): will be moved when accelerated effects are implemented.
  gfx::Transform pre_local;
  gfx::Transform local;
  gfx::Transform post_local;

  gfx::Transform to_parent;

  gfx::Transform to_target;
  gfx::Transform from_target;

  gfx::Transform to_screen;
  gfx::Transform from_screen;

  int target_id;
  // This id is used for all content that draws into a render surface associated
  // with this transform node.
  int content_target_id;

  // This is the node with respect to which source_offset is defined. This will
  // not be needed once layerization moves to cc, but is needed in order to
  // efficiently update the transform tree for changes to position in the layer
  // tree.
  int source_node_id;

  // TODO(vollick): will be moved when accelerated effects are implemented.
  bool needs_local_transform_update : 1;

  bool is_invertible : 1;
  bool ancestors_are_invertible : 1;

  bool is_animated : 1;
  bool to_screen_is_animated : 1;

  // Flattening, when needed, is only applied to a node's inherited transform,
  // never to its local transform.
  bool flattens_inherited_transform : 1;

  // This is true if the to_parent transform at every node on the path to the
  // root is flat.
  bool node_and_ancestors_are_flat : 1;

  // This is needed to know if a layer can use lcd text.
  bool node_and_ancestors_have_only_integer_translation : 1;

  bool scrolls : 1;

  bool needs_sublayer_scale : 1;

  // These are used to position nodes wrt the right or bottom of the inner or
  // outer viewport.
  bool affected_by_inner_viewport_bounds_delta_x : 1;
  bool affected_by_inner_viewport_bounds_delta_y : 1;
  bool affected_by_outer_viewport_bounds_delta_x : 1;
  bool affected_by_outer_viewport_bounds_delta_y : 1;

  // This is used as a fallback when we either cannot adjust raster scale or if
  // the raster scale cannot be extracted from the screen space transform.
  float layer_scale_factor;

  // TODO(vollick): will be moved when accelerated effects are implemented.
  float post_local_scale_factor;

  gfx::Vector2dF sublayer_scale;

  // TODO(vollick): will be moved when accelerated effects are implemented.
  gfx::ScrollOffset scroll_offset;

  // We scroll snap where possible, but this has an effect on scroll
  // compensation: the snap is yet more scrolling that must be compensated for.
  // This value stores the snapped amount for this purpose.
  gfx::Vector2dF scroll_snap;

  // TODO(vollick): will be moved when accelerated effects are implemented.
  gfx::Vector2dF source_offset;
  gfx::Vector2dF source_to_parent;

  void set_to_parent(const gfx::Transform& transform) {
    to_parent = transform;
    is_invertible = to_parent.IsInvertible();
  }

  void update_pre_local_transform(const gfx::Point3F& transform_origin);

  void update_post_local_transform(const gfx::PointF& position,
                                   const gfx::Point3F& transform_origin);
};

typedef TreeNode<TransformNodeData> TransformNode;

struct CC_EXPORT ClipNodeData {
  ClipNodeData();

  gfx::RectF clip;
  gfx::RectF combined_clip;
  int transform_id;
  int target_id;
};

typedef TreeNode<ClipNodeData> ClipNode;

struct CC_EXPORT OpacityNodeData {
  OpacityNodeData();

  float opacity;
  float screen_space_opacity;
};

typedef TreeNode<OpacityNodeData> OpacityNode;

template <typename T>
class CC_EXPORT PropertyTree {
 public:
  PropertyTree();
  virtual ~PropertyTree();

  int Insert(const T& tree_node, int parent_id);

  T* Node(int i) {
    // TODO(vollick): remove this.
    CHECK(i < static_cast<int>(nodes_.size()));
    return i > -1 ? &nodes_[i] : nullptr;
  }
  const T* Node(int i) const {
    // TODO(vollick): remove this.
    CHECK(i < static_cast<int>(nodes_.size()));
    return i > -1 ? &nodes_[i] : nullptr;
  }

  T* parent(const T* t) { return Node(t->parent_id); }
  const T* parent(const T* t) const { return Node(t->parent_id); }

  T* back() { return size() ? &nodes_[nodes_.size() - 1] : nullptr; }
  const T* back() const {
    return size() ? &nodes_[nodes_.size() - 1] : nullptr;
  }

  virtual void clear();
  size_t size() const { return nodes_.size(); }

  void set_needs_update(bool needs_update) { needs_update_ = needs_update; }
  bool needs_update() const { return needs_update_; }

 private:
  // Copy and assign are permitted. This is how we do tree sync.
  std::vector<T> nodes_;

  bool needs_update_;
};

class CC_EXPORT TransformTree final : public PropertyTree<TransformNode> {
 public:
  TransformTree();
  ~TransformTree() override;

  void clear() override;

  // Computes the change of basis transform from node |source_id| to |dest_id|.
  // The function returns false iff the inverse of a singular transform was
  // used (and the result should, therefore, not be trusted). Transforms may
  // be computed between any pair of nodes that have an ancestor/descendant
  // relationship. Transforms between other pairs of nodes may only be computed
  // if the following condition holds: let id1 the larger id and let id2 be the
  // other id; then the nearest ancestor of node id1 whose id is smaller than
  // id2 is the lowest common ancestor of the pair of nodes, and the transform
  // from this lowest common ancestor to node id2 is only a 2d translation.
  bool ComputeTransform(int source_id,
                        int dest_id,
                        gfx::Transform* transform) const;

  // Computes the change of basis transform from node |source_id| to |dest_id|,
  // including any sublayer scale at |dest_id|.  The function returns false iff
  // the inverse of a singular transform was used (and the result should,
  // therefore, not be trusted).
  bool ComputeTransformWithDestinationSublayerScale(
      int source_id,
      int dest_id,
      gfx::Transform* transform) const;

  // Computes the change of basis transform from node |source_id| to |dest_id|,
  // including any sublayer scale at |source_id|.  The function returns false
  // iff the inverse of a singular transform was used (and the result should,
  // therefore, not be trusted).
  bool ComputeTransformWithSourceSublayerScale(int source_id,
                                               int dest_id,
                                               gfx::Transform* transform) const;

  // Returns true iff the nodes indexed by |source_id| and |dest_id| are 2D axis
  // aligned with respect to one another.
  bool Are2DAxisAligned(int source_id, int dest_id) const;

  // Updates the parent, target, and screen space transforms and snapping.
  void UpdateTransforms(int id);

  // A TransformNode's source_to_parent value is used to account for the fact
  // that fixed-position layers are positioned by Blink wrt to their layer tree
  // parent (their "source"), but are parented in the transform tree by their
  // fixed-position container. This value needs to be updated on main-thread
  // property trees (for position changes initiated by Blink), but not on the
  // compositor thread (since the offset from a node corresponding to a
  // fixed-position layer to its fixed-position container is unaffected by
  // compositor-driven effects).
  void set_source_to_parent_updates_allowed(bool allowed) {
    source_to_parent_updates_allowed_ = allowed;
  }
  bool source_to_parent_updates_allowed() const {
    return source_to_parent_updates_allowed_;
  }

  void SetInnerViewportBoundsDelta(gfx::Vector2dF bounds_delta);
  gfx::Vector2dF inner_viewport_bounds_delta() const {
    return inner_viewport_bounds_delta_;
  }

  void SetOuterViewportBoundsDelta(gfx::Vector2dF bounds_delta);
  gfx::Vector2dF outer_viewport_bounds_delta() const {
    return outer_viewport_bounds_delta_;
  }

  void AddNodeAffectedByInnerViewportBoundsDelta(int node_id);
  void AddNodeAffectedByOuterViewportBoundsDelta(int node_id);

  bool HasNodesAffectedByInnerViewportBoundsDelta() const;
  bool HasNodesAffectedByOuterViewportBoundsDelta() const;

 private:
  // Returns true iff the node at |desc_id| is a descendant of the node at
  // |anc_id|.
  bool IsDescendant(int desc_id, int anc_id) const;

  // Computes the combined transform between |source_id| and |dest_id| and
  // returns false if the inverse of a singular transform was used. These two
  // nodes must be on the same ancestor chain.
  bool CombineTransformsBetween(int source_id,
                                int dest_id,
                                gfx::Transform* transform) const;

  // Computes the combined inverse transform between |source_id| and |dest_id|
  // and returns false if the inverse of a singular transform was used. These
  // two nodes must be on the same ancestor chain.
  bool CombineInversesBetween(int source_id,
                              int dest_id,
                              gfx::Transform* transform) const;

  void UpdateLocalTransform(TransformNode* node);
  void UpdateScreenSpaceTransform(TransformNode* node,
                                  TransformNode* parent_node,
                                  TransformNode* target_node);
  void UpdateSublayerScale(TransformNode* node);
  void UpdateTargetSpaceTransform(TransformNode* node,
                                  TransformNode* target_node);
  void UpdateIsAnimated(TransformNode* node, TransformNode* parent_node);
  void UpdateSnapping(TransformNode* node);
  void UpdateNodeAndAncestorsHaveIntegerTranslations(
      TransformNode* node,
      TransformNode* parent_node);
  bool NeedsSourceToParentUpdate(TransformNode* node);

  bool source_to_parent_updates_allowed_;
  gfx::Vector2dF inner_viewport_bounds_delta_;
  gfx::Vector2dF outer_viewport_bounds_delta_;
  std::vector<int> nodes_affected_by_inner_viewport_bounds_delta_;
  std::vector<int> nodes_affected_by_outer_viewport_bounds_delta_;
};

class CC_EXPORT ClipTree final : public PropertyTree<ClipNode> {};

class CC_EXPORT OpacityTree final : public PropertyTree<OpacityNode> {
 public:
  void UpdateOpacities(int id);
};

class CC_EXPORT PropertyTrees final {
 public:
  PropertyTrees();

  TransformTree transform_tree;
  OpacityTree opacity_tree;
  ClipTree clip_tree;
  bool needs_rebuild;
  int sequence_number;
};

}  // namespace cc

#endif  // CC_TREES_PROPERTY_TREE_H_