Revert 276827 "readability review for luken"

ui/gfx/geometry/r_tree_base.h

Index: ui/gfx/geometry/r_tree_base.h
===================================================================
--- ui/gfx/geometry/r_tree_base.h	(revision 277444)
+++ ui/gfx/geometry/r_tree_base.h	(working copy)
@@ -1,309 +0,0 @@
-// 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.
-
-// Provides an implementation the parts of the RTree data structure that don't
-// require knowledge of the generic key type. Don't use these objects directly,
-// rather specialize the RTree<> object in r_tree.h. This file defines the
-// internal objects of an RTree, namely Nodes (internal nodes of the tree) and
-// Records, which hold (key, rectangle) pairs.
-
-#ifndef UI_GFX_GEOMETRY_R_TREE_BASE_H_
-#define UI_GFX_GEOMETRY_R_TREE_BASE_H_
-
-#include <list>
-#include <vector>
-
-#include "base/containers/hash_tables.h"
-#include "base/macros.h"
-#include "base/memory/scoped_ptr.h"
-#include "base/memory/scoped_vector.h"
-#include "ui/gfx/geometry/rect.h"
-#include "ui/gfx/gfx_export.h"
-
-namespace gfx {
-
-class GFX_EXPORT RTreeBase {
- protected:
-  class NodeBase;
-  class RecordBase;
-
-  typedef std::vector<const RecordBase*> Records;
-  typedef ScopedVector<NodeBase> Nodes;
-
-  RTreeBase(size_t min_children, size_t max_children);
-  ~RTreeBase();
-
-  // Protected data structure class for storing internal Nodes or leaves with
-  // Records.
-  class GFX_EXPORT NodeBase {
-   public:
-    virtual ~NodeBase();
-
-    // Appends to |records_out| the set of Records in this subtree with rects
-    // that intersect |query_rect|.  Avoids clearing |records_out| so that it
-    // can be called recursively.
-    virtual void AppendIntersectingRecords(const Rect& query_rect,
-                                           Records* records_out) const = 0;
-
-    // Returns all records stored in the subtree rooted at this node. Appends to
-    // |matches_out| without clearing.
-    virtual void AppendAllRecords(Records* records_out) const = 0;
-
-    // Returns NULL if no children. Does not recompute bounds.
-    virtual scoped_ptr<NodeBase> RemoveAndReturnLastChild() = 0;
-
-    // Returns -1 for Records, or the height of this subtree for Nodes.  The
-    // height of a leaf Node (a Node containing only Records) is 0, a leaf's
-    // parent is 1, etc. Note that in an R*-Tree, all branches from the root
-    // Node will be the same height.
-    virtual int Level() const = 0;
-
-    // Recomputes our bounds by taking the union of all child rects, then calls
-    // recursively on our parent so that ultimately all nodes up to the root
-    // recompute their bounds.
-    void RecomputeBoundsUpToRoot();
-
-    NodeBase* parent() { return parent_; }
-    const NodeBase* parent() const { return parent_; }
-    void set_parent(NodeBase* parent) { parent_ = parent; }
-    const Rect& rect() const { return rect_; }
-    void set_rect(const Rect& rect) { rect_ = rect; }
-
-   protected:
-    NodeBase(const Rect& rect, NodeBase* parent);
-
-    // Bounds recomputation without calling parents to do the same.
-    virtual void RecomputeLocalBounds();
-
-   private:
-    friend class RTreeTest;
-    friend class RTreeNodeTest;
-
-    // This Node's bounding rectangle.
-    Rect rect_;
-
-    // A weak pointer to our parent Node in the RTree. The root node will have a
-    // NULL value for |parent_|.
-    NodeBase* parent_;
-
-    DISALLOW_COPY_AND_ASSIGN(NodeBase);
-  };
-
-  class GFX_EXPORT RecordBase : public NodeBase {
-   public:
-    explicit RecordBase(const Rect& rect);
-    virtual ~RecordBase();
-
-    virtual void AppendIntersectingRecords(const Rect& query_rect,
-                                           Records* records_out) const OVERRIDE;
-    virtual void AppendAllRecords(Records* records_out) const OVERRIDE;
-    virtual scoped_ptr<NodeBase> RemoveAndReturnLastChild() OVERRIDE;
-    virtual int Level() const OVERRIDE;
-
-   private:
-    friend class RTreeTest;
-    friend class RTreeNodeTest;
-
-    DISALLOW_COPY_AND_ASSIGN(RecordBase);
-  };
-
-  class GFX_EXPORT Node : public NodeBase {
-   public:
-    // Constructs an empty Node with |level_| of 0.
-    Node();
-    virtual ~Node();
-
-    virtual void AppendIntersectingRecords(const Rect& query_rect,
-                                           Records* records_out) const OVERRIDE;
-    virtual scoped_ptr<NodeBase> RemoveAndReturnLastChild() OVERRIDE;
-    virtual int Level() const OVERRIDE;
-    virtual void AppendAllRecords(Records* matches_out) const OVERRIDE;
-
-    // Constructs a new Node that is the parent of this Node and already has
-    // this Node as its sole child. Valid to call only on root Nodes, meaning
-    // Nodes with |parent_| NULL. Note that ownership of this Node is
-    // transferred to the parent returned by this function.
-    scoped_ptr<Node> ConstructParent();
-
-    // Removes |number_to_remove| children from this Node, and appends them to
-    // the supplied list. Does not repair bounds upon completion. Nodes are
-    // selected in the manner suggested in the Beckmann et al. paper, which
-    // suggests that the children should be sorted by the distance from the
-    // center of their bounding rectangle to their parent's bounding rectangle,
-    // and then the n closest children should be removed for re-insertion. This
-    // removal occurs at most once on each level of the tree when overflowing
-    // nodes that have exceeded the maximum number of children during an Insert.
-    void RemoveNodesForReinsert(size_t number_to_remove, Nodes* nodes);
-
-    // Given a pointer to a child node within this Node, removes it from our
-    // list. If that child had any children, appends them to the supplied orphan
-    // list. Returns the removed child. Does not recompute bounds, as the caller
-    // might subsequently remove this node as well, meaning the recomputation
-    // would be wasted work.
-    scoped_ptr<NodeBase> RemoveChild(NodeBase* child_node, Nodes* orphans);
-
-    // Returns the best parent for insertion of the provided |node| as a child.
-    Node* ChooseSubtree(NodeBase* node);
-
-    // Adds |node| as a child of this Node, and recomputes the bounds of this
-    // node after the addition of the child. Returns the new count of children
-    // stored in this Node. This node becomes the owner of |node|.
-    size_t AddChild(scoped_ptr<NodeBase> node);
-
-    // Returns a sibling to this Node with at least min_children and no greater
-    // than max_children of this Node's children assigned to it, and having the
-    // same parent. Bounds will be valid on both Nodes after this call.
-    scoped_ptr<NodeBase> Split(size_t min_children, size_t max_children);
-
-    size_t count() const { return children_.size(); }
-    const NodeBase* child(size_t i) const { return children_[i]; }
-    NodeBase* child(size_t i) { return children_[i]; }
-
-   private:
-    typedef std::vector<Rect> Rects;
-
-    explicit Node(int level);
-
-    // Given two arrays of bounds rectangles as computed by BuildLowBounds()
-    // and BuildHighBounds(), returns the index of the element in those arrays
-    // along which a split of the arrays would result in a minimum amount of
-    // overlap (area of intersection) in the two groups.
-    static size_t ChooseSplitIndex(size_t start_index,
-                                   size_t end_index,
-                                   const Rects& low_bounds,
-                                   const Rects& high_bounds);
-
-    // R*-Tree attempts to keep groups of rectangles that are roughly square
-    // in shape. It does this by comparing the "margins" of different bounding
-    // boxes, where margin is defined as the sum of the length of all four sides
-    // of a rectangle. For two rectangles of equal area, the one with the
-    // smallest margin will be the rectangle whose width and height differ the
-    // least. When splitting we decide to split along an axis chosen from the
-    // rectangles either sorted vertically or horizontally by finding the axis
-    // that would result in the smallest sum of margins between the two bounding
-    // boxes of the resulting split. Returns the smallest sum computed given the
-    // sorted bounding boxes and a range to look within.
-    static int SmallestMarginSum(size_t start_index,
-                                 size_t end_index,
-                                 const Rects& low_bounds,
-                                 const Rects& high_bounds);
-
-    // Sorts nodes primarily by increasing y coordinates, and secondarily by
-    // increasing height.
-    static bool CompareVertical(const NodeBase* a, const NodeBase* b);
-
-    // Sorts nodes primarily by increasing x coordinates, and secondarily by
-    // increasing width.
-    static bool CompareHorizontal(const NodeBase* a, const NodeBase* b);
-
-    // Sorts nodes by the distance of the center of their rectangles to the
-    // center of their parent's rectangles.
-    static bool CompareCenterDistanceFromParent(
-        const NodeBase* a, const NodeBase* b);
-
-    // Given two vectors of Nodes sorted by vertical or horizontal bounds,
-    // populates two vectors of Rectangles in which the ith element is the union
-    // of all bounding rectangles [0,i] in the associated sorted array of Nodes.
-    static void BuildLowBounds(const std::vector<NodeBase*>& vertical_sort,
-                               const std::vector<NodeBase*>& horizontal_sort,
-                               Rects* vertical_bounds,
-                               Rects* horizontal_bounds);
-
-    // Given two vectors of Nodes sorted by vertical or horizontal bounds,
-    // populates two vectors of Rectangles in which the ith element is the
-    // union of all bounding rectangles [i, count()) in the associated sorted
-    // array of Nodes.
-    static void BuildHighBounds(const std::vector<NodeBase*>& vertical_sort,
-                                const std::vector<NodeBase*>& horizontal_sort,
-                                Rects* vertical_bounds,
-                                Rects* horizontal_bounds);
-
-    virtual void RecomputeLocalBounds() OVERRIDE;
-
-    // Returns the increase in overlap value, as defined in Beckmann et al. as
-    // the sum of the areas of the intersection of all child rectangles
-    // (excepting the candidate child) with the argument rectangle. Here the
-    // |candidate_node| is one of our |children_|, and |expanded_rect| is the
-    // already-computed union of the candidate's rect and |rect|.
-    int OverlapIncreaseToAdd(const Rect& rect,
-                             const NodeBase* candidate_node,
-                             const Rect& expanded_rect) const;
-
-    // Returns a new node containing children [split_index, count()) within
-    // |sorted_children|.  Children before |split_index| remain with |this|.
-    scoped_ptr<NodeBase> DivideChildren(
-        const Rects& low_bounds,
-        const Rects& high_bounds,
-        const std::vector<NodeBase*>& sorted_children,
-        size_t split_index);
-
-    // Returns a pointer to the child node that will result in the least overlap
-    // increase with the addition of node_rect, or NULL if there's a tie found.
-    // Requires a precomputed vector of expanded rectangles where the ith
-    // rectangle in the vector is the union of |children_|[i] and node_rect.
-    // Overlap is defined in Beckmann et al. as the sum of the areas of
-    // intersection of all child rectangles with the |node_rect| argument
-    // rectangle.  This heuristic attempts to choose the node for which adding
-    // the new rectangle to their bounding box will result in the least overlap
-    // with the other rectangles, thus trying to preserve the usefulness of the
-    // bounding rectangle by keeping it from covering too much redundant area.
-    Node* LeastOverlapIncrease(const Rect& node_rect,
-                               const Rects& expanded_rects);
-
-    // Returns a pointer to the child node that will result in the least area
-    // enlargement if the argument node rectangle were to be added to that
-    // node's bounding box. Requires a precomputed vector of expanded rectangles
-    // where the ith rectangle in the vector is the union of children_[i] and
-    // |node_rect|.
-    Node* LeastAreaEnlargement(const Rect& node_rect,
-                               const Rects& expanded_rects);
-
-    const int level_;
-
-    Nodes children_;
-
-    friend class RTreeTest;
-    friend class RTreeNodeTest;
-
-    DISALLOW_COPY_AND_ASSIGN(Node);
-  };
-
-  // Inserts |node| into the tree. The |highest_reinsert_level| supports
-  // re-insertion as described by Beckmann et al. As Node overflows progagate
-  // up the tree the algorithm performs a reinsertion of the overflow Nodes
-  // (instead of a split) at most once per level of the tree. A starting value
-  // of -1 for |highest_reinsert_level| means that reinserts are permitted for
-  // every level of the tree. This should always be set to -1 except by
-  // recursive calls from within InsertNode().
-  void InsertNode(scoped_ptr<NodeBase> node, int* highest_reinsert_level);
-
-  // Removes |node| from the tree without deleting it.
-  scoped_ptr<NodeBase> RemoveNode(NodeBase* node);
-
-  // If |root_| has only one child, deletes the |root_| Node and replaces it
-  // with its only descendant child. Otherwise does nothing.
-  void PruneRootIfNecessary();
-
-  // Deletes the entire current tree and replaces it with an empty Node.
-  void ResetRoot();
-
-  const Node* root() const { return root_.get(); }
-
- private:
-  friend class RTreeTest;
-  friend class RTreeNodeTest;
-
-  // A pointer to the root node in the RTree.
-  scoped_ptr<Node> root_;
-
-  // The parameters used to define the shape of the RTree.
-  const size_t min_children_;
-  const size_t max_children_;
-
-  DISALLOW_COPY_AND_ASSIGN(RTreeBase);
-};
-
-}  // namespace gfx
-
-#endif  // UI_GFX_GEOMETRY_R_TREE_BASE_H_