1 // Copyright 2014 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
5 #ifndef UI_GFX_GEOMETRY_R_TREE_H_
6 #define UI_GFX_GEOMETRY_R_TREE_H_
10 #include "base/containers/hash_tables.h"
11 #include "base/gtest_prod_util.h"
12 #include "base/macros.h"
13 #include "base/memory/scoped_ptr.h"
14 #include "base/memory/scoped_vector.h"
15 #include "ui/gfx/geometry/rect.h"
16 #include "ui/gfx/gfx_export.h"
20 // Defines a heirarchical bounding rectangle data structure for Rect objects,
21 // associated with a generic unique key K for efficient spatial queries. The
22 // R*-tree algorithm is used to build the trees. Based on the papers:
24 // A Guttman 'R-trees: a dynamic index structure for spatial searching', Proc
25 // ACM SIGMOD Int Conf on Management of Data, 47-57, 1984
27 // N Beckmann, H-P Kriegel, R Schneider, B Seeger 'The R*-tree: an efficient and
28 // robust access method for points and rectangles', Proc ACM SIGMOD Int Conf on
29 // Management of Data, 322-331, 1990
30 class GFX_EXPORT RTree {
32 RTree(size_t min_children, size_t max_children);
35 // Insert a new rect into the tree, associated with provided key. Note that if
36 // rect is empty, this rect will not actually be inserted. Duplicate keys
37 // overwrite old entries.
38 void Insert(const Rect& rect, intptr_t key);
40 // If present, remove the supplied key from the tree.
41 void Remove(intptr_t key);
43 // Fills a supplied list matches_out with all keys having bounding rects
44 // intersecting query_rect.
45 void Query(const Rect& query_rect,
46 base::hash_set<intptr_t>* matches_out) const;
48 // Removes all objects from the tree.
52 // Private data structure class for storing internal nodes or leaves with keys
53 // of R-Trees. Note that "leaf" nodes can still have children, the children
54 // will all be Nodes with non-NULL record pointers.
55 class GFX_EXPORT Node {
57 // Level counts from -1 for "record" Nodes, that is Nodes that wrap key
58 // values, to 0 for leaf Nodes, that is Nodes that only have record
59 // children, up to the root Node, which has level equal to the height of the
61 explicit Node(int level);
63 // Builds a new record Node.
64 Node(const Rect& rect, intptr_t key);
68 // Deletes all children and any attached record.
71 // Recursive call to build a list of rects that intersect the query_rect.
72 void Query(const Rect& query_rect,
73 base::hash_set<intptr_t>* matches_out) const;
75 // Recompute our bounds by taking the union of all children rects. Will then
76 // call RecomputeBounds() on our parent for recursive bounds recalculation
78 void RecomputeBounds();
80 // Removes number_to_remove nodes from this Node, and appends them to the
81 // supplied list. Does not repair bounds upon completion.
82 void RemoveNodesForReinsert(size_t number_to_remove,
83 ScopedVector<Node>* nodes);
85 // Given a pointer to a child node within this Node, remove it from our
86 // list. If that child had any children, append them to the supplied orphan
87 // list. Returns the new count of this node after removal. Does not
88 // recompute bounds, as this node itself may be removed if it now has too
90 size_t RemoveChild(Node* child_node, ScopedVector<Node>* orphans);
92 // Does what it says on the tin. Returns NULL if no children. Does not
94 scoped_ptr<Node> RemoveAndReturnLastChild();
96 // Given a node, returns the best fit node for insertion of that node at
98 Node* ChooseSubtree(Node* node);
100 // Adds the provided node to this Node. Returns the new count of records
101 // stored in the Node. Will recompute the bounds of this node after
103 size_t AddChild(Node* node);
105 // Returns a sibling to this Node with at least min_children and no greater
106 // than max_children of this Node's children assigned to it, and having the
107 // same parent. Bounds will be valid on both Nodes after this call.
108 Node* Split(size_t min_children, size_t max_children);
110 // For record nodes only, to support re-insert, allows setting the rect.
111 void SetRect(const Rect& rect);
113 // Returns a pointer to the parent of this Node, or NULL if no parent.
114 Node* parent() const { return parent_; }
116 // 0 level() would mean that this Node is a leaf. 1 would mean that this
117 // Node has children that are leaves. Calling level() on root_ returns the
118 // height of the tree - 1. A level of -1 means that this is a Record node.
119 int level() const { return level_; }
121 const Rect& rect() const { return rect_; }
123 size_t count() const { return children_.size(); }
125 intptr_t key() const { return key_; }
128 // Returns all records stored in this node and its children.
129 void GetAllValues(base::hash_set<intptr_t>* matches_out) const;
131 // Used for sorting Nodes along vertical and horizontal axes
132 static bool CompareVertical(Node* a, Node* b);
134 static bool CompareHorizontal(Node* a, Node* b);
136 static bool CompareCenterDistanceFromParent(Node* a, Node* b);
138 // Returns the increase in overlap value, as defined in Beckmann et al as
139 // the sum of the areas of the intersection of each |children_| rectangle
140 // (excepting the candidate child) with the argument rectangle. The
141 // expanded_rect argument is computed as the union of the candidate child
142 // rect and the argument rect, and is included here to avoid recomputation.
143 // Here the candidate child is indicated by index in |children_|, and
144 // expanded_rect is the alread-computed union of candidate's rect and
146 int OverlapIncreaseToAdd(const Rect& rect,
148 const Rect& expanded_rect);
150 // Bounds recomputation without calling parents to do the same.
151 void RecomputeBoundsNoParents();
153 // Split() helper methods.
155 // Given two vectors of Nodes sorted by vertical or horizontal bounds, this
156 // function populates two vectors of Rectangles in which the ith element is
157 // the Union of all bounding rectangles [0,i] in the associated sorted array
159 static void BuildLowBounds(const std::vector<Node*>& vertical_sort,
160 const std::vector<Node*>& horizontal_sort,
161 std::vector<Rect>* vertical_bounds,
162 std::vector<Rect>* horizontal_bounds);
164 // Given two vectors of Nodes sorted by vertical or horizontal bounds, this
165 // function populates two vectors of Rectangles in which the ith element is
166 // the Union of all bounding rectangles [i, count()) in the associated
167 // sorted array of Nodes.
168 static void BuildHighBounds(const std::vector<Node*>& vertical_sort,
169 const std::vector<Node*>& horizontal_sort,
170 std::vector<Rect>* vertical_bounds,
171 std::vector<Rect>* horizontal_bounds);
173 // Returns true if this is a vertical split, false if a horizontal one.
174 // Based on ChooseSplitAxis algorithm in Beckmann et al. Chooses the axis
175 // with the lowest sum of margin values of bounding boxes.
176 static bool ChooseSplitAxis(const std::vector<Rect>& low_vertical_bounds,
177 const std::vector<Rect>& high_vertical_bounds,
178 const std::vector<Rect>& low_horizontal_bounds,
179 const std::vector<Rect>& high_horizontal_bounds,
181 size_t max_children);
183 // Used by SplitNode to calculate optimal index of split, after determining
184 // along which axis to sort and split the children rectangles. Returns the
185 // index to the first element in the split children as sorted by the bounds
187 static size_t ChooseSplitIndex(size_t min_children,
189 const std::vector<Rect>& low_bounds,
190 const std::vector<Rect>& high_bounds);
192 // Takes our children_ and divides them into a new node, starting at index
193 // split_index in sorted_children.
194 Node* DivideChildren(const std::vector<Rect>& low_bounds,
195 const std::vector<Rect>& high_bounds,
196 const std::vector<Node*>& sorted_children,
199 // Returns a pointer to the child node that will result in the least overlap
200 // increase with the addition of node_rect, as defined in the Beckmann et al
201 // paper, or NULL if there's a tie found. Requires a precomputed vector of
202 // expanded rectangles where the ith rectangle in the vector is the union of
203 // |children_|[i] and node_rect.
204 Node* LeastOverlapIncrease(const Rect& node_rect,
205 const std::vector<Rect>& expanded_rects);
207 // Returns a pointer to the child node that will result in the least area
208 // enlargement if the argument node rectangle were to be added to that
209 // nodes' bounding box. Requires a precomputed vector of expanded rectangles
210 // where the ith rectangle in the vector is the union of |children_|[i] and
212 Node* LeastAreaEnlargement(const Rect& node_rect,
213 const std::vector<Rect>& expanded_rects);
215 // This Node's bounding rectangle.
218 // The height of the node in the tree, counting from -1 at the record node
219 // to 0 at the leaf up to the root node which has level equal to the height
223 // Pointers to all of our children Nodes.
224 ScopedVector<Node> children_;
226 // A weak pointer to our parent Node in the RTree. The root node will have a
227 // NULL value for |parent_|.
230 // If this is a record Node, then |key_| will be non-NULL and will contain
231 // the key data. Otherwise, NULL.
234 friend class RTreeTest;
235 FRIEND_TEST_ALL_PREFIXES(RTreeTest, NodeBuildHighBounds);
236 FRIEND_TEST_ALL_PREFIXES(RTreeTest, NodeBuildLowBounds);
237 FRIEND_TEST_ALL_PREFIXES(RTreeTest, NodeChooseSplitAxisAndIndex);
238 FRIEND_TEST_ALL_PREFIXES(RTreeTest, NodeChooseSubtree);
239 FRIEND_TEST_ALL_PREFIXES(RTreeTest, NodeCompareCenterDistanceFromParent);
240 FRIEND_TEST_ALL_PREFIXES(RTreeTest, NodeCompareHorizontal);
241 FRIEND_TEST_ALL_PREFIXES(RTreeTest, NodeCompareVertical);
242 FRIEND_TEST_ALL_PREFIXES(RTreeTest, NodeDivideChildren);
243 FRIEND_TEST_ALL_PREFIXES(RTreeTest, NodeLeastAreaEnlargement);
244 FRIEND_TEST_ALL_PREFIXES(RTreeTest, NodeLeastOverlapIncrease);
245 FRIEND_TEST_ALL_PREFIXES(RTreeTest, NodeOverlapIncreaseToAdd);
246 FRIEND_TEST_ALL_PREFIXES(RTreeTest, NodeRemoveAndReturnLastChild);
247 FRIEND_TEST_ALL_PREFIXES(RTreeTest, NodeRemoveChildNoOrphans);
248 FRIEND_TEST_ALL_PREFIXES(RTreeTest, NodeRemoveChildOrphans);
249 FRIEND_TEST_ALL_PREFIXES(RTreeTest, NodeRemoveNodesForReinsert);
250 FRIEND_TEST_ALL_PREFIXES(RTreeTest, NodeSplit);
252 DISALLOW_COPY_AND_ASSIGN(Node);
255 // Supports re-insertion of Nodes based on the strategies outlined in
257 void InsertNode(Node* node, int* highset_reinsert_level);
259 // Supports removal of nodes for tree without deletion.
260 void RemoveNode(Node* node);
262 // A pointer to the root node in the RTree.
263 scoped_ptr<Node> root_;
265 // The parameters used to define the shape of the RTree.
266 size_t min_children_;
267 size_t max_children_;
269 // A map of supplied keys to their Node representation within the RTree, for
270 // efficient retrieval of keys without requiring a bounding rect.
271 base::hash_map<intptr_t, Node*> record_map_;
273 friend class RTreeTest;
274 FRIEND_TEST_ALL_PREFIXES(RTreeTest, NodeBuildHighBounds);
275 FRIEND_TEST_ALL_PREFIXES(RTreeTest, NodeBuildLowBounds);
276 FRIEND_TEST_ALL_PREFIXES(RTreeTest, NodeChooseSplitAxisAndIndex);
277 FRIEND_TEST_ALL_PREFIXES(RTreeTest, NodeChooseSubtree);
278 FRIEND_TEST_ALL_PREFIXES(RTreeTest, NodeCompareCenterDistanceFromParent);
279 FRIEND_TEST_ALL_PREFIXES(RTreeTest, NodeCompareHorizontal);
280 FRIEND_TEST_ALL_PREFIXES(RTreeTest, NodeCompareVertical);
281 FRIEND_TEST_ALL_PREFIXES(RTreeTest, NodeDivideChildren);
282 FRIEND_TEST_ALL_PREFIXES(RTreeTest, NodeLeastAreaEnlargement);
283 FRIEND_TEST_ALL_PREFIXES(RTreeTest, NodeLeastOverlapIncrease);
284 FRIEND_TEST_ALL_PREFIXES(RTreeTest, NodeOverlapIncreaseToAdd);
285 FRIEND_TEST_ALL_PREFIXES(RTreeTest, NodeRemoveAndReturnLastChild);
286 FRIEND_TEST_ALL_PREFIXES(RTreeTest, NodeRemoveChildNoOrphans);
287 FRIEND_TEST_ALL_PREFIXES(RTreeTest, NodeRemoveChildOrphans);
288 FRIEND_TEST_ALL_PREFIXES(RTreeTest, NodeRemoveNodesForReinsert);
289 FRIEND_TEST_ALL_PREFIXES(RTreeTest, NodeSplit);
291 DISALLOW_COPY_AND_ASSIGN(RTree);
296 #endif // UI_GFX_GEOMETRY_R_TREE_H_