SkTileGrid.h revision 363e546ed626b6dbbc42f5db87b3594bc0b5944b 
1
2/*
3 * Copyright 2012 Google Inc.
4 *
5 * Use of this source code is governed by a BSD-style license that can be
6 * found in the LICENSE file.
7 */
8
9#ifndef SkTileGrid_DEFINED
10#define SkTileGrid_DEFINED
11
12#include "SkBBoxHierarchy.h"
13#include "SkPictureStateTree.h"
14
15/**
16 * Subclass of SkBBoxHierarchy that stores elements in buckets that correspond
17 * to tile regions, disposed in a regular grid.  This is useful when the tile
18 * structure that will be use in search() calls is known prior to insertion.
19 * Calls to search will return in constant time.
20 *
21 * Note: Current implementation of search() only supports looking-up regions
22 * that are an exact match to a single tile.  Implementation could be augmented
23 * to support arbitrary rectangles, but performance would be sub-optimal.
24 */
25class SkTileGrid : public SkBBoxHierarchy {
26public:
27    typedef void* (*SkTileGridNextDatumFunctionPtr)(SkTDArray<void*>** tileData, SkTDArray<int>& tileIndices);
28
29    SkTileGrid(int tileWidth, int tileHeight, int xTileCount, int yTileCount,
30        SkTileGridNextDatumFunctionPtr nextDatumFunction);
31
32    virtual ~SkTileGrid();
33
34    /**
35     * Insert a data pointer and corresponding bounding box
36     * @param data The data pointer, may be NULL
37     * @param bounds The bounding box, should not be empty
38     * @param defer Ignored, TileArray does not defer insertions
39     */
40    virtual void insert(void* data, const SkIRect& bounds, bool) SK_OVERRIDE;
41
42    virtual void flushDeferredInserts() SK_OVERRIDE {};
43
44    /**
45     * Populate 'results' with data pointers corresponding to bounding boxes that intersect 'query'
46     * The query argument is expected to be an exact match to a tile of the grid
47     */
48    virtual void search(const SkIRect& query, SkTDArray<void*>* results) SK_OVERRIDE;
49
50    virtual void clear() SK_OVERRIDE;
51
52    /**
53     * Gets the number of insertions
54     */
55    virtual int getCount() const SK_OVERRIDE;
56
57    // Used by search() and in SkTileGridHelper implementations
58    enum {
59        kTileFinished = -1,
60    };
61private:
62    SkTDArray<void*>& tile(int x, int y);
63
64    int fTileWidth, fTileHeight, fXTileCount, fYTileCount, fTileCount;
65    SkTDArray<void*>* fTileData;
66    int fInsertionCount;
67    SkIRect fGridBounds;
68    SkTileGridNextDatumFunctionPtr fNextDatumFunction;
69
70    friend class TileGridTest;
71    typedef SkBBoxHierarchy INHERITED;
72};
73
74/**
75 * Generic implementation for SkTileGridNextDatumFunctionPtr. user code may instantiate
76 * this template to get a valid SkTileGridNextDatumFunction implementation
77 *
78 * Returns the next element of tileData[i][tileIndices[i]] for all i and advances
79 * tileIndices[] past them. The order in which data are returned by successive
80 * calls to this method must reflect the order in which the were originally
81 * recorded into the tile grid.
82 *
83 * \param tileData array of pointers to arrays of tile data
84 * \param tileIndices per-tile data indices, indices are incremented for tiles that contain
85 *     the next datum.
86 * \tparam T a type to which it is safe to cast a datum and that has an operator <
87 *     such that 'a < b' is true if 'a' was inserted into the tile grid before 'b'.
88 */
89template <typename T>
90void* SkTileGridNextDatum(SkTDArray<void*>** tileData, SkTDArray<int>& tileIndices) {
91    bool haveVal = false;
92    T* minVal;
93    int tileCount = tileIndices.count();
94    // Find the next Datum
95    for (int tile = 0; tile < tileCount; ++tile) {
96        int pos = tileIndices[tile];
97        if (pos != SkTileGrid::kTileFinished) {
98            T* candidate = (T*)(*tileData[tile])[pos];
99            if (!haveVal || (*candidate) < (*minVal)) {
100                minVal = candidate;
101                haveVal = true;
102            }
103        }
104    }
105    // Increment indices past the next datum
106    if (haveVal) {
107        for (int tile = 0; tile < tileCount; ++tile) {
108            int pos = tileIndices[tile];
109            if (pos != SkTileGrid::kTileFinished && (*tileData[tile])[pos] == minVal) {
110                if (++(tileIndices[tile]) >= tileData[tile]->count()) {
111                    tileIndices[tile] = SkTileGrid::kTileFinished;
112                }
113            }
114        }
115        return minVal;
116    }
117    return NULL;
118}
119
120#endif
121