michael@0: 
michael@0: /*
michael@0:  * Copyright 2012 Google Inc.
michael@0:  *
michael@0:  * Use of this source code is governed by a BSD-style license that can be
michael@0:  * found in the LICENSE file.
michael@0:  */
michael@0: 
michael@0: #ifndef SkTileGrid_DEFINED
michael@0: #define SkTileGrid_DEFINED
michael@0: 
michael@0: #include "SkBBoxHierarchy.h"
michael@0: #include "SkPictureStateTree.h"
michael@0: #include "SkTileGridPicture.h" // for TileGridInfo
michael@0: 
michael@0: /**
michael@0:  * Subclass of SkBBoxHierarchy that stores elements in buckets that correspond
michael@0:  * to tile regions, disposed in a regular grid.  This is useful when the tile
michael@0:  * structure that will be use in search() calls is known prior to insertion.
michael@0:  * Calls to search will return in constant time.
michael@0:  *
michael@0:  * Note: Current implementation of search() only supports looking-up regions
michael@0:  * that are an exact match to a single tile.  Implementation could be augmented
michael@0:  * to support arbitrary rectangles, but performance would be sub-optimal.
michael@0:  */
michael@0: class SkTileGrid : public SkBBoxHierarchy {
michael@0: public:
michael@0:     enum {
michael@0:         // Number of tiles for which data is allocated on the stack in
michael@0:         // SkTileGrid::search. If malloc becomes a bottleneck, we may consider
michael@0:         // increasing this number. Typical large web page, say 2k x 16k, would
michael@0:         // require 512 tiles of size 256 x 256 pixels.
michael@0:         kStackAllocationTileCount = 1024
michael@0:     };
michael@0: 
michael@0:     typedef void* (*SkTileGridNextDatumFunctionPtr)(SkTDArray<void*>** tileData, SkAutoSTArray<kStackAllocationTileCount, int>& tileIndices);
michael@0: 
michael@0:     SkTileGrid(int xTileCount, int yTileCount, const SkTileGridPicture::TileGridInfo& info,
michael@0:         SkTileGridNextDatumFunctionPtr nextDatumFunction);
michael@0: 
michael@0:     virtual ~SkTileGrid();
michael@0: 
michael@0:     /**
michael@0:      * Insert a data pointer and corresponding bounding box
michael@0:      * @param data The data pointer, may be NULL
michael@0:      * @param bounds The bounding box, should not be empty
michael@0:      * @param defer Ignored, TileArray does not defer insertions
michael@0:      */
michael@0:     virtual void insert(void* data, const SkIRect& bounds, bool) SK_OVERRIDE;
michael@0: 
michael@0:     virtual void flushDeferredInserts() SK_OVERRIDE {};
michael@0: 
michael@0:     /**
michael@0:      * Populate 'results' with data pointers corresponding to bounding boxes that intersect 'query'
michael@0:      * The query argument is expected to be an exact match to a tile of the grid
michael@0:      */
michael@0:     virtual void search(const SkIRect& query, SkTDArray<void*>* results) SK_OVERRIDE;
michael@0: 
michael@0:     virtual void clear() SK_OVERRIDE;
michael@0: 
michael@0:     /**
michael@0:      * Gets the number of insertions
michael@0:      */
michael@0:     virtual int getCount() const SK_OVERRIDE;
michael@0: 
michael@0:     virtual int getDepth() const SK_OVERRIDE { return -1; }
michael@0: 
michael@0:     virtual void rewindInserts() SK_OVERRIDE;
michael@0: 
michael@0:     // Used by search() and in SkTileGridHelper implementations
michael@0:     enum {
michael@0:         kTileFinished = -1,
michael@0:     };
michael@0: 
michael@0:     int tileCount(int x, int y);  // For testing only.
michael@0: 
michael@0: private:
michael@0:     SkTDArray<void*>& tile(int x, int y);
michael@0: 
michael@0:     int fXTileCount, fYTileCount, fTileCount;
michael@0:     SkTileGridPicture::TileGridInfo fInfo;
michael@0:     SkTDArray<void*>* fTileData;
michael@0:     int fInsertionCount;
michael@0:     SkIRect fGridBounds;
michael@0:     SkTileGridNextDatumFunctionPtr fNextDatumFunction;
michael@0: 
michael@0:     typedef SkBBoxHierarchy INHERITED;
michael@0: };
michael@0: 
michael@0: /**
michael@0:  * Generic implementation for SkTileGridNextDatumFunctionPtr. user code may instantiate
michael@0:  * this template to get a valid SkTileGridNextDatumFunction implementation
michael@0:  *
michael@0:  * Returns the next element of tileData[i][tileIndices[i]] for all i and advances
michael@0:  * tileIndices[] past them. The order in which data are returned by successive
michael@0:  * calls to this method must reflect the order in which the were originally
michael@0:  * recorded into the tile grid.
michael@0:  *
michael@0:  * \param tileData array of pointers to arrays of tile data
michael@0:  * \param tileIndices per-tile data indices, indices are incremented for tiles that contain
michael@0:  *     the next datum.
michael@0:  * \tparam T a type to which it is safe to cast a datum and that has an operator <
michael@0:  *     such that 'a < b' is true if 'a' was inserted into the tile grid before 'b'.
michael@0:  */
michael@0: template <typename T>
michael@0: void* SkTileGridNextDatum(SkTDArray<void*>** tileData, SkAutoSTArray<SkTileGrid::kStackAllocationTileCount, int>& tileIndices) {
michael@0:     T* minVal = NULL;
michael@0:     int tileCount = tileIndices.count();
michael@0:     int minIndex = tileCount;
michael@0:     int maxIndex = 0;
michael@0:     // Find the next Datum; track where it's found so we reduce the size of the second loop.
michael@0:     for (int tile = 0; tile < tileCount; ++tile) {
michael@0:         int pos = tileIndices[tile];
michael@0:         if (pos != SkTileGrid::kTileFinished) {
michael@0:             T* candidate = (T*)(*tileData[tile])[pos];
michael@0:             if (NULL == minVal || (*candidate) < (*minVal)) {
michael@0:                 minVal = candidate;
michael@0:                 minIndex = tile;
michael@0:                 maxIndex = tile;
michael@0:             } else if (!((*minVal) < (*candidate))) {
michael@0:                 // We don't require operator==; if !(candidate<minVal) && !(minVal<candidate),
michael@0:                 // candidate==minVal and we have to add this tile to the range searched.
michael@0:                 maxIndex = tile;
michael@0:             }
michael@0:         }
michael@0:     }
michael@0:     // Increment indices past the next datum
michael@0:     if (minVal != NULL) {
michael@0:         for (int tile = minIndex; tile <= maxIndex; ++tile) {
michael@0:             int pos = tileIndices[tile];
michael@0:             if (pos != SkTileGrid::kTileFinished && (*tileData[tile])[pos] == minVal) {
michael@0:                 if (++(tileIndices[tile]) >= tileData[tile]->count()) {
michael@0:                     tileIndices[tile] = SkTileGrid::kTileFinished;
michael@0:                 }
michael@0:             }
michael@0:         }
michael@0:         return minVal;
michael@0:     }
michael@0:     return NULL;
michael@0: }
michael@0: 
michael@0: #endif