diff -r 000000000000 -r 6474c204b198 gfx/skia/trunk/src/core/SkTileGrid.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gfx/skia/trunk/src/core/SkTileGrid.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,142 @@
+
+/*
+ * Copyright 2012 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkTileGrid_DEFINED
+#define SkTileGrid_DEFINED
+
+#include "SkBBoxHierarchy.h"
+#include "SkPictureStateTree.h"
+#include "SkTileGridPicture.h" // for TileGridInfo
+
+/**
+ * Subclass of SkBBoxHierarchy that stores elements in buckets that correspond
+ * to tile regions, disposed in a regular grid.  This is useful when the tile
+ * structure that will be use in search() calls is known prior to insertion.
+ * Calls to search will return in constant time.
+ *
+ * Note: Current implementation of search() only supports looking-up regions
+ * that are an exact match to a single tile.  Implementation could be augmented
+ * to support arbitrary rectangles, but performance would be sub-optimal.
+ */
+class SkTileGrid : public SkBBoxHierarchy {
+public:
+    enum {
+        // Number of tiles for which data is allocated on the stack in
+        // SkTileGrid::search. If malloc becomes a bottleneck, we may consider
+        // increasing this number. Typical large web page, say 2k x 16k, would
+        // require 512 tiles of size 256 x 256 pixels.
+        kStackAllocationTileCount = 1024
+    };
+
+    typedef void* (*SkTileGridNextDatumFunctionPtr)(SkTDArray<void*>** tileData, SkAutoSTArray<kStackAllocationTileCount, int>& tileIndices);
+
+    SkTileGrid(int xTileCount, int yTileCount, const SkTileGridPicture::TileGridInfo& info,
+        SkTileGridNextDatumFunctionPtr nextDatumFunction);
+
+    virtual ~SkTileGrid();
+
+    /**
+     * Insert a data pointer and corresponding bounding box
+     * @param data The data pointer, may be NULL
+     * @param bounds The bounding box, should not be empty
+     * @param defer Ignored, TileArray does not defer insertions
+     */
+    virtual void insert(void* data, const SkIRect& bounds, bool) SK_OVERRIDE;
+
+    virtual void flushDeferredInserts() SK_OVERRIDE {};
+
+    /**
+     * Populate 'results' with data pointers corresponding to bounding boxes that intersect 'query'
+     * The query argument is expected to be an exact match to a tile of the grid
+     */
+    virtual void search(const SkIRect& query, SkTDArray<void*>* results) SK_OVERRIDE;
+
+    virtual void clear() SK_OVERRIDE;
+
+    /**
+     * Gets the number of insertions
+     */
+    virtual int getCount() const SK_OVERRIDE;
+
+    virtual int getDepth() const SK_OVERRIDE { return -1; }
+
+    virtual void rewindInserts() SK_OVERRIDE;
+
+    // Used by search() and in SkTileGridHelper implementations
+    enum {
+        kTileFinished = -1,
+    };
+
+    int tileCount(int x, int y);  // For testing only.
+
+private:
+    SkTDArray<void*>& tile(int x, int y);
+
+    int fXTileCount, fYTileCount, fTileCount;
+    SkTileGridPicture::TileGridInfo fInfo;
+    SkTDArray<void*>* fTileData;
+    int fInsertionCount;
+    SkIRect fGridBounds;
+    SkTileGridNextDatumFunctionPtr fNextDatumFunction;
+
+    typedef SkBBoxHierarchy INHERITED;
+};
+
+/**
+ * Generic implementation for SkTileGridNextDatumFunctionPtr. user code may instantiate
+ * this template to get a valid SkTileGridNextDatumFunction implementation
+ *
+ * Returns the next element of tileData[i][tileIndices[i]] for all i and advances
+ * tileIndices[] past them. The order in which data are returned by successive
+ * calls to this method must reflect the order in which the were originally
+ * recorded into the tile grid.
+ *
+ * \param tileData array of pointers to arrays of tile data
+ * \param tileIndices per-tile data indices, indices are incremented for tiles that contain
+ *     the next datum.
+ * \tparam T a type to which it is safe to cast a datum and that has an operator <
+ *     such that 'a < b' is true if 'a' was inserted into the tile grid before 'b'.
+ */
+template <typename T>
+void* SkTileGridNextDatum(SkTDArray<void*>** tileData, SkAutoSTArray<SkTileGrid::kStackAllocationTileCount, int>& tileIndices) {
+    T* minVal = NULL;
+    int tileCount = tileIndices.count();
+    int minIndex = tileCount;
+    int maxIndex = 0;
+    // Find the next Datum; track where it's found so we reduce the size of the second loop.
+    for (int tile = 0; tile < tileCount; ++tile) {
+        int pos = tileIndices[tile];
+        if (pos != SkTileGrid::kTileFinished) {
+            T* candidate = (T*)(*tileData[tile])[pos];
+            if (NULL == minVal || (*candidate) < (*minVal)) {
+                minVal = candidate;
+                minIndex = tile;
+                maxIndex = tile;
+            } else if (!((*minVal) < (*candidate))) {
+                // We don't require operator==; if !(candidate<minVal) && !(minVal<candidate),
+                // candidate==minVal and we have to add this tile to the range searched.
+                maxIndex = tile;
+            }
+        }
+    }
+    // Increment indices past the next datum
+    if (minVal != NULL) {
+        for (int tile = minIndex; tile <= maxIndex; ++tile) {
+            int pos = tileIndices[tile];
+            if (pos != SkTileGrid::kTileFinished && (*tileData[tile])[pos] == minVal) {
+                if (++(tileIndices[tile]) >= tileData[tile]->count()) {
+                    tileIndices[tile] = SkTileGrid::kTileFinished;
+                }
+            }
+        }
+        return minVal;
+    }
+    return NULL;
+}
+
+#endif