src/gpu/GrBatchFontCache.h

/*
 * Copyright 2015 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef GrBatchFontCache_DEFINED
#define GrBatchFontCache_DEFINED

#include "GrBatchAtlas.h"
#include "GrDrawTarget.h"
#include "GrFontScaler.h"
#include "GrGlyph.h"
#include "SkTDynamicHash.h"
#include "SkVarAlloc.h"

class GrBatchFontCache;
class GrBatchTarget;
class GrGpu;

/**
 *  The GrBatchTextStrike manages a pool of CPU backing memory for Glyph Masks.  This backing memory
 *  is abstracted by GrGlyph, and indexed by a PackedID and GrFontScaler.  The GrFontScaler is what
 *  actually creates the mask.
 */
class GrBatchTextStrike {
public:
    GrBatchTextStrike(GrBatchFontCache*, const GrFontDescKey* fontScalerKey);
    ~GrBatchTextStrike();

    const GrFontDescKey* getFontScalerKey() const { return fFontScalerKey; }
    GrBatchFontCache* getBatchFontCache() const { return fBatchFontCache; }

    inline GrGlyph* getGlyph(GrGlyph::PackedID packed, GrFontScaler* scaler) {
        GrGlyph* glyph = fCache.find(packed);
        if (NULL == glyph) {
            glyph = this->generateGlyph(packed, scaler);
        }
        return glyph;
    }

    // returns true if glyph (or glyph+padding for distance field)
    // is too large to ever fit in texture atlas subregions (GrPlots)
    bool glyphTooLargeForAtlas(GrGlyph*);
    // returns true if glyph successfully added to texture atlas, false otherwise
    bool addGlyphToAtlas(GrBatchTarget*, GrGlyph*, GrFontScaler*);

    // testing
    int countGlyphs() const { return fCache.count(); }

    // remove any references to this plot
    void removeID(GrBatchAtlas::AtlasID);

    static const GrFontDescKey& GetKey(const GrBatchTextStrike& ts) {
        return *(ts.fFontScalerKey);
    }
    static uint32_t Hash(const GrFontDescKey& key) {
        return key.getHash();
    }

private:
    SkTDynamicHash<GrGlyph, GrGlyph::PackedID> fCache;
    SkAutoTUnref<const GrFontDescKey> fFontScalerKey;
    SkVarAlloc fPool;

    GrBatchFontCache* fBatchFontCache;
    int fAtlasedGlyphs;

    GrGlyph* generateGlyph(GrGlyph::PackedID packed, GrFontScaler* scaler);

    friend class GrBatchFontCache;
};

/*
 * GrBatchFontCache manages strikes which are indexed by a GrFontScaler.  These strikes can then be
 * used to individual Glyph Masks.  The GrBatchFontCache also manages GrBatchAtlases, though this is
 * more or less transparent to the client(aside from atlasGeneration, described below)
 */
class GrBatchFontCache {
public:
    GrBatchFontCache();
    ~GrBatchFontCache();

    // Initializes the GrBatchFontCache on the owning GrContext
    void init(GrContext*);

    inline GrBatchTextStrike* getStrike(GrFontScaler* scaler) {

        GrBatchTextStrike* strike = fCache.find(*(scaler->getKey()));
        if (NULL == strike) {
            strike = this->generateStrike(scaler);
        }
        return strike;
    }

    bool hasGlyph(GrGlyph* glyph);

    // To ensure the GrBatchAtlas does not evict the Glyph Mask from its texture backing store,
    // the client must pass in the currentToken from the GrBatchTarget along with the GrGlyph
    void setGlyphRefToken(GrGlyph*, GrBatchAtlas::BatchToken);

    // add to texture atlas that matches this format
    bool addToAtlas(GrBatchTextStrike*, GrBatchAtlas::AtlasID*, GrBatchTarget*,
                    GrMaskFormat, int width, int height, const void* image,
                    SkIPoint16* loc);

    // Some clients may wish to verify the integrity of the texture backing store of the
    // GrBatchAtlas.  The atlasGeneration returned below is a monitonically increasing number which
    // changes everytime something is removed from the texture backing store.
    uint64_t atlasGeneration(GrMaskFormat) const;

    void freeAll();

    GrTexture* getTexture(GrMaskFormat);
    GrPixelConfig getPixelConfig(GrMaskFormat) const;

    void dump() const;

private:
    // There is a 1:1 mapping between GrMaskFormats and atlas indices
    static int MaskFormatToAtlasIndex(GrMaskFormat);
    static GrMaskFormat AtlasIndexToMaskFormat(int atlasIndex);

    GrBatchTextStrike* generateStrike(GrFontScaler*);

    inline GrBatchAtlas* getAtlas(GrMaskFormat) const;

    static void HandleEviction(GrBatchAtlas::AtlasID, void*);

    SkTDynamicHash<GrBatchTextStrike, GrFontDescKey> fCache;

    GrBatchAtlas* fAtlases[kMaskFormatCount];
    GrBatchTextStrike* fPreserveStrike;
};

#endif