src/lazy/SkCachingPixelRef.h

/*
 * Copyright 2013 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef SkCachingPixelRef_DEFINED
#define SkCachingPixelRef_DEFINED

#include "SkImageInfo.h"
#include "SkImageGenerator.h"
#include "SkPixelRef.h"

class SkColorTable;

/**
 *  PixelRef which defers decoding until SkBitmap::lockPixels() is
 *  called.  Caches the decoded images in the global
 *  SkScaledImageCache.  When the pixels are unlocked, this cache may
 *  or be destroyed before the next lock.  If so, onLockPixels will
 *  attempt to re-decode.
 *
 *  Decoding is handled by the SkImageGenerator
 */
class SkCachingPixelRef : public SkPixelRef {
public:
    /**
     *  Takes ownership of SkImageGenerator.  If this method fails for
     *  whatever reason, it will return false and immediatetely delete
     *  the generator.  If it succeeds, it will modify destination
     *  bitmap.
     *
     *  If Install fails or when the SkCachingPixelRef that is
     *  installed into destination is destroyed, it will call
     *  SkDELETE() on the generator.  Therefore, generator should be
     *  allocated with SkNEW() or SkNEW_ARGS().
     */
    static bool Install(SkImageGenerator* gen, SkBitmap* dst);

protected:
    virtual ~SkCachingPixelRef();
    virtual void* onLockPixels(SkColorTable** colorTable) SK_OVERRIDE;
    virtual void onUnlockPixels() SK_OVERRIDE;
    virtual bool onLockPixelsAreWritable() const SK_OVERRIDE { return false; }

    virtual SkData* onRefEncodedData() SK_OVERRIDE {
        return fImageGenerator->refEncodedData();
    }
    // No need to flatten this object. When flattening an SkBitmap,
    // SkOrderedWriteBuffer will check the encoded data and write that
    // instead.
    // Future implementations of SkFlattenableWriteBuffer will need to
    // special case for onRefEncodedData as well.
    SK_DECLARE_UNFLATTENABLE_OBJECT()

private:
    SkImageGenerator* const fImageGenerator;
    bool                    fErrorInDecoding;
    void*                   fScaledCacheId;
    const size_t            fRowBytes;

    SkCachingPixelRef(const SkImageInfo&, SkImageGenerator*, size_t rowBytes);

    typedef SkPixelRef INHERITED;
};

#endif  // SkCachingPixelRef_DEFINED