SkDiscardablePixelRef.h revision 2ebc10dd12a6fe55fda37a9bd5b1e0c1c1e08232 
1/*
2 * Copyright 2013 Google Inc.
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8#ifndef SkDiscardablePixelRef_DEFINED
9#define SkDiscardablePixelRef_DEFINED
10
11#include "SkDiscardableMemory.h"
12#include "SkPixelRef.h"
13#include "SkImageGenerator.h"
14#include "SkImageInfo.h"
15
16/**
17 * An interface that allows a purgable PixelRef to re-decode an image.
18 */
19
20typedef SkDiscardableMemory* (*SkDiscardableMemoryFactory)(size_t bytes);
21
22
23class SkDiscardablePixelRef : public SkPixelRef {
24public:
25    /**
26     *  Takes ownership of SkImageGenerator.  If this method fails for
27     *  whatever reason, it will return false and immediatetely delete
28     *  the generator.  If it succeeds, it will modify destination
29     *  bitmap.
30     *
31     *  If Install fails or when the SkDiscardablePixelRef that is
32     *  installed into destination is destroyed, it will call
33     *  SkDELETE() on the generator.  Therefore, generator should be
34     *  allocated with SkNEW() or SkNEW_ARGS().
35     *
36     *  @param destination Upon success, this bitmap will be
37     *  configured and have a pixelref installed.
38     *
39     *  @param factory If not NULL, this object will be used as a
40     *  source of discardable memory when decoding.  If NULL, then
41     *  SkDiscardableMemory::Create() will be called.
42     *
43     *  @return true iff successful.
44     */
45    static bool Install(SkImageGenerator* generator,
46                        SkBitmap* destination,
47                        SkDiscardableMemory::Factory* factory = NULL);
48
49    SK_DECLARE_UNFLATTENABLE_OBJECT()
50
51protected:
52    ~SkDiscardablePixelRef();
53    virtual void* onLockPixels(SkColorTable**) SK_OVERRIDE;
54    virtual void onUnlockPixels() SK_OVERRIDE;
55    virtual bool onLockPixelsAreWritable() const SK_OVERRIDE { return false; }
56
57    virtual SkData* onRefEncodedData() SK_OVERRIDE {
58        return fGenerator->refEncodedData();
59    }
60
61private:
62    SkImageGenerator* const fGenerator;
63    SkDiscardableMemory::Factory* const fDMFactory;
64    const SkImageInfo fInfo;
65    const size_t fSize;  // size of memory to be allocated
66    const size_t fRowBytes;
67    // These const members should not change over the life of the
68    // PixelRef, since the SkBitmap doesn't expect them to change.
69
70    SkDiscardableMemory* fDiscardableMemory;
71
72    /* Takes ownership of SkImageGenerator. */
73    SkDiscardablePixelRef(SkImageGenerator* generator,
74                          const SkImageInfo& info,
75                          size_t size,
76                          size_t rowBytes,
77                          SkDiscardableMemory::Factory* factory);
78};
79#endif  // SkDiscardablePixelRef_DEFINED
80