1 /*
2  * Copyright 2008 The Android Open Source Project
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 SkPixelRef_DEFINED
9 #define SkPixelRef_DEFINED
10 
11 #include "include/core/SkBitmap.h"
12 #include "include/core/SkFilterQuality.h"
13 #include "include/core/SkImageInfo.h"
14 #include "include/core/SkPixmap.h"
15 #include "include/core/SkRefCnt.h"
16 #include "include/core/SkSize.h"
17 #include "include/core/SkString.h"
18 #include "include/private/SkMutex.h"
19 #include "include/private/SkTDArray.h"
20 
21 #include <atomic>
22 
23 struct SkIRect;
24 
25 class GrTexture;
26 class SkDiscardableMemory;
27 
28 /** \class SkPixelRef
29 
30     This class is the smart container for pixel memory, and is used with SkBitmap.
31     This class can be shared/accessed between multiple threads.
32 */
33 class SK_API SkPixelRef : public SkRefCnt {
34 public:
35     SkPixelRef(int width, int height, void* addr, size_t rowBytes);
36     ~SkPixelRef() override;
37 
width()38     int width() const { return fWidth; }
height()39     int height() const { return fHeight; }
pixels()40     void* pixels() const { return fPixels; }
rowBytes()41     size_t rowBytes() const { return fRowBytes; }
42 
43     /** Returns a non-zero, unique value corresponding to the pixels in this
44         pixelref. Each time the pixels are changed (and notifyPixelsChanged is
45         called), a different generation ID will be returned.
46     */
47     uint32_t getGenerationID() const;
48 
49     /**
50      *  Call this if you have changed the contents of the pixels. This will in-
51      *  turn cause a different generation ID value to be returned from
52      *  getGenerationID().
53      */
54     void notifyPixelsChanged();
55 
56     /** Returns true if this pixelref is marked as immutable, meaning that the
57         contents of its pixels will not change for the lifetime of the pixelref.
58     */
isImmutable()59     bool isImmutable() const { return fMutability != kMutable; }
60 
61     /** Marks this pixelref is immutable, meaning that the contents of its
62         pixels will not change for the lifetime of the pixelref. This state can
63         be set on a pixelref, but it cannot be cleared once it is set.
64     */
65     void setImmutable();
66 
67     // Register a listener that may be called the next time our generation ID changes.
68     //
69     // We'll only call the listener if we're confident that we are the only SkPixelRef with this
70     // generation ID.  If our generation ID changes and we decide not to call the listener, we'll
71     // never call it: you must add a new listener for each generation ID change.  We also won't call
72     // the listener when we're certain no one knows what our generation ID is.
73     //
74     // This can be used to invalidate caches keyed by SkPixelRef generation ID.
75     struct GenIDChangeListener {
~GenIDChangeListenerGenIDChangeListener76         virtual ~GenIDChangeListener() {}
77         virtual void onChange() = 0;
78     };
79 
80     // Takes ownership of listener.  Threadsafe.
81     void addGenIDChangeListener(GenIDChangeListener* listener);
82 
83     // Call when this pixelref is part of the key to a resourcecache entry. This allows the cache
84     // to know automatically those entries can be purged when this pixelref is changed or deleted.
notifyAddedToCache()85     void notifyAddedToCache() {
86         fAddedToCache.store(true);
87     }
88 
diagnostic_only_getDiscardable()89     virtual SkDiscardableMemory* diagnostic_only_getDiscardable() const { return nullptr; }
90 
91 protected:
92     void android_only_reset(int width, int height, size_t rowBytes);
93 
94 private:
95     int                 fWidth;
96     int                 fHeight;
97     void*               fPixels;
98     size_t              fRowBytes;
99 
100     // Bottom bit indicates the Gen ID is unique.
genIDIsUnique()101     bool genIDIsUnique() const { return SkToBool(fTaggedGenID.load() & 1); }
102     mutable std::atomic<uint32_t> fTaggedGenID;
103 
104     SkMutex                         fGenIDChangeListenersMutex;
105     SkTDArray<GenIDChangeListener*> fGenIDChangeListeners;  // pointers are owned
106 
107     // Set true by caches when they cache content that's derived from the current pixels.
108     std::atomic<bool> fAddedToCache;
109 
110     enum Mutability {
111         kMutable,               // PixelRefs begin mutable.
112         kTemporarilyImmutable,  // Considered immutable, but can revert to mutable.
113         kImmutable,             // Once set to this state, it never leaves.
114     } fMutability : 8;          // easily fits inside a byte
115 
116     void needsNewGenID();
117     void callGenIDChangeListeners();
118 
119     void setTemporarilyImmutable();
120     void restoreMutability();
121     friend class SkSurface_Raster;   // For the two methods above.
122 
123     void setImmutableWithID(uint32_t genID);
124     friend void SkBitmapCache_setImmutableWithID(SkPixelRef*, uint32_t);
125 
126     typedef SkRefCnt INHERITED;
127 };
128 
129 #endif
130