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/private/SkIDChangeListener.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 
dimensions()38     SkISize dimensions() const { return {fWidth, fHeight}; }
width()39     int width() const { return fWidth; }
height()40     int height() const { return fHeight; }
pixels()41     void* pixels() const { return fPixels; }
rowBytes()42     size_t rowBytes() const { return fRowBytes; }
43 
44     /** Returns a non-zero, unique value corresponding to the pixels in this
45         pixelref. Each time the pixels are changed (and notifyPixelsChanged is
46         called), a different generation ID will be returned.
47     */
48     uint32_t getGenerationID() const;
49 
50     /**
51      *  Call this if you have changed the contents of the pixels. This will in-
52      *  turn cause a different generation ID value to be returned from
53      *  getGenerationID().
54      */
55     void notifyPixelsChanged();
56 
57     /** Returns true if this pixelref is marked as immutable, meaning that the
58         contents of its pixels will not change for the lifetime of the pixelref.
59     */
isImmutable()60     bool isImmutable() const { return fMutability != kMutable; }
61 
62     /** Marks this pixelref is immutable, meaning that the contents of its
63         pixels will not change for the lifetime of the pixelref. This state can
64         be set on a pixelref, but it cannot be cleared once it is set.
65     */
66     void setImmutable();
67 
68     // Register a listener that may be called the next time our generation ID changes.
69     //
70     // We'll only call the listener if we're confident that we are the only SkPixelRef with this
71     // generation ID.  If our generation ID changes and we decide not to call the listener, we'll
72     // never call it: you must add a new listener for each generation ID change.  We also won't call
73     // the listener when we're certain no one knows what our generation ID is.
74     //
75     // This can be used to invalidate caches keyed by SkPixelRef generation ID.
76     // Takes ownership of listener.  Threadsafe.
77     void addGenIDChangeListener(sk_sp<SkIDChangeListener> listener);
78 
79     // Call when this pixelref is part of the key to a resourcecache entry. This allows the cache
80     // to know automatically those entries can be purged when this pixelref is changed or deleted.
notifyAddedToCache()81     void notifyAddedToCache() {
82         fAddedToCache.store(true);
83     }
84 
diagnostic_only_getDiscardable()85     virtual SkDiscardableMemory* diagnostic_only_getDiscardable() const { return nullptr; }
86 
87 protected:
88     void android_only_reset(int width, int height, size_t rowBytes);
89 
90 private:
91     int                 fWidth;
92     int                 fHeight;
93     void*               fPixels;
94     size_t              fRowBytes;
95 
96     // Bottom bit indicates the Gen ID is unique.
genIDIsUnique()97     bool genIDIsUnique() const { return SkToBool(fTaggedGenID.load() & 1); }
98     mutable std::atomic<uint32_t> fTaggedGenID;
99 
100     SkIDChangeListener::List fGenIDChangeListeners;
101 
102     // Set true by caches when they cache content that's derived from the current pixels.
103     std::atomic<bool> fAddedToCache;
104 
105     enum Mutability {
106         kMutable,               // PixelRefs begin mutable.
107         kTemporarilyImmutable,  // Considered immutable, but can revert to mutable.
108         kImmutable,             // Once set to this state, it never leaves.
109     } fMutability : 8;          // easily fits inside a byte
110 
111     void needsNewGenID();
112     void callGenIDChangeListeners();
113 
114     void setTemporarilyImmutable();
115     void restoreMutability();
116     friend class SkSurface_Raster;   // For the two methods above.
117 
118     void setImmutableWithID(uint32_t genID);
119     friend void SkBitmapCache_setImmutableWithID(SkPixelRef*, uint32_t);
120 
121     typedef SkRefCnt INHERITED;
122 };
123 
124 #endif
125