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      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 "../private/SkMutex.h"
     12 #include "../private/SkTDArray.h"
     13 #include "SkBitmap.h"
     14 #include "SkFilterQuality.h"
     15 #include "SkImageInfo.h"
     16 #include "SkPixmap.h"
     17 #include "SkRefCnt.h"
     18 #include "SkSize.h"
     19 #include "SkString.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 
     38     int width() const { return fWidth; }
     39     int height() const { return fHeight; }
     40     void* pixels() const { return fPixels; }
     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     */
     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 {
     76         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.
     85     void notifyAddedToCache() {
     86         fAddedToCache.store(true);
     87     }
     88 
     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.
    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