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* Copyright 2008 The Android Open Source Project
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
#ifndef SkPixelRef_DEFINED
#define SkPixelRef_DEFINED
#include "../private/SkAtomics.h"
#include "../private/SkMutex.h"
#include "../private/SkTDArray.h"
#include "SkBitmap.h"
#include "SkFilterQuality.h"
#include "SkImageInfo.h"
#include "SkPixmap.h"
#include "SkRefCnt.h"
#include "SkSize.h"
#include "SkString.h"
class SkColorTable;
struct SkIRect;
class GrTexture;
class SkDiscardableMemory;
/** \class SkPixelRef
This class is the smart container for pixel memory, and is used with
SkBitmap. A pixelref is installed into a bitmap, and then the bitmap can
access the actual pixel memory by calling lockPixels/unlockPixels.
This class can be shared/accessed between multiple threads.
class SK_API SkPixelRef : public SkRefCnt {
explicit SkPixelRef(const SkImageInfo&);
virtual ~SkPixelRef();
const SkImageInfo& info() const {
return fInfo;
/** Return the pixel memory returned from lockPixels, or null if the
lockCount is 0.
void* pixels() const { return fRec.fPixels; }
/** Return the current colorTable (if any) if pixels are locked, or null.
SkColorTable* colorTable() const { return fRec.fColorTable; }
size_t rowBytes() const { return fRec.fRowBytes; }
* To access the actual pixels of a pixelref, it must be "locked".
* Calling lockPixels returns a LockRec struct (on success).
struct LockRec {
LockRec() : fPixels(NULL), fColorTable(NULL) {}
void* fPixels;
SkColorTable* fColorTable;
size_t fRowBytes;
void zero() { sk_bzero(this, sizeof(*this)); }
bool isZero() const {
return NULL == fPixels && NULL == fColorTable && 0 == fRowBytes;
SkDEBUGCODE(bool isLocked() const { return fLockCount > 0; })
SkDEBUGCODE(int getLockCount() const { return fLockCount; })
* Call to access the pixel memory. Return true on success. Balance this
* with a call to unlockPixels().
bool lockPixels();
* Call to access the pixel memory. On success, return true and fill out
* the specified rec. On failure, return false and ignore the rec parameter.
* Balance this with a call to unlockPixels().
bool lockPixels(LockRec* rec);
/** Call to balanace a previous call to lockPixels(). Returns the pixels
(or null) after the unlock. NOTE: lock calls can be nested, but the
matching number of unlock calls must be made in order to free the
memory (if the subclass implements caching/deferred-decoding.)
void unlockPixels();
* Some bitmaps can return a copy of their pixels for lockPixels(), but
* that copy, if modified, will not be pushed back. These bitmaps should
* not be used as targets for a raster device/canvas (since all pixels
* modifications will be lost when unlockPixels() is called.)
bool lockPixelsAreWritable() const;
/** Returns a non-zero, unique value corresponding to the pixels in this
pixelref. Each time the pixels are changed (and notifyPixelsChanged is
called), a different generation ID will be returned.
uint32_t getGenerationID() const;
/** Returns a non-zero, unique value corresponding to this SkPixelRef.
Unlike the generation ID, this ID remains the same even when the pixels
are changed. IDs are not reused (until uint32_t wraps), so it is safe
to consider this ID unique even after this SkPixelRef is deleted.
Can be used as a key which uniquely identifies this SkPixelRef
regardless of changes to its pixels or deletion of this object.
uint32_t getStableID() const { return fStableID; }
* Call this if you have changed the contents of the pixels. This will in-
* turn cause a different generation ID value to be returned from
* getGenerationID().
void notifyPixelsChanged();
* Change the info's AlphaType. Note that this does not automatically
* invalidate the generation ID. If the pixel values themselves have
* changed, then you must explicitly call notifyPixelsChanged() as well.
void changeAlphaType(SkAlphaType at);
/** Returns true if this pixelref is marked as immutable, meaning that the
contents of its pixels will not change for the lifetime of the pixelref.
bool isImmutable() const { return fMutability != kMutable; }
/** Marks this pixelref is immutable, meaning that the contents of its
pixels will not change for the lifetime of the pixelref. This state can
be set on a pixelref, but it cannot be cleared once it is set.
void setImmutable();
/** Return the optional URI string associated with this pixelref. May be
const char* getURI() const { return fURI.size() ? fURI.c_str() : NULL; }
/** Copy a URI string to this pixelref, or clear the URI if the uri is null
void setURI(const char uri[]) {
/** Copy a URI string to this pixelref
void setURI(const char uri[], size_t len) {
fURI.set(uri, len);
/** Assign a URI string to this pixelref.
void setURI(const SkString& uri) { fURI = uri; }
struct LockRequest {
SkISize fSize;
SkFilterQuality fQuality;
struct LockResult {
LockResult() : fPixels(NULL), fCTable(NULL) {}
void (*fUnlockProc)(void* ctx);
void* fUnlockContext;
const void* fPixels;
SkColorTable* fCTable; // should be NULL unless colortype is kIndex8
size_t fRowBytes;
SkISize fSize;
void unlock() {
if (fUnlockProc) {
fUnlockProc = NULL; // can't unlock twice!
bool requestLock(const LockRequest&, LockResult*);
/** Populates dst with the pixels of this pixelRef, converting them to colorType. */
bool readPixels(SkBitmap* dst, SkColorType colorType, const SkIRect* subset = NULL);
// Register a listener that may be called the next time our generation ID changes.
// We'll only call the listener if we're confident that we are the only SkPixelRef with this
// generation ID. If our generation ID changes and we decide not to call the listener, we'll
// never call it: you must add a new listener for each generation ID change. We also won't call
// the listener when we're certain no one knows what our generation ID is.
// This can be used to invalidate caches keyed by SkPixelRef generation ID.
struct GenIDChangeListener {
virtual ~GenIDChangeListener() {}
virtual void onChange() = 0;
// Takes ownership of listener.
void addGenIDChangeListener(GenIDChangeListener* listener);
// Call when this pixelref is part of the key to a resourcecache entry. This allows the cache
// to know automatically those entries can be purged when this pixelref is changed or deleted.
void notifyAddedToCache() {;
virtual SkDiscardableMemory* diagnostic_only_getDiscardable() const { return NULL; }
* Returns true if the pixels are generated on-the-fly (when required).
bool isLazyGenerated() const { return this->onIsLazyGenerated(); }
* On success, returns true and fills out the LockRec for the pixels. On
* failure returns false and ignores the LockRec parameter.
* The caller will have already acquired a mutex for thread safety, so this
* method need not do that.
virtual bool onNewLockPixels(LockRec*) = 0;
* Balancing the previous successful call to onNewLockPixels. The locked
* pixel address will no longer be referenced, so the subclass is free to
* move or discard that memory.
* The caller will have already acquired a mutex for thread safety, so this
* method need not do that.
virtual void onUnlockPixels() = 0;
/** Default impl returns true */
virtual bool onLockPixelsAreWritable() const;
* For pixelrefs that don't have access to their raw pixels, they may be
* able to make a copy of them (e.g. if the pixels are on the GPU).
* The base class implementation returns false;
virtual bool onReadPixels(SkBitmap* dst, SkColorType colorType, const SkIRect* subsetOrNull);
// default impl does nothing.
virtual void onNotifyPixelsChanged();
* Returns the size (in bytes) of the internally allocated memory.
* This should be implemented in all serializable SkPixelRef derived classes.
* SkBitmap::fPixelRefOffset + SkBitmap::getSafeSize() should never overflow this value,
* otherwise the rendering code may attempt to read memory out of bounds.
* @return default impl returns 0.
virtual size_t getAllocatedSizeInBytes() const;
virtual bool onRequestLock(const LockRequest&, LockResult*);
virtual bool onIsLazyGenerated() const { return false; }
/** Return the mutex associated with this pixelref. This value is assigned
in the constructor, and cannot change during the lifetime of the object.
SkBaseMutex* mutex() const { return &fMutex; }
// only call from constructor. Flags this to always be locked, removing
// the need to grab the mutex and call onLockPixels/onUnlockPixels.
// Performance tweak to avoid those calls (esp. in multi-thread use case).
void setPreLocked(void*, size_t rowBytes, SkColorTable*);
mutable SkMutex fMutex;
// mostly const. fInfo.fAlpahType can be changed at runtime.
const SkImageInfo fInfo;
// LockRec is only valid if we're in a locked state (isLocked())
LockRec fRec;
int fLockCount;
bool lockPixelsInsideMutex();
// Bottom bit indicates the Gen ID is unique.
bool genIDIsUnique() const { return SkToBool(fTaggedGenID.load() & 1); }
mutable SkAtomic<uint32_t> fTaggedGenID;
const uint32_t fStableID;
SkTDArray<GenIDChangeListener*> fGenIDChangeListeners; // pointers are owned
SkString fURI;
// Set true by caches when they cache content that's derived from the current pixels.
SkAtomic<bool> fAddedToCache;
enum {
kMutable, // PixelRefs begin mutable.
kTemporarilyImmutable, // Considered immutable, but can revert to mutable.
kImmutable, // Once set to this state, it never leaves.
} fMutability : 8; // easily fits inside a byte
// only ever set in constructor, const after that
bool fPreLocked;
void needsNewGenID();
void callGenIDChangeListeners();
void setTemporarilyImmutable();
void restoreMutability();
friend class SkSurface_Raster; // For the two methods above.
bool isPreLocked() const { return fPreLocked; }
friend class SkImage_Raster;
friend class SkSpecialImage_Raster;
// When copying a bitmap to another with the same shape and config, we can safely
// clone the pixelref generation ID too, which makes them equivalent under caching.
friend class SkBitmap; // only for cloneGenID
void cloneGenID(const SkPixelRef&);
void setImmutableWithID(uint32_t genID);
friend class SkImage_Gpu;
friend class SkImageCacherator;
friend class SkSpecialImage_Gpu;
typedef SkRefCnt INHERITED;
class SkPixelRefFactory : public SkRefCnt {
* Allocate a new pixelref matching the specified ImageInfo, allocating
* the memory for the pixels. If the ImageInfo requires a ColorTable,
* the pixelref will ref() the colortable.
* On failure return NULL.
virtual SkPixelRef* create(const SkImageInfo&, size_t rowBytes, SkColorTable*) = 0;