Proactive SkPixelRef invalidation

include/core/SkPixelRef.h

 
 /*
  * 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 "SkBitmap.h"
 #include "SkRefCnt.h"
 #include "SkString.h"
 #include "SkFlattenable.h"
+#include "SkTDArray.h"
 
 #ifdef SK_DEBUG
     /**
      *  Defining SK_IGNORE_PIXELREF_SETPRELOCKED will force all pixelref
      *  subclasses to correctly handle lock/unlock pixels. For performance
      *  reasons, simple malloc-based subclasses call setPreLocked() to skip
      *  the overhead of implementing these calls.
      *
      *  This build-flag disables that optimization, to add in debugging our
      *  call-sites, to ensure that they correctly balance their calls of
@@ skipping 15 matching lines @@
     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 SkFlattenable {
 public:
     SK_DECLARE_INST_COUNT(SkPixelRef)
 
     explicit SkPixelRef(SkBaseMutex* mutex = NULL);
+    virtual ~SkPixelRef();
 
     /** Return the pixel memory returned from lockPixels, or null if the
         lockCount is 0.
     */
     void* pixels() const { return fPixels; }
 
     /** Return the current colorTable (if any) if pixels are locked, or null.
     */
     SkColorTable* colorTable() const { return fColorTable; }
 
@@ skipping 138 matching lines @@
     virtual void globalRef(void* data=NULL);
 
     /**
      *  Release a "global" ref on this object.
      *  The default implementation just calls unref(), but subclasses can override
      *  this method to implement additional behavior.
      */
     virtual void globalUnref();
 #endif
 
+    // 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.

[bsalomon, 2013/10/23 15:32:28]

clear to me

[scroggo, 2013/10/23 15:39:19]

Thanks for the new comments, which are much clearer.

Maybe a better name might be GenIDChangeListener?

[mtklein, 2013/10/23 16:07:10]

Changed all the names to variants of GenIDChangeListener.

+    struct InvalidationListener {
+        virtual ~InvalidationListener() {}
+        virtual void onInvalidate() = 0;
+    };
+
+    // Takes ownership of listener.
+    void addInvalidationListener(InvalidationListener* listener);
+
 protected:
     /** Called when the lockCount goes from 0 to 1. The caller will have already
         acquire a mutex for thread safety, so this method need not do that.
     */
     virtual void* onLockPixels(SkColorTable**) = 0;
     /** Called when the lock count goes from 1 to 0. The caller will have
         already acquire a mutex for thread safety, so this method need not do
         that.
     */
     virtual void onUnlockPixels() = 0;
@@ skipping 25 matching lines @@
     // serialization
     SkPixelRef(SkFlattenableReadBuffer&, SkBaseMutex*);
     virtual void flatten(SkFlattenableWriteBuffer&) const SK_OVERRIDE;
 
     // 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* pixels, SkColorTable* ctable);
 
 private:
-
     SkBaseMutex*    fMutex; // must remain in scope for the life of this object
     void*           fPixels;
     SkColorTable*   fColorTable;    // we do not track ownership, subclass does
     int             fLockCount;
 
     mutable uint32_t fGenerationID;
+    mutable bool     fUniqueGenerationID;
 
-    // SkBitmap is only a friend so that when copying, it can modify the new SkPixelRef to have the
-    // same fGenerationID as the original.
-    friend class SkBitmap;
+    SkTDArray<InvalidationListener*> fInvalidationListeners;  // pointers are owned
 
     SkString    fURI;
 
     // can go from false to true, but never from true to false
     bool    fIsImmutable;
     // only ever set in constructor, const after that
     bool    fPreLocked;
 
+    void needsNewGenID();
+    void callInvalidationListeners();

[scroggo, 2013/10/23 15:39:19]

+1 to the new name (unless you change the name of InvalidationListener)

+
     void setMutex(SkBaseMutex* mutex);
 
+    // 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&);
+
     typedef SkFlattenable INHERITED;
 };
 
 #endif