add optional SkAlphaType parameter to notifyPixelsChanged

src/core/SkPixelRef.cpp

 
 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #include "SkPixelRef.h"
 #include "SkFlattenableBuffers.h"
 #include "SkThread.h"
@@ skipping 246 matching lines @@
 void SkPixelRef::notifyPixelsChanged() {
 #ifdef SK_DEBUG
     if (fIsImmutable) {
         SkDebugf("========== notifyPixelsChanged called on immutable pixelref");
     }
 #endif
     this->callGenIDChangeListeners();
     this->needsNewGenID();
 }
 
+void SkPixelRef::notifyAlphaTypeChanged(SkAlphaType at) {
+    if (fInfo.fAlphaType != at) {
+        *const_cast<SkAlphaType*>(&fInfo.fAlphaType) = at;
+        this->callGenIDChangeListeners();

[scroggo, 2014/01/24 20:50:52]

I kind of think these two functions should be the same (or perhaps one should
call the other). The only time we call one but not the other is in the
destructor, when we don't need to call needsNewGenID, but setting two fields
needlessly might be a low price to pay to ensure we never accidentally call one
without the other.

[reed1, 2014/01/27 13:46:14]

I'll sync with the GPU guys, who invented this pattern I think.

+        this->needsNewGenID();
+    }
+}
+
 void SkPixelRef::setImmutable() {
     fIsImmutable = true;
 }
 
 bool SkPixelRef::readPixels(SkBitmap* dst, const SkIRect* subset) {
     return this->onReadPixels(dst, subset);
 }
 
 bool SkPixelRef::onReadPixels(SkBitmap* dst, const SkIRect* subset) {
     return false;
@@ skipping 34 matching lines @@
 
 #ifdef SK_BUILD_FOR_ANDROID
 void SkPixelRef::globalRef(void* data) {
     this->ref();
 }
 
 void SkPixelRef::globalUnref() {
     this->unref();
 }
 #endif