Make peekPixels() usable with raster surface snapshots

src/image/SkImagePriv.h

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkImagePriv_DEFINED
 #define SkImagePriv_DEFINED
 
 #include "SkImage.h"
 #include "SkSurface.h"
 
 // Call this if you explicitly want to use/share this pixelRef in the image
 extern SkImage* SkNewImageFromPixelRef(const SkImageInfo&, SkPixelRef*,
                                        const SkIPoint& pixelRefOrigin,
                                        size_t rowBytes,
                                        const SkSurfaceProps*);
 
 /**
  *  Examines the bitmap to decide if it can share the existing pixelRef, or
- *  if it needs to make a deep-copy of the pixels. The bitmap's pixelref will
- *  be shared if either the bitmap is marked as immutable, or canSharePixelRef
- *  is true.
+ *  if it needs to make a deep-copy of the pixels.
+ *
+ *  The bitmap's pixelref will be shared if either the bitmap is marked as
+ *  immutable, or forceSharePixelRef is true.  Shared pixel refs are also
+ *  locked when kLocked_SharedPixelRefMode is specified.
+ *
+ *  Passing kLocked_SharedPixelRefMode allows the image's peekPixels() method
+ *  to succeed, but it will force any lazy decodes/generators to execute if
+ *  they exist on the pixelref.
  *
  *  It is illegal to call this with a texture-backed bitmap.
  *
  *  If the bitmap's colortype cannot be converted into a corresponding
  *  SkImageInfo, or the bitmap's pixels cannot be accessed, this will return
  *  NULL.
  */
+enum SharedPixelRefMode {
+    kLocked_SharedPixelRefMode,
+    kUnlocked_SharedPixelRefMode
+};
 extern SkImage* SkNewImageFromRasterBitmap(const SkBitmap&, bool forceSharePixelRef,
-                                           const SkSurfaceProps*);
+                                           const SkSurfaceProps*, SharedPixelRefMode);
 
 static inline size_t SkImageMinRowBytes(const SkImageInfo& info) {
     size_t minRB = info.minRowBytes();
     if (kIndex_8_SkColorType != info.colorType()) {
         minRB = SkAlign4(minRB);
     }
     return minRB;
 }
 
 // Given an image created from SkNewImageFromBitmap, return its pixelref. This
 // may be called to see if the surface and the image share the same pixelref,
 // in which case the surface may need to perform a copy-on-write.
 extern const SkPixelRef* SkBitmapImageGetPixelRef(const SkImage* rasterImage);
 
 // When a texture is shared by a surface and an image its budgeted status is that of the
 // surface. This function is used when the surface makes a new texture for itself in order
 // for the orphaned image to determine whether the original texture counts against the
 // budget or not.
 extern void SkTextureImageApplyBudgetedDecision(SkImage* textureImage);
 
 // Update the texture wrapped by an image created with NewTexture. This
 // is called when a surface and image share the same GrTexture and the
 // surface needs to perform a copy-on-write
 extern void SkTextureImageSetTexture(SkImage* image, GrTexture* texture);
 
 GrTexture* GrDeepCopyTexture(GrTexture* src, bool isBudgeted);
 
 #endif