Fixes for SkPictureShader.

include/core/SkShader.h

 /*
  * Copyright 2006 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 SkShader_DEFINED
 #define SkShader_DEFINED
@@ skipping 358 matching lines @@
      *  @param tmx  The tiling mode to use when sampling the bitmap in the x-direction.
      *  @param tmy  The tiling mode to use when sampling the bitmap in the y-direction.
      *  @return     Returns a new shader object. Note: this function never returns null.
     */
     static SkShader* CreateBitmapShader(const SkBitmap& src,
                                         TileMode tmx, TileMode tmy);
 
     /** Call this to create a new shader that will draw with the specified picture.
      *
      *  @param src  The picture to use inside the shader (if not NULL, its ref count
-     *              is incremented).
+     *              is incremented). The SkPicture must not be changed after
+     *              successfully creating a picture shader.
+     *              FIXME: It may make more sense to take ownership than to add a

[scroggo, 2014/04/15 19:15:49]

From a code search of Chromium, it looks like they're not using this yet, but
perhaps code search is out of date. If Chromium is not using this, I say let's
go ahead and change the model from ref to takes ownership.

(OTOH, if we change to the read only playback portion of an SkPicture, it's fine
to ref.)

[robertphillips, 2014/04/15 19:26:44]

SkPictures that are functionally immutable should land this week. At that point
this entry point should be able to just take a ref on a const SkPicture.

[f(malita), 2014/04/15 19:40:40]

Chromium is not using this yet, so it would be fine to switch. But with const
pictures around the corner, I'd prefer to move to that model instead.

[scroggo, 2014/04/15 20:33:20]

Sounds good. I've just left it a ref, and made a note that it cannot be const
due to internals. IIUC Robert's comment, SkPicture will soon be the const
SkPicture, so I'll leave the comment out about the future playback class.

+     *              reference. Once we split SkPicture into record and playback, this
+     *              should take a playback.
      *  @param tmx  The tiling mode to use when sampling the bitmap in the x-direction.
      *  @param tmy  The tiling mode to use when sampling the bitmap in the y-direction.
      *  @return     Returns a new shader object. Note: this function never returns null.
     */
     static SkShader* CreatePictureShader(SkPicture* src, TileMode tmx, TileMode tmy);
 
     SK_TO_STRING_VIRT()
     SK_DEFINE_FLATTENABLE_TYPE(SkShader)
 
 protected:
 
     SkShader(SkReadBuffer& );
     virtual void flatten(SkWriteBuffer&) const SK_OVERRIDE;
 
 private:
     SkMatrix            fLocalMatrix;
 
     bool computeTotalInverse(const SkMatrix& matrix, SkMatrix* totalInverse) const;
 
     typedef SkFlattenable INHERITED;
 };
 
 #endif