add SkDrawPictureCallback optional parameter to drawPicture(), which can abort the picture drawing.

include/core/SkPicture.h

 
 /*
  * Copyright 2007 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 SkPicture_DEFINED
 #define SkPicture_DEFINED
 
 #include "SkBitmap.h"
 #include "SkRefCnt.h"
 
 class SkBBoxHierarchy;
 class SkCanvas;
+class SkDrawPictureCallback;
 class SkPicturePlayback;
 class SkPictureRecord;
 class SkStream;
 class SkWStream;
 
 /** \class SkPicture
 
     The SkPicture class records the drawing commands made to a canvas, to
     be played back at a later time.
 */
@@ skipping 115 matching lines @@
     SkCanvas* getRecordingCanvas() const;
     /** Signal that the caller is done recording. This invalidates the canvas
         returned by beginRecording/getRecordingCanvas, and prepares the picture
         for drawing. Note: this happens implicitly the first time the picture
         is drawn.
     */
     void endRecording();
 
     /** Replays the drawing commands on the specified canvas. This internally
         calls endRecording() if that has not already been called.
-        @param surface the canvas receiving the drawing commands.
+        @param canvas the canvas receiving the drawing commands.

[robertphillips, 2013/05/20 17:05:19]

document 'callback' parameter?

     */
-    void draw(SkCanvas* surface);
+    void draw(SkCanvas* canvas, SkDrawPictureCallback* = NULL);
 
     /** Return the width of the picture's recording canvas. This
         value reflects what was passed to setSize(), and does not necessarily
         reflect the bounds of what has been recorded into the picture.
         @return the width of the picture's recording canvas
     */
     int width() const { return fWidth; }
 
     /** Return the height of the picture's recording canvas. This
         value reflects what was passed to setSize(), and does not necessarily
@@ skipping 73 matching lines @@
 
     /** Return the canvas to draw into for recording into the picture.
     */
     SkCanvas* getRecordingCanvas() const { return fCanvas; }
 
 private:
     SkPicture*  fPicture;
     SkCanvas*   fCanvas;
 };
 
+/**
+ *  Subclasses of this can be passed to canvas.drawPicture. During the drawing
+ *  of the picture, this callback will periodically be invoked. If its
+ *  abortDrawing() returns true, then picture playback will be interrupted.
+ *
+ *  The resulting drawing is undefined, as there is no guarantee how often the
+ *  callback will be invoked. If the abort happens inside some level of nested
+ *  calls to save(), restore will automatically be called to return the state
+ *  to the same level it was before the drawPicture call was made.
+ */
+class SkDrawPictureCallback {
+public:
+    SkDrawPictureCallback() {}
+    virtual ~SkDrawPictureCallback() {}
+    
+    virtual bool abortDrawing() = 0;
+};
 
 #endif