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

include/core/SkCanvas.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 SkCanvas_DEFINED
@@ skipping 12 matching lines @@
 
 class SkBounder;
 class SkDevice;
 class SkDraw;
 class SkDrawFilter;
 class SkMetaData;
 class SkPicture;
 class SkRRect;
 class SkSurface_Base;
 
+/**
+ *  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;
+};
+
 /** \class SkCanvas
 
     A Canvas encapsulates all of the state about drawing into a device (bitmap).
     This includes a reference to the device itself, and a stack of matrix/clip
     values. For any given draw call (e.g. drawRect), the geometry of the object
     being drawn is transformed by the concatenation of all the matrices in the
     stack. The transformed geometry is clipped by the intersection of all of
     the clips in the stack.
 
     While the Canvas holds the state of the drawing device, the state (style)
@@ skipping 758 matching lines @@
         @param pos      Array of positions, used to position each character
         @param paint    The paint used for the text (e.g. color, size, style)
         @param path The path to draw on
         @param matrix The canvas matrix
         */
     void drawPosTextOnPath(const void* text, size_t byteLength,
                            const SkPoint pos[], const SkPaint& paint,
                            const SkPath& path, const SkMatrix* matrix);
 #endif
 
+    
     /** Draw the picture into this canvas. This method effective brackets the
         playback of the picture's draw calls with save/restore, so the state
         of this canvas will be unchanged after this call.
         @param picture The recorded drawing commands to playback into this
                        canvas.
     */
-    virtual void drawPicture(SkPicture& picture);
+    virtual void drawPicture(SkPicture& picture, SkDrawPictureCallback* = NULL);
 
     enum VertexMode {
         kTriangles_VertexMode,
         kTriangleStrip_VertexMode,
         kTriangleFan_VertexMode
     };
 
     /** Draw the array of vertices, interpreted as triangles (based on mode).
         @param vmode How to interpret the array of vertices
         @param vertexCount The number of points in the vertices array (and
@@ skipping 304 matching lines @@
             fCanvas = NULL;
         }
     }
 
 private:
     SkCanvas*   fCanvas;
     int         fSaveCount;
 };
 
 #endif