Create SkLayerRasterizer w/o destroying Builder.

include/effects/SkLayerRasterizer.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 SkLayerRasterizer_DEFINED
@@ skipping 21 matching lines @@
         /**
           *  Add a new layer (above any previous layers) to the rasterizer.
           *  The layer will extract those fields that affect the mask from
           *  the specified paint, but will not retain a reference to the paint
           *  object itself, so it may be reused without danger of side-effects.
           */
         void addLayer(const SkPaint& paint, SkScalar dx, SkScalar dy);
 
         /**
           *  Pass queue of layers on to newly created layer rasterizer and return it. The builder
-          *  cannot be used any more after calling this function.
+          *  *cannot* be used any more after calling this function.
+          *
+          *  The caller is responsible for calling unref() on the returned object.
           */
         SkLayerRasterizer* detachRasterizer();
 
+        /**
+          *  Create and return a new immutable SkLayerRasterizer that contains a shapshot of the
+          *  layers that were added to the Builder, without modifying the Builder. The Builder
+          *  *may* be used after calling this function. It will continue to hold any layers
+          *  previously added, so consecutive calls to this function will return identical objects,
+          *  and objects returned by future calls to this function contain all the layers in
+          *  previously returned objects.
+          *
+          *  Future calls to addLayer will not affect rasterizers previously returned by this call.
+          *
+          *  The caller is responsible for calling unref() on the returned object.
+          */
+        SkLayerRasterizer* snapshotRasterizer() const;

[reed1, 2014/04/10 20:16:42]

can this guy be const? Does it have to be? I'd be fine if it wasn't, but I leave
that to you.

[scroggo, 2014/04/10 20:21:37]

As stated in person, it can, but does not have to be const. I like declaring it
const because the whole point of this function is that it returns a layer
rasterizer without modifying the builder.

+
     private:
         SkDeque* fLayers;
     };
 
 #ifdef SK_SUPPORT_LEGACY_LAYERRASTERIZER_API
     void addLayer(const SkPaint& paint) {
         this->addLayer(paint, 0, 0);
     }
 
     /**    Add a new layer (above any previous layers) to the rasterizer.
@@ skipping 23 matching lines @@
 
 private:
 #ifdef SK_SUPPORT_LEGACY_LAYERRASTERIZER_API
     SkDeque* fLayers;
 #else
     const SkDeque* const fLayers;
 #endif
 
     static SkDeque* ReadLayers(SkReadBuffer& buffer);
 
+    friend class LayerRasterizerTester;
+
     typedef SkRasterizer INHERITED;
 };
 
 #endif