Builder class for SkLayerRasterizer.

include/effects/SkLayerRasterizer.h

Index: include/effects/SkLayerRasterizer.h
diff --git a/include/effects/SkLayerRasterizer.h b/include/effects/SkLayerRasterizer.h
index be81a2ba3defd30f273788967bfb95481ec50d51..8096d784337d766a089c01b101cef3ac02bb12cd 100644
--- a/include/effects/SkLayerRasterizer.h
+++ b/include/effects/SkLayerRasterizer.h
@@ -21,6 +21,33 @@ public:
             SkLayerRasterizer();
     virtual ~SkLayerRasterizer();
 
+    class SK_API Builder {
+    public:
+        Builder();
+        ~Builder();
+
+        void addLayer(const SkPaint& paint) {
+            this->addLayer(paint, 0, 0);
+        }
+
+        /**
+          *  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.
+          */
+        SkLayerRasterizer* detachRasterizer();
+
+    private:
+        SkDeque* fLayers;
+    };
+
     void addLayer(const SkPaint& paint) {

[reed1, 2014/02/24 13:35:40]

Consider adding a build-guard here, to remind us to eliminate callers to the
non-builder calls like this one.

#ifndef SK_SUPPORT_LEGACY_LAYERRASTERIZER_API
    void addLayer(...);
#endif

Then we can *not* define this for skia builds (since we can fix all the callers
w/ this CL), but can #define this for Chrome if needed.

[Dominik Grewe, 2014/02/24 13:54:34]

Done.

         this->addLayer(paint, 0, 0);
     }
@@ -35,6 +62,7 @@ public:
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkLayerRasterizer)
 
 protected:
+    SkLayerRasterizer(SkDeque* layers);
     SkLayerRasterizer(SkReadBuffer&);
     virtual void flatten(SkWriteBuffer&) const SK_OVERRIDE;
 
@@ -44,7 +72,7 @@ protected:
                              SkMask* mask, SkMask::CreateMode mode) const;
 
 private:
-    SkDeque fLayers;
+    SkDeque* fLayers;
 
     typedef SkRasterizer INHERITED;
 };