[WIP] Add Context to SkDrawLooper.

include/core/SkDrawLooper.h

Index: include/core/SkDrawLooper.h
diff --git a/include/core/SkDrawLooper.h b/include/core/SkDrawLooper.h
index 4609c1dcf90ddb67a4708909ea209b5063fcfe18..04db0bed829c1f743ea62280d7f0c9a4a33dc98f 100644
--- a/include/core/SkDrawLooper.h
+++ b/include/core/SkDrawLooper.h
@@ -30,10 +30,19 @@ public:
     SK_DECLARE_INST_COUNT(SkDrawLooper)
 
     /**
+     *  Holds state during a draw. A new object is returned by init() and must
+     *  be passed into all subsequent calls of next(). The final call to next()
+     *  will also delete the context.
+     *  Subclasses of SkDrawLooper should create a subclass of this object to
+     *  hold state specific to their subclass.
+     */
+    struct SK_API DrawContext {};
+
+    /**
      *  Called right before something is being drawn. This will be followed by
      *  calls to next() until next() returns false.
      */
-    virtual void init(SkCanvas*) = 0;
+    virtual DrawContext* init(SkCanvas*) const = 0;
 
     /**
      *  Called in a loop (after init()). Each time true is returned, the object
@@ -47,7 +56,7 @@ public:
      *  that the canvas has been restored to the state it was initially, before
      *  init() was first called.
      */
-    virtual bool next(SkCanvas*, SkPaint* paint) = 0;
+    bool next(SkCanvas* canvas, SkPaint* paint, DrawContext* context) const;

[scroggo, 2014/02/06 17:57:13]

It's a little weird that the parameter that's passed in may be deleted, but it
may be the right way to do it. Could you add a comment here explaining that.
(Assuming it is still dynamically allocated. Also, I know there's a comment
above DrawContext, but I think it should be here as well.)

 
     /**
      * The fast bounds functions are used to enable the paint to be culled early
@@ -70,6 +79,9 @@ protected:
     SkDrawLooper() {}
     SkDrawLooper(SkReadBuffer& buffer) : INHERITED(buffer) {}
 
+    virtual bool next_internal(

[scroggo, 2014/02/06 17:57:13]

I think our typical naming convention would be onNext().

+        SkCanvas* canvas, SkPaint* paint, DrawContext* context) const = 0;
+
 private:
     typedef SkFlattenable INHERITED;
 };