add asAShadowBlur for android to drawlooper

include/core/SkDrawLooper.h

 
 /*
  * Copyright 2011 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 SkDrawLooper_DEFINED
 #define SkDrawLooper_DEFINED
 
 #include "SkFlattenable.h"
+#include "SkPoint.h"
+#include "SkColor.h"
 
 class SkCanvas;
 class SkPaint;
 struct SkRect;
 class SkString;
 
 /** \class SkDrawLooper
     Subclasses of SkDrawLooper can be attached to a SkPaint. Where they are,
     and something is drawn to a canvas with that paint, the looper subclass will
     be called, allowing it to modify the canvas and/or paint for that draw call.
@@ skipping 57 matching lines @@
      * returns false then computeFastBounds behavior is undefined otherwise it
      * is expected to have the following behavior. Given the parent paint and
      * the parent's bounding rect the subclass must fill in and return the
      * storage rect, where the storage rect is with the union of the src rect
      * and the looper's bounding rect.
      */
     virtual bool canComputeFastBounds(const SkPaint& paint) const;
     virtual void computeFastBounds(const SkPaint& paint,
                                    const SkRect& src, SkRect* dst) const;
 
+    struct BlurShadowRec {
+        SkScalar    fRadius;

[djsollen, 2014/04/28 13:55:40]

As we discussed offline, I think this should return sigma so we can let the
caller do the conversion if they want to.

+        SkVector    fOffset;
+        SkColor     fColor;
+    };
+    /**
+     *  If this looper can be interpreted as having two layers, such that
+     *      1. The first layer (bottom most) just has a color, blur, and translate
+     *      2. The second layer has no modifications to either paint or canvas
+     *      3. No other layers.
+     *  then return true, and if not null, fill out the BlurShadowRec).
+     *
+     *  If any of the above are not met, return false and ignore the BlurShadowRec parameter.
+     */
+    virtual bool asABlurShadow(BlurShadowRec*) const;

[scroggo, 2014/04/28 13:28:06]

Does this need to be on the base class? It seems very specific to one subclass.

[djsollen, 2014/04/28 13:55:40]

It does need to be on the base class since it allows you to inspect any
DrawLooper and see if it is just implementing a blur.  The subclasses that do
not will just return false.

+
     SK_TO_STRING_PUREVIRT()
     SK_DEFINE_FLATTENABLE_TYPE(SkDrawLooper)
 
 protected:
     SkDrawLooper() {}
     SkDrawLooper(SkReadBuffer& buffer) : INHERITED(buffer) {}
 
 private:
     typedef SkFlattenable INHERITED;
 };
 
 #endif