Adding an option to render only the shadow in SkDropShadowImageFilter

include/effects/SkDropShadowImageFilter.h

Index: include/effects/SkDropShadowImageFilter.h
diff --git a/include/effects/SkDropShadowImageFilter.h b/include/effects/SkDropShadowImageFilter.h
index 0d6c24e4337a7bb806ea7812e591a0e428b51184..49b607f32d1b0e308518b97c4a9f08e512b8fc92 100644
--- a/include/effects/SkDropShadowImageFilter.h
+++ b/include/effects/SkDropShadowImageFilter.h
@@ -11,20 +11,37 @@
 
 class SK_API SkDropShadowImageFilter : public SkImageFilter {
 public:
+    enum ShadowMode {
+        kDrawShadowAndForeground_ShadowMode,
+        kDrawShadowOnly_ShadowMode
+    };
+
+    /** @deprecated use other Create function below instead */
+    static SkDropShadowImageFilter* Create(SkScalar dx, SkScalar dy,
+                                           SkScalar sigmaX, SkScalar sigmaY, SkColor color,
+                                           SkImageFilter* input = NULL,
+                                           const CropRect* cropRect = NULL,
+                                           uint32_t uniqueID = 0) {
+        return SkNEW_ARGS(SkDropShadowImageFilter, (dx, dy, sigmaX, sigmaY, color,
+                                                    kDrawShadowAndForeground_ShadowMode,
+                                                    input, cropRect, uniqueID));
+    }
     static SkDropShadowImageFilter* Create(SkScalar dx, SkScalar dy,
                                            SkScalar sigmaX, SkScalar sigmaY, SkColor color,
+                                           ShadowMode shadowMode,
                                            SkImageFilter* input = NULL,

[reed1, 2014/10/23 19:01:53]

nit: while we're adding a new entry-point, can we arrange to not have so many
default parameters?

[Stephen White, 2014/10/23 19:23:03]

The uniqueID param can be removed once the non-SkRecord path has been removed
from Skia (has it?)

The rest I'd prefer to keep, since from a Skia API POV I think it's nice to
avoid having to think about DAGs and crop rects if all you care about is adding
a correct drop shadow to your primitive.

                                            const CropRect* cropRect = NULL,
                                            uint32_t uniqueID = 0) {
-        return SkNEW_ARGS(SkDropShadowImageFilter, (dx, dy, sigmaX, sigmaY,
-                                                    color, input, cropRect, uniqueID));
+        return SkNEW_ARGS(SkDropShadowImageFilter, (dx, dy, sigmaX, sigmaY, color,
+                                                    shadowMode, input, cropRect, uniqueID));
     }
     virtual void computeFastBounds(const SkRect&, SkRect*) const SK_OVERRIDE;
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkDropShadowImageFilter)
 
 protected:
     SkDropShadowImageFilter(SkScalar dx, SkScalar dy, SkScalar sigmaX, SkScalar sigmaY, SkColor,
-                            SkImageFilter* input, const CropRect* cropRect, uint32_t uniqueID);
+                            ShadowMode shadowMode, SkImageFilter* input, const CropRect* cropRect,
+                            uint32_t uniqueID);
 #ifdef SK_SUPPORT_LEGACY_DEEPFLATTENING
     explicit SkDropShadowImageFilter(SkReadBuffer&);
 #endif
@@ -36,5 +53,6 @@ protected:
 private:
     SkScalar fDx, fDy, fSigmaX, fSigmaY;
     SkColor fColor;
+    ShadowMode fShadowMode;
     typedef SkImageFilter INHERITED;
 };