Factory methods for heap-allocated SkImageFilter objects.

include/effects/SkDropShadowImageFilter.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkColor.h"
 #include "SkImageFilter.h"
 #include "SkScalar.h"
 
 class SK_API SkDropShadowImageFilter : public SkImageFilter {
 public:
-    SkDropShadowImageFilter(SkScalar dx, SkScalar dy, SkScalar sigma, SkColor, SkImageFilter* input = NULL);
-    SkDropShadowImageFilter(SkScalar dx, SkScalar dy, SkScalar sigmaX, SkScalar sigmaY, SkColor, SkImageFilter* input = NULL, const CropRect* cropRect = NULL);
+    static SkDropShadowImageFilter* Create(SkScalar dx, SkScalar dy, SkScalar sigma,
+                                           SkColor color, SkImageFilter* input = NULL) {
+        return SkNEW_ARGS(SkDropShadowImageFilter, (dx, dy, sigma, color, input));

[reed1, 2014/03/03 18:23:19]

Perhaps not needed in this CL, but the filter team should be encouraged to
document (now that we're using factories) that the factory might return NULL for
mal-formed parameters (not just dropshadow, but in general).

Factories also enable us to use specialized/alternate impls based on input,
rather than forcing us to create the actual subclass the client thought they
were asking for.

[Stephen White, 2014/03/03 19:48:04]

Yep! It would be great to move to factories for deserialization (SkReadBuffer
construction) too, so that we can fail gracefully without having to early-out
and an invalid object.

+    }
+    static SkDropShadowImageFilter* Create(SkScalar dx, SkScalar dy,
+                                           SkScalar sigmaX, SkScalar sigmaY, SkColor color,
+                                           SkImageFilter* input = NULL,
+                                           const CropRect* cropRect = NULL) {
+        return SkNEW_ARGS(SkDropShadowImageFilter, (dx, dy, sigmaX, sigmaY,
+                                                    color, input, cropRect));
+    }
     virtual void computeFastBounds(const SkRect&, SkRect*) const SK_OVERRIDE;
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkDropShadowImageFilter)
 
 protected:
     explicit SkDropShadowImageFilter(SkReadBuffer&);
     virtual void flatten(SkWriteBuffer&) const SK_OVERRIDE;
     virtual bool onFilterImage(Proxy*, const SkBitmap& source, const SkMatrix&, SkBitmap* result, SkIPoint* loc) const SK_OVERRIDE;
     virtual bool onFilterBounds(const SkIRect& src, const SkMatrix&,
                                 SkIRect* dst) const SK_OVERRIDE;
 
-
+#ifdef SK_SUPPORT_LEGACY_PUBLICEFFECTCONSTRUCTORS
+public:
+#endif
+    SkDropShadowImageFilter(SkScalar dx, SkScalar dy, SkScalar sigma, SkColor,
+                            SkImageFilter* input = NULL);
+    SkDropShadowImageFilter(SkScalar dx, SkScalar dy, SkScalar sigmaX, SkScalar sigmaY, SkColor,
+                            SkImageFilter* input = NULL, const CropRect* cropRect = NULL);
 
 private:
     SkScalar fDx, fDy, fSigmaX, fSigmaY;
     SkColor fColor;
     typedef SkImageFilter INHERITED;
 };