Implement an SkPicture image filter source. This is required for the external-SVG reference feature…

include/effects/SkPictureImageFilter.h

+/*
+ * Copyright 2013 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 SkPictureImageFilter_DEFINED
+#define SkPictureImageFilter_DEFINED
+
+#include "SkImageFilter.h"
+#include "SkPicture.h"
+
+class SK_API SkPictureImageFilter : public SkImageFilter {
+public:
+    explicit SkPictureImageFilter(SkPicture* picture);

[reed1, 2013/12/12 21:28:39]

Sorry I wasn't clearer. I was asking for some dox in the header itself

e.g.

// Calls ref on the picture argument

[Stephen White, 2013/12/12 21:46:56]

Done.

+    SkPictureImageFilter(SkPicture* picture, const SkRect& rect);

[reed1, 2013/12/12 21:28:39]

e.g.

// Calls ref on the picture argument.
// The picture is scaled to fit inside the rect parameter

That rect parameter is like a convenience form of just passing a matrix to go
with the picture, right?

[Stephen White, 2013/12/12 21:46:56]

No, it's essentially a "crop or expand" rect. It doesn't resize, just affects
which subset or superset of the picture is drawn. I've tried to explain that in
the comments; let me know if I could do better.

+    ~SkPictureImageFilter();

[reed1, 2013/12/12 21:28:39]

style nit: virtual ~SkPictureImageFilter();

[Stephen White, 2013/12/12 21:46:56]

Done.

+
+    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkPictureImageFilter)
+
+protected:
+    explicit SkPictureImageFilter(SkFlattenableReadBuffer& buffer);
+    virtual void flatten(SkFlattenableWriteBuffer&) const SK_OVERRIDE;
+    virtual bool onFilterImage(Proxy*, const SkBitmap& src, const SkMatrix&,
+                               SkBitmap* result, SkIPoint* offset) SK_OVERRIDE;
+
+private:
+    SkPicture* fPicture;
+    SkRect     fRect;
+    typedef SkImageFilter INHERITED;
+};
+
+#endif