Add SkRRect::transform.

include/core/SkRRect.h

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkRRect_DEFINED
 #define SkRRect_DEFINED
 
 #include "SkRect.h"
 #include "SkPoint.h"
 
 class SkPath;
+class SkMatrix;
 
 // Path forward:
 //   core work
 //      add validate method (all radii positive, all radii sums < rect size, etc.)
 //      add contains(SkRect&)  - for clip stack
 //      add contains(SkRRect&) - for clip stack
 //      add heart rect computation (max rect inside RR)
 //      add 9patch rect computation
 //      add growToInclude(SkPath&)
 //   analysis
@@ skipping 245 matching lines @@
      */
     uint32_t writeToMemory(void* buffer) const;
 
     /**
      *  Read the rrect from the specified buffer. This is guaranteed to always
      *  read kSizeInMemory bytes, and that value is guaranteed to always be
      *  a multiple of 4. Return kSizeInMemory.
      */
     uint32_t readFromMemory(const void* buffer);
 
+    /**
+     *  Transform by the specified matrix, and put the result in dst.
+     *
+     *  @param matrix SkMatrix specifying the transform. Must only contain
+     *      scale and/or translate, or this call will fail.
+     *  @param dst SkRRect to store the result. It is an error to use this,

[reed1, 2013/11/04 20:21:09]

FYI -- we explicitly support modifying self in SkPath, allowing the 2nd
parameter to be this. We even offer a built-in helper for this:

e.g.

bool SkRRect::transform(const SkMatrix& matrix) {
    return this->transform(matrix, this);
}

[scroggo, 2013/11/04 22:29:55]

In patch set 1 I allowed modifying the SkRRect, following the pattern of SkPath
(though I didn't add the helper), but Robert and I ultimately agreed that we
didn't like that API, which allows modifying a const object through a const
method.

+     *      which would make this function no longer const.
+     *  @return true on success, false on failure. If false, dst is unmodified.
+     */
+    bool transform(const SkMatrix& matrix, SkRRect* dst) const;
+
 private:
     SkRect fRect;
     // Radii order is UL, UR, LR, LL. Use Corner enum to index into fRadii[]
     SkVector fRadii[4];
     mutable Type fType;
     // TODO: add padding so we can use memcpy for flattening and not copy
     // uninitialized data
 
     void computeType() const;
     bool checkCornerContainment(SkScalar x, SkScalar y) const;
 
     // to access fRadii directly
     friend class SkPath;
 };
 
 #endif