Define cc::TransformOperations and webkit::WebTransformOperationsImpl

cc/transform_operations.h

+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CC_TRANSFORM_OPERATIONS_H_
+#define CC_TRANSFORM_OPERATIONS_H_
+
+#include "base/memory/scoped_ptr.h"
+#include "cc/cc_export.h"
+#include "third_party/WebKit/Source/Platform/chromium/public/WebTransformationMatrix.h"
+
+namespace cc {
+
+struct TransformOperationsPrivate;
+
+// Transform operations are a decomposed transformation matrix. It can be
+// applied to obtain a WebTransformationMatrix at any time, and can be blended
+// intelligently with other transform operations, so long as they represent the
+// same decomposition. For example, if we have a transform that is made up of
+// a rotation followed by skew, it can be blended intelligently with another
+// transform made up of a rotation followed by a skew. Blending is possible if
+// we have two dissimilar sets of transform operations, but the effect may not
+// be what was intended. For more information, see the comments for the blend
+// function below.
+class CC_EXPORT TransformOperations {
+ public:
+  TransformOperations();
+  TransformOperations(const TransformOperations& other);
+  virtual ~TransformOperations();

[jamesr, 2013/01/15 06:23:01]

why virtual?

[ajuma, 2013/01/15 19:24:30]

Fixed.

+
+  // Returns a transformation matrix representing these transform operations.
+  virtual WebKit::WebTransformationMatrix Apply() const;

[jamesr, 2013/01/15 06:23:01]

why virtual? (same comment for the rest of the interface)

[ajuma, 2013/01/15 19:24:30]

Fixed.

+
+  // Given another set of transform operations and a progress in the range
+  // [0, 1], returns a transformation matrix representing the intermediate
+  // value. If this->MatchesTypes(from), then each of the operations are
+  // blended separately and then combined. Otherwise, the two sets of
+  // transforms are baked to matrices (using apply), and the matrices are
+  // then decomposed and interpolated. For more information, see
+  // http://www.w3.org/TR/2011/WD-css3-2d-transforms-20111215/#matrix-decomposition.
+  virtual WebKit::WebTransformationMatrix Blend(
+      const TransformOperations& from, double progress) const;
+
+  // Returns true if this operation and its descendants have the same types
+  // as other and its descendants.
+  virtual bool MatchesTypes(const TransformOperations& other) const;
+
+  // Returns true if these operations can be blended. It will only return
+  // false if we must resort to matrix interpolation, and matrix interpolation
+  // fails (this can happen if either matrix cannot be decomposed).
+  virtual bool CanBlendWith(const TransformOperations& other) const;
+
+  virtual void AppendTranslate(double x, double y, double z);
+  virtual void AppendRotate(
+      double x, double y, double z, double degrees);
+  virtual void AppendScale(double x, double y, double z);
+  virtual void AppendSkew(double x, double y);
+  virtual void AppendPerspective(double depth);
+  virtual void AppendMatrix(const WebKit::WebTransformationMatrix& matrix);
+  virtual void AppendIdentity();
+  virtual bool IsIdentity() const;
+
+ private:
+  void Initialize();
+  void Initialize(const TransformOperations& prototype);
+  bool BlendInternal(const TransformOperations& from, double progress,
+                     WebKit::WebTransformationMatrix& result) const;
+
+  scoped_ptr<TransformOperationsPrivate> private_;

[jamesr, 2013/01/15 06:23:01]

why the Private indirection?

In the WebKit API version of this, this pattern was used since there isn't a
growable array type that can be exposed in a public WebKit API type.  here, I
can't see any issue with forward-declaring a TransformOperation type and having
this be a std::vector<TransformOperation> operations_;

[ajuma, 2013/01/15 19:24:30]

Done.

+};
+
+}  // namespace cc
+
+#endif  // CC_TRANSFORM_OPERATIONS_H_