cc/animation/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_ANIMATION_TRANSFORM_OPERATIONS_H_
#define CC_ANIMATION_TRANSFORM_OPERATIONS_H_

#include <vector>

#include "base/memory/scoped_ptr.h"
#include "cc/animation/transform_operation.h"
#include "cc/base/cc_export.h"
#include "ui/gfx/transform.h"

namespace gfx {
class BoxF;
struct DecomposedTransform;
}

namespace cc {

// Transform operations are a decomposed transformation matrix. It can be
// applied to obtain a gfx::Transform 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);
  ~TransformOperations();

  // Returns a transformation matrix representing these transform operations.
  gfx::Transform Apply() const;

  // 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.
  gfx::Transform Blend(const TransformOperations& from,
                       SkMScalar progress) const;

  // Sets |bounds| be the bounding box for the region within which |box| will
  // exist when it is transformed by the result of calling Blend on |from| and
  // with progress in the range [min_progress, max_progress]. If this region
  // cannot be computed, returns false.
  bool BlendedBoundsForBox(const gfx::BoxF& box,
                           const TransformOperations& from,
                           SkMScalar min_progress,
                           SkMScalar max_progress,
                           gfx::BoxF* bounds) const;

  // Returns true if these operations affect scale.
  bool AffectsScale() const;

  // Returns true if these operations are only translations.
  bool IsTranslation() const;

  // Returns false if the operations affect 2d axis alignment.
  bool PreservesAxisAlignment() const;

  // Returns true if this operation and its descendants have the same types
  // as other and its descendants.
  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).
  bool CanBlendWith(const TransformOperations& other) const;

  // If these operations have no more than one scale operation, and if the only
  // other operations are translations, sets |scale| to the scale component
  // of these operations. Otherwise, returns false.
  bool ScaleComponent(gfx::Vector3dF* scale) const;

  void AppendTranslate(SkMScalar x, SkMScalar y, SkMScalar z);
  void AppendRotate(SkMScalar x, SkMScalar y, SkMScalar z, SkMScalar degrees);
  void AppendScale(SkMScalar x, SkMScalar y, SkMScalar z);
  void AppendSkew(SkMScalar x, SkMScalar y);
  void AppendPerspective(SkMScalar depth);
  void AppendMatrix(const gfx::Transform& matrix);
  void AppendIdentity();
  bool IsIdentity() const;

 private:
  bool BlendInternal(const TransformOperations& from,
                     SkMScalar progress,
                     gfx::Transform* result) const;

  std::vector<TransformOperation> operations_;

  bool ComputeDecomposedTransform() const;

  // For efficiency, we cache the decomposed transform.
  mutable scoped_ptr<gfx::DecomposedTransform> decomposed_transform_;
  mutable bool decomposed_transform_dirty_;

  DISALLOW_ASSIGN(TransformOperations);
};

}  // namespace cc

#endif  // CC_ANIMATION_TRANSFORM_OPERATIONS_H_