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// Copyright 2015 Google Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#ifndef COBALT_CSSOM_TRANSFORM_MATRIX_H_
#define COBALT_CSSOM_TRANSFORM_MATRIX_H_
#include "cobalt/cssom/transform_function.h"
#include "cobalt/math/matrix3_f.h"
#include "cobalt/math/size_f.h"
#include "cobalt/math/vector2d_f.h"
namespace cobalt {
namespace cssom {
// Matrices that represent CSS transforms are special since a transform can
// be specified in terms of length or percentage translate values, and these
// values can then be combined (e.g. through animations like CSS Transitions)
// into a matrix. Therefore, to support arbitrary combinations of length and
// percentage translate values, we must maintain this information in a special
// matrix where each translation value (e.g. x and y) is actually a triplet:
//
// ( offset in pixels,
// offset as a percentage of used width,
// offset as a percentage of used height )
//
// The reason why we must maintain a percentage of height component for the
// x translation unit (and vice-versa with width and y axis) is because one may
// specify a transform as follows:
//
// transform: rotate(90deg) translateX(50%)
//
// In this case, since a percentage value is given for translateX, it is
// interpreted as a percentage of width, however it is then rotated 90 degrees,
// and so we now have a translation along the y axis that is expressed as
// a percentage of the used width.
//
class TransformMatrix {
public:
TransformMatrix();
explicit TransformMatrix(const math::Matrix3F& matrix);
// Collapses this TransformMatrix to a normal Matrix3F. In order to do this,
// percentage values must be resolved, and so a used_size must be provided.
math::Matrix3F ToMatrix3F(const math::SizeF& used_size) const;
// Returns true if the percentage data for this matrix is zero (e.g. this
// matrix does not depend on a used size).
bool percentage_fields_zero() const {
return width_percentage_translation_.IsZero() &&
height_percentage_translation_.IsZero();
}
// Modifies this matrix by post-multiplying by the matrix associated with
// the specified transformation.
void PostMultiplyByTransform(const TransformFunction* function);
// Returns a matrix representing the current transformation, where the
// translation represented by the matrix is in units of pixels. This method
// is mostly useful for testing purposes only.
const math::Matrix3F& offset_matrix() const { return matrix_; }
// Returns the width percentage units of translation expressed by this matrix.
// This method is mostly useful for testing purposes only.
const math::Vector2dF& width_percentage_translation() const {
return width_percentage_translation_;
}
// Returns the height percentage units of translation expressed by this
// matrix. This method is mostly useful for testing purposes only.
const math::Vector2dF& height_percentage_translation() const {
return height_percentage_translation_;
}
bool operator==(const TransformMatrix& rhs) const {
return matrix_ == rhs.matrix_ &&
width_percentage_translation_ == rhs.width_percentage_translation_ &&
height_percentage_translation_ == rhs.height_percentage_translation_;
}
private:
TransformMatrix(const math::Matrix3F& matrix,
const math::Vector2dF& width_percentage_translation,
const math::Vector2dF& height_percentage_translation)
: matrix_(matrix),
width_percentage_translation_(width_percentage_translation),
height_percentage_translation_(height_percentage_translation) {}
// Translation of pixel units is represented in the matrix (along with all
// non-translate transformations).
math::Matrix3F matrix_;
// Translation of width/height percentage units is represented in the
// following two vectors.
math::Vector2dF width_percentage_translation_;
math::Vector2dF height_percentage_translation_;
friend TransformMatrix InterpolateTransformMatrices(const TransformMatrix& a,
const TransformMatrix& b,
float progress);
};
// Interpolates from one TransformMatrix to another.
TransformMatrix InterpolateTransformMatrices(const TransformMatrix& a,
const TransformMatrix& b,
float progress);
} // namespace cssom
} // namespace cobalt
#endif // COBALT_CSSOM_TRANSFORM_MATRIX_H_