src/cobalt/cssom/length_value.h

// Copyright 2014 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_LENGTH_VALUE_H_
#define COBALT_CSSOM_LENGTH_VALUE_H_

#include <string>

#include "base/basictypes.h"
#include "base/compiler_specific.h"
#include "cobalt/base/polymorphic_equatable.h"
#include "cobalt/cssom/property_value.h"

namespace cobalt {
namespace cssom {

// TODO: Add more units.
// When adding a unit, please add the name in kUnitNames im length_value.cc.
enum LengthUnit {
  kPixelsUnit,
  kAbsoluteUnitMax =
      kPixelsUnit,  // The units above are absolute, the rest are relative.
  kFontSizesAkaEmUnit,
  kRootElementFontSizesAkaRemUnit,
  kViewportWidthPercentsAkaVwUnit,
  kViewportHeightPercentsAkaVhUnit,
};

// Represents distance or size.
// Applies to properties such as left, width, font-size, etc.
// See https://www.w3.org/TR/css3-values/#lengths for details.
class LengthValue : public PropertyValue {
 public:
  LengthValue(float value, LengthUnit unit) : value_(value), unit_(unit) {}

  void Accept(PropertyValueVisitor* visitor) OVERRIDE;

  float value() const { return value_; }
  LengthUnit unit() const { return unit_; }
  bool IsUnitRelative() const { return unit_ > kAbsoluteUnitMax; }

  std::string ToString() const OVERRIDE;

  bool operator==(const LengthValue& other) const {
    return value_ == other.value_ && unit_ == other.unit_;
  }

  bool operator>=(const LengthValue& other) const {
    DCHECK_EQ(unit_, other.unit_) << "Value larger comparison of length values "
                                     "can only be done for matching unit types";
    return value_ >= other.value_;
  }

  bool operator<=(const LengthValue& other) const {
    DCHECK_EQ(unit_, other.unit_) << "Value smaller comparison of length "
                                     "values can only be done for matching "
                                     "unit types";
    return value_ <= other.value_;
  }

  DEFINE_POLYMORPHIC_EQUATABLE_TYPE(LengthValue);

 private:
  ~LengthValue() OVERRIDE {}

  const float value_;
  const LengthUnit unit_;

  DISALLOW_COPY_AND_ASSIGN(LengthValue);
};

}  // namespace cssom
}  // namespace cobalt

#endif  // COBALT_CSSOM_LENGTH_VALUE_H_