ScaleFactor.h

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef MOZILLA_GFX_SCALEFACTOR_H_
#define MOZILLA_GFX_SCALEFACTOR_H_

#include "mozilla/Attributes.h"

#include "gfxPoint.h"

namespace mozilla {
namespace gfx {

/*
 * This class represents a scaling factor between two different pixel unit
 * systems. This is effectively a type-safe float, intended to be used in
 * combination with the known-type instances of gfx::Point, gfx::Rect, etc.
 *
 * This class is meant to be used in cases where a single scale applies to
 * both the x and y axes. For cases where two diferent scales apply, use
 * ScaleFactors2D.
 */
template <class src, class dst>
struct ScaleFactor {
  float scale;

  constexpr ScaleFactor() : scale(1.0) {}
  constexpr ScaleFactor(const ScaleFactor<src, dst>& aCopy)
      : scale(aCopy.scale) {}
  explicit constexpr ScaleFactor(float aScale) : scale(aScale) {}

  ScaleFactor<dst, src> Inverse() { return ScaleFactor<dst, src>(1 / scale); }

  bool operator==(const ScaleFactor<src, dst>& aOther) const {
    return scale == aOther.scale;
  }

  bool operator!=(const ScaleFactor<src, dst>& aOther) const {
    return !(*this == aOther);
  }

  bool operator<(const ScaleFactor<src, dst>& aOther) const {
    return scale < aOther.scale;
  }

  bool operator<=(const ScaleFactor<src, dst>& aOther) const {
    return scale <= aOther.scale;
  }

  bool operator>(const ScaleFactor<src, dst>& aOther) const {
    return scale > aOther.scale;
  }

  bool operator>=(const ScaleFactor<src, dst>& aOther) const {
    return scale >= aOther.scale;
  }

  template <class other>
  ScaleFactor<other, dst> operator/(
      const ScaleFactor<src, other>& aOther) const {
    return ScaleFactor<other, dst>(scale / aOther.scale);
  }

  template <class other>
  ScaleFactor<src, other> operator/(
      const ScaleFactor<other, dst>& aOther) const {
    return ScaleFactor<src, other>(scale / aOther.scale);
  }

  template <class other>
  ScaleFactor<src, other> operator*(
      const ScaleFactor<dst, other>& aOther) const {
    return ScaleFactor<src, other>(scale * aOther.scale);
  }

  template <class other>
  ScaleFactor<other, dst> operator*(
      const ScaleFactor<other, src>& aOther) const {
    return ScaleFactor<other, dst>(scale * aOther.scale);
  }
};

}  // namespace gfx
}  // namespace mozilla

#endif /* MOZILLA_GFX_SCALEFACTOR_H_ */