gfx/2d/ScaleFactor.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef MOZILLA_GFX_SCALEFACTOR_H_
   8 #define MOZILLA_GFX_SCALEFACTOR_H_
   9
  10 #include <ostream>
  11
  12 #include "mozilla/Attributes.h"
  13
  14 #include "gfxPoint.h"
  15
  16 namespace mozilla {
  17 namespace gfx {
  18
  19 /*
  20  * This class represents a scaling factor between two different pixel unit
  21  * systems. This is effectively a type-safe float, intended to be used in
  22  * combination with the known-type instances of gfx::Point, gfx::Rect, etc.
  23  *
  24  * This class is meant to be used in cases where a single scale applies to
  25  * both the x and y axes. For cases where two diferent scales apply, use
  26  * ScaleFactors2D.
  27  */
  28 template <class src, class dst>
  29 struct ScaleFactor {
  30   float scale;
  31
  32   constexpr ScaleFactor() : scale(1.0) {}
  33   constexpr ScaleFactor(const ScaleFactor<src, dst>& aCopy)
  34       : scale(aCopy.scale) {}
  35   explicit constexpr ScaleFactor(float aScale) : scale(aScale) {}
  36
  37   ScaleFactor<dst, src> Inverse() { return ScaleFactor<dst, src>(1 / scale); }
  38
  39   ScaleFactor<src, dst>& operator=(const ScaleFactor<src, dst>&) = default;
  40
  41   bool operator==(const ScaleFactor<src, dst>& aOther) const {
  42     return scale == aOther.scale;
  43   }
  44
  45   bool operator!=(const ScaleFactor<src, dst>& aOther) const {
  46     return !(*this == aOther);
  47   }
  48
  49   bool operator<(const ScaleFactor<src, dst>& aOther) const {
  50     return scale < aOther.scale;
  51   }
  52
  53   bool operator<=(const ScaleFactor<src, dst>& aOther) const {
  54     return scale <= aOther.scale;
  55   }
  56
  57   bool operator>(const ScaleFactor<src, dst>& aOther) const {
  58     return scale > aOther.scale;
  59   }
  60
  61   bool operator>=(const ScaleFactor<src, dst>& aOther) const {
  62     return scale >= aOther.scale;
  63   }
  64
  65   template <class other>
  66   ScaleFactor<other, dst> operator/(
  67       const ScaleFactor<src, other>& aOther) const {
  68     return ScaleFactor<other, dst>(scale / aOther.scale);
  69   }
  70
  71   template <class other>
  72   ScaleFactor<src, other> operator/(
  73       const ScaleFactor<other, dst>& aOther) const {
  74     return ScaleFactor<src, other>(scale / aOther.scale);
  75   }
  76
  77   template <class other>
  78   ScaleFactor<src, other> operator*(
  79       const ScaleFactor<dst, other>& aOther) const {
  80     return ScaleFactor<src, other>(scale * aOther.scale);
  81   }
  82
  83   template <class other>
  84   ScaleFactor<other, dst> operator*(
  85       const ScaleFactor<other, src>& aOther) const {
  86     return ScaleFactor<other, dst>(scale * aOther.scale);
  87   }
  88
  89   friend std::ostream& operator<<(std::ostream& aStream,
  90                                   const ScaleFactor<src, dst>& aSF) {
  91     return aStream << aSF.scale;
  92   }
  93 };
  94
  95 }  // namespace gfx
  96 }  // namespace mozilla
  97
  98 #endif /* MOZILLA_GFX_SCALEFACTOR_H_ */