gfx/2d/BaseCoord.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_BASECOORD_H_
   8 #define MOZILLA_GFX_BASECOORD_H_
   9
  10 #include <ostream>
  11
  12 #include "mozilla/Attributes.h"
  13 #include "mozilla/MathAlgorithms.h"
  14
  15 namespace mozilla::gfx {
  16
  17 /**
  18  * Do not use this class directly. Subclass it, pass that subclass as the
  19  * Sub parameter, and only use that subclass. This allows methods to safely
  20  * cast 'this' to 'Sub*'.
  21  */
  22 template <class T, class Sub>
  23 struct BaseCoord {
  24   T value;
  25
  26   // Constructors
  27   constexpr BaseCoord() : value(0) {}
  28   explicit constexpr BaseCoord(T aValue) : value(aValue) {}
  29
  30   // Note that '=' isn't defined so we'll get the
  31   // compiler generated default assignment operator
  32
  33   friend constexpr Sub Abs(BaseCoord aCoord) { return Abs(aCoord.value); }
  34
  35   constexpr operator T() const { return value; }
  36
  37   friend constexpr bool operator==(Sub aA, Sub aB) {
  38     return aA.value == aB.value;
  39   }
  40   friend constexpr bool operator!=(Sub aA, Sub aB) {
  41     return aA.value != aB.value;
  42   }
  43
  44   friend constexpr Sub operator+(Sub aA, Sub aB) {
  45     return Sub(aA.value + aB.value);
  46   }
  47   friend constexpr Sub operator-(Sub aA, Sub aB) {
  48     return Sub(aA.value - aB.value);
  49   }
  50   friend constexpr Sub operator*(Sub aCoord, T aScale) {
  51     return Sub(aCoord.value * aScale);
  52   }
  53   friend constexpr Sub operator*(T aScale, Sub aCoord) {
  54     return Sub(aScale * aCoord.value);
  55   }
  56   friend constexpr Sub operator/(Sub aCoord, T aScale) {
  57     return Sub(aCoord.value / aScale);
  58   }
  59   // 'scale / coord' is intentionally omitted because it doesn't make sense.
  60
  61   constexpr Sub& operator+=(Sub aCoord) {
  62     value += aCoord.value;
  63     return *static_cast<Sub*>(this);
  64   }
  65   constexpr Sub& operator-=(Sub aCoord) {
  66     value -= aCoord.value;
  67     return *static_cast<Sub*>(this);
  68   }
  69   constexpr Sub& operator*=(T aScale) {
  70     value *= aScale;
  71     return *static_cast<Sub*>(this);
  72   }
  73   constexpr Sub& operator/=(T aScale) {
  74     value /= aScale;
  75     return *static_cast<Sub*>(this);
  76   }
  77
  78   // Since BaseCoord is implicitly convertible to its value type T, we need
  79   // mixed-type operator overloads to avoid ambiguities at mixed-type call
  80   // sites. As we transition more of our code to strongly-typed classes, we
  81   // may be able to remove some or all of these overloads.
  82   friend constexpr bool operator==(Sub aA, T aB) { return aA.value == aB; }
  83   friend constexpr bool operator==(T aA, Sub aB) { return aA == aB.value; }
  84   friend constexpr bool operator!=(Sub aA, T aB) { return aA.value != aB; }
  85   friend constexpr bool operator!=(T aA, Sub aB) { return aA != aB.value; }
  86   friend constexpr T operator+(Sub aA, T aB) { return aA.value + aB; }
  87   friend constexpr T operator+(T aA, Sub aB) { return aA + aB.value; }
  88   friend constexpr T operator-(Sub aA, T aB) { return aA.value - aB; }
  89   friend constexpr T operator-(T aA, Sub aB) { return aA - aB.value; }
  90
  91   constexpr Sub operator-() const { return Sub(-value); }
  92
  93   friend std::ostream& operator<<(std::ostream& aStream,
  94                                   const BaseCoord<T, Sub>& aCoord) {
  95     return aStream << aCoord.value;
  96   }
  97 };
  98
  99 }  // namespace mozilla::gfx
 100
 101 #endif /* MOZILLA_GFX_BASECOORD_H_ */