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 14 namespace mozilla { 15 namespace 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 BaseCoordBaseCoord27 constexpr BaseCoord() : value(0) {} BaseCoordBaseCoord28 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 TBaseCoord33 operator T() const { return value; } 34 35 friend bool operator==(Sub aA, Sub aB) { return aA.value == aB.value; } 36 friend bool operator!=(Sub aA, Sub aB) { return aA.value != aB.value; } 37 38 friend Sub operator+(Sub aA, Sub aB) { return Sub(aA.value + aB.value); } 39 friend Sub operator-(Sub aA, Sub aB) { return Sub(aA.value - aB.value); } 40 friend Sub operator*(Sub aCoord, T aScale) { 41 return Sub(aCoord.value * aScale); 42 } 43 friend Sub operator*(T aScale, Sub aCoord) { 44 return Sub(aScale * aCoord.value); 45 } 46 friend Sub operator/(Sub aCoord, T aScale) { 47 return Sub(aCoord.value / aScale); 48 } 49 // 'scale / coord' is intentionally omitted because it doesn't make sense. 50 51 Sub& operator+=(Sub aCoord) { 52 value += aCoord.value; 53 return *static_cast<Sub*>(this); 54 } 55 Sub& operator-=(Sub aCoord) { 56 value -= aCoord.value; 57 return *static_cast<Sub*>(this); 58 } 59 Sub& operator*=(T aScale) { 60 value *= aScale; 61 return *static_cast<Sub*>(this); 62 } 63 Sub& operator/=(T aScale) { 64 value /= aScale; 65 return *static_cast<Sub*>(this); 66 } 67 68 // Since BaseCoord is implicitly convertible to its value type T, we need 69 // mixed-type operator overloads to avoid ambiguities at mixed-type call 70 // sites. As we transition more of our code to strongly-typed classes, we 71 // may be able to remove some or all of these overloads. 72 friend bool operator==(Sub aA, T aB) { return aA.value == aB; } 73 friend bool operator==(T aA, Sub aB) { return aA == aB.value; } 74 friend bool operator!=(Sub aA, T aB) { return aA.value != aB; } 75 friend bool operator!=(T aA, Sub aB) { return aA != aB.value; } 76 friend T operator+(Sub aA, T aB) { return aA.value + aB; } 77 friend T operator+(T aA, Sub aB) { return aA + aB.value; } 78 friend T operator-(Sub aA, T aB) { return aA.value - aB; } 79 friend T operator-(T aA, Sub aB) { return aA - aB.value; } 80 81 Sub operator-() const { return Sub(-value); } 82 83 friend std::ostream& operator<<(std::ostream& aStream, 84 const BaseCoord<T, Sub>& aCoord) { 85 return aStream << aCoord.value; 86 } 87 }; 88 89 } // namespace gfx 90 } // namespace mozilla 91 92 #endif /* MOZILLA_GFX_BASECOORD_H_ */ 93