/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- * 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_BASECOORD_H_ #define MOZILLA_GFX_BASECOORD_H_ #include "mozilla/Attributes.h" namespace mozilla { namespace gfx { /** * Do not use this class directly. Subclass it, pass that subclass as the * Sub parameter, and only use that subclass. This allows methods to safely * cast 'this' to 'Sub*'. */ template <class T, class Sub> struct BaseCoord { T value; // Constructors constexpr BaseCoord() : value(0) {} explicit constexpr BaseCoord(T aValue) : value(aValue) {} // Note that '=' isn't defined so we'll get the // compiler generated default assignment operator operator T() const { return value; } friend bool operator==(Sub aA, Sub aB) { return aA.value == aB.value; } friend bool operator!=(Sub aA, Sub aB) { return aA.value != aB.value; } friend Sub operator+(Sub aA, Sub aB) { return Sub(aA.value + aB.value); } friend Sub operator-(Sub aA, Sub aB) { return Sub(aA.value - aB.value); } friend Sub operator*(Sub aCoord, T aScale) { return Sub(aCoord.value * aScale); } friend Sub operator*(T aScale, Sub aCoord) { return Sub(aScale * aCoord.value); } friend Sub operator/(Sub aCoord, T aScale) { return Sub(aCoord.value / aScale); } // 'scale / coord' is intentionally omitted because it doesn't make sense. Sub& operator+=(Sub aCoord) { value += aCoord.value; return *static_cast<Sub*>(this); } Sub& operator-=(Sub aCoord) { value -= aCoord.value; return *static_cast<Sub*>(this); } Sub& operator*=(T aScale) { value *= aScale; return *static_cast<Sub*>(this); } Sub& operator/=(T aScale) { value /= aScale; return *static_cast<Sub*>(this); } // Since BaseCoord is implicitly convertible to its value type T, we need // mixed-type operator overloads to avoid ambiguities at mixed-type call // sites. As we transition more of our code to strongly-typed classes, we // may be able to remove some or all of these overloads. friend bool operator==(Sub aA, T aB) { return aA.value == aB; } friend bool operator==(T aA, Sub aB) { return aA == aB.value; } friend bool operator!=(Sub aA, T aB) { return aA.value != aB; } friend bool operator!=(T aA, Sub aB) { return aA != aB.value; } friend T operator+(Sub aA, T aB) { return aA.value + aB; } friend T operator+(T aA, Sub aB) { return aA + aB.value; } friend T operator-(Sub aA, T aB) { return aA.value - aB; } friend T operator-(T aA, Sub aB) { return aA - aB.value; } Sub operator-() const { return Sub(-value); } }; } // namespace gfx } // namespace mozilla #endif /* MOZILLA_GFX_BASECOORD_H_ */