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/* -*- 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_ */
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