michael@0: /* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
michael@0:  * This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #ifndef MOZILLA_GFX_SCALEFACTOR_H_
michael@0: #define MOZILLA_GFX_SCALEFACTOR_H_
michael@0: 
michael@0: #include "mozilla/Attributes.h"
michael@0: 
michael@0: #include "gfxPoint.h"
michael@0: 
michael@0: namespace mozilla {
michael@0: namespace gfx {
michael@0: 
michael@0: /*
michael@0:  * This class represents a scaling factor between two different pixel unit
michael@0:  * systems. This is effectively a type-safe float, intended to be used in
michael@0:  * combination with the known-type instances of gfx::Point, gfx::Rect, etc.
michael@0:  *
michael@0:  * Note that some parts of the code that pre-date this class used separate
michael@0:  * scaling factors for the x and y axes. However, at runtime these values
michael@0:  * were always expected to be the same, so this class uses only one scale
michael@0:  * factor for both axes. The two constructors that take two-axis scaling
michael@0:  * factors check to ensure that this assertion holds.
michael@0:  */
michael@0: template<class src, class dst>
michael@0: struct ScaleFactor {
michael@0:   float scale;
michael@0: 
michael@0:   MOZ_CONSTEXPR ScaleFactor() : scale(1.0) {}
michael@0:   MOZ_CONSTEXPR ScaleFactor(const ScaleFactor<src, dst>& aCopy) : scale(aCopy.scale) {}
michael@0:   explicit MOZ_CONSTEXPR ScaleFactor(float aScale) : scale(aScale) {}
michael@0: 
michael@0:   explicit ScaleFactor(float aX, float aY) : scale(aX) {
michael@0:     MOZ_ASSERT(fabs(aX - aY) < 1e-6);
michael@0:   }
michael@0: 
michael@0:   ScaleFactor<dst, src> Inverse() {
michael@0:     return ScaleFactor<dst, src>(1 / scale);
michael@0:   }
michael@0: 
michael@0:   bool operator==(const ScaleFactor<src, dst>& aOther) const {
michael@0:     return scale == aOther.scale;
michael@0:   }
michael@0: 
michael@0:   bool operator!=(const ScaleFactor<src, dst>& aOther) const {
michael@0:     return !(*this == aOther);
michael@0:   }
michael@0: 
michael@0:   bool operator<(const ScaleFactor<src, dst>& aOther) const {
michael@0:     return scale < aOther.scale;
michael@0:   }
michael@0: 
michael@0:   bool operator<=(const ScaleFactor<src, dst>& aOther) const {
michael@0:     return scale <= aOther.scale;
michael@0:   }
michael@0: 
michael@0:   bool operator>(const ScaleFactor<src, dst>& aOther) const {
michael@0:     return scale > aOther.scale;
michael@0:   }
michael@0: 
michael@0:   bool operator>=(const ScaleFactor<src, dst>& aOther) const {
michael@0:     return scale >= aOther.scale;
michael@0:   }
michael@0: 
michael@0:   template<class other>
michael@0:   ScaleFactor<other, dst> operator/(const ScaleFactor<src, other>& aOther) const {
michael@0:     return ScaleFactor<other, dst>(scale / aOther.scale);
michael@0:   }
michael@0: 
michael@0:   template<class other>
michael@0:   ScaleFactor<src, other> operator/(const ScaleFactor<other, dst>& aOther) const {
michael@0:     return ScaleFactor<src, other>(scale / aOther.scale);
michael@0:   }
michael@0: 
michael@0:   template<class other>
michael@0:   ScaleFactor<src, other> operator*(const ScaleFactor<dst, other>& aOther) const {
michael@0:     return ScaleFactor<src, other>(scale * aOther.scale);
michael@0:   }
michael@0: 
michael@0:   template<class other>
michael@0:   ScaleFactor<other, dst> operator*(const ScaleFactor<other, src>& aOther) const {
michael@0:     return ScaleFactor<other, dst>(scale * aOther.scale);
michael@0:   }
michael@0: };
michael@0: 
michael@0: }
michael@0: }
michael@0: 
michael@0: #endif /* MOZILLA_GFX_SCALEFACTOR_H_ */