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