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143 lines
4.7 KiB
C++
143 lines
4.7 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_COORD_H_
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#define MOZILLA_GFX_COORD_H_
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#include "mozilla/Attributes.h"
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#include "Types.h"
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#include "BaseCoord.h"
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#include <cmath>
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namespace mozilla {
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template <typename> struct IsPixel;
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namespace gfx {
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template <class units> struct IntCoordTyped;
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template <class units> struct CoordTyped;
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// CommonType<coord, primitive> is a metafunction that returns the type of the
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// result of an arithmetic operation on the underlying type of a strongly-typed
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// coordinate type 'coord', and a primitive type 'primitive'. C++ rules for
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// arithmetic conversions are designed to avoid losing information - for
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// example, the result of adding an int and a float is a float - and we want
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// the same behaviour when mixing our coordinate types with primitive types.
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// We get C++ to compute the desired result type using 'decltype'.
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template <class coord, class primitive>
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struct CommonType;
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template <class units, class primitive>
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struct CommonType<IntCoordTyped<units>, primitive> {
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typedef decltype(int32_t() + primitive()) type;
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};
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template <class units, class primitive>
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struct CommonType<CoordTyped<units>, primitive> {
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typedef decltype(Float() + primitive()) type;
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};
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// This is a base class that provides mixed-type operator overloads between
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// a strongly-typed Coord and a primitive value. It is needed to avoid
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// ambiguities at mixed-type call sites, because Coord classes are implicitly
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// convertible to their underlying value type. As we transition more of our code
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// to strongly-typed classes, we may be able to remove some or all of these
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// overloads.
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template <class coord, class primitive>
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struct CoordOperatorsHelper {
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friend bool operator==(coord aA, primitive aB) {
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return aA.value == aB;
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}
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friend bool operator==(primitive aA, coord aB) {
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return aA == aB.value;
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}
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friend bool operator!=(coord aA, primitive aB) {
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return aA.value != aB;
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}
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friend bool operator!=(primitive aA, coord aB) {
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return aA != aB.value;
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}
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typedef typename CommonType<coord, primitive>::type result_type;
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friend result_type operator+(coord aA, primitive aB) {
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return aA.value + aB;
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}
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friend result_type operator+(primitive aA, coord aB) {
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return aA + aB.value;
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}
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friend result_type operator-(coord aA, primitive aB) {
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return aA.value - aB;
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}
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friend result_type operator-(primitive aA, coord aB) {
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return aA - aB.value;
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}
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friend result_type operator*(coord aCoord, primitive aScale) {
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return aCoord.value * aScale;
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}
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friend result_type operator*(primitive aScale, coord aCoord) {
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return aScale * aCoord.value;
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}
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friend result_type operator/(coord aCoord, primitive aScale) {
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return aCoord.value / aScale;
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}
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// 'scale / coord' is intentionally omitted because it doesn't make sense.
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};
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// Note: 'IntCoordTyped<units>' and 'CoordTyped<units>' do not derive from
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// 'units' to work around https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61959.
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template<class units>
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struct IntCoordTyped :
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public BaseCoord< int32_t, IntCoordTyped<units> >,
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public CoordOperatorsHelper< IntCoordTyped<units>, float >,
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public CoordOperatorsHelper< IntCoordTyped<units>, double > {
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static_assert(IsPixel<units>::value,
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"'units' must be a coordinate system tag");
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typedef BaseCoord< int32_t, IntCoordTyped<units> > Super;
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MOZ_CONSTEXPR IntCoordTyped() : Super() {}
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MOZ_CONSTEXPR MOZ_IMPLICIT IntCoordTyped(int32_t aValue) : Super(aValue) {}
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};
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template<class units>
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struct CoordTyped :
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public BaseCoord< Float, CoordTyped<units> >,
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public CoordOperatorsHelper< CoordTyped<units>, int32_t >,
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public CoordOperatorsHelper< CoordTyped<units>, uint32_t >,
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public CoordOperatorsHelper< CoordTyped<units>, double > {
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static_assert(IsPixel<units>::value,
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"'units' must be a coordinate system tag");
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typedef BaseCoord< Float, CoordTyped<units> > Super;
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MOZ_CONSTEXPR CoordTyped() : Super() {}
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MOZ_CONSTEXPR MOZ_IMPLICIT CoordTyped(Float aValue) : Super(aValue) {}
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explicit MOZ_CONSTEXPR CoordTyped(const IntCoordTyped<units>& aCoord) : Super(float(aCoord.value)) {}
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void Round() {
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this->value = floor(this->value + 0.5);
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}
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void Truncate() {
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this->value = int32_t(this->value);
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}
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IntCoordTyped<units> Rounded() const {
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return IntCoordTyped<units>(int32_t(floor(this->value + 0.5)));
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}
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IntCoordTyped<units> Truncated() const {
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return IntCoordTyped<units>(int32_t(this->value));
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}
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};
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}
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}
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#endif /* MOZILLA_GFX_COORD_H_ */
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