gfx/2d/BasePoint.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef MOZILLA_GFX_BASEPOINT_H_
   8 #define MOZILLA_GFX_BASEPOINT_H_
   9
  10 #include <cmath>
  11 #include <ostream>
  12 #include <type_traits>
  13 #include "mozilla/Attributes.h"
  14 #include "mozilla/FloatingPoint.h"
  15
  16 namespace mozilla {
  17 namespace gfx {
  18
  19 /**
  20  * Do not use this class directly. Subclass it, pass that subclass as the
  21  * Sub parameter, and only use that subclass. This allows methods to safely
  22  * cast 'this' to 'Sub*'.
  23  */
  24 template <class T, class Sub, class Coord = T>
  25 struct BasePoint {
  26   union {
  27     struct {
  28       Coord x, y;
  29     };
  30     Coord components[2];
  31   };
  32
  33   // Constructors
  34   constexpr BasePoint() : x(0), y(0) {}
  35   constexpr BasePoint(Coord aX, Coord aY) : x(aX), y(aY) {}
  36
  37   MOZ_ALWAYS_INLINE Coord X() const { return x; }
  38   MOZ_ALWAYS_INLINE Coord Y() const { return y; }
  39
  40   void MoveTo(Coord aX, Coord aY) {
  41     x = aX;
  42     y = aY;
  43   }
  44   void MoveBy(Coord aDx, Coord aDy) {
  45     x += aDx;
  46     y += aDy;
  47   }
  48
  49   // Note that '=' isn't defined so we'll get the
  50   // compiler generated default assignment operator
  51
  52   bool operator==(const Sub& aPoint) const {
  53     return x == aPoint.x && y == aPoint.y;
  54   }
  55   bool operator!=(const Sub& aPoint) const {
  56     return x != aPoint.x || y != aPoint.y;
  57   }
  58
  59   Sub operator+(const Sub& aPoint) const {
  60     return Sub(x + aPoint.x, y + aPoint.y);
  61   }
  62   Sub operator-(const Sub& aPoint) const {
  63     return Sub(x - aPoint.x, y - aPoint.y);
  64   }
  65   Sub& operator+=(const Sub& aPoint) {
  66     x += aPoint.x;
  67     y += aPoint.y;
  68     return *static_cast<Sub*>(this);
  69   }
  70   Sub& operator-=(const Sub& aPoint) {
  71     x -= aPoint.x;
  72     y -= aPoint.y;
  73     return *static_cast<Sub*>(this);
  74   }
  75
  76   Sub operator*(T aScale) const { return Sub(x * aScale, y * aScale); }
  77   Sub operator/(T aScale) const { return Sub(x / aScale, y / aScale); }
  78
  79   Sub operator-() const { return Sub(-x, -y); }
  80
  81   T DotProduct(const Sub& aPoint) const {
  82     return x.value * aPoint.x.value + y.value * aPoint.y.value;
  83   }
  84
  85   // FIXME: Maybe Length() should return a float Coord event for integer Points?
  86   Coord Length() const {
  87     return static_cast<decltype(x.value)>(hypot(x.value, y.value));
  88   }
  89
  90   T LengthSquare() const { return x.value * x.value + y.value * y.value; }
  91
  92   // Round() is *not* rounding to nearest integer if the values are negative.
  93   // They are always rounding as floor(n + 0.5).
  94   // See https://bugzilla.mozilla.org/show_bug.cgi?id=410748#c14
  95   Sub& Round() {
  96     x = Coord(std::floor(T(x) + T(0.5f)));
  97     y = Coord(std::floor(T(y) + T(0.5f)));
  98     return *static_cast<Sub*>(this);
  99   }
 100
 101   // "Finite" means not inf and not NaN
 102   bool IsFinite() const {
 103     using FloatType =
 104         std::conditional_t<std::is_same_v<T, float>, float, double>;
 105     return (std::isfinite(FloatType(x)) && std::isfinite(FloatType(y)));
 106   }
 107
 108   void Clamp(Coord aMaxAbsValue) {
 109     x = std::max(std::min(x, aMaxAbsValue), -aMaxAbsValue);
 110     y = std::max(std::min(y, aMaxAbsValue), -aMaxAbsValue);
 111   }
 112
 113   friend std::ostream& operator<<(std::ostream& stream,
 114                                   const BasePoint<T, Sub, Coord>& aPoint) {
 115     return stream << '(' << aPoint.x << ',' << aPoint.y << ')';
 116   }
 117 };
 118
 119 }  // namespace gfx
 120 }  // namespace mozilla
 121
 122 #endif /* MOZILLA_GFX_BASEPOINT_H_ */