1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #include "ui/gfx/geometry/quad_f.h" 6 7 #include <limits> 8 9 #include "base/strings/stringprintf.h" 10 11 namespace gfx { 12 13 void QuadF::operator=(const RectF& rect) { 14 p1_ = PointF(rect.x(), rect.y()); 15 p2_ = PointF(rect.right(), rect.y()); 16 p3_ = PointF(rect.right(), rect.bottom()); 17 p4_ = PointF(rect.x(), rect.bottom()); 18 } 19 20 std::string QuadF::ToString() const { 21 return base::StringPrintf("%s;%s;%s;%s", 22 p1_.ToString().c_str(), 23 p2_.ToString().c_str(), 24 p3_.ToString().c_str(), 25 p4_.ToString().c_str()); 26 } 27 28 static inline bool WithinEpsilon(float a, float b) { 29 return std::abs(a - b) < std::numeric_limits<float>::epsilon(); 30 } 31 32 bool QuadF::IsRectilinear() const { 33 return 34 (WithinEpsilon(p1_.x(), p2_.x()) && WithinEpsilon(p2_.y(), p3_.y()) && 35 WithinEpsilon(p3_.x(), p4_.x()) && WithinEpsilon(p4_.y(), p1_.y())) || 36 (WithinEpsilon(p1_.y(), p2_.y()) && WithinEpsilon(p2_.x(), p3_.x()) && 37 WithinEpsilon(p3_.y(), p4_.y()) && WithinEpsilon(p4_.x(), p1_.x())); 38 } 39 40 bool QuadF::IsCounterClockwise() const { 41 // This math computes the signed area of the quad. Positive area 42 // indicates the quad is clockwise; negative area indicates the quad is 43 // counter-clockwise. Note carefully: this is backwards from conventional 44 // math because our geometric space uses screen coordiantes with y-axis 45 // pointing downards. 46 // Reference: http://mathworld.wolfram.com/PolygonArea.html 47 48 // Up-cast to double so this cannot overflow. 49 double determinant1 = static_cast<double>(p1_.x()) * p2_.y() 50 - static_cast<double>(p2_.x()) * p1_.y(); 51 double determinant2 = static_cast<double>(p2_.x()) * p3_.y() 52 - static_cast<double>(p3_.x()) * p2_.y(); 53 double determinant3 = static_cast<double>(p3_.x()) * p4_.y() 54 - static_cast<double>(p4_.x()) * p3_.y(); 55 double determinant4 = static_cast<double>(p4_.x()) * p1_.y() 56 - static_cast<double>(p1_.x()) * p4_.y(); 57 58 return determinant1 + determinant2 + determinant3 + determinant4 < 0; 59 } 60 61 static inline bool PointIsInTriangle(const PointF& point, 62 const PointF& r1, 63 const PointF& r2, 64 const PointF& r3) { 65 // Compute the barycentric coordinates (u, v, w) of |point| relative to the 66 // triangle (r1, r2, r3) by the solving the system of equations: 67 // 1) point = u * r1 + v * r2 + w * r3 68 // 2) u + v + w = 1 69 // This algorithm comes from Christer Ericson's Real-Time Collision Detection. 70 71 Vector2dF r31 = r1 - r3; 72 Vector2dF r32 = r2 - r3; 73 Vector2dF r3p = point - r3; 74 75 float denom = r32.y() * r31.x() - r32.x() * r31.y(); 76 float u = (r32.y() * r3p.x() - r32.x() * r3p.y()) / denom; 77 float v = (r31.x() * r3p.y() - r31.y() * r3p.x()) / denom; 78 float w = 1.f - u - v; 79 80 // Use the barycentric coordinates to test if |point| is inside the 81 // triangle (r1, r2, r2). 82 return (u >= 0) && (v >= 0) && (w >= 0); 83 } 84 85 bool QuadF::Contains(const PointF& point) const { 86 return PointIsInTriangle(point, p1_, p2_, p3_) 87 || PointIsInTriangle(point, p1_, p3_, p4_); 88 } 89 90 void QuadF::Scale(float x_scale, float y_scale) { 91 p1_.Scale(x_scale, y_scale); 92 p2_.Scale(x_scale, y_scale); 93 p3_.Scale(x_scale, y_scale); 94 p4_.Scale(x_scale, y_scale); 95 } 96 97 void QuadF::operator+=(const Vector2dF& rhs) { 98 p1_ += rhs; 99 p2_ += rhs; 100 p3_ += rhs; 101 p4_ += rhs; 102 } 103 104 void QuadF::operator-=(const Vector2dF& rhs) { 105 p1_ -= rhs; 106 p2_ -= rhs; 107 p3_ -= rhs; 108 p4_ -= rhs; 109 } 110 111 QuadF operator+(const QuadF& lhs, const Vector2dF& rhs) { 112 QuadF result = lhs; 113 result += rhs; 114 return result; 115 } 116 117 QuadF operator-(const QuadF& lhs, const Vector2dF& rhs) { 118 QuadF result = lhs; 119 result -= rhs; 120 return result; 121 } 122 123 } // namespace gfx 124
