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
operator =(const RectF & rect)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
ToString() const20 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
WithinEpsilon(float a,float b)28 static inline bool WithinEpsilon(float a, float b) {
29 return std::abs(a - b) < std::numeric_limits<float>::epsilon();
30 }
31
IsRectilinear() const32 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
IsCounterClockwise() const40 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 // The equation can be written:
48 // Signed area = determinant1 + determinant2 + determinant3 + determinant4
49 // In practise, Refactoring the computation of adding determinants so that
50 // reducing the number of operations. The equation is:
51 // Signed area = element1 + element2 - element3 - element4
52
53 float p24 = p2_.y() - p4_.y();
54 float p31 = p3_.y() - p1_.y();
55
56 // Up-cast to double so this cannot overflow.
57 double element1 = static_cast<double>(p1_.x()) * p24;
58 double element2 = static_cast<double>(p2_.x()) * p31;
59 double element3 = static_cast<double>(p3_.x()) * p24;
60 double element4 = static_cast<double>(p4_.x()) * p31;
61
62 return element1 + element2 < element3 + element4;
63 }
64
PointIsInTriangle(const PointF & point,const PointF & r1,const PointF & r2,const PointF & r3)65 static inline bool PointIsInTriangle(const PointF& point,
66 const PointF& r1,
67 const PointF& r2,
68 const PointF& r3) {
69 // Translate point and triangle so that point lies at origin.
70 // Then checking if the origin is contained in the translated triangle.
71 // The origin O lies inside ABC if and only if the triangles OAB, OBC,
72 // and OCA are all either clockwise or counterclockwise.
73 // This algorithm is from Real-Time Collision Detection (Chaper 5.4.2).
74
75 Vector2dF a = r1 - point;
76 Vector2dF b = r2 - point;
77 Vector2dF c = r3 - point;
78
79 double u = CrossProduct(b, c);
80 double v = CrossProduct(c, a);
81 double w = CrossProduct(a, b);
82 return ((u * v < 0) || ((u * w) < 0) || ((v * w) < 0)) ? false : true;
83 }
84
Contains(const PointF & point) const85 bool QuadF::Contains(const PointF& point) const {
86 return PointIsInTriangle(point, p1_, p2_, p3_)
87 || PointIsInTriangle(point, p1_, p3_, p4_);
88 }
89
Scale(float x_scale,float y_scale)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
operator +=(const Vector2dF & rhs)97 void QuadF::operator+=(const Vector2dF& rhs) {
98 p1_ += rhs;
99 p2_ += rhs;
100 p3_ += rhs;
101 p4_ += rhs;
102 }
103
operator -=(const Vector2dF & rhs)104 void QuadF::operator-=(const Vector2dF& rhs) {
105 p1_ -= rhs;
106 p2_ -= rhs;
107 p3_ -= rhs;
108 p4_ -= rhs;
109 }
110
operator +(const QuadF & lhs,const Vector2dF & rhs)111 QuadF operator+(const QuadF& lhs, const Vector2dF& rhs) {
112 QuadF result = lhs;
113 result += rhs;
114 return result;
115 }
116
operator -(const QuadF & lhs,const Vector2dF & rhs)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