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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/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 of |point| relative to the triangle | |
66 // (r1, r2, r3). This algorithm comes from Christer Ericson's Real-Time | |
67 // Collision Detection. | |
68 Vector2dF v0 = r2 - r1; | |
69 Vector2dF v1 = r3 - r1; | |
70 Vector2dF v2 = point - r1; | |
71 | |
72 double dot00 = DotProduct(v0, v0); | |
73 double dot01 = DotProduct(v0, v1); | |
74 double dot11 = DotProduct(v1, v1); | |
75 double dot20 = DotProduct(v2, v0); | |
76 double dot21 = DotProduct(v2, v1); | |
77 | |
78 double denom = dot00 * dot11 - dot01 * dot01; | |
79 | |
80 double v = (dot11 * dot20 - dot01 * dot21) / denom; | |
81 double w = (dot00 * dot21 - dot01 * dot20) / denom; | |
82 double u = 1 - v - w; | |
83 | |
84 // Use the barycentric coordinates to test if |point| is inside the | |
85 // triangle (r1, r2, r2). | |
86 return (v >= 0) && (w >= 0) && (u >= 0); | |
87 } | |
88 | |
89 bool QuadF::Contains(const PointF& point) const { | |
90 return PointIsInTriangle(point, p1_, p2_, p3_) | |
91 || PointIsInTriangle(point, p1_, p3_, p4_); | |
92 } | |
93 | |
94 void QuadF::Scale(float x_scale, float y_scale) { | |
95 p1_.Scale(x_scale, y_scale); | |
96 p2_.Scale(x_scale, y_scale); | |
97 p3_.Scale(x_scale, y_scale); | |
98 p4_.Scale(x_scale, y_scale); | |
99 } | |
100 | |
101 void QuadF::operator+=(const Vector2dF& rhs) { | |
102 p1_ += rhs; | |
103 p2_ += rhs; | |
104 p3_ += rhs; | |
105 p4_ += rhs; | |
106 } | |
107 | |
108 void QuadF::operator-=(const Vector2dF& rhs) { | |
109 p1_ -= rhs; | |
110 p2_ -= rhs; | |
111 p3_ -= rhs; | |
112 p4_ -= rhs; | |
113 } | |
114 | |
115 QuadF operator+(const QuadF& lhs, const Vector2dF& rhs) { | |
116 QuadF result = lhs; | |
117 result += rhs; | |
118 return result; | |
119 } | |
120 | |
121 QuadF operator-(const QuadF& lhs, const Vector2dF& rhs) { | |
122 QuadF result = lhs; | |
123 result -= rhs; | |
124 return result; | |
125 } | |
126 | |
127 } // namespace gfx | |
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