| // Copyright (c) 2012 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #include "ui/gfx/geometry/quad_f.h" |
| |
| #include <limits> |
| |
| #include "base/strings/stringprintf.h" |
| |
| namespace gfx { |
| |
| void QuadF::operator=(const RectF& rect) { |
| p1_ = PointF(rect.x(), rect.y()); |
| p2_ = PointF(rect.right(), rect.y()); |
| p3_ = PointF(rect.right(), rect.bottom()); |
| p4_ = PointF(rect.x(), rect.bottom()); |
| } |
| |
| std::string QuadF::ToString() const { |
| return base::StringPrintf("%s;%s;%s;%s", |
| p1_.ToString().c_str(), |
| p2_.ToString().c_str(), |
| p3_.ToString().c_str(), |
| p4_.ToString().c_str()); |
| } |
| |
| static inline bool WithinEpsilon(float a, float b) { |
| return std::abs(a - b) < std::numeric_limits<float>::epsilon(); |
| } |
| |
| bool QuadF::IsRectilinear() const { |
| return |
| (WithinEpsilon(p1_.x(), p2_.x()) && WithinEpsilon(p2_.y(), p3_.y()) && |
| WithinEpsilon(p3_.x(), p4_.x()) && WithinEpsilon(p4_.y(), p1_.y())) || |
| (WithinEpsilon(p1_.y(), p2_.y()) && WithinEpsilon(p2_.x(), p3_.x()) && |
| WithinEpsilon(p3_.y(), p4_.y()) && WithinEpsilon(p4_.x(), p1_.x())); |
| } |
| |
| bool QuadF::IsCounterClockwise() const { |
| // This math computes the signed area of the quad. Positive area |
| // indicates the quad is clockwise; negative area indicates the quad is |
| // counter-clockwise. Note carefully: this is backwards from conventional |
| // math because our geometric space uses screen coordiantes with y-axis |
| // pointing downards. |
| // Reference: http://mathworld.wolfram.com/PolygonArea.html. |
| // The equation can be written: |
| // Signed area = determinant1 + determinant2 + determinant3 + determinant4 |
| // In practise, Refactoring the computation of adding determinants so that |
| // reducing the number of operations. The equation is: |
| // Signed area = element1 + element2 - element3 - element4 |
| |
| float p24 = p2_.y() - p4_.y(); |
| float p31 = p3_.y() - p1_.y(); |
| |
| // Up-cast to double so this cannot overflow. |
| double element1 = static_cast<double>(p1_.x()) * p24; |
| double element2 = static_cast<double>(p2_.x()) * p31; |
| double element3 = static_cast<double>(p3_.x()) * p24; |
| double element4 = static_cast<double>(p4_.x()) * p31; |
| |
| return element1 + element2 < element3 + element4; |
| } |
| |
| static inline bool PointIsInTriangle(const PointF& point, |
| const PointF& r1, |
| const PointF& r2, |
| const PointF& r3) { |
| // Compute the barycentric coordinates (u, v, w) of |point| relative to the |
| // triangle (r1, r2, r3) by the solving the system of equations: |
| // 1) point = u * r1 + v * r2 + w * r3 |
| // 2) u + v + w = 1 |
| // This algorithm comes from Christer Ericson's Real-Time Collision Detection. |
| |
| Vector2dF r31 = r1 - r3; |
| Vector2dF r32 = r2 - r3; |
| Vector2dF r3p = point - r3; |
| |
| float denom = r32.y() * r31.x() - r32.x() * r31.y(); |
| float u = (r32.y() * r3p.x() - r32.x() * r3p.y()) / denom; |
| float v = (r31.x() * r3p.y() - r31.y() * r3p.x()) / denom; |
| float w = 1.f - u - v; |
| |
| // Use the barycentric coordinates to test if |point| is inside the |
| // triangle (r1, r2, r2). |
| return (u >= 0) && (v >= 0) && (w >= 0); |
| } |
| |
| bool QuadF::Contains(const PointF& point) const { |
| return PointIsInTriangle(point, p1_, p2_, p3_) |
| || PointIsInTriangle(point, p1_, p3_, p4_); |
| } |
| |
| void QuadF::Scale(float x_scale, float y_scale) { |
| p1_.Scale(x_scale, y_scale); |
| p2_.Scale(x_scale, y_scale); |
| p3_.Scale(x_scale, y_scale); |
| p4_.Scale(x_scale, y_scale); |
| } |
| |
| void QuadF::operator+=(const Vector2dF& rhs) { |
| p1_ += rhs; |
| p2_ += rhs; |
| p3_ += rhs; |
| p4_ += rhs; |
| } |
| |
| void QuadF::operator-=(const Vector2dF& rhs) { |
| p1_ -= rhs; |
| p2_ -= rhs; |
| p3_ -= rhs; |
| p4_ -= rhs; |
| } |
| |
| QuadF operator+(const QuadF& lhs, const Vector2dF& rhs) { |
| QuadF result = lhs; |
| result += rhs; |
| return result; |
| } |
| |
| QuadF operator-(const QuadF& lhs, const Vector2dF& rhs) { |
| QuadF result = lhs; |
| result -= rhs; |
| return result; |
| } |
| |
| } // namespace gfx |