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// 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
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