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LibGfx: Add a Line class and a Rect<T>::RelativeLocation class
These helpers will be useful in preparation for supporting multiple displays, e.g. to measure distances to other screens or figure out where rectangles are located relative to each other.
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155
Userland/Libraries/LibGfx/Line.h
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155
Userland/Libraries/LibGfx/Line.h
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/*
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* Copyright (c) 2021, the SerenityOS developers.
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#include <AK/Optional.h>
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#include <AK/StdLibExtras.h>
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#include <LibGfx/Forward.h>
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#include <LibGfx/Point.h>
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#include <LibGfx/Rect.h>
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#include <math.h>
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#include <stdlib.h>
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namespace Gfx {
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template<typename T>
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class Line {
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public:
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Line() { }
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Line(Point<T> a, Point<T> b)
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: m_a(a)
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, m_b(b)
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{
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}
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template<typename U>
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Line(U a, U b)
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: m_a(a)
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, m_b(b)
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{
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}
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template<typename U>
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explicit Line(Line<U> const& other)
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: m_a(other.a())
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, m_b(other.b())
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{
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}
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bool intersects(Line const& other) const
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{
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return intersected(other).has_value();
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}
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Optional<Point<T>> intersected(Line const& other) const
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{
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auto cross_product = [](Point<T> const& p1, Point<T> const& p2) {
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return p1.x() * p2.y() - p1.y() * p2.x();
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};
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auto r = m_b - m_a;
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auto s = other.m_b - other.m_a;
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auto delta_a = other.m_a - m_a;
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auto num = cross_product(delta_a, r);
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auto denom = cross_product(r, s);
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if (denom == 0) {
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if (num == 0) {
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// Lines are collinear, check if line ends are touching
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if (m_a == other.m_a || m_a == other.m_b)
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return m_a;
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if (m_b == other.m_a || m_b == other.m_b)
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return m_b;
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// Check if they're overlapping
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if (!(m_b.x() - m_a.x() < 0 && m_b.x() - other.m_a.x() < 0 && other.m_b.x() - m_a.x() && other.m_b.x() - other.m_a.x())) {
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// Overlapping
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// TODO find center point?
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}
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if (!(m_b.y() - m_a.y() < 0 && m_b.y() - other.m_a.y() < 0 && other.m_b.y() - m_a.y() && other.m_b.y() - other.m_a.y())) {
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// Overlapping
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// TODO find center point?
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}
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return {};
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} else {
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// Lines are parallel and not intersecting
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return {};
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}
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}
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auto u = static_cast<float>(num) / static_cast<float>(denom);
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if (u < 0.0f || u > 1.0f) {
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// Lines are not parallel and don't intersect
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return {};
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}
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auto t = static_cast<float>(cross_product(delta_a, s)) / static_cast<float>(denom);
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if (t < 0.0f || t > 1.0f) {
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// Lines are not parallel and don't intersect
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return {};
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}
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// TODO: round if we're dealing with int
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return Point<T> { m_a.x() + static_cast<T>(t * r.x()), m_a.y() + static_cast<T>(t * r.y()) };
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}
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float length() const
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{
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return m_a.distance_from(m_b);
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}
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Point<T> closest_to(Point<T> const& point) const
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{
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if (m_a == m_b)
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return m_a;
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auto delta_a = point.x() - m_a.x();
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auto delta_b = point.y() - m_a.y();
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auto delta_c = m_b.x() - m_a.x();
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auto delta_d = m_b.y() - m_a.y();
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auto len_sq = delta_c * delta_c + delta_d * delta_d;
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float param = -1.0;
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if (len_sq != 0)
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param = static_cast<float>(delta_a * delta_c + delta_b * delta_d) / static_cast<float>(len_sq);
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if (param < 0)
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return m_a;
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if (param > 1)
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return m_b;
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// TODO: round if we're dealing with int
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return { static_cast<T>(m_a.x() + param * delta_c), static_cast<T>(m_a.y() + param * delta_d) };
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}
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Line<T> shortest_line_to(Point<T> const& point) const
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{
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return { closest_to(point), point };
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}
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float distance_to(Point<T> const& point) const
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{
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return shortest_line_to(point).length();
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}
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Point<T> const& a() const { return m_a; }
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Point<T> const& b() const { return m_b; }
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void set_a(Point<T> const& a) { m_a = a; }
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void set_b(Point<T> const& b) { m_b = b; }
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String to_string() const;
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private:
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Point<T> m_a;
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Point<T> m_b;
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};
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template<>
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inline String IntLine::to_string() const
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{
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return String::formatted("[{},{} -> {}x{}]", m_a.x(), m_a.y(), m_b.x(), m_b.y());
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}
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template<>
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inline String FloatLine::to_string() const
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{
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return String::formatted("[{},{} {}x{}]", m_a.x(), m_a.y(), m_b.x(), m_b.y());
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}
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}
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