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MapPolypoint implementation

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ClemensFischer 2024-07-15 09:09:15 +02:00
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103
MapControl/Shared/Intersections.cs
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@ -1,103 +0,0 @@
// XAML Map Control - https://github.com/ClemensFischer/XAML-Map-Control
// Copyright © 2024 Clemens Fischer
// Licensed under the Microsoft Public License (Ms-PL)
using System;
#if WPF
using System.Windows;
#endif
namespace MapControl
{
public static class Intersections
{
/// <summary>
/// Returns the intersection point of two line segments given by (p1,p2) and (p3,p4),
/// or null if no intersection exists. See https://stackoverflow.com/a/1968345.
/// </summary>
public static Point? GetIntersection(Point p1, Point p2, Point p3, Point p4)
{
var x12 = p2.X - p1.X;
var y12 = p2.Y - p1.Y;
var x34 = p4.X - p3.X;
var y34 = p4.Y - p3.Y;
var x13 = p3.X - p1.X;
var y13 = p3.Y - p1.Y;
var d = x12 * y34 - x34 * y12;
var s = (x13 * y12 - y13 * x12) / d;
var t = (x13 * y34 - y13 * x34) / d;
if (s >= 0d && s <= 1d && t >= 0d && t <= 1d)
{
return new Point(p1.X + t * x12, p1.Y + t * y12);
}
return null;
}
/// <summary>
/// Calculates the potential intersections of a line segment given by (p1,p2) with a rectangle.
/// Updates either p1, p2, or both with any found intersection and returns a value that indicates
/// whether the segment intersects or lies inside the rectangle.
/// </summary>
public static bool GetIntersections(ref Point p1, ref Point p2, Rect rect)
{
if (rect.Contains(p1) && rect.Contains(p2))
{
return true;
}
var topLeft = new Point(rect.X, rect.Y);
var topRight = new Point(rect.X + rect.Width, rect.Y);
var bottomLeft = new Point(rect.X, rect.Y + rect.Height);
var bottomRight = new Point(rect.X + rect.Width, rect.Y + rect.Height);
var numIntersections = 0;
if (GetIntersection(ref p1, ref p2, topLeft, bottomLeft, p => p.X <= rect.X)) // left edge
{
numIntersections++;
}
if (GetIntersection(ref p1, ref p2, topLeft, topRight, p => p.Y <= rect.Y)) // top edge
{
numIntersections++;
}
if (numIntersections < 2 &&
GetIntersection(ref p1, ref p2, topRight, bottomRight, p => p.X >= rect.X + rect.Width)) // right edge
{
numIntersections++;
}
if (numIntersections < 2 &&
GetIntersection(ref p1, ref p2, bottomLeft, bottomRight, p => p.Y >= rect.Y + rect.Height)) // bottom edge
{
numIntersections++;
}
return numIntersections > 0;
}
private static bool GetIntersection(ref Point p1, ref Point p2, Point p3, Point p4, Predicate<Point> predicate)
{
var intersection = GetIntersection(p1, p2, p3, p4);
if (!intersection.HasValue)
{
return false;
}
if (predicate(p1))
{
p1 = intersection.Value;
}
else
{
p2 = intersection.Value;
}
return true;
}
}
}