MapPolypoint implementation

MapControl/Avalonia/MapPolypoint.Avalonia.cs

@@ -51,39 +51,31 @@ namespace MapControl
 
         protected void UpdateData(IEnumerable<Location> locations, bool closed)
         {
-            var pathFigures = new PathFigures();
+            var pathFigure = new PathFigure();
 
-            if (ParentMap != null && locations != null)
+            if (ParentMap != null && locations?.Count() >= 2)
             {
-                var longitudeOffset = GetLongitudeOffset(Location ?? locations.FirstOrDefault());
+                var longitudeOffset = GetLongitudeOffset(Location ?? locations.First());
 
-                AddPolylinePoints(pathFigures, locations, longitudeOffset, closed);
+                AddPolylinePoints(pathFigure, locations, longitudeOffset, closed);
             }
 
-            ((PathGeometry)Data).Figures = pathFigures;
+            ((PathGeometry)Data).Figures = new PathFigures { pathFigure };
 
-            InvalidateGeometry();
+            InvalidateGeometry(); // ignores an empty PathGeometry.Figures collection
         }
 
-        private void AddPolylinePoints(PathFigures pathFigures, IEnumerable<Location> locations, double longitudeOffset, bool closed)
+        private void AddPolylinePoints(PathFigure pathFigure, IEnumerable<Location> locations, double longitudeOffset, bool closed)
         {
-            if (locations.Count() >= 2)
+            var points = locations
-            {
+                .Select(location => LocationToView(location, longitudeOffset))
-                var points = locations
+                .Where(point => point.HasValue)
-                    .Select(location => LocationToView(location, longitudeOffset))
+                .Select(point => point.Value);
-                    .Where(point => point.HasValue)
-                    .Select(point => point.Value);
 
-                var figure = new PathFigure
+            pathFigure.StartPoint = points.First();
-                {
+            pathFigure.Segments.Add(new PolyLineSegment(points.Skip(1)));
-                    StartPoint = points.First(),
+            pathFigure.IsClosed = closed;
-                    IsClosed = closed,
+            pathFigure.IsFilled = true;
-                    IsFilled = true
-                };
-
-                figure.Segments.Add(new PolyLineSegment(points.Skip(1)));
-                pathFigures.Add(figure);
-            }
         }
     }
 }

MapControl/Shared/Intersections.cs

@@ -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;
-        }
-    }
-}

MapControl/UWP/MapControl.UWP.csproj

@@ -89,9 +89,6 @@
     <Compile Include="..\Shared\ImageLoader.cs">
       <Link>ImageLoader.cs</Link>
     </Compile>
-    <Compile Include="..\Shared\Intersections.cs">
-      <Link>Intersections.cs</Link>
-    </Compile>
     <Compile Include="..\Shared\Location.cs">
       <Link>Location.cs</Link>
     </Compile>

MapControl/WPF/MapPolypoint.WPF.cs

@@ -60,9 +60,9 @@ namespace MapControl
         {
             using (var context = ((StreamGeometry)Data).Open())
             {
-                if (ParentMap != null && locations != null)
+                if (ParentMap != null && locations?.Count() >= 2)
                 {
-                    var longitudeOffset = GetLongitudeOffset(Location ?? locations.FirstOrDefault());
+                    var longitudeOffset = GetLongitudeOffset(Location ?? locations.First());
 
                     AddPolylinePoints(context, locations, longitudeOffset, closed);
                 }
@@ -77,7 +77,7 @@ namespace MapControl
                 {
                     var longitudeOffset = GetLongitudeOffset(Location);
 
-                    foreach (var polygon in polygons)
+                    foreach (var polygon in polygons.Where(p => p?.Count() >= 2))
                     {
                         AddPolylinePoints(context, polygon, longitudeOffset, true);
                     }
@@ -87,16 +87,13 @@ namespace MapControl
 
         private void AddPolylinePoints(StreamGeometryContext context, IEnumerable<Location> locations, double longitudeOffset, bool closed)
         {
-            if (locations.Count() >= 2)
+            var points = locations
-            {
+                .Select(location => LocationToView(location, longitudeOffset))
-                var points = locations
+                .Where(point => point.HasValue)
-                    .Select(location => LocationToView(location, longitudeOffset))
+                .Select(point => point.Value);
-                    .Where(point => point.HasValue)
-                    .Select(point => point.Value);
 
-                context.BeginFigure(points.First(), true, closed);
+            context.BeginFigure(points.First(), true, closed);
-                context.PolyLineTo(points.Skip(1).ToList(), true, true);
+            context.PolyLineTo(points.Skip(1).ToList(), true, true);
-            }
         }
     }
 }

MapControl/WinUI/MapPolypoint.WinUI.cs

@@ -2,6 +2,7 @@
 // Copyright © 2024 Clemens Fischer
 // Licensed under the Microsoft Public License (Ms-PL)
 
+using System;
 using System.Collections;
 using System.Collections.Generic;
 using System.Collections.Specialized;
@@ -61,9 +62,9 @@ namespace MapControl
             var pathFigures = ((PathGeometry)Data).Figures;
             pathFigures.Clear();
 
-            if (ParentMap != null && locations != null)
+            if (ParentMap != null && locations?.Count() >= 2)
             {
-                var longitudeOffset = GetLongitudeOffset(Location ?? locations.FirstOrDefault());
+                var longitudeOffset = GetLongitudeOffset(Location ?? locations.First());
 
                 AddPolylinePoints(pathFigures, locations, longitudeOffset, closed);
             }
@@ -71,77 +72,157 @@ namespace MapControl
 
         private void AddPolylinePoints(PathFigureCollection pathFigures, IEnumerable<Location> locations, double longitudeOffset, bool closed)
         {
-            if (locations.Count() >= 2)
+            var points = locations
+                .Select(location => LocationToView(location, longitudeOffset))
+                .Where(point => point.HasValue)
+                .Select(point => point.Value);
+
+            if (closed)
             {
-                var points = locations
+                var figure = new PathFigure
-                    .Select(location => LocationToView(location, longitudeOffset))
-                    .Where(point => point.HasValue)
-                    .Select(point => point.Value);
-
-                if (closed)
                 {
-                    var figure = new PathFigure
+                    StartPoint = points.First(),
-                    {
+                    IsClosed = true,
-                        StartPoint = points.First(),
+                    IsFilled = true
-                        IsClosed = closed,
+                };
-                        IsFilled = true
-                    };
 
-                    var polyline = new PolyLineSegment();
+                var polyline = new PolyLineSegment();
 
-                    foreach (var point in points.Skip(1))
+                foreach (var point in points.Skip(1))
-                    {
+                {
-                        polyline.Points.Add(point);
+                    polyline.Points.Add(point);
-                    }
-
-                    figure.Segments.Add(polyline);
-                    pathFigures.Add(figure);
                 }
-                else
-                {
-                    var pointList = points.ToList();
 
-                    if (closed)
+                figure.Segments.Add(polyline);
+                pathFigures.Add(figure);
+            }
+            else
+            {
+                PathFigure figure = null;
+                PolyLineSegment polyline = null;
+                var viewport = new Rect(0, 0, ParentMap.RenderSize.Width, ParentMap.RenderSize.Height);
+                var pointList = points.ToList();
+
+                for (int i = 1; i < pointList.Count; i++)
+                {
+                    var p1 = pointList[i - 1];
+                    var p2 = pointList[i];
+                    var inside = GetIntersections(ref p1, ref p2, viewport);
+
+                    if (inside)
                     {
-                        pointList.Add(pointList[0]);
+                        if (figure == null)
+                        {
+                            figure = new PathFigure
+                            {
+                                StartPoint = p1,
+                                IsClosed = false,
+                                IsFilled = true
+                            };
+
+                            polyline = new PolyLineSegment();
+                            figure.Segments.Add(polyline);
+                            pathFigures.Add(figure);
+                        }
+
+                        polyline.Points.Add(p2);
                     }
 
-                    var viewport = new Rect(0, 0, ParentMap.RenderSize.Width, ParentMap.RenderSize.Height);
+                    if (!inside || p2 != pointList[i])
-                    PathFigure figure = null;
-                    PolyLineSegment polyline = null;
-
-                    for (int i = 1; i < pointList.Count; i++)
                     {
-                        var p1 = pointList[i - 1];
+                        figure = null;
-                        var p2 = pointList[i];
-                        var inside = Intersections.GetIntersections(ref p1, ref p2, viewport);
-
-                        if (inside)
-                        {
-                            if (figure == null)
-                            {
-                                figure = new PathFigure
-                                {
-                                    StartPoint = p1,
-                                    IsClosed = false,
-                                    IsFilled = true
-                                };
-
-                                polyline = new PolyLineSegment();
-                                figure.Segments.Add(polyline);
-                                pathFigures.Add(figure);
-                            }
-
-                            polyline.Points.Add(p2);
-                        }
-
-                        if (!inside || p2 != pointList[i])
-                        {
-                            figure = 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>
+        private 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;
+        }
+
+        /// <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>
+        private 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;
+        }
     }
 }