Reworked MapGraticule

MapControl/Shared/MapGraticule.cs

@@ -3,13 +3,20 @@
 // Licensed under the Microsoft Public License (Ms-PL)
 
 using System;
+using System.Collections.Generic;
 using System.Globalization;
+using System.Linq;
 #if WINUI
 using Microsoft.UI.Xaml;
+using Microsoft.UI.Xaml.Media;
+using Windows.Foundation;
 #elif UWP
+using Windows.Foundation;
 using Windows.UI.Xaml;
+using Windows.UI.Xaml.Media;
 #else
 using System.Windows;
+using System.Windows.Media;
 #endif
 
 namespace MapControl
@@ -19,9 +26,22 @@ namespace MapControl
     /// </summary>
     public partial class MapGraticule : MapOverlay
     {
+        private class Label
+        {
+            public string LatitudeText { get; set; }
+            public string LongitudeText { get; set; }
+            public Point Position { get; set; }
+            public double Rotation { get; set; }
+        }
+
+        private const double LineInterpolationResolution = 2d;
+
         public static readonly DependencyProperty MinLineDistanceProperty = DependencyProperty.Register(
             nameof(MinLineDistance), typeof(double), typeof(MapGraticule), new PropertyMetadata(150d));
 
+        private double lineDistance;
+        private string labelFormat;
+
         /// <summary>
         /// Minimum graticule line distance in pixels. The default value is 150.
         /// </summary>
@@ -31,7 +51,7 @@ namespace MapControl
             set { SetValue(MinLineDistanceProperty, value); }
         }
 
-        private double GetLineDistance()
+        private void SetLineDistance()
         {
             var minDistance = MinLineDistance / PixelPerLongitudeDegree(ParentMap.Center);
             var scale = minDistance < 1d / 60d ? 3600d : minDistance < 1d ? 60d : 1d;
@@ -45,7 +65,10 @@ namespace MapControl
                 i++;
             }
 
-            return Math.Min(lineDistances[i] / scale, 30d);
+            lineDistance = Math.Min(lineDistances[i] / scale, 30d);
+
+            labelFormat = lineDistance < 1d / 60d ? "{0} {1}°{2:00}'{3:00}\""
+                        : lineDistance < 1d ? "{0} {1}°{2:00}'" : "{0} {1}°";
         }
 
         private double PixelPerLongitudeDegree(Location location)
@@ -55,13 +78,7 @@ namespace MapControl
                 Math.Cos(location.Latitude * Math.PI / 180d) * MapProjection.Wgs84MeterPerDegree);
         }
 
-        private static string GetLabelFormat(double lineDistance)
-        {
-            return lineDistance < 1d / 60d ? "{0} {1}°{2:00}'{3:00}\""
-                 : lineDistance < 1d ? "{0} {1}°{2:00}'" : "{0} {1}°";
-        }
-
-        private static string GetLabelText(double value, string format, string hemispheres)
+        private string GetLabelText(double value, string hemispheres)
         {
             var hemisphere = hemispheres[0];
 
@@ -76,7 +93,252 @@ namespace MapControl
             var seconds = (int)Math.Round(value * 3600d);
 
             return string.Format(CultureInfo.InvariantCulture,
-                format, hemisphere, seconds / 3600, seconds / 60 % 60, seconds % 60);
+                labelFormat, hemisphere, seconds / 3600, seconds / 60 % 60, seconds % 60);
+        }
+
+        private void AddLabel(ICollection<Label> labels, Point position, Location location, double? rotation = null)
+        {
+            if (MapProjection.IsValid(position) &&
+                position.X >= 0d && position.X <= ParentMap.RenderSize.Width &&
+                position.Y >= 0d && position.Y <= ParentMap.RenderSize.Height)
+            {
+                if (!rotation.HasValue)
+                {
+                    var pos = ParentMap.LocationToView(new Location(
+                        location.Latitude, location.Longitude + 10d / PixelPerLongitudeDegree(location)));
+
+                    if (MapProjection.IsValid(pos))
+                    {
+                        rotation = Math.Atan2(pos.Y - position.Y, pos.X - position.X) * 180d / Math.PI;
+                    }
+                }
+
+                if (rotation.HasValue)
+                {
+                    labels.Add(new Label
+                    {
+                        LatitudeText = GetLabelText(location.Latitude, "NS"),
+                        LongitudeText = GetLabelText(Location.NormalizeLongitude(location.Longitude), "EW"),
+                        Position = position,
+                        Rotation = rotation.Value
+                    });
+                }
+            }
+        }
+
+        private void GetLatitudeRange(double lineDistance, ref double minLatitude, ref double maxLatitude)
+        {
+            var width = ParentMap.RenderSize.Width;
+            var height = ParentMap.RenderSize.Height;
+            var northPole = ParentMap.LocationToView(new Location(90d, 0d));
+            var southPole = ParentMap.LocationToView(new Location(-90d, 0d));
+
+            if (northPole.X >= 0d && northPole.Y >= 0d && northPole.X <= width && northPole.Y <= height)
+            {
+                maxLatitude = 90d;
+            }
+
+            if (southPole.X >= 0d && southPole.Y >= 0d && southPole.X <= width && southPole.Y <= height)
+            {
+                minLatitude = -90d;
+            }
+
+            if (minLatitude > -90d || maxLatitude < 90d)
+            {
+                var locations = new Location[]
+                {
+                    ParentMap.ViewToLocation(new Point(0d, 0d)),
+                    ParentMap.ViewToLocation(new Point(width / 2d, 0d)),
+                    ParentMap.ViewToLocation(new Point(width, 0d)),
+                    ParentMap.ViewToLocation(new Point(width, height / 2d)),
+                    ParentMap.ViewToLocation(new Point(width, height)),
+                    ParentMap.ViewToLocation(new Point(width / 2d, height)),
+                    ParentMap.ViewToLocation(new Point(0d, height)),
+                    ParentMap.ViewToLocation(new Point(0d, height / 2)),
+                };
+
+                var latitudes = locations.Where(loc => loc != null).Select(loc => loc.Latitude);
+                var south = -90d;
+                var north = 90d;
+
+                if (latitudes.Distinct().Count() >= 2)
+                {
+                    south = latitudes.Min();
+                    north = latitudes.Max();
+                }
+
+                if (minLatitude > -90d)
+                {
+                    minLatitude = Math.Max(Math.Floor(south / lineDistance) * lineDistance, -90d);
+                }
+
+                if (maxLatitude < 90d)
+                {
+                    maxLatitude = Math.Min(Math.Ceiling(north / lineDistance) * lineDistance, 90d);
+                }
+            }
+        }
+
+        private void DrawCylindricalGraticule(PathFigureCollection figures, ICollection<Label> labels)
+        {
+            var bounds = ParentMap.ViewRectToBoundingBox(new Rect(0, 0, ParentMap.RenderSize.Width, ParentMap.RenderSize.Height));
+            var latLabelStart = Math.Ceiling(bounds.South / lineDistance) * lineDistance;
+            var lonLabelStart = Math.Ceiling(bounds.West / lineDistance) * lineDistance;
+
+            for (var lat = latLabelStart; lat <= bounds.North; lat += lineDistance)
+            {
+                var p1 = ParentMap.LocationToView(new Location(lat, bounds.West));
+                var p2 = ParentMap.LocationToView(new Location(lat, bounds.East));
+
+                if (MapProjection.IsValid(p1) && MapProjection.IsValid(p2))
+                {
+                    figures.Add(CreateLineFigure(p1, p2));
+                }
+            }
+
+            for (var lon = lonLabelStart; lon <= bounds.East; lon += lineDistance)
+            {
+                var p1 = ParentMap.LocationToView(new Location(bounds.South, lon));
+                var p2 = ParentMap.LocationToView(new Location(bounds.North, lon));
+
+                if (MapProjection.IsValid(p1) && MapProjection.IsValid(p2))
+                {
+                    figures.Add(CreateLineFigure(p1, p2));
+                }
+            }
+
+            for (var lat = latLabelStart; lat <= bounds.North; lat += lineDistance)
+            {
+                for (var lon = lonLabelStart; lon <= bounds.East; lon += lineDistance)
+                {
+                    var location = new Location(lat, lon);
+                    var position = ParentMap.LocationToView(location);
+
+                    AddLabel(labels, position, location, ParentMap.ViewTransform.Rotation);
+                }
+            }
+        }
+
+        private void DrawGraticule(PathFigureCollection figures, ICollection<Label> labels)
+        {
+            var minLat = 0d;
+            var maxLat = 0d;
+
+            GetLatitudeRange(lineDistance, ref minLat, ref maxLat);
+
+            var latSegments = (int)Math.Round(Math.Abs(maxLat - minLat) / lineDistance);
+            var interpolationCount = Math.Max(1, (int)Math.Ceiling(lineDistance / LineInterpolationResolution));
+            var interpolationDistance = lineDistance / interpolationCount;
+            var latPoints = latSegments * interpolationCount;
+
+            var centerLon = Math.Round(ParentMap.Center.Longitude / lineDistance) * lineDistance;
+            var westLimit = centerLon - 180d;
+            var eastLimit = centerLon + 180d;
+
+            if (ParentMap.MapProjection.Type == MapProjectionType.TransverseCylindrical)
+            {
+                westLimit = ParentMap.MapProjection.Center.Longitude - 15d;
+                eastLimit = ParentMap.MapProjection.Center.Longitude + 15d;
+                westLimit = Math.Floor(westLimit / lineDistance) * lineDistance;
+                eastLimit = Math.Ceiling(eastLimit / lineDistance) * lineDistance;
+            }
+
+            var minLon = centerLon - lineDistance;
+            var maxLon = centerLon + lineDistance;
+
+            if (DrawMeridian(figures, centerLon, minLat, interpolationDistance, latPoints))
+            {
+                while (DrawMeridian(figures, minLon, minLat, interpolationDistance, latPoints) &&
+                    minLon > westLimit)
+                {
+                    minLon -= lineDistance;
+                }
+
+                while (DrawMeridian(figures, maxLon, minLat, interpolationDistance, latPoints) &&
+                    maxLon < eastLimit)
+                {
+                    maxLon += lineDistance;
+                }
+            }
+
+            var lonSegments = (int)Math.Round(Math.Abs(maxLon - minLon) / lineDistance);
+
+            for (var i = 1; i < latSegments; i++)
+            {
+                var lat = minLat + i * lineDistance;
+                var lon = minLon;
+                var location = new Location(lat, lon);
+                var points = new List<Point>();
+                var position = ParentMap.LocationToView(location);
+
+                if (MapProjection.IsValid(position))
+                {
+                    points.Add(position);
+                    AddLabel(labels, position, location);
+                }
+
+                for (int j = 0; j < lonSegments; j++)
+                {
+                    for (int k = 1; k <= interpolationCount; k++)
+                    {
+                        lon = minLon + j * lineDistance + k * interpolationDistance;
+                        location = new Location(lat, lon);
+                        position = ParentMap.LocationToView(location);
+
+                        if (MapProjection.IsValid(position))
+                        {
+                            points.Add(position);
+                        }
+                    }
+
+                    AddLabel(labels, position, location);
+                }
+
+                if (points.Count >= 2)
+                {
+                    figures.Add(CreatePolylineFigure(points));
+                }
+            }
+        }
+
+        private bool DrawMeridian(PathFigureCollection figures,
+            double longitude, double startLatitude, double deltaLatitude, int numPoints)
+        {
+            var points = new List<Point>();
+            var visible = false;
+
+            for (int i = 0; i <= numPoints; i++)
+            {
+                var p = ParentMap.LocationToView(new Location(startLatitude + i * deltaLatitude, longitude));
+
+                if (MapProjection.IsValid(p))
+                {
+                    visible = visible ||
+                        p.X >= 0d && p.X <= ParentMap.RenderSize.Width &&
+                        p.Y >= 0d && p.Y <= ParentMap.RenderSize.Height;
+
+                    points.Add(p);
+                }
+            }
+
+            if (points.Count >= 2)
+            {
+                figures.Add(CreatePolylineFigure(points));
+            }
+
+            return visible;
+        }
+
+        private static PathFigure CreateLineFigure(Point p1, Point p2)
+        {
+            var figure = new PathFigure
+            {
+                StartPoint = p1,
+                IsFilled = false
+            };
+
+            figure.Segments.Add(new LineSegment { Point = p2 });
+            return figure;
         }
     }
 }