Added MetricGrid

MapControl/Shared/MetricGrid.cs

@@ -0,0 +1,84 @@
+using System;
+using System.Collections.Generic;
+#if WPF
+using System.Windows;
+using System.Windows.Media;
+#elif UWP
+using Windows.UI.Xaml.Media;
+#elif WINUI
+using Microsoft.UI.Xaml.Media;
+#elif AVALONIA
+using Avalonia;
+using PathFigureCollection = Avalonia.Media.PathFigures;
+#endif
+
+namespace MapControl
+{
+    /// <summary>
+    /// Draws a metric grid overlay.
+    /// </summary>
+    public partial class MetricGrid : MapGrid
+    {
+        protected override void DrawGrid(PathFigureCollection figures, List<Label> labels)
+        {
+            var minLineDistance = MinLineDistance / ParentMap.ViewTransform.Scale;
+            var lineDistance = Math.Pow(10d, Math.Ceiling(Math.Log10(minLineDistance)));
+
+            if (lineDistance * 0.5 >= minLineDistance)
+            {
+                lineDistance *= 0.5;
+
+                if (lineDistance * 0.4 >= minLineDistance)
+                {
+                    lineDistance *= 0.4;
+                }
+            }
+
+            var mapRect = ParentMap.ViewTransform.ViewToMapBounds(new Rect(0d, 0d, ParentMap.ActualWidth, ParentMap.ActualHeight));
+            var minX = Math.Ceiling(mapRect.X / lineDistance) * lineDistance;
+            var minY = Math.Ceiling(mapRect.Y / lineDistance) * lineDistance;
+
+            for (var x = minX; x <= mapRect.X + mapRect.Width; x += lineDistance)
+            {
+                var p1 = ParentMap.ViewTransform.MapToView(new Point(x, mapRect.Y));
+                var p2 = ParentMap.ViewTransform.MapToView(new Point(x, mapRect.Y + mapRect.Height));
+                figures.Add(CreateLineFigure(p1, p2));
+            }
+
+            for (var y = minY; y <= mapRect.Y + mapRect.Height; y += lineDistance)
+            {
+                var p1 = ParentMap.ViewTransform.MapToView(new Point(mapRect.X, y));
+                var p2 = ParentMap.ViewTransform.MapToView(new Point(mapRect.X + mapRect.Width, y));
+                figures.Add(CreateLineFigure(p1, p2));
+
+                for (var x = minX; x <= mapRect.X + mapRect.Width; x += lineDistance)
+                {
+                    AddLabel(labels, x, y);
+                }
+            }
+        }
+
+        private void AddLabel(List<Label> labels, double x, double y)
+        {
+            var position = ParentMap.ViewTransform.MapToView(new Point(x, y));
+
+            if (ParentMap.InsideViewBounds(position))
+            {
+                var rotation = ParentMap.ViewTransform.Rotation;
+
+                if (rotation < -90d)
+                {
+                    rotation += 180d;
+                }
+                else if (rotation > 90d)
+                {
+                    rotation -= 180d;
+                }
+
+                var text = string.Format("{0:F0}\n{1:F0}", y, x);
+
+                labels.Add(new Label(text, position.X, position.Y, rotation));
+            }
+        }
+    }
+}