Fixed MapItem.MapTransform implementation

MapControl/Shared/MapItem.cs

@@ -0,0 +1,105 @@
+// XAML Map Control - https://github.com/ClemensFischer/XAML-Map-Control
+// Copyright © 2023 Clemens Fischer
+// Licensed under the Microsoft Public License (Ms-PL)
+
+#if WINUI
+using Microsoft.UI.Xaml.Controls;
+using Microsoft.UI.Xaml.Media;
+#elif UWP
+using Windows.UI.Xaml.Controls;
+using Windows.UI.Xaml.Media;
+#else
+using System.Windows.Controls;
+using System.Windows.Media;
+#endif
+
+namespace MapControl
+{
+    /// <summary>
+    /// Container class for an item in a MapItemsControl.
+    /// </summary>
+    public partial class MapItem : ListBoxItem, IMapElement
+    {
+        private MapBase parentMap;
+        private MatrixTransform mapTransform;
+
+        /// <summary>
+        /// Gets/sets MapPanel.AutoCollapse.
+        /// </summary>
+        public bool AutoCollapse
+        {
+            get => (bool)GetValue(AutoCollapseProperty);
+            set => SetValue(AutoCollapseProperty, value);
+        }
+
+        /// <summary>
+        /// Gets/sets MapPanel.Location.
+        /// </summary>
+        public Location Location
+        {
+            get => (Location)GetValue(LocationProperty);
+            set => SetValue(LocationProperty, value);
+        }
+
+        /// <summary>
+        /// Implements IMapElement.ParentMap.
+        /// </summary>
+        public MapBase ParentMap
+        {
+            get => parentMap;
+            set
+            {
+                if (parentMap != null)
+                {
+                    parentMap.ViewportChanged -= OnViewportChanged;
+                }
+
+                parentMap = value;
+
+                if (parentMap != null && mapTransform != null)
+                {
+                    // Attach ViewportChanged handler only if MapTransform is actually used.
+                    //
+                    parentMap.ViewportChanged += OnViewportChanged;
+                    UpdateMapTransform(Location);
+                }
+            }
+        }
+
+        /// <summary>
+        /// Gets a Transform for scaling and rotating geometries
+        /// in map coordinates (meters) to view coordinates (pixels).
+        /// </summary>
+        public Transform MapTransform
+        {
+            get
+            {
+                if (mapTransform == null)
+                {
+                    mapTransform = new MatrixTransform();
+
+                    if (parentMap != null)
+                    {
+                        parentMap.ViewportChanged += OnViewportChanged;
+                        UpdateMapTransform(Location);
+                    }
+                }
+
+                return mapTransform;
+            }
+        }
+
+        private void OnViewportChanged(object sender, ViewportChangedEventArgs e)
+        {
+            UpdateMapTransform(Location);
+        }
+
+        private void UpdateMapTransform(Location location)
+        {
+            if (mapTransform != null && parentMap != null && location != null)
+            {
+                mapTransform.Matrix = parentMap.GetMapTransform(location);
+            }
+        }
+    }
+}