XAML-Map-Control/MapControl/Shared/MapPath.cs

#if WPF
using System.Windows;
using System.Windows.Media;
#elif UWP
using Windows.UI.Xaml;
using Windows.UI.Xaml.Media;
#elif WINUI
using Microsoft.UI.Xaml;
using Microsoft.UI.Xaml.Media;
#elif AVALONIA
using Avalonia;
using Avalonia.Media;
#endif

namespace MapControl;

/// <summary>
/// A path element with a Data property that holds a Geometry in view coordinates or
/// projected map coordinates that are relative to an origin Location.
/// </summary>
public partial class MapPath : IMapElement
{
    public static readonly DependencyProperty LocationProperty =
        DependencyPropertyHelper.Register<MapPath, Location>(nameof(Location), null,
            (path, oldValue, newValue) => path.UpdateData());

    /// <summary>
    /// Gets or sets a Location that is either used as
    /// - the origin point of a geometry specified in projected map coordinates (meters) or
    /// - as an optional anchor point to constrain the view position of MapPaths with
    ///   multiple Locations (like MapPolyline or MapPolygon) to the visible map viewport,
    ///   as done for elements where the MapPanel.Location property is set.
    /// </summary>
    public Location Location
    {
        get => (Location)GetValue(LocationProperty);
        set => SetValue(LocationProperty, value);
    }

    /// <summary>
    /// Implements IMapElement.ParentMap.
    /// </summary>
    public MapBase ParentMap
    {
        get;
        set
        {
            if (field != null)
            {
                field.ViewportChanged -= OnViewportChanged;
            }

            field = value;

            if (field != null)
            {
                field.ViewportChanged += OnViewportChanged;
            }

            UpdateData();
        }
    }

    private void OnViewportChanged(object sender, ViewportChangedEventArgs e)
    {
        UpdateData();
    }

    protected void SetDataTransform(Matrix matrix)
    {
        if (Data.Transform is MatrixTransform transform
#if WPF
            && !transform.IsFrozen
#endif
            )
        {
            transform.Matrix = matrix;
        }
        else
        {
            Data.Transform = new MatrixTransform { Matrix = matrix };
        }
    }

    protected virtual void UpdateData()
    {
        if (Data != null && ParentMap != null && Location != null)
        {
            SetDataTransform(ParentMap.GetMapToViewTransform(Location));
        }

        MapPanel.SetLocation(this, Location);
    }

    protected Point LocationToMap(Location location, double longitudeOffset)
    {
        var point = ParentMap.MapProjection.LocationToMap(location.Latitude, location.Longitude + longitudeOffset);

        if (point.Y == double.PositiveInfinity)
        {
            point = new Point(point.X, 1e9);
        }
        else if (point.Y == double.NegativeInfinity)
        {
            point = new Point(point.X, -1e9);
        }

        return point;
    }

    protected Point LocationToView(Location location, double longitudeOffset)
    {
        return ParentMap.ViewTransform.MapToView(LocationToMap(location, longitudeOffset));
    }
}