XAML-Map-Control/MBTiles/Shared/MBTileLayer.cs

using Microsoft.Extensions.Logging;
using System;
using System.Threading.Tasks;
#if WPF
using System.Windows;
#elif UWP
using Windows.UI.Xaml;
#elif WINUI
using Microsoft.UI.Xaml;
#elif AVALONIA
using DependencyProperty = Avalonia.AvaloniaProperty;
#endif

namespace MapControl.MBTiles;

/// <summary>
/// MapTileLayer that uses an MBTiles SQLite Database. See https://wiki.openstreetmap.org/wiki/MBTiles.
/// </summary>
public class MBTileLayer : MapTileLayer
{
    private static ILogger Logger => field ??= ImageLoader.LoggerFactory?.CreateLogger<MBTileLayer>();

    public static readonly DependencyProperty FileProperty =
        DependencyPropertyHelper.Register<MBTileLayer, string>(nameof(File), null,
            async (layer, oldValue, newValue) => await layer.FilePropertyChanged(newValue));

    public string File
    {
        get => (string)GetValue(FileProperty);
        set => SetValue(FileProperty, value);
    }

    /// <summary>
    /// May be overridden to create a derived MBTileSource that handles other tile formats than png and jpg.
    /// </summary>
    protected virtual async Task<MBTileSource> CreateTileSourceAsync(string file)
    {
        var tileSource = new MBTileSource();

        await tileSource.OpenAsync(file);

        if (tileSource.Metadata.TryGetValue("format", out string format) && format != "png" && format != "jpg")
        {
            tileSource.Dispose();

            throw new NotSupportedException($"Tile image format {format} is not supported.");
        }

        return tileSource;
    }

    private async Task FilePropertyChanged(string file)
    {
        (TileSource as MBTileSource)?.Close();

        ClearValue(TileSourceProperty);
        ClearValue(SourceNameProperty);
        ClearValue(DescriptionProperty);
        ClearValue(MinZoomLevelProperty);
        ClearValue(MaxZoomLevelProperty);

        if (!string.IsNullOrEmpty(file))
        {
            try
            {
                var tileSource = await CreateTileSourceAsync(file);

                TileSource = tileSource;

                if (tileSource.Metadata.TryGetValue("name", out string value))
                {
                    SourceName = value;
                }

                if (tileSource.Metadata.TryGetValue("description", out value))
                {
                    Description = value;
                }

                if (tileSource.Metadata.TryGetValue("minzoom", out value) && int.TryParse(value, out int zoomLevel))
                {
                    MinZoomLevel = zoomLevel;
                }

                if (tileSource.Metadata.TryGetValue("maxzoom", out value) && int.TryParse(value, out zoomLevel))
                {
                    MaxZoomLevel = zoomLevel;
                }
            }
            catch (Exception ex)
            {
                Logger?.LogError(ex, "Invalid file: {file}", file);
            }
        }
    }
}