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

// XAML Map Control - https://github.com/ClemensFischer/XAML-Map-Control
// © 2022 Clemens Fischer
// Licensed under the Microsoft Public License (Ms-PL)

using System;
using System.Collections.Generic;
using System.Threading.Tasks;
#if WINUI
using Microsoft.UI.Xaml;
using Microsoft.UI.Xaml.Controls;
using Microsoft.UI.Xaml.Media;
using DispatcherTimer = Microsoft.UI.Dispatching.DispatcherQueueTimer;
#elif UWP
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Media;
#else
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;
using System.Windows.Threading;
#endif

namespace MapControl
{
    public interface ITileImageLoader
    {
        IProgress<double> Progress { get; set; }

        TileSource TileSource { get; }

        Task LoadTiles(IEnumerable<Tile> tiles, TileSource tileSource, string cacheName);
    }

    public abstract class MapTileLayerBase : Panel, IMapLayer
    {
        public static readonly DependencyProperty TileSourceProperty = DependencyProperty.Register(
            nameof(TileSource), typeof(TileSource), typeof(MapTileLayerBase),
            new PropertyMetadata(null, async (o, e) => await ((MapTileLayerBase)o).Update()));

        public static readonly DependencyProperty SourceNameProperty = DependencyProperty.Register(
            nameof(SourceName), typeof(string), typeof(MapTileLayerBase), new PropertyMetadata(null));

        public static readonly DependencyProperty DescriptionProperty = DependencyProperty.Register(
            nameof(Description), typeof(string), typeof(MapTileLayerBase), new PropertyMetadata(null));

        public static readonly DependencyProperty MaxBackgroundLevelsProperty = DependencyProperty.Register(
            nameof(MaxBackgroundLevels), typeof(int), typeof(MapTileLayerBase), new PropertyMetadata(5));

        public static readonly DependencyProperty UpdateIntervalProperty = DependencyProperty.Register(
            nameof(UpdateInterval), typeof(TimeSpan), typeof(MapTileLayerBase),
            new PropertyMetadata(TimeSpan.FromSeconds(0.2), (o, e) => ((MapTileLayerBase)o).updateTimer.Interval = (TimeSpan)e.NewValue));

        public static readonly DependencyProperty UpdateWhileViewportChangingProperty = DependencyProperty.Register(
            nameof(UpdateWhileViewportChanging), typeof(bool), typeof(MapTileLayerBase), new PropertyMetadata(true));

        public static readonly DependencyProperty MapBackgroundProperty = DependencyProperty.Register(
            nameof(MapBackground), typeof(Brush), typeof(MapTileLayerBase), new PropertyMetadata(null));

        public static readonly DependencyProperty MapForegroundProperty = DependencyProperty.Register(
            nameof(MapForeground), typeof(Brush), typeof(MapTileLayerBase), new PropertyMetadata(null));

        public static readonly DependencyProperty LoadingProgressProperty = DependencyProperty.Register(
            nameof(LoadingProgress), typeof(double), typeof(MapTileLayerBase), new PropertyMetadata(1d));

        private readonly DispatcherTimer updateTimer;
        private MapBase parentMap;

        protected MapTileLayerBase(ITileImageLoader tileImageLoader)
        {
            RenderTransform = new MatrixTransform();

            TileImageLoader = tileImageLoader;
            TileImageLoader.Progress = new Progress<double>(p => LoadingProgress = p);

            updateTimer = this.CreateTimer(UpdateInterval);
            updateTimer.Tick += async (s, e) => await Update();

#if WINUI || UWP
            MapPanel.InitMapElement(this);
#endif
        }

        public ITileImageLoader TileImageLoader { get; }

        /// <summary>
        /// Provides map tile URIs or images.
        /// </summary>
        public TileSource TileSource
        {
            get => (TileSource)GetValue(TileSourceProperty);
            set => SetValue(TileSourceProperty, value);
        }

        /// <summary>
        /// Name of the TileSource. Used as component of a tile cache key.
        /// </summary>
        public string SourceName
        {
            get => (string)GetValue(SourceNameProperty);
            set => SetValue(SourceNameProperty, value);
        }

        /// <summary>
        /// Description of the layer. Used to display copyright information on top of the map.
        /// </summary>
        public string Description
        {
            get => (string)GetValue(DescriptionProperty);
            set => SetValue(DescriptionProperty, value);
        }

        /// <summary>
        /// Maximum number of background tile levels. Default value is 5.
        /// Only effective in a MapTileLayer or WmtsTileLayer that is the MapLayer of its ParentMap.
        /// </summary>
        public int MaxBackgroundLevels
        {
            get => (int)GetValue(MaxBackgroundLevelsProperty);
            set => SetValue(MaxBackgroundLevelsProperty, value);
        }

        /// <summary>
        /// Minimum time interval between tile updates.
        /// </summary>
        public TimeSpan UpdateInterval
        {
            get => (TimeSpan)GetValue(UpdateIntervalProperty);
            set => SetValue(UpdateIntervalProperty, value);
        }

        /// <summary>
        /// Controls if tiles are updated while the viewport is still changing.
        /// </summary>
        public bool UpdateWhileViewportChanging
        {
            get => (bool)GetValue(UpdateWhileViewportChangingProperty);
            set => SetValue(UpdateWhileViewportChangingProperty, value);
        }

        /// <summary>
        /// Optional background brush. Sets MapBase.Background if not null and this layer is the base map layer.
        /// </summary>
        public Brush MapBackground
        {
            get => (Brush)GetValue(MapBackgroundProperty);
            set => SetValue(MapBackgroundProperty, value);
        }

        /// <summary>
        /// Optional foreground brush. Sets MapBase.Foreground if not null and this layer is the base map layer.
        /// </summary>
        public Brush MapForeground
        {
            get => (Brush)GetValue(MapForegroundProperty);
            set => SetValue(MapForegroundProperty, value);
        }

        /// <summary>
        /// Gets the progress of the TileImageLoader as a double value between 0 and 1.
        /// </summary>
        public double LoadingProgress
        {
            get => (double)GetValue(LoadingProgressProperty);
            private set => SetValue(LoadingProgressProperty, value);
        }

        public MapBase ParentMap
        {
            get => parentMap;
            set
            {
                if (parentMap != null)
                {
                    parentMap.ViewportChanged -= OnViewportChanged;
                }

                parentMap = value;

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

                updateTimer.Run();
            }
        }

        protected bool IsBaseMapLayer => parentMap != null && parentMap.Children.Count > 0 && parentMap.Children[0] == this;

        protected abstract void SetRenderTransform();

        protected abstract Task UpdateTileLayer();

        private Task Update()
        {
            updateTimer.Stop();

            return UpdateTileLayer();
        }

        private async void OnViewportChanged(object sender, ViewportChangedEventArgs e)
        {
            if (Children.Count == 0 || e.ProjectionChanged || Math.Abs(e.LongitudeOffset) > 180d)
            {
                await Update(); // update immediately when projection has changed or center has moved across 180° longitude
            }
            else
            {
                SetRenderTransform();

                updateTimer.Run(!UpdateWhileViewportChanging);
            }
        }
    }
}