ClemensFischer/XAML-Map-Control
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Image loading with cancellation

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ClemensFischer 2025-08-19 23:20:11 +02:00
parent 81eabef257
commit 69bba213f0
13 changed files with 103 additions and 88 deletions
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47
MapControl/Shared/TileImageLoader.cs
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@ -8,6 +8,8 @@ using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Threading.Tasks;
using System.Threading;
#if WPF
using System.Windows.Media;
#elif UWP
@ -24,6 +26,8 @@ namespace MapControl
public interface ITileImageLoader
{
Task LoadTilesAsync(IEnumerable<Tile> tiles, TileSource tileSource, string cacheName, IProgress<double> progress);
void CancelLoadTiles();
}
public partial class TileImageLoader : ITileImageLoader
@ -71,17 +75,26 @@ namespace MapControl
private ConcurrentStack<Tile> pendingTiles = new ConcurrentStack<Tile>();
private CancellationTokenSource cancellationTokenSource;
public void CancelLoadTiles()
{
pendingTiles.Clear();
if (cancellationTokenSource != null)
{
cancellationTokenSource.Cancel();
cancellationTokenSource = null;
}
}
/// <summary>
/// Loads all pending tiles from the tiles collection. Tile image caching is enabled when the Cache
/// property is non-null and tileSource.UriFormat starts with "http" and cacheName is a non-empty string.
/// property is not null and tileSource.UriFormat starts with "http" and cacheName is a non-empty string.
/// </summary>
public async Task LoadTilesAsync(IEnumerable<Tile> tiles, TileSource tileSource, string cacheName, IProgress<double> progress)
{
if (!pendingTiles.IsEmpty)
{
pendingTiles.Clear();
progress?.Report(1d);
}
CancelLoadTiles();
if (tileSource != null && tiles != null && (tiles = tiles.Where(tile => tile.IsPending)).Any())
{
@ -102,22 +115,24 @@ namespace MapControl
var tasks = new Task[taskCount];
var tileStack = pendingTiles; // pendingTiles member may change while tasks are running
cancellationTokenSource = new CancellationTokenSource();
async Task LoadTilesFromQueueAsync()
{
while (tileStack.TryPop(out var tile)) // use captured tileStack variable in local function
{
tile.IsPending = false;
progress?.Report((double)(tileCount - tileStack.Count) / tileCount);
try
{
await LoadTileImage(tile, tileSource, cacheName).ConfigureAwait(false);
await LoadTileImage(tile, tileSource, cacheName, cancellationTokenSource.Token).ConfigureAwait(false);
}
catch (Exception ex)
{
Logger?.LogError(ex, "Failed loading tile image {zoom}/{column}/{row}", tile.ZoomLevel, tile.Column, tile.Row);
}
progress?.Report((double)(tileCount - tileStack.Count) / tileCount);
}
}
@ -131,14 +146,14 @@ namespace MapControl
}
}
private static async Task LoadTileImage(Tile tile, TileSource tileSource, string cacheName)
private static async Task LoadTileImage(Tile tile, TileSource tileSource, string cacheName, CancellationToken cancellationToken)
{
// Pass tileSource.LoadImageAsync calls to platform-specific method
// LoadTileImage(Tile, Func<Task<ImageSource>>) for execution on the UI thread in WinUI and UWP.
if (string.IsNullOrEmpty(cacheName))
{
Task<ImageSource> LoadImage() => tileSource.LoadImageAsync(tile.Column, tile.Row, tile.ZoomLevel);
Task<ImageSource> LoadImage() => tileSource.LoadImageAsync(tile.Column, tile.Row, tile.ZoomLevel, cancellationToken);
await LoadTileImage(tile, LoadImage).ConfigureAwait(false);
}
@ -148,7 +163,7 @@ namespace MapControl
if (uri != null)
{
var buffer = await LoadCachedBuffer(tile, uri, cacheName).ConfigureAwait(false);
var buffer = await LoadCachedBuffer(tile, uri, cacheName, cancellationToken).ConfigureAwait(false);
if (buffer != null && buffer.Length > 0)
{
@ -160,7 +175,7 @@ namespace MapControl
}
}
private static async Task<byte[]> LoadCachedBuffer(Tile tile, Uri uri, string cacheName)
private static async Task<byte[]> LoadCachedBuffer(Tile tile, Uri uri, string cacheName, CancellationToken cancellationToken)
{
byte[] buffer = null;
@ -175,7 +190,7 @@ namespace MapControl
try
{
buffer = await Cache.GetAsync(cacheKey).ConfigureAwait(false);
buffer = await Cache.GetAsync(cacheKey, cancellationToken).ConfigureAwait(false);
}
catch (Exception ex)
{
@ -184,7 +199,7 @@ namespace MapControl
if (buffer == null)
{
var response = await ImageLoader.GetHttpResponseAsync(uri).ConfigureAwait(false);
var response = await ImageLoader.GetHttpResponseAsync(uri, null, cancellationToken).ConfigureAwait(false);
if (response != null)
{
@ -201,7 +216,7 @@ namespace MapControl
: response.MaxAge.Value
};
await Cache.SetAsync(cacheKey, buffer, options).ConfigureAwait(false);
await Cache.SetAsync(cacheKey, buffer, options, cancellationToken).ConfigureAwait(false);
}
catch (Exception ex)
{