170 lines
8.7 KiB
C#
170 lines
8.7 KiB
C#
using System.Diagnostics;
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using System.IO;
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using System.Net.Http;
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using System.Windows.Controls;
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using System.Windows.Data;
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using System.Windows.Media.Imaging;
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using System.Windows.Media;
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using System.Windows;
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namespace Main.Test;
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/// <summary>配套图片列：自动使用所属 StyledDataGrid 的拖动暂停和图片缓存能力。</summary>
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public class StyledDataGridImageColumn : DataGridBoundColumn
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{
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private static readonly Style DefaultImageStyle = CreateDefaultStyle();
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/// <summary>可选的逐行占位图；未设置时显示空白。</summary>
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public BindingBase? PlaceholderBinding { get; set; }
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protected override FrameworkElement GenerateElement(DataGridCell cell, object dataItem)
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{
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var image = new NetworkThumbnail { Style = ElementStyle ?? DefaultImageStyle };
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if (Binding != null) BindingOperations.SetBinding(image, NetworkThumbnail.UrlProperty, Binding);
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if (PlaceholderBinding != null)
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BindingOperations.SetBinding(image, NetworkThumbnail.PlaceholderProperty, PlaceholderBinding);
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return image;
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}
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protected override FrameworkElement GenerateEditingElement(DataGridCell cell, object dataItem) => GenerateElement(cell, dataItem);
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private static Style CreateDefaultStyle()
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{
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var style = new Style(typeof(NetworkThumbnail));
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style.Setters.Add(new Setter(FrameworkElement.WidthProperty, 58d));
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style.Setters.Add(new Setter(FrameworkElement.HeightProperty, 58d));
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style.Setters.Add(new Setter(System.Windows.Controls.Image.StretchProperty, Stretch.Uniform));
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style.Seal(); return style;
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}
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}
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/// <summary>仅为已生成的可见单元格加载图片；回收时取消，避免旧图片覆盖新行。</summary>
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public sealed class NetworkThumbnail : Image
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{
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public static readonly DependencyProperty CacheEnabledProperty = DependencyProperty.RegisterAttached("CacheEnabled", typeof(bool), typeof(NetworkThumbnail), new FrameworkPropertyMetadata(true, FrameworkPropertyMetadataOptions.Inherits, Changed));
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public static bool GetCacheEnabled(DependencyObject target) => (bool)target.GetValue(CacheEnabledProperty);
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public static void SetCacheEnabled(DependencyObject target, bool value) => target.SetValue(CacheEnabledProperty, value);
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public static readonly DependencyProperty IsLoadingSuspendedProperty = DependencyProperty.RegisterAttached(
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"IsLoadingSuspended", typeof(bool), typeof(NetworkThumbnail),
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new FrameworkPropertyMetadata(false, FrameworkPropertyMetadataOptions.Inherits, SuspensionChanged));
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public static bool GetIsLoadingSuspended(DependencyObject target) => (bool)target.GetValue(IsLoadingSuspendedProperty);
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public static void SetIsLoadingSuspended(DependencyObject target, bool value) => target.SetValue(IsLoadingSuspendedProperty, value);
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private static void SuspensionChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
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{
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if (d is not NetworkThumbnail image) return;
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image.CancelLoading();
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image.Source = null;
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if (!(bool)e.NewValue) image.QueueRefresh();
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}
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public static readonly DependencyProperty UrlProperty = DependencyProperty.Register(nameof(Url), typeof(string), typeof(NetworkThumbnail), new PropertyMetadata(null, Changed));
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public static readonly DependencyProperty PlaceholderProperty = DependencyProperty.Register(nameof(Placeholder), typeof(ImageSource), typeof(NetworkThumbnail), new PropertyMetadata(null, Changed));
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public string? Url { get => (string?)GetValue(UrlProperty); set => SetValue(UrlProperty, value); }
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public ImageSource? Placeholder { get => (ImageSource?)GetValue(PlaceholderProperty); set => SetValue(PlaceholderProperty, value); }
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private CancellationTokenSource? loading;
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private bool refreshPending;
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public NetworkThumbnail()
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{
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Loaded += (_, _) => QueueRefresh();
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Unloaded += (_, _) => CancelLoading();
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}
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private static void Changed(DependencyObject d, DependencyPropertyChangedEventArgs e)
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{
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if (d is not NetworkThumbnail image) return;
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image.CancelLoading();
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image.Source = GetIsLoadingSuspended(image) ? null : image.Placeholder;
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// 回收行时多个绑定会依次变更，等本轮绑定完成后只加载一次新 URL。
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image.QueueRefresh();
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}
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private void QueueRefresh()
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{
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if (!IsLoaded || refreshPending) return;
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refreshPending = true;
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Dispatcher.BeginInvoke(System.Windows.Threading.DispatcherPriority.Loaded, new Action(() =>
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{
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refreshPending = false;
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if (IsLoaded) StartLoading();
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}));
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}
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private void CancelLoading()
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{
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loading?.Cancel(); loading?.Dispose(); loading = null;
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}
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private async void StartLoading()
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{
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CancelLoading(); ToolTip = null;
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if (GetIsLoadingSuspended(this)) { Source = null; return; }
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Source = Placeholder;
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if (string.IsNullOrWhiteSpace(Url)) return;
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var request = new CancellationTokenSource(); loading = request;
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var token = request.Token;
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try
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{
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var bitmap = await ThumbnailLoader.LoadAsync(Url, GetCacheEnabled(this), token);
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if (!token.IsCancellationRequested && ReferenceEquals(loading, request)) Source = bitmap;
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}
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catch (OperationCanceledException) when (token.IsCancellationRequested) { }
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catch (Exception ex)
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{
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if (!token.IsCancellationRequested && ReferenceEquals(loading, request)) ToolTip = $"图片加载失败：{ex.Message}";
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}
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}
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}
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internal static class ThumbnailLoader
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{
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private static readonly HttpClient Client = new() { Timeout = TimeSpan.FromSeconds(12) };
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private static readonly SemaphoreSlim Slots = new(4);
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private static readonly object CacheLock = new();
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private static readonly Dictionary<string, BitmapSource> Cache = new();
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private static readonly Queue<string> CacheOrder = new();
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private static long started, succeeded, failed, canceled, cacheHits, bytes, totalTicks;
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private static int active, pending;
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public static int Pending => Volatile.Read(ref pending);
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public static string Statistics => $"网络图片：请求 {Interlocked.Read(ref started)} / 成功 {Interlocked.Read(ref succeeded)} / 失败 {Interlocked.Read(ref failed)} / 取消 {Interlocked.Read(ref canceled)} / 缓存命中 {Interlocked.Read(ref cacheHits)} | 活跃 {Volatile.Read(ref active)}，待完成 {Pending} | 下载 {Interlocked.Read(ref bytes) / 1024d:N0} KB | 成功平均 {AverageMilliseconds:N0} ms";
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private static double AverageMilliseconds => Interlocked.Read(ref succeeded) == 0 ? 0 : Interlocked.Read(ref totalTicks) * 1000d / Stopwatch.Frequency / Interlocked.Read(ref succeeded);
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public static async Task<BitmapSource> LoadAsync(string url, bool cacheEnabled, CancellationToken token)
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{
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var cacheKey = url;
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lock (CacheLock)
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if (cacheEnabled && Cache.TryGetValue(cacheKey, out var cached)) { Interlocked.Increment(ref cacheHits); return cached; }
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Interlocked.Increment(ref pending);
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var acquired = false;
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try
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{
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await Slots.WaitAsync(token).ConfigureAwait(false); acquired = true;
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Interlocked.Increment(ref active); Interlocked.Increment(ref started);
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var watch = Stopwatch.StartNew();
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var data = await Client.GetByteArrayAsync(url, token).ConfigureAwait(false);
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Interlocked.Add(ref bytes, data.Length);
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var bitmap = await Task.Run(() =>
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{
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token.ThrowIfCancellationRequested();
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using var stream = new MemoryStream(data);
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var image = new BitmapImage(); image.BeginInit(); image.CacheOption = BitmapCacheOption.OnLoad;
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image.DecodePixelWidth = 72; image.StreamSource = stream; image.EndInit(); image.Freeze();
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return image;
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}, token).ConfigureAwait(false);
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token.ThrowIfCancellationRequested();
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lock (CacheLock)
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{
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if (cacheEnabled && !Cache.ContainsKey(cacheKey))
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{
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if (Cache.Count >= 128) Cache.Remove(CacheOrder.Dequeue());
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Cache.Add(cacheKey, bitmap); CacheOrder.Enqueue(cacheKey);
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}
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}
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Interlocked.Increment(ref succeeded); Interlocked.Add(ref totalTicks, watch.ElapsedTicks);
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return bitmap;
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}
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catch (OperationCanceledException) when (token.IsCancellationRequested) { Interlocked.Increment(ref canceled); throw; }
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catch { Interlocked.Increment(ref failed); throw; }
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finally
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{
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if (acquired) { Interlocked.Decrement(ref active); Slots.Release(); }
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Interlocked.Decrement(ref pending);
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}
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}
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}
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