合并控件

Main.Test/StyledDataGrid.ImageLoading.cs

@@ -0,0 +1,100 @@
+using System.Windows;
+using System.Windows.Controls;
+using System.Windows.Controls.Primitives;
+using System.Windows.Media;
+using System.Windows.Threading;
+
+namespace Main.Test;
+
+public partial class StyledDataGrid
+{
+    private DispatcherTimer? imageResumeTimer;
+    private bool draggingScrollThumb;
+
+    private void InitializeImageLoadingPause()
+    {
+        imageResumeTimer = new DispatcherTimer(DispatcherPriority.Background, Dispatcher)
+        {
+            Interval = TimeSpan.FromMilliseconds(500)
+        };
+        imageResumeTimer.Tick += (_, _) =>
+        {
+            imageResumeTimer.Stop();
+            if (!draggingScrollThumb && IsLoaded) SetImageLoadingSuspended(false);
+        };
+        AddHandler(Thumb.DragStartedEvent, new DragStartedEventHandler(ScrollThumbDragStarted), true);
+        AddHandler(Thumb.DragCompletedEvent, new DragCompletedEventHandler(ScrollThumbDragCompleted), true);
+        AddHandler(ScrollViewer.ScrollChangedEvent, new ScrollChangedEventHandler(ImageScrollChanged), true);
+        Unloaded += (_, _) =>
+        {
+            imageResumeTimer.Stop(); draggingScrollThumb = false;
+            SetImageLoadingSuspended(true);
+        };
+        Loaded += (_, _) => { ApplyImageLoadingOptions(); SetImageLoadingSuspended(false); };
+        ApplyImageLoadingOptions();
+    }
+
+    private void SetImageLoadingSuspended(bool suspended)
+    {
+        SetValue(IsImageLoadingSuspendedPropertyKey, suspended);
+        NetworkThumbnail.SetIsLoadingSuspended(this, suspended);
+    }
+
+    private void ApplyImageLoadingOptions()
+    {
+        NetworkThumbnail.SetCacheEnabled(this, EnableImageCache);
+        if (imageResumeTimer == null) return;
+        if (!PauseImageLoadingWhileDragging)
+        {
+            imageResumeTimer.Stop(); draggingScrollThumb = false; SetImageLoadingSuspended(false);
+        }
+    }
+
+    private bool IsOwnScrollBar(DependencyObject? source)
+    {
+        var foundScrollBar = false;
+        for (var parent = source; parent != null; parent = VisualTreeHelper.GetParent(parent))
+        {
+            if (parent is ScrollBar) foundScrollBar = true;
+            if (parent is DataGrid) return ReferenceEquals(parent, this) && foundScrollBar;
+        }
+        return false;
+    }
+
+    private void ScrollThumbDragStarted(object sender, DragStartedEventArgs e)
+    {
+        if (!PauseImageLoadingWhileDragging || !IsOwnScrollBar(e.OriginalSource as DependencyObject)) return;
+        draggingScrollThumb = true;
+        imageResumeTimer!.Stop();
+        // 继承到可见图片及随后回收生成的新行，立即取消请求并清空图片。
+        SetImageLoadingSuspended(true);
+    }
+
+    private void ScrollThumbDragCompleted(object sender, DragCompletedEventArgs e)
+    {
+        if (!PauseImageLoadingWhileDragging || !IsOwnScrollBar(e.OriginalSource as DependencyObject)) return;
+        draggingScrollThumb = false;
+        RestartImageResumeTimer();
+    }
+
+    private void ImageScrollChanged(object sender, ScrollChangedEventArgs e)
+    {
+        if (!NetworkThumbnail.GetIsLoadingSuspended(this) || draggingScrollThumb ||
+            (e.VerticalChange == 0 && e.HorizontalChange == 0) ||
+            !IsOwnScrollViewer(e.OriginalSource as DependencyObject)) return;
+        RestartImageResumeTimer();
+    }
+
+    private bool IsOwnScrollViewer(DependencyObject? source)
+    {
+        for (var parent = source; parent != null; parent = VisualTreeHelper.GetParent(parent))
+            if (parent is DataGrid) return ReferenceEquals(parent, this);
+        return false;
+    }
+
+    private void RestartImageResumeTimer()
+    {
+        imageResumeTimer!.Stop();
+        imageResumeTimer.Start();
+    }
+}