fix: side-by-side diff scroll desync on hidden-tab rebuild and tab switch

Author: JC-Chung

src/Views/TextDiffView.axaml.cs

@@ -8,6 +8,7 @@
 
 using Avalonia;
 using Avalonia.Controls;
+using Avalonia.Controls.Primitives;
 using Avalonia.Data;
 using Avalonia.Input;
 using Avalonia.Interactivity;
@@ -1010,16 +1011,23 @@ public class CombinedTextDiffPresenter : ThemedTextDiffPresenter
             TextArea.LeftMargins.Add(new LineModifyTypeMargin());
         }
 
+        protected override void OnApplyTemplate(TemplateAppliedEventArgs e)
+        {
+            base.OnApplyTemplate(e);
+
+            _scrollViewer = e.NameScope.Find<ScrollViewer>("PART_ScrollViewer");
+            if (_scrollViewer != null)
+                _scrollViewer.Bind(ScrollViewer.OffsetProperty, new Binding("ScrollOffset", BindingMode.TwoWay));
+        }
+
         protected override void OnLoaded(RoutedEventArgs e)
         {
             base.OnLoaded(e);
 
-            _scrollViewer = this.FindDescendantOfType<ScrollViewer>();
+            ApplyTemplate();
+
             if (_scrollViewer != null)
-            {
-                _scrollViewer.Bind(ScrollViewer.OffsetProperty, new Binding("ScrollOffset", BindingMode.TwoWay));
                 _scrollViewer.ScrollChanged += OnTextViewScrollChanged;
-            }
         }
 
         protected override void OnUnloaded(RoutedEventArgs e)
@@ -1195,25 +1203,29 @@ protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs chang
             }
         }
 
+        protected override void OnApplyTemplate(TemplateAppliedEventArgs e)
+        {
+            base.OnApplyTemplate(e);
+
+            _scrollViewer = e.NameScope.Find<ScrollViewer>("PART_ScrollViewer");
+            if (_scrollViewer != null)
+                _scrollViewer.Bind(ScrollViewer.OffsetProperty, new Binding("ScrollOffset", BindingMode.OneWay));
+        }
+
         protected override void OnLoaded(RoutedEventArgs e)
         {
             base.OnLoaded(e);
 
-            _scrollViewer = this.FindDescendantOfType<ScrollViewer>();
+            ApplyTemplate();
+
             if (_scrollViewer != null)
-            {
                 _scrollViewer.ScrollChanged += OnTextViewScrollChanged;
-                _scrollViewer.Bind(ScrollViewer.OffsetProperty, new Binding("ScrollOffset", BindingMode.OneWay));
-            }
         }
 
         protected override void OnUnloaded(RoutedEventArgs e)
         {
             if (_scrollViewer != null)
-            {
                 _scrollViewer.ScrollChanged -= OnTextViewScrollChanged;
-                _scrollViewer = null;
-            }
 
             base.OnUnloaded(e);
             GC.Collect();