Speedup contextmenu by caching

src/RepoM.App/Controls/AcrylicMenuItem.cs

@@ -8,6 +8,7 @@ namespace RepoM.App.Controls;
 
 public class AcrylicMenuItem : MenuItem
 {
+    private RoutedEventHandler? _evt;
     private static readonly Brush _solidColorBrush = new SolidColorBrush(Color.FromArgb(80, 0, 0, 0));
 
     protected override void OnSubmenuOpened(RoutedEventArgs e)
@@ -31,7 +32,7 @@ private void BlurSubMenu()
             return;
         }
 
-        DependencyObject parent = container;
+        DependencyObject? parent = container;
         var borderIndex = 0;
 
         while (parent != null)
@@ -51,4 +52,22 @@ private void BlurSubMenu()
 
         AcrylicHelper.EnableBlur(container);
     }
+
+    public void SetClick(RoutedEventHandler routedEventHandler)
+    {
+        ClearClick();
+        Click += routedEventHandler;
+        _evt = routedEventHandler;
+    }
+
+    public void ClearClick()
+    {
+        if (_evt == null)
+        {
+            return;
+        }
+
+        Click -= _evt;
+        _evt = null;
+    }
 }

src/RepoM.App/MainWindow.xaml.cs

@@ -51,6 +51,17 @@
     private readonly IUserMenuActionMenuFactory _userMenuActionFactory;
     private readonly IAppDataPathProvider _appDataPathProvider;
 
+    private readonly List<Separator> _separators = new();
+    private readonly List<AcrylicMenuItem> _menuItems = new();
+    private int _separatorIndex = 0;
+    private int _menuItemIndex = 0;
+
+    private readonly AcrylicMenuItem _loadingMenuItem = new()
+        {
+            Header = "Loading ..",
+            IsEnabled = true,
+        };
+
     public MainWindow(
         IRepositoryInformationAggregator aggregator,
         IRepositoryMonitor repositoryMonitor,
@@ -248,6 +259,7 @@
 
     private async Task<bool> LstRepositoriesContextMenuOpeningAsync(ContextMenu ctxMenu)
     {
+        ResetIndex();
         if (lstRepositories.SelectedItem is not RepositoryViewModel vm)
         {
             return false;
@@ -267,19 +279,15 @@
         // }
 
         ctxMenu.Items.Clear();
-        ctxMenu.Items.Add(new AcrylicMenuItem
-            {
-                Header = "Loading ..",
-                IsEnabled = true,
-            });
+        ctxMenu.Items.Add(_loadingMenuItem);
 
         await foreach (UserInterfaceRepositoryActionBase action in _userMenuActionFactory.CreateMenuAsync(vm.Repository).ConfigureAwait(true))
         {
             if (action is UserInterfaceSeparatorRepositoryAction)
             {
                 if (items.Count > 0 && items[^1] is not Separator)
                 {
-                    items.Add(new Separator());
+                    items.Add(GetSeparator());
                 }
             }
             else if (action is DeferredSubActionsUserInterfaceRepositoryAction or UserInterfaceRepositoryAction)
@@ -496,7 +504,7 @@
     {
         if (action is RepositorySeparatorAction)
         {
-            return new Separator();
+            return GetSeparator();
         }
 
         if (action is not RepositoryAction repositoryAction)
@@ -525,12 +533,10 @@
                 }
             };
 
-        var item = new AcrylicMenuItem
-            {
-                Header = repositoryAction.Name,
-                IsEnabled = repositoryAction.CanExecute,
-            };
-        item.Click += new RoutedEventHandler(clickAction);
+        AcrylicMenuItem item = GetMenuItem();
+        item.Header = repositoryAction.Name;
+        item.IsEnabled = repositoryAction.CanExecute;
+        item.SetClick(new RoutedEventHandler(clickAction));
 
         // this is a deferred submenu. We want to make sure that the context menu can pop up
         // fast, while submenus are not evaluated yet. We don't want to make the context menu
@@ -577,7 +583,7 @@
     {
         if (action is UserInterfaceSeparatorRepositoryAction)
         {
-            return new Separator();
+            return GetSeparator();
         }
 
         // UserInterfaceRepositoryAction
@@ -609,12 +615,10 @@
             }
         };
 
-        var item = new AcrylicMenuItem
-        {
-            Header = repositoryAction.Name,
-            IsEnabled = repositoryAction.CanExecute,
-        };
-        item.Click += new RoutedEventHandler(clickAction);
+        AcrylicMenuItem item = GetMenuItem();
+        item.Header = repositoryAction.Name;
+        item.IsEnabled = repositoryAction.CanExecute;
+        item.SetClick(new RoutedEventHandler(clickAction));
 
         // this is a deferred submenu. We want to make sure that the context menu can pop up
         // fast, while submenus are not evaluated yet. We don't want to make the context menu
@@ -665,7 +669,7 @@
             // menu item. this item gets removed when the real subitems are created
             item.Items.Add("Loading..");
 
             async void SelfDetachingEventHandler1(object _, RoutedEventArgs evtArgs)
             {
                 item.SubmenuOpened -= SelfDetachingEventHandler1;
                 item.Items.Clear();
@@ -853,6 +857,35 @@
         var item = (ListBoxItem)lstRepositories.ItemContainerGenerator.ContainerFromIndex(0);
         item?.Focus();
     }
+
+    private void ResetIndex()
+    {
+        _separatorIndex = 0;
+        _menuItemIndex = 0;
+    }
+
+    private Separator GetSeparator()
+    {
+        while (_separatorIndex >= _separators.Count)
+        {
+            _separators.Add(new Separator());
+        }
+
+        return _separators[_separatorIndex++];
+    }
+
+    private AcrylicMenuItem GetMenuItem()
+    {
+        while (_menuItemIndex >= _menuItems.Count)
+        {
+            _menuItems.Add(new AcrylicMenuItem());
+        }
+
+        AcrylicMenuItem result = _menuItems[_menuItemIndex++];
+        result.Items.Clear();
+        result.ClearClick();
+        return result;
+    }
 
     public bool IsShown => Visibility == Visibility.Visible && IsActive;
 }