fix: [22091] Fixed PopupFlyoutBase.Opening not passing CancelEventArgs

Author: David M. Fritz

samples/ControlCatalog/Pages/ContextFlyoutPage.xaml.cs

@@ -32,12 +32,9 @@ private void ContextFlyoutPage_Closing(object? sender, CancelEventArgs e)
             e.Cancel = CancelCloseCheckBox?.IsChecked ?? false;
         }
 
-        private void ContextFlyoutPage_Opening(object? sender, EventArgs e)
+        private void ContextFlyoutPage_Opening(object? sender, CancelEventArgs e)
         {
-            if (e is CancelEventArgs cancelArgs)
-            {
-                cancelArgs.Cancel = CancelCloseCheckBox?.IsChecked ?? false;
-            }
+            e.Cancel = CancelCloseCheckBox?.IsChecked ?? false;
         }
 
         private void CloseFlyout(object? sender, RoutedEventArgs e)

src/Avalonia.Controls/Flyouts/PopupFlyoutBase.cs

@@ -178,7 +178,7 @@ event Action<IPopupHost?>? IPopupHostProvider.PopupHostChanged
         }
 
         public event EventHandler<CancelEventArgs>? Closing;
-        public event EventHandler? Opening;
+        public event EventHandler<CancelEventArgs>? Opening;
 
         /// <summary>
         /// Pre-registers a control as the default placement target for this flyout.

tests/Avalonia.Controls.UnitTests/FlyoutTests.cs

@@ -77,10 +77,7 @@ public void Opening_Is_Cancellable()
                 f.Opening += (s, e) =>
                 {
                     tracker++;
-                    if (e is CancelEventArgs cancelEventArgs)
-                    {
-                        cancelEventArgs.Cancel = true;
-                    }
+                    e.Cancel = true;
                 };
                 f.ShowAt(window);
 
@@ -834,8 +831,7 @@ public void IsOpen_SetTrue_Cancelled_Opening_Reverts_To_False()
 
                 flyout.Opening += (s, e) =>
                 {
-                    if (e is CancelEventArgs cancelArgs)
-                        cancelArgs.Cancel = true;
+                    e.Cancel = true;
                 };
 
                 flyout.IsOpen = true;