DialogHost: don't wait 300 ms to focus when transitions are disabled, and keep focus already inside the dialog

src/MaterialDesignThemes.Wpf/DialogHost.cs

@@ -431,17 +431,28 @@ private static void IsOpenPropertyChangedCallback(DependencyObject dependencyObj
         dialogHost.DialogOpenedCallback?.Invoke(dialogHost, dialogOpenedEventArgs);
         dialogHost._asyncShowOpenedEventHandler?.Invoke(dialogHost, dialogOpenedEventArgs);
 
-        //https://github.com/MaterialDesignInXAML/MaterialDesignInXamlToolkit/issues/187
-        //totally not happy about this, but on immediate validation we can get some weird looking stuff...give WPF a kick to refresh...
-        Task.Delay(300).ContinueWith(t => dialogHost.Dispatcher.BeginInvoke(DispatcherPriority.Background, new Action(() =>
+        if (TransitionAssist.GetDisableTransitions(dialogHost))
         {
-            CommandManager.InvalidateRequerySuggested();
+            //Without a transition there is nothing to wait for: the dialog is complete on the next frame,
+            //and waiting would send the first keys typed into it to the controls behind the dialog
+            dialogHost.Dispatcher.BeginInvoke(DispatcherPriority.Background, new Action(OnDialogShown));
+        }
+        else
+        {
+            //https://github.com/MaterialDesignInXAML/MaterialDesignInXamlToolkit/issues/187
+            //totally not happy about this, but on immediate validation we can get some weird looking stuff...give WPF a kick to refresh...
             //Delay focusing the popup until after the animation has some time, Issue #2912
-            UIElement? child = dialogHost.FocusPopup();
+            Task.Delay(300).ContinueWith(t => dialogHost.Dispatcher.BeginInvoke(DispatcherPriority.Background, new Action(OnDialogShown)));
+        }
 
-            child?.InvalidateVisual();
+        void OnDialogShown()
+        {
+            CommandManager.InvalidateRequerySuggested();
+            //If the content has already moved the focus into the dialog (for example when it loaded), leave it there
+            UIElement? child = dialogHost.FocusPopup(keepFocusWithin: true);
 
-        })));
+            child?.InvalidateVisual();
+        }
     }
 
     /// <summary>
@@ -891,13 +902,16 @@ internal void InternalClose(object? parameter)
     /// <summary>
     /// Attempts to focus the content of a popup.
     /// </summary>
+    /// <param name="keepFocusWithin">When true, the focus is left alone if it is already inside the popup content.</param>
     /// <returns>The popup content.</returns>
-    internal UIElement? FocusPopup()
+    internal UIElement? FocusPopup(bool keepFocusWithin = false)
     {
         var child = _popup?.Child ?? _popupContentControl;
         if (child is null) return null;
 
         CommandManager.InvalidateRequerySuggested();
+        if (keepFocusWithin && child.IsKeyboardFocusWithin) return child;
+
         var focusable = child.VisualDepthFirstTraversal().OfType<UIElement>().FirstOrDefault(ui => ui.Focusable);
         if (focusable is null) return null;
 

tests/MaterialDesignThemes.UITests/WPF/DialogHosts/DialogHostTests.cs

@@ -574,12 +574,99 @@ public async Task DialogHost_TrapsFocusInsidePopup_WhenTabbing(string dialogHost
         await Wait.For(async () => await Assert.That(await textBoxOne.GetIsFocused()).IsTrue());
 
         recorder.Success();
+    }
+
+    [Test]
+    [Description("Issue 4097")]
+    [Arguments("")]
+    [Arguments("MaterialDesignEmbeddedDialogHost")]
+    public async Task DialogHost_WithTransitionsDisabled_FocusesDialogWithoutWaitingForTransition(string dialogHostStyle)
+    {
+        await using var recorder = new TestRecorder(App);
+
+        var dialogHost = await LoadXaml<DialogHost>("""
+    <materialDesign:DialogHost materialDesign:TransitionAssist.DisableTransitions="True">
+        <materialDesign:DialogHost.DialogContent>
+            <TextBox x:Name="DialogTextBox" Width="200" />
+        </materialDesign:DialogHost.DialogContent>
+    </materialDesign:DialogHost>
+    """);
+
+        if (!string.IsNullOrEmpty(dialogHostStyle))
+        {
+            await dialogHost.RemoteExecute(SetDialogHostStyle, dialogHostStyle);
+        }
+
+        string? focusedElementName = await dialogHost.RemoteExecute(OpenAndGetFocusedElementName);
+
+        await Assert.That(focusedElementName).IsEqualTo("DialogTextBox");
+
+        recorder.Success();
+
+        static async Task<string?> OpenAndGetFocusedElementName(DialogHost dialogHost)
+        {
+            // Opened and closed once first, so the check below does not include loading the templates
+            dialogHost.IsOpen = true;
+            await Task.Delay(500);
+            dialogHost.IsOpen = false;
+            await Task.Delay(500);
+
+            dialogHost.IsOpen = true;
+            // Well within the 300 ms the dialog host waits for when there is a transition
+            await Task.Delay(100);
+            return (Keyboard.FocusedElement as FrameworkElement)?.Name;
+        }
+    }
+
+    [Test]
+    [Description("Issue 4097")]
+    [Arguments("")]
+    [Arguments("MaterialDesignEmbeddedDialogHost")]
+    public async Task DialogHost_FocusMovedInsideDialogWhileOpening_IsKept(string dialogHostStyle)
+    {
+        await using var recorder = new TestRecorder(App);
 
-        static object SetDialogHostStyle(DialogHost dialogHost, string styleName)
+        var dialogHost = await LoadXaml<DialogHost>("""
+    <materialDesign:DialogHost>
+        <materialDesign:DialogHost.DialogContent>
+            <StackPanel Width="300">
+                <TextBox x:Name="TextBoxOne" />
+                <TextBox x:Name="TextBoxTwo" />
+            </StackPanel>
+        </materialDesign:DialogHost.DialogContent>
+    </materialDesign:DialogHost>
+    """);
+
+        if (!string.IsNullOrEmpty(dialogHostStyle))
         {
-            var style = (Style)dialogHost.FindResource(styleName);
-            dialogHost.Style = style;
-            return null!;
+            await dialogHost.RemoteExecute(SetDialogHostStyle, dialogHostStyle);
+        }
+
+        string? focusedElementName = await dialogHost.RemoteExecute(OpenFocusSecondTextBoxAndWait);
+
+        await Assert.That(focusedElementName).IsEqualTo("TextBoxTwo");
+
+        recorder.Success();
+
+        static async Task<string?> OpenFocusSecondTextBoxAndWait(DialogHost dialogHost)
+        {
+            dialogHost.IsOpen = true;
+            await Task.Delay(50);
+
+            // As when the user clicks the second TextBox right after the dialog appears
+            var content = (Panel)dialogHost.DialogContent!;
+            Keyboard.Focus(content.Children[1]);
+
+            // Past the delay after which the dialog host moves the focus into the dialog
+            await Task.Delay(800);
+            return (Keyboard.FocusedElement as FrameworkElement)?.Name;
         }
     }
+
+    private static object SetDialogHostStyle(DialogHost dialogHost, string styleName)
+    {
+        var style = (Style)dialogHost.FindResource(styleName);
+        dialogHost.Style = style;
+        return null!;
+    }
 }