fixes #3654 - NumericUpDown not focusable by pressing tab

src/MaterialDesignThemes.Wpf/UpDownBase.cs

@@ -1,4 +1,4 @@
-using System.ComponentModel;
+using System.ComponentModel;
 using System.Globalization;
 
 namespace MaterialDesignThemes.Wpf;
@@ -191,9 +191,7 @@ public override void OnApplyTemplate()
         if (_textBoxField != null)
             _textBoxField.TextChanged -= OnTextBoxFocusLost;
 
-        _increaseButton = GetTemplateChild(IncreaseButtonPartName) as RepeatButton;
-        _decreaseButton = GetTemplateChild(DecreaseButtonPartName) as RepeatButton;
-        _textBoxField = GetTemplateChild(TextBoxPartName) as TextBox;
+        base.OnApplyTemplate();
 
         if (_increaseButton != null)
             _increaseButton.Click += IncreaseButtonOnClick;
@@ -207,7 +205,6 @@ public override void OnApplyTemplate()
             _textBoxField.Text = Value?.ToString();
         }
 
-        base.OnApplyTemplate();
     }
 
     private void OnTextBoxFocusLost(object sender, EventArgs e)
@@ -279,6 +276,55 @@ public class UpDownBase : Control
     protected RepeatButton? _decreaseButton;
     protected RepeatButton? _increaseButton;
 
+    static UpDownBase()
+    {
+        EventManager.RegisterClassHandler(typeof(UpDownBase), GotFocusEvent, new RoutedEventHandler(OnGotFocus));
+    }
+
+    // Based on work in MahApps
+    // https://github.com/MahApps/MahApps.Metro/blob/f7ba30586e9670f07c2f7b6553d129a9e32fc673/src/MahApps.Metro/Controls/NumericUpDown.cs#L966
+    private static void OnGotFocus(object sender, RoutedEventArgs e)
+    {
+        // When NumericUpDown gets logical focus, select the text inside us.
+        // If we're an editable NumericUpDown, forward focus to the TextBox element
+        if (!e.Handled)
+        {
+            var numericUpDown = (UpDownBase)sender;
+            if (numericUpDown.Focusable && e.OriginalSource == numericUpDown)
+            {
+                // MoveFocus takes a TraversalRequest as its argument.
+                var focusDirection = Keyboard.Modifiers.HasFlag(ModifierKeys.Shift)
+                    ? FocusNavigationDirection.Previous
+                    : FocusNavigationDirection.Next;
+
+                var request = new TraversalRequest(focusDirection);
+                // Gets the element with keyboard focus.
+                // And change the keyboard focus.
+                if (Keyboard.FocusedElement is UIElement elementWithFocus)
+                {
+                    elementWithFocus.MoveFocus(request);
+                }
+                else
+                {
+                    numericUpDown.Focus();
+                }
+
+                e.Handled = true;
+            }
+        }
+    }
+
+    public override void OnApplyTemplate()
+    {
+        _increaseButton = GetTemplateChild(IncreaseButtonPartName) as RepeatButton;
+        _decreaseButton = GetTemplateChild(DecreaseButtonPartName) as RepeatButton;
+        _textBoxField = GetTemplateChild(TextBoxPartName) as TextBox;
+
+        base.OnApplyTemplate();
+    }
+
+    public void SelectAll() => _textBoxField?.SelectAll();
+
     public object? IncreaseContent
     {
         get => GetValue(IncreaseContentProperty);

tests/MaterialDesignThemes.UITests/WPF/UpDownControls/DecimalUpDownTests.cs

@@ -1,4 +1,6 @@
-namespace MaterialDesignThemes.UITests.WPF.UpDownControls;
+using System.ComponentModel;
+
+namespace MaterialDesignThemes.UITests.WPF.UpDownControls;
 
 public class DecimalUpDownTests(ITestOutputHelper output) : TestBase(output)
 {
@@ -115,4 +117,34 @@ public async Task MaxAndMinAssignments_CoerceValueToBeInRange()
         Assert.Equal(3, await numericUpDown.GetMinimum());
         Assert.Equal(3, await numericUpDown.GetMaximum());
     }
+
+    [Fact]
+    [Description("Issue 3654")]
+    public async Task InternalTextBoxIsFocused_WhenGettingKeyboardFocus()
+    {
+        await using var recorder = new TestRecorder(App);
+
+        // Arrange
+        var stackPanel = await LoadXaml<StackPanel>("""
+        <StackPanel>
+          <TextBox />
+          <materialDesign:DecimalUpDown />
+        </StackPanel>
+        """);
+
+        var textBox = await stackPanel.GetElement<TextBox>("/TextBox");
+        var part_textBox = await stackPanel.GetElement<TextBox>("PART_TextBox");
+
+        // Act
+        await textBox.MoveKeyboardFocus();
+        await Task.Delay(50);
+        await textBox.SendInput(new KeyboardInput(Key.Tab));
+        await Task.Delay(50);
+
+        // Assert
+        Assert.False(await textBox.GetIsFocused());
+        Assert.True(await part_textBox.GetIsFocused());
+
+        recorder.Success();
+    }
 }

tests/MaterialDesignThemes.UITests/WPF/UpDownControls/NumericUpDownTests.cs

@@ -1,4 +1,6 @@
-namespace MaterialDesignThemes.UITests.WPF.UpDownControls;
+using System.ComponentModel;
+
+namespace MaterialDesignThemes.UITests.WPF.UpDownControls;
 
 
 public class NumericUpDownTests(ITestOutputHelper output) : TestBase(output)
@@ -116,4 +118,34 @@ public async Task MaxAndMinAssignments_CoerceValueToBeInRange()
         Assert.Equal(3, await numericUpDown.GetMinimum());
         Assert.Equal(3, await numericUpDown.GetMaximum());
     }
+
+    [Fact]
+    [Description("Issue 3654")]
+    public async Task InternalTextBoxIsFocused_WhenGettingKeyboardFocus()
+    {
+        await using var recorder = new TestRecorder(App);
+
+        // Arrange
+        var stackPanel = await LoadXaml<StackPanel>("""
+        <StackPanel>
+          <TextBox />
+          <materialDesign:NumericUpDown />
+        </StackPanel>
+        """);
+
+        var textBox = await stackPanel.GetElement<TextBox>("/TextBox");
+        var part_textBox = await stackPanel.GetElement<TextBox>("PART_TextBox");
+
+        // Act
+        await textBox.MoveKeyboardFocus();
+        await Task.Delay(50);
+        await textBox.SendInput(new KeyboardInput(Key.Tab));
+        await Task.Delay(50);
+
+        // Assert
+        Assert.False(await textBox.GetIsFocused());
+        Assert.True(await part_textBox.GetIsFocused());
+
+        recorder.Success();
+    }
 }