fixes #3650 - TimePicker tab navigation (#3655)

* fixes #3650 added logic (and tests) for TimePicker to move to previous element when pressing Shift+Tab

* Adjusting fix so that it leverages the WPF focus scopes

This removes the need to manually handle the key strokes

---------

Co-authored-by: Kevin Bost <[email protected]>

Author: corvinsz

src/MaterialDesignThemes.Wpf/Themes/MaterialDesignTheme.TimePicker.xaml

@@ -39,6 +39,7 @@
     <Setter Property="HorizontalContentAlignment" Value="Stretch" />
     <Setter Property="IsHeaderVisible" Value="True" />
     <Setter Property="Padding" Value="{x:Static wpf:Constants.TextBoxDefaultPadding}" />
+    <Setter Property="Focusable" Value="False" />
     <Setter Property="Template">
       <Setter.Value>
         <ControlTemplate TargetType="{x:Type wpf:TimePicker}">
@@ -101,7 +102,6 @@
                                    wpf:TextFieldAssist.UnderlineCornerRadius="{TemplateBinding wpf:TextFieldAssist.UnderlineCornerRadius}"
                                    internal:InternalTextFieldAssist.IsMouseOver="{TemplateBinding IsMouseOver}"
                                    BorderBrush="{TemplateBinding BorderBrush}"
-                                   Focusable="{TemplateBinding Focusable}"
                                    Style="{DynamicResource NestedTextBoxStyle}">
               <wpf:TimePickerTextBox.BorderThickness>
                 <PriorityBinding>

src/MaterialDesignThemes.Wpf/TimePicker.cs

@@ -371,7 +371,7 @@ private bool ProcessKey(KeyEventArgs keyEventArgs)
                     {
                         case Key.Down:
                             {
-                                if ((Keyboard.Modifiers & ModifierKeys.Alt) == ModifierKeys.Alt)
+                                if (Keyboard.Modifiers.HasFlag(ModifierKeys.Alt))
                                 {
                                     TogglePopup();
                                     return true;

tests/MaterialDesignThemes.UITests/WPF/TimePickers/TimePickerTests.cs

@@ -560,7 +560,7 @@ public async Task TimePicker_WithOutlinedStyleAndNoCustomHintBackgroundSet_Shoul
         var timePickerTextBox = await timePicker.GetElement<TimePickerTextBox>("/TimePickerTextBox");
         var hintBackgroundGrid = await timePicker.GetElement<Grid>("HintBackgroundGrid");
 
-        var defaultBackground = Colors.Transparent; 
+        var defaultBackground = Colors.Transparent;
         var defaultFloatedBackground = await GetThemeColor("MaterialDesign.Brush.Background");
 
         // Assert (unfocused state)
@@ -643,6 +643,36 @@ public async Task TimePicker_ShouldApplyIsMouseOverTriggers_WhenHoveringTimeButt
 
         recorder.Success();
     }
+
+    [Fact]
+    [Description("Issue 3650")]
+    public async Task TimePicker_MovesFocusToPrevious_WhenShiftAndTabIsPressed()
+    {
+        await using var recorder = new TestRecorder(App);
+
+        // Arrange
+        var stackPanel = await LoadXaml<StackPanel>("""
+            <StackPanel>
+              <TextBox />
+              <materialDesign:TimePicker />
+            </StackPanel>
+            """);
+
+        var textBox = await stackPanel.GetElement<TextBox>("/TextBox");
+        var timePickerTextBox = await stackPanel.GetElement<TimePickerTextBox>("/TimePickerTextBox");
+
+        // Act
+        await timePickerTextBox.MoveKeyboardFocus();
+        await Task.Delay(50);
+        await timePickerTextBox.SendInput(new KeyboardInput(Key.LeftShift, Key.Tab));
+        await Task.Delay(50);
+
+        // Assert
+        Assert.True(await textBox.GetIsFocused());
+        Assert.False(await timePickerTextBox.GetIsFocused());
+
+        recorder.Success();
+    }
 }
 
 public class OnlyTenOClockValidationRule : ValidationRule