Provide an API for determining if the "main" component of a control has focus.

Formerly “NumberBox FocusState value remains to Unfocused even after getting focus”

Describe the bug So the FocusState value seems to remain unchanged regardless of the actual focus state of the control.

Steps to reproduce the bug

1. Minimal Xaml :

<Page
    x:Class="Test.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:winui="using:Microsoft.UI.Xaml.Controls"
    Background="{ThemeResource ApplicationPageBackgroundThemeBrush}"
    mc:Ignorable="d">

    <Grid>
        <winui:NumberBox x:Name="MyNumberBox" GotFocus="MyNumberBox_GotFocus" />
    </Grid>
</Page>

2. Code behind:

public MainPage()
{
	this.InitializeComponent();
}

private void MyNumberBox_GotFocus(object sender, RoutedEventArgs e)
{
	System.Diagnostics.Debug.WriteLine(MyNumberBox.FocusState);
}

1. Build and Run. Now focus and unfocus the NumberBox by clicking it and clicking in blank space, do it several times and notice in the output window, even in the GotFocus event, the FocusState value is Unfocused.

Version Info WinUI Nuget Package Version :

NuGet package version:

Microsoft.UI.Xaml 2.4.2]

Windows 10 version	Saw the problem?
1909	Yes

Device form factor	Saw the problem?
Desktop	Yes

Additional context

[Austin-Lamb]

WPF has an API that we could consider copying - UIElement.IsKeyboardFocusWithin

[StephenLPeters]

In the mean time you could call FocusManager.GetFocusedElement and then use VisualTreeHelper.GetParent to walk up the tree looking for your numberbox and if you find it then you know the internal text box has it.

Alternatively you can use the OriginalSource api on the event args and check if that is a text box, if so then it is presumably the numberbox’s template part.