citelao/FocusService

Focus Service

Note

This service is implemented as a demo to aid discussion with the XAML team.

This is an example implementation of a WPF-style focus helper for WinAppSDK (formerly UWP) XAML. They help you write containers that work well with arrow keys.

Specifically, these tools help you:

• Add focus "memory" to any container - when I tab away from your container, remember that focus so that I may return to it when I tab back.
• Support default-focused elements for complicated controls - e.g. in a dialog, reliably put default focus on the primary button.

Usage

The tool is best used through XAML attached properties. To make an arbitrary panel in the UI "fully" keyboard accessible:

<StackPanel
    Style="{StaticResource CardStyle}"
    XYFocusKeyboardNavigation="Enabled"
    TabFocusNavigation="Once"
    local:FocusService.RememberFocusedIndex="True"
    local:FocusService.DefaultFocusedElement="{x:Bind ButtonB}"
    local:FocusService.IsFocusScope="True">
    <Button>Remember focus</Button>
    <Button x:Name="ButtonB">Default</Button>
    <Button>Test</Button>
    <Button>Test</Button>
</StackPanel>

• XYFocusKeyboardNavigation="Enabled" - builtin to enable arrow keys through the container.
• TabFocusNavigation="Once" - only take tab focus once for the entire container.
• local:FocusService.RememberFocusedIndex="True" - remember the last-focused element in the container & refocus it when focus returns.
• Optional: local:FocusService.DefaultFocusedElement="..." - set a default first focus for the container (useful for complicated UI, e.g. a dialog with a default button)
• local:FocusService.IsFocusScope="True" - attach a GettingFocus handler that automatically

Also required for accessibility, but not implemented here (for laziness):

• Size of set/Pos in set (UIA properties)
• Home & end support

Note

None of the FocusService flags will have any effect by default unless you add local:FocusService.IsFocusScope="True".