Getting non-repeating KeyUp/KeyDown events?

[BrodyB]

Hey folks!

I'm trying to make an application that keeps track of key and button states: are they currently pressed or released? Seems like a very simple thing: I implement protected override void OnKeyDown(KeyEventArgs e) and OnKeyUp on my window, create a boolean that turns on when OnKeyDown's e.Key is Space, turns the bool off when OnKeyUp is Space. Simple.

But what happens is I get repeating, alternating Space Up/Space Down signals.

What is the intended workflow to get a keyboard key's IsCurrentlyDown state?

[BrodyB]

Right now, this is what my Window code looks like (just while I'm trying to get this working as expected):

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
    }

    protected override void OnKeyDown(KeyEventArgs e)
    {
        base.OnKeyDown(e);

        if (e.Key == Key.Space && !e.Handled)
        {
            Console.WriteLine($"Space Down / {e.Route}");
            e.Handled = true;
        }
    }

    protected override void OnKeyUp(KeyEventArgs e)
    {
        base.OnKeyUp(e);
        if (e.Key == Key.Space && !e.Handled)
        {
            Console.WriteLine($"Space Up / {e.Route}");
            e.Handled = true;
        }
	}
}

and the result I get when I simply hold the Spacebar down:

Space Down / Bubble
Space Up / Bubble
Space Down / Bubble
Space Up / Bubble
Space Down / Bubble
Space Up / Bubble
Space Down / Bubble
Space Up / Bubble
Space Down / Bubble
Space Up / Bubble
Space Down / Bubble
Space Up / Bubble
Space Down / Bubble
Space Up / Bubble
Space Down / Bubble
Space Up / Bubble
Space Down / Bubble
Space Up / Bubble

This reads to me like it's going by the expected behavior for keyboard text input. But I just want to know simply if the key has been pressed down or released up, similar to OnPointerPressed/OnPointerReleased.

[LaurentInSeattle]

Abstracting mouse, touch and pen events is hard and sometimes creates difficulties.
If you are Windows only, you could maybe consider this:
https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-getkeystate

(MacOS has a similar API)

[BrodyB]

I'm not trying to abstract the input events. I just want "just pressed" and "just released" triggers. In standard .NET, the KeyEventArgs has an IsRepeat bool you can check against. This seems to be absent from Avalonia.

Is there an intended event or hook in Avalonia to achieve the same kind of check?

[stevemonaco]

The API surface area is not guaranteed from platform to platform and even if it is, that's at least 6 platform implementations to write. Or some middleware like the following that Avalonia probably can't provide because of edge cases with input devices, windows leaving focus, etc.

If KeyDown repeats itself on all platforms, then you simply keep a HashSet<Key>. Add when the event is KeyDown, remove when KeyUp. Have a timer for a safeguard to clear the set when a KeyDown hasn't been seen in say 500ms.

It's like 20 LoC and you can move on with your life.