How to implement a full-screen overlay?

[BlueRaja]

(Cross posted to Stackoverflow here)

I would like to draw a semi-transparent overlay over the entire screen.

screenshot of the feature working in Xamarin

The most obvious solution is to use an AbsoluteLayout + GraphicsView. However, this doesn't work because Xamarin/Maui don't allow AbsoluteLayout to draw things over the NavigationPage navigation bar.

---

The solution in Xamarin was to write a custom NavigationPageRenderer and override DispatchDraw

[assembly: ExportRenderer(typeof(NavigationPage), typeof(MyNavigationPageRenderer))]
public class MyNavigationPageRenderer : NavigationPageRenderer
{
    ...
    protected override void DispatchDraw(Canvas screenCanvas)
    {
        base.DispatchDraw(screenCanvas);
        // Custom drawing code here - screenCanvas can draw on the entire screen
    }
}

In Maui, you have two choices:

1. Use a compatibility renderer via .AddCompatibilityRenderer. However, as far as I can tell, these are just completely broken. Even a completely empty one crashes the app.

2. Use a Maui handler. However, these seem to be significantly less powerful than renderers. There is no way to override methods on native controls; there is no draw event to hook into on either the native or platform control; and there is no draw command in the CommandMapper. So I can't figure out any way to draw things.

So, how can this feature be implemented in Maui?