decePubClient/Shared/MainLayout.razor

@inherits LayoutComponentBase
@implements IDisposable

@* The page and its menu. The overlays it holds (dialogs, menus, sheets: IDOverlayHost, cascaded) close with the phone's
   Back button: while one is open, Back closes the newest instead of leaving the page; a link followed or the app's own
   navigation closes them all and goes on. *@
<CascadingValue Value="(IDOverlayHost)Overlays" IsFixed="true">
	<div class="relative flex flex-col md:flex-row w-full h-full">
		<NavMenu />

		<div class="block flex-1 relative w-full h-full">
			<div class="block absolute overflow-y-auto w-full h-full p-3 md:py-4 md:pl-2 md:pr-4">
				@Body
			</div>
		</div>
	</div>

	<ToastHost />
	<PublicNoticeHost />
	<ConfirmHost />
</CascadingValue>

@code {
	[Inject] OverlayService Overlays { get; set; }
	[Inject] NavigationManager Navigation { get; set; }
	[Inject] AppStatusService Status { get; set; }

	IDisposable changing;

	protected override void OnInitialized() => changing = Navigation.RegisterLocationChangingHandler(OnLocationChanging);

	async ValueTask OnLocationChanging(LocationChangingContext context)
	{
		var back = !context.IsNavigationIntercepted && Status.TookBack();
		if (!Overlays.HasOpen)
			return;
		if (back)
		{
			context.PreventNavigation();
			await Overlays.CloseTop(context.CancellationToken);
			return;
		}
		await Overlays.CloseAll(context.CancellationToken);
	}

	public void Dispose() => changing?.Dispose();
}