Back closes what is open

On a phone the Back button left the page under an open menu, sheet or dialog. An open overlay now says so (new
IDOverlayHost, cascaded by MainLayout; OverlayService keeps them newest last): DModal and DDropdown through the
cascade, so the D components stay free of app services, and the nav menu, PhoneSheet and the full-screen globe through
the service. MainLayout's location-changing handler lets Back close the newest overlay instead of leaving the page; a
link followed or the app's own navigation (signing out after its question, say) closes them all and goes on. Blazor
can't tell Back from the app's navigation, so a capture-phase popstate listener in main.js marks Back
(AppStatusService.TookBack). No history entries are pushed. Phone flow: Back closes the menu, a card's More sheet, the
composer and the full-screen globe one after another without leaving the feed, and with nothing open goes back.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LsXgEaXee4GCU1hwYgPJXw

Components/Daisy/Actions/DDropdown.razor

@@ -1,4 +1,5 @@
 @inherits DComponentBase
+@implements IDisposable
 
 @* daisyUI Dropdown: https://daisyui.com/components/dropdown/ . The open state lives in C# (@bind-IsOpen):
    dropdown-open shows the content and dropdown-close keeps the focus-within rule from showing it while closed.
@@ -42,8 +43,12 @@
 		+ "max-md:overflow-y-auto max-md:overscroll-contain max-md:rounded-b-none max-md:translate-none max-md:scale-100 "
 		+ "max-md:p-3 max-md:pb-[max(0.75rem,env(safe-area-inset-bottom))]";
 
+	/// <summary>Where it says it is open, so the Back button closes it (cascaded by the app; none, none said).</summary>
+	[CascadingParameter] IDOverlayHost Overlays { get; set; }
+
 	ElementReference trigger;
 	ElementReference content;
+	IDisposable overlay;
 	bool focusContent;
 	bool focusTrigger;
 
@@ -65,6 +70,25 @@
 		_ => null
 	};
 
+	protected override void OnParametersSet() => TrackOverlay();
+
+	void TrackOverlay()
+	{
+		if (IsOpen && overlay is null)
+			overlay = Overlays?.Open(() => InvokeAsync(async () =>
+			{
+				await SetOpen(false, true);
+				StateHasChanged();
+			}));
+		else if (!IsOpen && overlay is not null)
+		{
+			overlay.Dispose();
+			overlay = null;
+		}
+	}
+
+	public void Dispose() => overlay?.Dispose();
+
 	protected override async Task OnAfterRenderAsync(bool firstRender)
 	{
 		if (focusContent)
@@ -93,6 +117,7 @@
 		focusContent = isOpen && !IsOpen;
 		focusTrigger = !isOpen && IsOpen && giveFocusBack;
 		IsOpen = isOpen;
+		TrackOverlay();
 		await IsOpenChanged.InvokeAsync(isOpen);
 	}
 }

Components/Daisy/Actions/DModal.razor

@@ -1,4 +1,5 @@
 @inherits DComponentBase
+@implements IDisposable
 
 @* daisyUI Modal: https://daisyui.com/components/modal/ . Always rendered; the open state lives in C# (@bind-IsOpen)
    and shows as modal-open. On opening, the box takes the focus (Blazor's FocusAsync) so that Escape, handled on the
@@ -58,7 +59,11 @@
 	[Parameter] public bool ShowClose { get; set; } = true;
 	[Parameter] public string BoxClass { get; set; }
 
+	/// <summary>Where it says it is open, so the Back button closes it (cascaded by the app; none, none said).</summary>
+	[CascadingParameter] IDOverlayHost Overlays { get; set; }
+
 	readonly string uid = "d" + Guid.NewGuid().ToString("N")[..8];
+	IDisposable overlay;
 	ElementReference box;
 	bool wasOpen;
 	bool focusPending;
@@ -80,8 +85,26 @@
 		if (IsOpen && !wasOpen)
 			focusPending = true;
 		wasOpen = IsOpen;
+		TrackOverlay();
 	}
 
+	void TrackOverlay()
+	{
+		if (IsOpen && overlay is null)
+			overlay = Overlays?.Open(() => InvokeAsync(async () =>
+			{
+				await SetOpen(false);
+				StateHasChanged();
+			}));
+		else if (!IsOpen && overlay is not null)
+		{
+			overlay.Dispose();
+			overlay = null;
+		}
+	}
+
+	public void Dispose() => overlay?.Dispose();
+
 	protected override async Task OnAfterRenderAsync(bool firstRender)
 	{
 		if (!focusPending)
@@ -98,6 +121,7 @@
 	{
 		IsOpen = isOpen;
 		wasOpen = isOpen;
+		TrackOverlay();
 		await IsOpenChanged.InvokeAsync(isOpen);
 	}
 }

Components/Daisy/IDOverlayHost.cs

@@ -0,0 +1,11 @@
+namespace decePubClient.Components.Daisy;
+
+/// <summary>
+/// Where an open overlay (a dialog, a menu, a sheet) says it is open, so that the phone's Back button closes it instead
+/// of leaving the page: Open registers how to close it and returns what ends the registration once it is closed. The
+/// app cascades one (OverlayService, from MainLayout); a component without one simply doesn't register.
+/// </summary>
+public interface IDOverlayHost
+{
+	IDisposable Open(Func<Task> close);
+}