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

Services/AppStatusService.cs

@@ -42,6 +42,9 @@ public class AppStatusService(IJSRuntime jsRuntime)
 
 		public bool IsMobileMedia() => JsSyncRuntime.Invoke<bool>("isMobileMedia");
 
+		// whether the navigation being decided came from the Back (or Forward) button
+		public bool TookBack() => JsSyncRuntime.Invoke<bool>("tookBack");
+
 		// whether the pointer can hover (a mouse); a touch screen can't, so what shows on hover there opens on a tap
 		public bool CanHover() => JsSyncRuntime.Invoke<bool>("canHover");
 

Services/OverlayService.cs

@@ -0,0 +1,64 @@
+using decePubClient.Components.Daisy;
+
+namespace decePubClient.Services
+{
+	/// <summary>
+	/// The overlays open now, newest last (IDOverlayHost): MainLayout closes the newest when the Back button is pressed
+	/// while one is open, and all of them when the app goes elsewhere.
+	/// </summary>
+	public class OverlayService : IDOverlayHost
+	{
+		readonly List<Entry> open = [];
+
+		public bool HasOpen
+		{
+			get
+			{
+				lock (open)
+					return open.Count > 0;
+			}
+		}
+
+		public IDisposable Open(Func<Task> close)
+		{
+			var entry = new Entry(this, close);
+			lock (open)
+				open.Add(entry);
+			return entry;
+		}
+
+		public async Task CloseTop(CancellationToken cancellationToken = default)
+		{
+			Entry top;
+			lock (open)
+				top = open.LastOrDefault();
+			if (top is null)
+				return;
+			top.Dispose();
+			await top.Close();
+		}
+
+		public async Task CloseAll(CancellationToken cancellationToken = default)
+		{
+			Entry[] all;
+			lock (open)
+			{
+				all = [.. open];
+				open.Clear();
+			}
+			foreach (var entry in all.Reverse())
+				await entry.Close();
+		}
+
+		sealed class Entry(OverlayService owner, Func<Task> close) : IDisposable
+		{
+			public Func<Task> Close { get; } = close;
+
+			public void Dispose()
+			{
+				lock (owner.open)
+					owner.open.Remove(this);
+			}
+		}
+	}
+}