Centralise and improve messaging around online state

When the server requests a disconnect due to a user connecting
via a second device, the client will now log the user out on the first
device and show a notification informing them of the cause of
disconnection.

osu.Game/Online/HubClientConnector.cs

@@ -100,7 +100,11 @@ namespace osu.Game.Online
             return Task.FromResult((PersistentEndpointClient)new HubClient(newConnection));
         }
 
-        Task IHubClientConnector.Disconnect() => base.Disconnect();
+        async Task IHubClientConnector.Disconnect()
+        {
+            await Disconnect().ConfigureAwait(false);
+            API.Logout();
+        }
 
         protected override string ClientName { get; }
     }

osu.Game/Online/Multiplayer/MultiplayerClient.cs

@@ -12,7 +12,6 @@ using osu.Framework.Allocation;
 using osu.Framework.Bindables;
 using osu.Framework.Development;
 using osu.Framework.Graphics;
-using osu.Framework.Logging;
 using osu.Game.Database;
 using osu.Game.Online.API;
 using osu.Game.Online.API.Requests.Responses;
@@ -88,6 +87,11 @@ namespace osu.Game.Online.Multiplayer
         /// </summary>
         public event Action? ResultsReady;
 
+        /// <summary>
+        /// Invoked just prior to disconnection requested by the server via <see cref="IStatefulUserHubClient.DisconnectRequested"/>.
+        /// </summary>
+        public event Action? Disconnecting;
+
         /// <summary>
         /// Whether the <see cref="MultiplayerClient"/> is currently connected.
         /// This is NOT thread safe and usage should be scheduled.
@@ -155,10 +159,7 @@ namespace osu.Game.Online.Multiplayer
             {
                 // clean up local room state on server disconnect.
                 if (!connected.NewValue && Room != null)
-                {
-                    Logger.Log("Clearing room due to multiplayer server connection loss.", LoggingTarget.Runtime, LogLevel.Important);
                     LeaveRoom();
-                }
             }));
         }
 
@@ -881,7 +882,11 @@ namespace osu.Game.Online.Multiplayer
 
         Task IStatefulUserHubClient.DisconnectRequested()
         {
-            Schedule(() => DisconnectInternal());
+            Schedule(() =>
+            {
+                Disconnecting?.Invoke();
+                DisconnectInternal();
+            });
             return Task.CompletedTask;
         }
     }

osu.Game/Online/OnlineStatusNotifier.cs

@@ -0,0 +1,120 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System;
+using osu.Framework.Allocation;
+using osu.Framework.Bindables;
+using osu.Framework.Extensions.ObjectExtensions;
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.Sprites;
+using osu.Framework.Screens;
+using osu.Game.Online.API;
+using osu.Game.Online.Multiplayer;
+using osu.Game.Online.Spectator;
+using osu.Game.Overlays;
+using osu.Game.Overlays.Notifications;
+using osu.Game.Screens.OnlinePlay;
+
+namespace osu.Game.Online
+{
+    public partial class OnlineStatusNotifier : Component
+    {
+        private readonly Func<IScreen> getCurrentScreen;
+
+        [Resolved]
+        private MultiplayerClient multiplayerClient { get; set; } = null!;
+
+        [Resolved]
+        private SpectatorClient spectatorClient { get; set; } = null!;
+
+        [Resolved]
+        private INotificationOverlay? notificationOverlay { get; set; }
+
+        private IBindable<APIState> apiState = null!;
+        private IBindable<bool> multiplayerState = null!;
+        private IBindable<bool> spectatorState = null!;
+        private bool forcedDisconnection;
+
+        public OnlineStatusNotifier(Func<IScreen> getCurrentScreen)
+        {
+            this.getCurrentScreen = getCurrentScreen;
+        }
+
+        [BackgroundDependencyLoader]
+        private void load(IAPIProvider api)
+        {
+            apiState = api.State.GetBoundCopy();
+            multiplayerState = multiplayerClient.IsConnected.GetBoundCopy();
+            spectatorState = spectatorClient.IsConnected.GetBoundCopy();
+
+            multiplayerClient.Disconnecting += notifyAboutForcedDisconnection;
+            spectatorClient.Disconnecting += notifyAboutForcedDisconnection;
+        }
+
+        private void notifyAboutForcedDisconnection()
+        {
+            if (forcedDisconnection)
+                return;
+
+            forcedDisconnection = true;
+            notificationOverlay?.Post(new SimpleErrorNotification
+            {
+                Icon = FontAwesome.Solid.ExclamationCircle,
+                Text = "You have been logged out on this device due to a login to your account on another device."
+            });
+        }
+
+        protected override void LoadComplete()
+        {
+            base.LoadComplete();
+
+            apiState.BindValueChanged(_ =>
+            {
+                if (apiState.Value == APIState.Online)
+                    forcedDisconnection = false;
+
+                Scheduler.AddOnce(updateState);
+            });
+            multiplayerState.BindValueChanged(_ => Scheduler.AddOnce(updateState));
+            spectatorState.BindValueChanged(_ => Scheduler.AddOnce(updateState));
+        }
+
+        private void updateState()
+        {
+            if (forcedDisconnection)
+                return;
+
+            if (apiState.Value == APIState.Offline && getCurrentScreen() is OnlinePlayScreen)
+            {
+                notificationOverlay?.Post(new SimpleErrorNotification
+                {
+                    Icon = FontAwesome.Solid.ExclamationCircle,
+                    Text = "API connection was lost. Can't continue with online play."
+                });
+                return;
+            }
+
+            if (!multiplayerClient.IsConnected.Value && multiplayerClient.Room != null)
+            {
+                notificationOverlay?.Post(new SimpleErrorNotification
+                {
+                    Icon = FontAwesome.Solid.ExclamationCircle,
+                    Text = "Connection to the multiplayer server was lost. Exiting multiplayer."
+                });
+            }
+
+            // TODO: handle spectator server failure somehow?
+        }
+
+        protected override void Dispose(bool isDisposing)
+        {
+            base.Dispose(isDisposing);
+
+            if (spectatorClient.IsNotNull())
+                spectatorClient.Disconnecting -= notifyAboutForcedDisconnection;
+
+            if (multiplayerClient.IsNotNull())
+                multiplayerClient.Disconnecting -= notifyAboutForcedDisconnection;
+        }
+    }
+}

osu.Game/Online/Spectator/OnlineSpectatorClient.cs

@@ -115,12 +115,14 @@ namespace osu.Game.Online.Spectator
             return connection.InvokeAsync(nameof(ISpectatorServer.EndWatchingUser), userId);
         }
 
-        protected override Task DisconnectInternal()
+        protected override async Task DisconnectInternal()
         {
-            if (connector == null)
+            await base.DisconnectInternal().ConfigureAwait(false);
-                return Task.CompletedTask;
 
-            return connector.Disconnect();
+            if (connector == null)
+                return;
+
+            await connector.Disconnect().ConfigureAwait(false);
         }
     }
 }

osu.Game/Online/Spectator/SpectatorClient.cs

@@ -70,6 +70,11 @@ namespace osu.Game.Online.Spectator
         /// </summary>
         public virtual event Action<int, long>? OnUserScoreProcessed;
 
+        /// <summary>
+        /// Invoked just prior to disconnection requested by the server via <see cref="IStatefulUserHubClient.DisconnectRequested"/>.
+        /// </summary>
+        public event Action? Disconnecting;
+
         /// <summary>
         /// A dictionary containing all users currently being watched, with the number of watching components for each user.
         /// </summary>
@@ -297,7 +302,11 @@ namespace osu.Game.Online.Spectator
 
         protected abstract Task StopWatchingUserInternal(int userId);
 
-        protected abstract Task DisconnectInternal();
+        protected virtual Task DisconnectInternal()
+        {
+            Disconnecting?.Invoke();
+            return Task.CompletedTask;
+        }
 
         protected override void Update()
         {

osu.Game/OsuGame.cs

@@ -1054,6 +1054,7 @@ namespace osu.Game
             Add(difficultyRecommender);
             Add(externalLinkOpener = new ExternalLinkOpener());
             Add(new MusicKeyBindingHandler());
+            Add(new OnlineStatusNotifier(() => ScreenStack.CurrentScreen));
 
             // side overlays which cancel each other.
             var singleDisplaySideOverlays = new OverlayContainer[] { Settings, Notifications, FirstRunOverlay };

osu.Game/Screens/OnlinePlay/OnlinePlayScreen.cs

@@ -71,7 +71,7 @@ namespace osu.Game.Screens.OnlinePlay
                     screenStack = new OnlinePlaySubScreenStack { RelativeSizeAxes = Axes.Both },
                     new Header(ScreenTitle, screenStack),
                     RoomManager,
-                    ongoingOperationTracker
+                    ongoingOperationTracker,
                 }
             };
         }
@@ -79,10 +79,7 @@ namespace osu.Game.Screens.OnlinePlay
         private void onlineStateChanged(ValueChangedEvent<APIState> state) => Schedule(() =>
         {
             if (state.NewValue != APIState.Online)
-            {
-                Logger.Log("API connection was lost, can't continue with online play", LoggingTarget.Network, LogLevel.Important);
                 Schedule(forcefullyExit);
-            }
         });
 
         protected override void LoadComplete()

osu.Game/Tests/Visual/Spectator/TestSpectatorClient.cs

@@ -181,10 +181,10 @@ namespace osu.Game.Tests.Visual.Spectator
             });
         }
 
-        protected override Task DisconnectInternal()
+        protected override async Task DisconnectInternal()
         {
+            await base.DisconnectInternal().ConfigureAwait(false);
             isConnected.Value = false;
-            return Task.CompletedTask;
         }
     }
 }