Add helper to track ongoing operations in UI

osu.Game/Screens/OnlinePlay/OngoingOperationTracker.cs

@@ -0,0 +1,47 @@
+// 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.Bindables;
+
+namespace osu.Game.Screens.OnlinePlay
+{
+    /// <summary>
+    /// Utility class to track ongoing online operations' progress.
+    /// Can be used to disable interactivity while waiting for a response from online sources.
+    /// </summary>
+    public class OngoingOperationTracker
+    {
+        /// <summary>
+        /// Whether there is an online operation in progress.
+        /// </summary>
+        public IBindable<bool> InProgress => inProgress;
+
+        private readonly Bindable<bool> inProgress = new BindableBool();
+
+        private LeasedBindable<bool> leasedInProgress;
+
+        /// <summary>
+        /// Begins tracking a new online operation.
+        /// </summary>
+        /// <exception cref="InvalidOperationException">An operation has already been started.</exception>
+        public void BeginOperation()
+        {
+            if (leasedInProgress != null)
+                throw new InvalidOperationException("Cannot begin operation while another is in progress.");
+
+            leasedInProgress = inProgress.BeginLease(true);
+            leasedInProgress.Value = true;
+        }
+
+        /// <summary>
+        /// Ends tracking an online operation.
+        /// Does nothing if an operation has not been begun yet.
+        /// </summary>
+        public void EndOperation()
+        {
+            leasedInProgress?.Return();
+            leasedInProgress = null;
+        }
+    }
+}