Perform elevated check asynchronously, use a separate function w/ switch statement

osu.Desktop/Security/ElevatedPrivilegesChecker.cs

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+// 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 System.Security.Principal;
+using osu.Framework;
+using osu.Framework.Allocation;
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.Sprites;
+using osu.Game.Graphics;
+using osu.Game.Overlays;
+using osu.Game.Overlays.Notifications;
+
+namespace osu.Desktop.Security
+{
+    /// <summary>
+    /// Checks if the game is running with elevated privileges (as admin in Windows, root in Unix) and displays a warning notification if so.
+    /// </summary>
+    public class ElevatedPrivilegesChecker : Component
+    {
+        [Resolved]
+        protected NotificationOverlay Notifications { get; private set; }
+
+        private bool elevated;
+
+        protected override void LoadComplete()
+        {
+            base.LoadComplete();
+
+            if (!elevated)
+                return;
+
+            Notifications.Post(new ElevatedPrivilegesNotification());
+        }
+
+        [BackgroundDependencyLoader]
+        private void load()
+        {
+            elevated = isElevated();
+        }
+
+        private bool isElevated()
+        {
+            switch (RuntimeInfo.OS)
+            {
+                case RuntimeInfo.Platform.Windows:
+                {
+                    if (!OperatingSystem.IsWindows()) return false;
+
+                    var windowsIdentity = WindowsIdentity.GetCurrent();
+                    var windowsPrincipal = new WindowsPrincipal(windowsIdentity);
+
+                    return windowsPrincipal.IsInRole(WindowsBuiltInRole.Administrator);
+                }
+
+                case RuntimeInfo.Platform.macOS:
+                case RuntimeInfo.Platform.Linux:
+                    return Mono.Unix.Native.Syscall.geteuid() == 0;
+
+                default:
+                    return false;
+            }
+        }
+
+        private class ElevatedPrivilegesNotification : SimpleNotification
+        {
+            public override bool IsImportant => true;
+
+            public ElevatedPrivilegesNotification()
+            {
+                Text = $"Running osu! as {(RuntimeInfo.IsUnix ? "root" : "administrator")} does not improve performance and poses a security risk. Please run the game as a normal user.";
+            }
+
+            [BackgroundDependencyLoader]
+            private void load(OsuColour colours, NotificationOverlay notificationOverlay)
+            {
+                Icon = FontAwesome.Solid.ShieldAlt;
+                IconBackgound.Colour = colours.YellowDark;
+
+                Activated = delegate
+                {
+                    notificationOverlay.Hide();
+                    return true;
+                };
+            }
+        }
+    }
+}