Warn if Windows compatibility mode flags are detected on startup

osu.Desktop/OsuGameDesktop.cs

@@ -145,6 +145,9 @@ protected override void LoadComplete()
 
  LoadComponentAsync(new ElevatedPrivilegesChecker(), Add);
 
+ if (RuntimeInfo.OS == RuntimeInfo.Platform.Windows)
+ LoadComponentAsync(new CompatibilityModeChecker(), Add);
+
  osuSchemeLinkIPCChannel = new OsuSchemeLinkIPCChannel(Host, this);
  archiveImportIPCChannel = new ArchiveImportIPCChannel(Host, this);
  }

osu.Desktop/Program.cs

@@ -52,10 +52,6 @@ public static void Main(string[] args)
  // See https://www.mongodb.com/docs/realm/sdk/dotnet/compatibility/
  if (windowsVersion.Major < 6 || (windowsVersion.Major == 6 && windowsVersion.Minor <= 2))
  {
- // If users running in compatibility mode becomes more of a common thing, we may want to provide better guidance or even consider
- // disabling it ourselves.
- // We could also better detect compatibility mode if required:
- // https://stackoverflow.com/questions/10744651/how-i-can-detect-if-my-application-is-running-under-compatibility-mode#comment58183249_10744730
  SDL.SDL_ShowSimpleMessageBox(SDL.SDL_MessageBoxFlags.SDL_MESSAGEBOX_ERROR,
  "Your operating system is too old to run osu!",
  "This version of osu! requires at least Windows 8.1 to run.\n"

osu.Desktop/Security/CompatibilityModeChecker.cs

@@ -0,0 +1,58 @@
+// Copyright (c) ppy Pty Ltd <[email protected]>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System;
+using System.Linq;
+using Microsoft.Win32;
+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 windows compatibility optimizations which could cause issues. Displays a warning notification if so.
+ /// </summary>
+ public partial class CompatibilityModeChecker : Component
+ {
+ [Resolved]
+ private INotificationOverlay notifications { get; set; } = null!;
+
+ [BackgroundDependencyLoader]
+ private void load()
+ {
+ if (checkCompatibilityMode())
+ notifications.Post(new CompatibilityModeNotification());
+ }
+
+ private bool checkCompatibilityMode()
+ {
+ if (!OperatingSystem.IsWindows())
+ return false;
+
+ using var layers = Registry.CurrentUser.OpenSubKey(@"Software\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\Layers");
+
+ return layers != null && layers.GetValueNames().Any(name => name.EndsWith("osu!.exe", StringComparison.OrdinalIgnoreCase));
+ }
+
+ private partial class CompatibilityModeNotification : SimpleNotification
+ {
+ public override bool IsImportant => true;
+
+ public CompatibilityModeNotification()
+ {
+ Text = "osu! is running in compatibility mode. This may cause issues with the game. Please ensure osu! is not set to run in compatibility mode.";
+ }
+
+ [BackgroundDependencyLoader]
+ private void load(OsuColour colours)
+ {
+ Icon = FontAwesome.Solid.ShieldAlt;
+ IconContent.Colour = colours.YellowDark;
+ }
+ }
+ }
+}