Add libgamemode support on Linux

osu.Framework/Platform/Linux/LinuxGameHost.cs

@@ -6,6 +6,7 @@
 using osu.Framework.Input;
 using osu.Framework.Input.Handlers;
 using osu.Framework.Input.Handlers.Mouse;
+using osu.Framework.Platform.Linux.Native;
 
 namespace osu.Framework.Platform.Linux
 {
@@ -46,5 +47,17 @@ protected override IEnumerable<InputHandler> CreateAvailableInputHandlers()
 
             return handlers;
         }
+
+        protected override void SetupForRun()
+        {
+            Gamemode.RequestStart();
+            base.SetupForRun();
+        }
+
+        protected override void Dispose(bool isDisposing)
+        {
+            Gamemode.RequestEnd();
+            base.Dispose(isDisposing);
+        }
     }
 }

osu.Framework/Platform/Linux/Native/Gamemode.cs

@@ -0,0 +1,62 @@
+// 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.Runtime.InteropServices;
+using osu.Framework.Logging;
+
+namespace osu.Framework.Platform.Linux.Native
+{
+    internal class Gamemode
+    {
+        [DllImport("libgamemode.so.0", EntryPoint = "real_gamemode_request_start", ExactSpelling = true)]
+        private static extern int gamemode_request_start();
+
+        [DllImport("libgamemode.so.0", EntryPoint = "real_gamemode_request_end", ExactSpelling = true)]
+        private static extern int gamemode_request_end();
+
+        /// <summary>
+        /// Requests gamemode activation. Silently does nothing if libgamemode is not installed.
+        /// </summary>
+        public static void RequestStart()
+        {
+            try
+            {
+                if (gamemode_request_start() < 0)
+                {
+                    Logger.Log("gamemode_request_start: failed.", LoggingTarget.Runtime, LogLevel.Debug);
+                }
+            }
+            catch (DllNotFoundException)
+            {
+                // libgamemode is not installed; this is not an error.
+            }
+            catch (Exception e)
+            {
+                Logger.Log($"gamemode_request_start threw an unexpected exception: {e}", LoggingTarget.Runtime, LogLevel.Debug);
+            }
+        }
+
+        /// <summary>
+        /// Requests gamemode deactivation. Silently does nothing if libgamemode is not installed.
+        /// </summary>
+        public static void RequestEnd()
+        {
+            try
+            {
+                if (gamemode_request_end() < 0)
+                {
+                    Logger.Log("gamemode_request_end: failed.", LoggingTarget.Runtime, LogLevel.Debug);
+                }
+            }
+            catch (DllNotFoundException)
+            {
+                // libgamemode is not installed; this is not an error.
+            }
+            catch (Exception e)
+            {
+                Logger.Log($"gamemode_request_end threw an unexpected exception: {e}", LoggingTarget.Runtime, LogLevel.Debug);
+            }
+        }
+    }
+}