Disable windows key while in gameplay.

osu.Desktop/Windows/WindowsKey.cs

@@ -0,0 +1,82 @@
+// 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;
+
+namespace osu.Desktop.Windows
+{
+    internal class WindowsKey
+    {
+        private delegate int LowLevelKeyboardProcDelegate(int nCode, int wParam, ref KdDllHookStruct lParam);
+
+        private static bool isBlocked;
+
+        private const int wh_keyboard_ll = 13;
+        private const int wm_keydown = 256;
+        private const int wm_syskeyup = 261;
+
+        //Resharper disable once NotAccessedField.Local
+        private static LowLevelKeyboardProcDelegate keyboardHookDelegate; // keeping a reference alive for the GC
+        private static IntPtr keyHook;
+
+        [StructLayout(LayoutKind.Explicit)]
+        private struct KdDllHookStruct
+        {
+            [FieldOffset(0)]
+            public readonly int VkCode;
+
+            [FieldOffset(8)]
+            public readonly int Flags;
+        }
+
+        private static int lowLevelKeyboardProc(int nCode, int wParam, ref KdDllHookStruct lParam)
+        {
+            if (wParam >= wm_keydown && wParam <= wm_syskeyup)
+            {
+                switch (lParam.VkCode)
+                {
+                    case 0x09 when lParam.Flags == 32: // alt + tab
+                    case 0x1b when lParam.Flags == 32: // alt + esc
+                    case 0x5B: // left windows key
+                    case 0x5C: // right windows key
+                        return 1;
+                }
+            }
+
+            return callNextHookEx(0, nCode, wParam, ref lParam);
+        }
+
+        internal static void Disable()
+        {
+            if (keyHook != IntPtr.Zero || isBlocked)
+                return;
+
+            keyHook = setWindowsHookEx(wh_keyboard_ll, (keyboardHookDelegate = lowLevelKeyboardProc), Marshal.GetHINSTANCE(System.Reflection.Assembly.GetExecutingAssembly().GetModules()[0]), 0);
+
+            isBlocked = true;
+        }
+
+        internal static void Enable()
+        {
+            if (keyHook == IntPtr.Zero || !isBlocked)
+                return;
+
+            keyHook = unhookWindowsHookEx(keyHook);
+            keyboardHookDelegate = null;
+
+            keyHook = IntPtr.Zero;
+
+            isBlocked = false;
+        }
+
+        [DllImport(@"user32.dll", EntryPoint = @"SetWindowsHookExA")]
+        private static extern IntPtr setWindowsHookEx(int idHook, LowLevelKeyboardProcDelegate lpfn, IntPtr hMod, int dwThreadId);
+
+        [DllImport(@"user32.dll", EntryPoint = @"UnhookWindowsHookEx")]
+        private static extern IntPtr unhookWindowsHookEx(IntPtr hHook);
+
+        [DllImport(@"user32.dll", EntryPoint = @"CallNextHookEx")]
+        private static extern int callNextHookEx(int hHook, int nCode, int wParam, ref KdDllHookStruct lParam);
+    }
+}