Use Function Pointer to handle the low level keyboard proc

Author: taooceros

Flow.Launcher.Infrastructure/Hotkey/GlobalHotkey.cs

@@ -9,41 +9,29 @@ namespace Flow.Launcher.Infrastructure.Hotkey
     /// Listens keyboard globally.
     /// <remarks>Uses WH_KEYBOARD_LL.</remarks>
     /// </summary>
-    public class GlobalHotkey : IDisposable
+    public unsafe static class GlobalHotkey
     {
-        private static GlobalHotkey instance;
-        private InterceptKeys.LowLevelKeyboardProc hookedLowLevelKeyboardProc;
-        private IntPtr hookId = IntPtr.Zero;
+        private static readonly IntPtr hookId;
+        
+        
+        
         public delegate bool KeyboardCallback(KeyEvent keyEvent, int vkCode, SpecialKeyState state);
-        public event KeyboardCallback hookedKeyboardCallback;
+        internal static Func<KeyEvent, int, SpecialKeyState, bool> hookedKeyboardCallback;
 
         //Modifier key constants
         private const int VK_SHIFT = 0x10;
         private const int VK_CONTROL = 0x11;
         private const int VK_ALT = 0x12;
         private const int VK_WIN = 91;
 
-        public static GlobalHotkey Instance
+        static GlobalHotkey()
         {
-            get
-            {
-                if (instance == null)
-                {
-                    instance = new GlobalHotkey();
-                }
-                return instance;
-            }
-        }
-
-        private GlobalHotkey()
-        {
-            // We have to store the LowLevelKeyboardProc, so that it is not garbage collected runtime
-            hookedLowLevelKeyboardProc = LowLevelKeyboardProc;
             // Set the hook
-            hookId = InterceptKeys.SetHook(hookedLowLevelKeyboardProc);
+            hookId = InterceptKeys.SetHook(& LowLevelKeyboardProc);
+            AppDomain.CurrentDomain.ProcessExit += (_, _) => Dispose();
         }
 
-        public SpecialKeyState CheckModifiers()
+        public static SpecialKeyState CheckModifiers()
         {
             SpecialKeyState state = new SpecialKeyState();
             if ((InterceptKeys.GetKeyState(VK_SHIFT) & 0x8000) != 0)
@@ -71,7 +59,7 @@ public SpecialKeyState CheckModifiers()
         }
 
         [MethodImpl(MethodImplOptions.NoInlining)]
-        private IntPtr LowLevelKeyboardProc(int nCode, UIntPtr wParam, IntPtr lParam)
+        private static IntPtr LowLevelKeyboardProc(int nCode, UIntPtr wParam, IntPtr lParam)
         {
             bool continues = true;
 
@@ -94,12 +82,7 @@ private IntPtr LowLevelKeyboardProc(int nCode, UIntPtr wParam, IntPtr lParam)
             return (IntPtr)1;
         }
 
-        ~GlobalHotkey()
-        {
-            Dispose();
-        }
-
-        public void Dispose()
+        public static void Dispose()
         {
             InterceptKeys.UnhookWindowsHookEx(hookId);
         }

Flow.Launcher.Infrastructure/Hotkey/InterceptKeys.cs

@@ -4,13 +4,13 @@
 
 namespace Flow.Launcher.Infrastructure.Hotkey
 {
-    internal static class InterceptKeys
+    internal static unsafe class InterceptKeys
     {
         public delegate IntPtr LowLevelKeyboardProc(int nCode, UIntPtr wParam, IntPtr lParam);
 
         private const int WH_KEYBOARD_LL = 13;
 
-        public static IntPtr SetHook(LowLevelKeyboardProc proc)
+        public static IntPtr SetHook(delegate*<int, UIntPtr, IntPtr, IntPtr> proc)
         {
             using (Process curProcess = Process.GetCurrentProcess())
             using (ProcessModule curModule = curProcess.MainModule)
@@ -20,7 +20,7 @@ public static IntPtr SetHook(LowLevelKeyboardProc proc)
         }
 
         [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
-        public static extern IntPtr SetWindowsHookEx(int idHook, LowLevelKeyboardProc lpfn, IntPtr hMod, uint dwThreadId);
+        public static extern IntPtr SetWindowsHookEx(int idHook, delegate*<int, UIntPtr, IntPtr, IntPtr> lpfn, IntPtr hMod, uint dwThreadId);
 
         [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
         [return: MarshalAs(UnmanagedType.Bool)]

Flow.Launcher/HotkeyControl.xaml.cs

@@ -33,7 +33,7 @@ void TbHotkey_OnPreviewKeyDown(object sender, KeyEventArgs e)
             //when alt is pressed, the real key should be e.SystemKey
             Key key = (e.Key == Key.System ? e.SystemKey : e.Key);
 
-            SpecialKeyState specialKeyState = GlobalHotkey.Instance.CheckModifiers();
+            SpecialKeyState specialKeyState = GlobalHotkey.CheckModifiers();
 
             var hotkeyModel = new HotkeyModel(
                 specialKeyState.AltPressed,

Flow.Launcher/PublicAPIInstance.cs

@@ -40,7 +40,7 @@ public PublicAPIInstance(SettingWindowViewModel settingsVM, MainViewModel mainVM
             _settingsVM = settingsVM;
             _mainVM = mainVM;
             _alphabet = alphabet;
-            GlobalHotkey.Instance.hookedKeyboardCallback += KListener_hookedKeyboardCallback;
+            GlobalHotkey.hookedKeyboardCallback += KListener_hookedKeyboardCallback;
             WebRequest.RegisterPrefix("data", new DataWebRequestFactory());
         }
 

Flow.Launcher/ViewModel/MainViewModel.cs

@@ -227,7 +227,7 @@ private void InitializeKeyCommands()
                 {
                     bool hideWindow = result.Action != null && result.Action(new ActionContext
                     {
-                        SpecialKeyState = GlobalHotkey.Instance.CheckModifiers()
+                        SpecialKeyState = GlobalHotkey.CheckModifiers()
                     });
 
                     if (hideWindow)