Centralized hotkey registration

Only one window handle is required for all hotkeys.
Simplifies maintaining multiple hotkeys spreaded over multiple windows.

Business/KeyboardInput.cs

@@ -13,7 +13,7 @@ namespace SystemTrayMenu.Handler
 
     internal class KeyboardInput : IDisposable
     {
-        private readonly KeyboardHook hook = new();
+        private GlobalHotkeys.HotkeyRegistrationHandle? hotkeyHandle;
 
         private Menu? focussedMenu;
 
@@ -27,7 +27,7 @@ namespace SystemTrayMenu.Handler
 
         public void Dispose()
         {
-            hook.Dispose();
+            GlobalHotkeys.Unregister(hotkeyHandle);
         }
 
         internal bool RegisterHotKey(string hotKeyString)
@@ -36,14 +36,15 @@ namespace SystemTrayMenu.Handler
             {
                 try
                 {
-                    hook.RegisterHotKey(hotKeyString);
-                    hook.KeyPressed += (_, _) => HotKeyPressed?.Invoke();
+                    hotkeyHandle = GlobalHotkeys.Register(hotKeyString);
                 }
                 catch (InvalidOperationException ex)
                 {
                     Log.Warn($"Hotkey cannot be set: '{hotKeyString}'", ex);
                     return false;
                 }
+
+                hotkeyHandle.KeyPressed += (_) => HotKeyPressed?.Invoke();
             }
 
             return true;

Helpers/GlobalHotkeys.cs

@@ -7,94 +7,109 @@
 namespace SystemTrayMenu.Helpers
 {
     using System;
+    using System.Collections.Generic;
     using System.Text;
+    using System.Windows;
     using System.Windows.Input;
+    using System.Windows.Interop;
     using SystemTrayMenu.DllImports;
     using SystemTrayMenu.Utilities;
 
     internal static class GlobalHotkeys
     {
-        private static readonly object LastIdLock = new();
-        private static int lastId = 0;
+        private static readonly HwndSourceHook Hook = new (WndProc);
+        private static readonly Window Window = new();
+        private static readonly HwndSource HWnd;
 
-        /// <summary>
-        /// Registers a global hotkey in a thread safe manner.
-        /// Throws an InvalidOperationException on error.
-        /// The caller needs to call UnregisterHotkey to free up ressources.
-        /// </summary>
-        /// <param name="hWnd">Window handle receiving the events.</param>
-        /// <param name="modifiers">Hotkey modifiers.</param>
-        /// <param name="key">Hotkey major key.</param>
-        /// <returns>ID of registered key.</returns>
-        internal static int RegisterHotkeyGlobal(IntPtr hWnd, ModifierKeys modifiers, Key key)
+        private static readonly List<HotkeyRegistration> Registrations = new();
+        private static readonly object CriticalSectionLock = new();
+
+        static GlobalHotkeys()
         {
-            lock (LastIdLock)
-            {
-                lastId = RegisterHotkeyLocal(hWnd, lastId + 1, modifiers, key);
-            }
-
-            return lastId;
+            HWnd = HwndSource.FromHwnd(new WindowInteropHelper(Window).EnsureHandle());
+            HWnd.AddHook(Hook);
         }
 
         /// <summary>
-        /// Registers a global hotkey in a thread safe manner.
+        /// Registers a global hotkey.
+        /// Function is thread safe.
         /// Throws an InvalidOperationException on error.
         /// The caller needs to call UnregisterHotkey to free up ressources.
         /// </summary>
-        /// <param name="hWnd">Window handle receiving the events.</param>
-        /// <param name="hotKeyString">Hotkey string description.</param>
-        /// <returns>ID of registered key.</returns>
-        internal static int RegisterHotkeyGlobal(IntPtr hWnd, string hotKeyString)
-        {
-            ModifierKeys modifiers = ModifierKeysFromString(hotKeyString);
-            Key key = KeyFromString(hotKeyString);
-            return RegisterHotkeyGlobal(hWnd, modifiers, key);
-        }
-
-        /// <summary>
-        /// Registers a local hotkey (with given ID).
-        /// Throws an InvalidOperationException on error.
-        /// The caller needs to call UnregisterHotkey to free up ressources.
-        /// </summary>
-        /// <param name="hWnd">Window handle receiving the events.</param>
-        /// <param name="id">ID for the registration.</param>
         /// <param name="modifiers">Hotkey modifiers.</param>
         /// <param name="key">Hotkey major key.</param>
-        /// <returns>ID of registered key.</returns>
-        internal static int RegisterHotkeyLocal(IntPtr hWnd, int id, ModifierKeys modifiers, Key key)
+        /// <returns>Handle of this registration.</returns>
+        internal static HotkeyRegistrationHandle Register(ModifierKeys modifiers, Key key)
         {
             int virtualKeyCode = KeyInterop.VirtualKeyFromKey(key);
-            if (!NativeMethods.User32RegisterHotKey(hWnd, id, (uint)modifiers, (uint)virtualKeyCode))
+            int id = 0;
+
+            lock (CriticalSectionLock)
             {
-                string errorHint = NativeMethods.GetLastErrorHint();
-                throw new InvalidOperationException(Translator.GetText("Could not register the hot key.") + " (" + errorHint + ")");
+                foreach (var reg in Registrations)
+                {
+                    if (id < reg.Id)
+                    {
+                        id = reg.Id;
+                    }
+                }
+
+                if (!NativeMethods.User32RegisterHotKey(HWnd.Handle, id, (uint)modifiers, (uint)virtualKeyCode))
+                {
+                    string errorHint = NativeMethods.GetLastErrorHint();
+                    throw new InvalidOperationException(Translator.GetText("Could not register the hot key.") + " (" + errorHint + ")");
+                }
             }
 
-            return id;
+            HotkeyRegistration regHandle = new()
+            {
+                Id = id,
+                Modifiers = modifiers,
+                Key = key,
+            };
+            Registrations.Add(regHandle);
+            return regHandle;
         }
 
         /// <summary>
-        /// Registers a local hotkey (with given ID).
+        /// Registers a global hotkey.
+        /// Function is thread safe.
         /// Throws an InvalidOperationException on error.
         /// The caller needs to call UnregisterHotkey to free up ressources.
         /// </summary>
-        /// <param name="hWnd">Window handle receiving the events.</param>
-        /// <param name="id">ID for the registration.</param>
-        /// <param name="hotKeyString">Hotkey string description.</param>
-        /// <returns>ID of registered key.</returns>
-        internal static int RegisterHotkeyLocal(IntPtr hWnd, int id, string hotKeyString)
+        /// <param name="hotKeyString">Hotkey string representation.</param>
+        /// <returns>Handle of this registration.</returns>
+        internal static HotkeyRegistrationHandle Register(string hotKeyString)
         {
-            ModifierKeys modifiers = ModifierKeysFromString(hotKeyString);
-            Key key = KeyFromString(hotKeyString);
-            return RegisterHotkeyLocal(hWnd, id, modifiers, key);
+            var (modifiers, key) = ParseKeysAndModifiersFromString(hotKeyString);
+            return Register(modifiers, key);
         }
 
         /// <summary>
-        /// Unregisters a local or global hotkey.
+        /// Unregisters a global hotkey in a thread safe manner.
+        /// Function is thread safe.
         /// </summary>
-        /// <param name="hWnd">Window handle.</param>
-        /// <param name="id">ID for the registration.</param>
-        internal static void UnregisterHotkey(IntPtr hWnd, int id) => NativeMethods.User32UnregisterHotKey(hWnd, id);
+        /// <param name="regHandle">Handle of the registration.</param>
+        /// <returns>true: Success or false: Failure.</returns>
+        internal static bool Unregister(HotkeyRegistrationHandle? regHandle)
+        {
+            if (regHandle == null || regHandle is not HotkeyRegistration reg || Registrations.Contains(reg))
+            {
+                return true;
+            }
+
+            lock (CriticalSectionLock)
+            {
+                if (!NativeMethods.User32UnregisterHotKey(HWnd.Handle, reg.Id))
+                {
+                    return false;
+                }
+
+                Registrations.Remove(reg);
+            }
+
+            return true;
+        }
 
         internal static ModifierKeys ModifierKeysFromString(string modifiersString)
         {
@@ -264,5 +279,56 @@ namespace SystemTrayMenu.Helpers
                 return key.ToString();
             }
         }
+
+        private static (ModifierKeys, Key) ParseKeysAndModifiersFromString(string hotKeyString) => (ModifierKeysFromString(hotKeyString), KeyFromString(hotKeyString));
+
+        private static IntPtr WndProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
+        {
+            const int WmHotkey = 0x0312;
+
+            // check if we got a hot key pressed.
+            if (msg == WmHotkey)
+            {
+                ModifierKeys modifiers = (ModifierKeys)((int)lParam & 0xFFFF);
+                int virtualKeyCode = ((int)lParam >> 16) & 0xFFFF;
+                Key key = KeyInterop.KeyFromVirtualKey(virtualKeyCode);
+
+                HotkeyRegistration? reg = null;
+                lock (CriticalSectionLock)
+                {
+                    foreach (var regHandle in Registrations)
+                    {
+                        if (modifiers == regHandle.Modifiers && key == regHandle.Key)
+                        {
+                            reg = regHandle;
+                            break;
+                        }
+                    }
+                }
+
+                reg?.OnKeyPressed();
+            }
+
+            handled = false;
+            return IntPtr.Zero;
+        }
+
+        internal abstract class HotkeyRegistrationHandle
+        {
+            internal event Action<HotkeyRegistrationHandle>? KeyPressed;
+
+            protected void RiseKeyPressed() => KeyPressed?.Invoke(this);
+        }
+
+        private class HotkeyRegistration : HotkeyRegistrationHandle
+        {
+            internal int Id { get; init; }
+
+            internal ModifierKeys Modifiers { get; set; }
+
+            internal Key Key { get; set; }
+
+            internal void OnKeyPressed() => RiseKeyPressed();
+        }
     }
 }

Helpers/KeyboardHook.cs

@@ -1,73 +0,0 @@
-// <copyright file="KeyboardHook.cs" company="PlaceholderCompany">
-// Copyright (c) PlaceholderCompany. All rights reserved.
-// </copyright>
-
-namespace SystemTrayMenu.Helpers
-{
-    using System;
-    using System.Windows;
-    using System.Windows.Input;
-    using System.Windows.Interop;
-
-    // TODO: Move this whole class into mainMenu to spare creating additional Win32 window handles by using Menu's Window directly.
-    internal class KeyboardHook : IDisposable
-    {
-        private readonly HwndSourceHook hook;
-        private readonly HwndSource hwnd;
-        private readonly Window window = new();
-        private int currentId;
-
-        public KeyboardHook()
-        {
-            hwnd = HwndSource.FromHwnd(new WindowInteropHelper(window).EnsureHandle());
-            hook = new HwndSourceHook(WndProc);
-            hwnd.AddHook(hook);
-        }
-
-        /// <summary>
-        /// A hot key has been pressed.
-        /// </summary>
-        internal event Action<Key, ModifierKeys>? KeyPressed;
-
-        public void Dispose()
-        {
-            // On regular App.Dispose the handle was already invalidated
-            if (hwnd.Handle != IntPtr.Zero)
-            {
-                // unregister all the registered hot keys.
-                for (int i = currentId; i > 0; i--)
-                {
-                    GlobalHotkeys.UnregisterHotkey(hwnd.Handle, i);
-                }
-
-                hwnd.RemoveHook(hook);
-            }
-
-            hwnd.Dispose();
-        }
-
-        internal void RegisterHotKey(ModifierKeys modifiers, Key key) => currentId = GlobalHotkeys.RegisterHotkeyLocal(hwnd.Handle, currentId + 1, modifiers, key);
-
-        internal void RegisterHotKey(string hotKeyString) => currentId = GlobalHotkeys.RegisterHotkeyLocal(hwnd.Handle, currentId + 1, hotKeyString);
-
-        private IntPtr WndProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
-        {
-            const int WmHotkey = 0x0312;
-
-            // check if we got a hot key pressed.
-            if (msg == WmHotkey)
-            {
-                // get the keys.
-                ModifierKeys modifiers = (ModifierKeys)((int)lParam & 0xFFFF);
-                int virtualKeyCode = ((int)lParam >> 16) & 0xFFFF;
-                Key key = KeyInterop.KeyFromVirtualKey(virtualKeyCode);
-
-                // invoke the event to notify the parent.
-                KeyPressed?.Invoke(key, modifiers);
-            }
-
-            handled = false;
-            return IntPtr.Zero;
-        }
-    }
-}

UserInterface/HotkeySelector.cs

@@ -14,14 +14,14 @@ namespace SystemTrayMenu.UserInterface
     using SystemTrayMenu.Helpers;
     using SystemTrayMenu.Utilities;
 
-    public sealed class HotkeySelector : TextBox, IDisposable
+    public sealed class HotkeySelector : TextBox
     {
         // ArrayLists used to enforce the use of proper modifiers.
         // Shift+A isn't a valid hotkey, for instance, as it would screw up when the user is typing.
         private readonly IList<int> needNonShiftModifier = new List<int>();
         private readonly IList<int> needNonAltGrModifier = new List<int>();
 
-        private KeyboardHook hook = new();
+        private GlobalHotkeys.HotkeyRegistrationHandle? hotkeyHandle;
 
         // These variables store the current hotkey and modifier(s)
         private Key hotkey = Key.None;
@@ -75,7 +75,10 @@ namespace SystemTrayMenu.UserInterface
             PopulateModifierLists();
         }
 
-        ~HotkeySelector() => Dispose();
+        ~HotkeySelector()
+        {
+            GlobalHotkeys.Unregister(hotkeyHandle);
+        }
 
         /// <summary>
         /// Gets or sets used to get/set the hotkey (e.g. Key.A).
@@ -131,12 +134,6 @@ namespace SystemTrayMenu.UserInterface
             return hotkeyString.ToString() + key.ToString();
         }
 
-        public void Dispose()
-        {
-            hook.Dispose();
-            GC.SuppressFinalize(this);
-        }
-
         public override string ToString() => HotkeyToString(modifiers, hotkey);
 
         /// <summary>
@@ -166,7 +163,7 @@ namespace SystemTrayMenu.UserInterface
 
             try
             {
-                hook.RegisterHotKey(modifiers, key);
+                hotkeyHandle = GlobalHotkeys.Register(modifiers, key);
             }
             catch (InvalidOperationException ex)
             {
@@ -175,7 +172,7 @@ namespace SystemTrayMenu.UserInterface
             }
 
             this.handler = handler;
-            hook.KeyPressed += (_, _) => handler.Invoke();
+            hotkeyHandle.KeyPressed += (_) => handler.Invoke();
             return 1;
         }
 
@@ -189,9 +186,8 @@ namespace SystemTrayMenu.UserInterface
 
         private void UnregisterHotKey()
         {
-            // TODO: Rework to allow deregistration?
-            hook.Dispose();
-            hook = new();
+            GlobalHotkeys.Unregister(hotkeyHandle);
+            hotkeyHandle = null;
         }
 
         /// <summary>