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Merge pull request #12 from stnkl/master
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Add support for blocking hotkeys (#11)
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@kfirprods
kfirprods authored Oct 19, 2022
2 parents d5a17a6 + aea8fad commit c2509e1
Showing 1 changed file with 50 additions and 48 deletions.
98 changes: 50 additions & 48 deletions source/NonInvasiveKeyboardHook/NonInvasiveKeyboardHookLibrary/KeyboardHookManager.cs
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Original file line number Diff line number Diff line change
@@ -1,35 +1,34 @@
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Runtime.InteropServices;
using System.Threading;

namespace NonInvasiveKeyboardHookLibrary
{
internal struct KeyboardParams
{
public IntPtr wParam;
public int vkCode;

public KeyboardParams(IntPtr wParam, int vkCode)
{
this.wParam = wParam;
this.vkCode = vkCode;
}
}

/// <summary>
/// A hotkey manager that uses a low-level global keyboard hook, but eventually only fires events for
/// pre-registered hotkeys, i.e. not invading a user's privacy.
/// </summary>
public class KeyboardHookManager
{
internal class CallbackStruct
{
public readonly Action Action;
public readonly bool Blocking;

public CallbackStruct(Action action, bool blocking)
{
this.Action = action;
this.Blocking = blocking;
}
}

#region Private Attributes
/// <summary>
/// Keeps track of all registered hotkeys
/// </summary>
private readonly Dictionary<KeybindStruct, Action> _registeredCallbacks;
private readonly Dictionary<KeybindStruct, CallbackStruct> _registeredCallbacks;
/// <summary>
/// Keeps track of modifier keys that are held down
/// </summary>
Expand All @@ -52,7 +51,7 @@ public class KeyboardHookManager
/// </summary>
public KeyboardHookManager()
{
this._registeredCallbacks = new Dictionary<KeybindStruct, Action>();
this._registeredCallbacks = new Dictionary<KeybindStruct, CallbackStruct>();
this._downModifierKeys = new HashSet<ModifierKeys>();
this._downKeys = new HashSet<int>();
}
Expand Down Expand Up @@ -90,11 +89,12 @@ public void Stop()
/// </summary>
/// <param name="virtualKeyCode">The virtual key code of the hotkey</param>
/// <param name="action">The callback action to invoke when this hotkey is pressed</param>
/// <param name="blocking">Boolean indicating wether to block the original shortcut from propagating</param>
/// <exception cref="HotkeyAlreadyRegisteredException">Thrown when the given key is already mapped to a callback</exception>
/// /// <returns>Unique identifier of this hotkey, which can be used to remove it later</returns>
public Guid RegisterHotkey(int virtualKeyCode, Action action)
public Guid RegisterHotkey(int virtualKeyCode, Action action, bool blocking = false)
{
return this.RegisterHotkey(new ModifierKeys[0], virtualKeyCode, action);
return this.RegisterHotkey(new ModifierKeys[0], virtualKeyCode, action, blocking);
}

/// <summary>
Expand All @@ -103,16 +103,17 @@ public Guid RegisterHotkey(int virtualKeyCode, Action action)
/// <param name="modifiers">Modifiers that must be held while hitting the key. Multiple modifiers can be provided using the flags bitwise OR operation</param>
/// <param name="virtualKeyCode">The virtual key code of the standard key</param>
/// <param name="action">The callback action to invoke when this combination is pressed</param>
/// <param name="blocking">Boolean indicating wether to block the original shortcut from propagating</param>
/// <exception cref="HotkeyAlreadyRegisteredException">Thrown when the given key combination is already mapped to a callback</exception>
/// <returns>Unique identifier of this hotkey, which can be used to remove it later</returns>
public Guid RegisterHotkey(ModifierKeys modifiers, int virtualKeyCode, Action action)
public Guid RegisterHotkey(ModifierKeys modifiers, int virtualKeyCode, Action action, bool blocking = false)
{
var allModifiers = Enum.GetValues(typeof(ModifierKeys)).Cast<ModifierKeys>().ToArray();

// Get the modifiers that were chained with bitwise OR operation as an array of modifiers
var selectedModifiers = allModifiers.Where(modifier => modifiers.HasFlag(modifier)).ToArray();

return RegisterHotkey(selectedModifiers, virtualKeyCode, action);
return RegisterHotkey(selectedModifiers, virtualKeyCode, action, blocking);
}

/// <summary>
Expand All @@ -121,9 +122,10 @@ public Guid RegisterHotkey(ModifierKeys modifiers, int virtualKeyCode, Action ac
/// <param name="modifiers">Modifiers that must be held while hitting the key</param>
/// <param name="virtualKeyCode">The virtual key code of the standard key</param>
/// <param name="action">The callback action to invoke when this combination is pressed</param>
/// <param name="blocking">Boolean indicating wether to block the original shortcut from propagating</param>
/// <exception cref="HotkeyAlreadyRegisteredException">Thrown when the given key combination is already mapped to a callback</exception>
/// <returns>Unique identifier of this hotkey, which can be used to remove it later</returns>
public Guid RegisterHotkey(ModifierKeys[] modifiers, int virtualKeyCode, Action action)
public Guid RegisterHotkey(ModifierKeys[] modifiers, int virtualKeyCode, Action action, bool blocking = false)
{
var keybindIdentity = Guid.NewGuid();
var keybind = new KeybindStruct(modifiers, virtualKeyCode, keybindIdentity);
Expand All @@ -132,7 +134,8 @@ public Guid RegisterHotkey(ModifierKeys[] modifiers, int virtualKeyCode, Action
throw new HotkeyAlreadyRegisteredException();
}

this._registeredCallbacks[keybind] = action;
var callbackStruct = new CallbackStruct(action, blocking);
this._registeredCallbacks[keybind] = callbackStruct;
return keybindIdentity;
}

Expand Down Expand Up @@ -182,24 +185,29 @@ public void UnregisterHotkey(Guid keybindIdentity)
if (keybindToRemove == null || !this._registeredCallbacks.Remove(keybindToRemove))
{
throw new HotkeyNotRegisteredException();
}
}
}
#endregion

#region Private methods
private void HandleKeyPress(int virtualKeyCode)
private void InvokeAction(object actionObj)
{
var action = (Action)actionObj;
action.Invoke();
}

private bool HandleKeyPress(int virtualKeyCode)
{
var currentKey = new KeybindStruct(this._downModifierKeys, virtualKeyCode);

if (!this._registeredCallbacks.ContainsKey(currentKey))
if (this._registeredCallbacks.ContainsKey(currentKey) &&
this._registeredCallbacks.TryGetValue(currentKey, out var callbackStruct))
{
return;
ThreadPool.QueueUserWorkItem(this.InvokeAction, callbackStruct.Action);
return callbackStruct.Blocking;
}

if (this._registeredCallbacks.TryGetValue(currentKey, out var callback))
{
callback.Invoke();
}
return false;
}
#endregion

Expand All @@ -217,36 +225,28 @@ private static IntPtr SetHook(LowLevelKeyboardProc proc)
{
var userLibrary = LoadLibrary("User32");

return SetWindowsHookEx(WH_KEYBOARD_LL, proc,
userLibrary, 0);
return SetWindowsHookEx(WH_KEYBOARD_LL, proc, userLibrary, 0);
}

private IntPtr HookCallback(int nCode, IntPtr wParam, IntPtr lParam)
{
if (nCode >= 0)
{
var vkCode = Marshal.ReadInt32(lParam);

// Debug.WriteLine("Starting");
// To prevent slowing keyboard input down, we use handle keyboard inputs in a separate thread
ThreadPool.QueueUserWorkItem(this.HandleSingleKeyboardInput, new KeyboardParams(wParam, vkCode));
// Debug.WriteLine("Ending");
var blocking = this.HandleSingleKeyboardInput(wParam, vkCode);

if (blocking)
return (IntPtr)1;
}

return CallNextHookEx(_hookId, nCode, wParam, lParam);
}

/// <summary>
/// Handles a keyboard event based on the KeyboardParams it receives
/// </summary>
/// <param name="keyboardParamsObj">KeyboardParams struct (object type to comply with QueueUserWorkItem)</param>
private void HandleSingleKeyboardInput(object keyboardParamsObj)
private bool HandleSingleKeyboardInput(IntPtr wParam, int vkCode)
{
var keyboardParams = (KeyboardParams)keyboardParamsObj;
var wParam = keyboardParams.wParam;
var vkCode = keyboardParams.vkCode;

var modifierKey = ModifierKeysUtilities.GetModifierKeyFromCode(vkCode);
var blocking = false;

// If the keyboard event is a KeyDown event (i.e. key pressed)
if (wParam == (IntPtr)WM_KEYDOWN || wParam == (IntPtr)WM_SYSKEYDOWN)
Expand All @@ -263,7 +263,7 @@ private void HandleSingleKeyboardInput(object keyboardParamsObj)
// Trigger callbacks that are registered for this key, but only once per key press
if (!this._downKeys.Contains(vkCode))
{
this.HandleKeyPress(vkCode);
blocking = this.HandleKeyPress(vkCode);
this._downKeys.Add(vkCode);
}
}
Expand All @@ -282,6 +282,8 @@ private void HandleSingleKeyboardInput(object keyboardParamsObj)

this._downKeys.Remove(vkCode);
}

return blocking;
}

private delegate IntPtr LowLevelKeyboardProc(int nCode, IntPtr wParam, IntPtr lParam);
Expand All @@ -298,7 +300,7 @@ private static extern IntPtr SetWindowsHookEx(int idHook,
[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
private static extern IntPtr CallNextHookEx(IntPtr hhk, int nCode,
IntPtr wParam, IntPtr lParam);

/// <summary>
/// Loads the library.
/// </summary>
Expand All @@ -322,4 +324,4 @@ public class HotkeyNotRegisteredException : NonInvasiveKeyboardHookException
{
}
#endregion
}
}

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