using System;
using System.Runtime.InteropServices;
using System.Windows.Forms;
namespace SystemTrayMenu.Helper
{
public sealed class KeyboardHook : IDisposable
{
// Registers a hot key with Windows.
[DllImport("user32.dll")]
private static extern bool RegisterHotKey(IntPtr hWnd, int id, uint fsModifiers, uint vk);
// Unregisters the hot key with Windows.
[DllImport("user32.dll")]
private static extern bool UnregisterHotKey(IntPtr hWnd, int id);
///
/// Represents the window that is used internally to get the messages.
///
private class Window : NativeWindow, IDisposable
{
private static int WM_HOTKEY = 0x0312;
public Window()
{
// create the handle for the window.
this.CreateHandle(new CreateParams());
}
///
/// Overridden to get the notifications.
///
///
protected override void WndProc(ref Message m)
{
base.WndProc(ref m);
// check if we got a hot key pressed.
if (m.Msg == WM_HOTKEY)
{
// get the keys.
Keys key = (Keys)(((int)m.LParam >> 16) & 0xFFFF);
KeyboardHookModifierKeys modifier = (KeyboardHookModifierKeys)((int)m.LParam & 0xFFFF);
// invoke the event to notify the parent.
if (KeyPressed != null)
KeyPressed(this, new KeyPressedEventArgs(modifier, key));
}
}
public event EventHandler KeyPressed;
#region IDisposable Members
public void Dispose()
{
this.DestroyHandle();
}
#endregion
}
private Window _window = new Window();
private int _currentId;
public KeyboardHook()
{
// register the event of the inner native window.
_window.KeyPressed += delegate (object sender, KeyPressedEventArgs args)
{
if (KeyPressed != null)
KeyPressed(this, args);
};
}
///
/// Registers a hot key in the system.
///
/// The modifiers that are associated with the hot key.
/// The key itself that is associated with the hot key.
public void RegisterHotKey(KeyboardHookModifierKeys modifier, Keys key)
{
// increment the counter.
_currentId = _currentId + 1;
// register the hot key.
if (!RegisterHotKey(_window.Handle, _currentId, (uint)modifier, (uint)key))
throw new InvalidOperationException("Couldn’t register the hot key.");
}
///
/// A hot key has been pressed.
///
public event EventHandler KeyPressed;
#region IDisposable Members
public void Dispose()
{
// unregister all the registered hot keys.
for (int i = _currentId; i > 0; i--)
{
UnregisterHotKey(_window.Handle, i);
}
// dispose the inner native window.
_window.Dispose();
}
#endregion
}
///
/// Event Args for the event that is fired after the hot key has been pressed.
///
public class KeyPressedEventArgs : EventArgs
{
private KeyboardHookModifierKeys _modifier;
private Keys _key;
internal KeyPressedEventArgs(KeyboardHookModifierKeys modifier, Keys key)
{
_modifier = modifier;
_key = key;
}
public KeyboardHookModifierKeys Modifier
{
get { return _modifier; }
}
public Keys Key
{
get { return _key; }
}
}
///
/// The enumeration of possible modifiers.
///
[Flags]
public enum KeyboardHookModifierKeys : uint
{
Alt = 1,
Control = 2,
Shift = 4,
Win = 8
}
}