/// <summary>
/// A callback function which will be called every time a keyboard activity detected.
/// https://docs.microsoft.com/en-us/windows/win32/winmsg/lowlevelkeyboardproc
/// </summary>
/// <param name="code">
/// Specifies whether the hook procedure must process the message.
/// If code is HC_ACTION, the hook procedure must process the message.
/// If code is less than zero, the hook procedure must pass the message to the
/// CallNextHookEx function without further processing and must return the
/// value returned by CallNextHookEx.
/// </param>
/// <param name="wParam">
/// Specifies whether the message was sent by the current thread.
/// If the message was sent by the current thread, it is nonzero; otherwise, it is zero.
/// </param>
/// <param name="lParam">
/// Pointer to a CWPSTRUCT structure that contains details about the message.
/// </param>
/// <returns>
/// If code is less than zero, the hook procedure must return the value returned by CallNextHookEx.
/// If code is greater than or equal to zero, it is highly recommended that you call CallNextHookEx
/// and return the value it returns; otherwise, other applications that have installed WH_CALLWNDPROC
/// hooks will not receive hook notifications and may behave incorrectly as a result. If the hook
/// procedure does not call CallNextHookEx, the return value should be zero.
/// </returns>
private IntPtr KeyboardHookProc(int code, uint wParam, IntPtr lParam)
{
//Indicates if any of the underlaying events set the e.Handled flag.
var handled = false;
//If it was Ok and there are no listeners.
if (code < 0 || KeyDown == null && KeyUp == null && KeyPress == null)
{
return(User32.CallNextHookEx(_keyboardHookHandle, code, wParam, lParam));
}
//Read structure KeyboardHookStruct at lParam
var keyboard = (KeyboardHook)Marshal.PtrToStructure(lParam, typeof(KeyboardHook));
var isInjected = (keyboard.Flags & 0x10) != 0;
if (KeyDown != null && (wParam == MessageKeydown || wParam == MessageSystemKeyDown))
{
#region Raise KeyDown
var isDownShift = (User32.GetKeyState(KeyShift) & 0x80) == 0x80;
var isDownCapslock = User32.GetKeyState(KeyCapital) != 0;
var e = new CustomKeyEventArgs(KeyInterop.KeyFromVirtualKey(keyboard.KeyCode), isDownCapslock ^ isDownShift, isInjected);
KeyDown?.Invoke(this, e);
handled = e.Handled;
#endregion
}
if (KeyPress != null && wParam == MessageKeydown)
{
#region Raise KeyPress
var isDownShift = (User32.GetKeyState(KeyShift) & 0x80) == 0x80;
var isDownCapslock = User32.GetKeyState(KeyCapital) != 0;
var keyState = new byte[256];
User32.GetKeyboardState(keyState);
var inBuffer = new byte[2];
if (User32.ToAscii(keyboard.KeyCode, keyboard.ScanCode, keyState, inBuffer, keyboard.Flags) == 1)
{
var key = (char)inBuffer[0];
if (isDownCapslock ^ isDownShift && char.IsLetter(key))
{
key = char.ToUpper(key);
}
var e = new CustomKeyPressEventArgs(key);
KeyPress?.Invoke(this, e);
handled = handled || e.Handled;
}
#endregion
}
if (KeyUp != null && (wParam == MessageKeyUp || wParam == MessageSystemKeyUp))
{
#region Raise KeyUp
var e = new CustomKeyEventArgs(KeyInterop.KeyFromVirtualKey(keyboard.KeyCode), false, isInjected);
KeyUp?.Invoke(this, e);
handled = handled || e.Handled;
#endregion
}
//If event handled in application do not handoff to other listeners.
return(handled ? new IntPtr(1) : User32.CallNextHookEx(_keyboardHookHandle, code, wParam, lParam));
}
