ToUnicodeEx and dead keys inside system wide hooks

Hello there. I'm new here and I want to ask help to you on solving this problem. I'm trying to detect which character is produced whenever the user presses a key. For this, I'm using the ToUnicodeEx function, which translates the specified virtual-key code and keyboard state to the corresponding Unicode character, inside a keyboard system wide hook. However, every time the user presses dead keys, such as the ones producing '¨', '~' or '´', strange things happen. Here is sample code of the first version:

Code:

---

private static int KeyboardHookProc(int nCode, Int32 wParam, IntPtr lParam)
{
        //indicates if any of underlaing events set e.Handled flag
        bool handled = false;

        if (nCode >= 0)
        {
                //read structure KeyboardHookStruct at lParam
                KeyboardHookStruct MyKeyboardHookStruct = (KeyboardHookStruct)Marshal.PtrToStructure(lParam, typeof(KeyboardHookStruct));
                //raise KeyDown
                if (s_KeyDown != null && (wParam == WM_KEYDOWN || wParam == WM_SYSKEYDOWN))
                {
                        Keys keyData = (Keys)MyKeyboardHookStruct.VirtualKeyCode;
                        KeyEventArgs e = new KeyEventArgs(keyData);
                        s_KeyDown.Invoke(null, e);
                        handled = e.Handled;
                }

                // raise KeyPress
                if (s_KeyPress != null && wParam == WM_KEYDOWN)
                {
                        bool isDownShift = ((GetKeyState(VK_SHIFT) & 0x80) == 0x80 ? true : false);
                        bool isDownCapslock = (GetKeyState(VK_CAPITAL) != 0 ? true : false);

                        byte[] keyState = new byte[256];
                        GetKeyboardState(keyState);
                        System.Text.StringBuilder sbString = new System.Text.StringBuilder();
                        IntPtr HKL = GetKeyboardLayout(0);

                        switch (ToUnicodeEx((uint)MyKeyboardHookStruct.VirtualKeyCode,
                                (uint)MyKeyboardHookStruct.ScanCode,
                                keyState,
                                sbString,
                                5,
                                (uint)MyKeyboardHookStruct.Flags,
                                HKL))
                        {
                                case 1:
                                        char key = sbString.ToString()[0];
                                        if ((isDownCapslock ^ isDownShift) && Char.IsLetter(key)) key = Char.ToUpper(key);
                                        KeyPressEventArgs e = new KeyPressEventArgs(key);
                                        s_KeyPress.Invoke(null, e);
                                        handled = handled || e.Handled;
                                        break;
                        }
                }

                // raise KeyUp
                if (s_KeyUp != null && (wParam == WM_KEYUP || wParam == WM_SYSKEYUP))
                {
                        Keys keyData = (Keys)MyKeyboardHookStruct.VirtualKeyCode;
                        KeyEventArgs e = new KeyEventArgs(keyData);
                        s_KeyUp.Invoke(null, e);
                        handled = handled || e.Handled;
                }

        }

        //if event handled in application do not handoff to other listeners
        if (handled)
                return -1;

        //forward to other application
        return CallNextHookEx(s_KeyboardHookHandle, nCode, wParam, lParam);
}

---

(I know the sample code I'm posting is C#, but it is really easy to read and the question here is about the ToUnicodeEx WinAPI call.)

With this code I faced the following problem: Whenever I tried to type "á" in notepad, which requires '´' to be pressed before 'a', the result would be "´´a". Although the captured character by ToUnicodeEx was 'á', I can't admit that my application prevents the user from using characters such as 'á'.

So, I worked around this problem by avoiding ToUnicodeEx to be called whenever a dead key is pressed. This way, I can avoid the ToUnicodeEx function from messing with the keyboard state. Here is the current version code:

Code:

---

private static int KeyboardHookProc(int nCode, Int32 wParam, IntPtr lParam)
{
        //indicates if any of underlaing events set e.Handled flag
        bool handled = false;

        if (nCode >= 0)
        {
                //read structure KeyboardHookStruct at lParam
                KeyboardHookStruct MyKeyboardHookStruct = (KeyboardHookStruct)Marshal.PtrToStructure(lParam, typeof(KeyboardHookStruct));
                //raise KeyDown
                if (s_KeyDown != null && (wParam == WM_KEYDOWN || wParam == WM_SYSKEYDOWN))
                {
                        Keys keyData = (Keys)MyKeyboardHookStruct.VirtualKeyCode;
                        KeyEventArgs e = new KeyEventArgs(keyData);
                        s_KeyDown.Invoke(null, e);
                        handled = e.Handled;
                }

                // raise KeyPress
                if (s_KeyPress != null && wParam == WM_KEYDOWN)
                {
                        bool isDownShift = ((GetKeyState(VK_SHIFT) & 0x80) == 0x80 ? true : false);
                        bool isDownCapslock = (GetKeyState(VK_CAPITAL) != 0 ? true : false);

                        byte[] keyState = new byte[256];
                        GetKeyboardState(keyState);
                        System.Text.StringBuilder sbString = new System.Text.StringBuilder();
                        IntPtr HKL = GetKeyboardLayout(0);

                        if (!IsDeadKey((uint)MyKeyboardHookStruct.VirtualKeyCode))
                        {
                                switch (ToUnicodeEx((uint)MyKeyboardHookStruct.VirtualKeyCode,
                                        (uint)MyKeyboardHookStruct.ScanCode,
                                        keyState,
                                        sbString,
                                        5,
                                        (uint)MyKeyboardHookStruct.Flags,
                                        HKL))
                                {
                                        case 1:
                                                char key = sbString.ToString()[0];
                                                if ((isDownCapslock ^ isDownShift) && Char.IsLetter(key)) key = Char.ToUpper(key);
                                                KeyPressEventArgs e = new KeyPressEventArgs(key);
                                                s_KeyPress.Invoke(null, e);
                                                handled = handled || e.Handled;
                                                break;
                                }
                        }
                }

                // raise KeyUp
                if (s_KeyUp != null && (wParam == WM_KEYUP || wParam == WM_SYSKEYUP))
                {
                        Keys keyData = (Keys)MyKeyboardHookStruct.VirtualKeyCode;
                        KeyEventArgs e = new KeyEventArgs(keyData);
                        s_KeyUp.Invoke(null, e);
                        handled = handled || e.Handled;
                }

        }

        //if event handled in application do not handoff to other listeners
        if (handled)
                return -1;

        //forward to other application
        return CallNextHookEx(s_KeyboardHookHandle, nCode, wParam, lParam);
}

static bool IsDeadKey(uint key)
{
        if ((MapVirtualKey(key, 2) & 2147483648) == 2147483648)
        {
                return true;
        }
        else
        {
                return false;
        }
}

---

I though this solution would solve my problem, but I was wrong. The result has improved, but it's not quite what I wanted. Now, typing 'á' in notepad results in 'a'. Notice that the accent '´' is missing.

Does anyone know how to work around this issue? My current method already captures the correct character, but prevents the user from producing characters with accents or diacritics. I think the KeyboardHookProc method just need a few changes, but I can't figure them out.

Thanks in advance.

PS: I tried the solution described in the following link: http://social.msdn.microsoft.com/For...1-33c7ccea735c. However, the result is quite the same as in my current version. That code only erases the keyboard buffer, which deletes the accents, therefore not allowing the user to use them.