I'm trying to send mouse clicks to a program. As I don't want the mouse to move, I don't want to use SendInput or mouse_event, and because the window that should receive the clicks doesn't really use Buttons or other GUI events, I can't send messages to these buttons.

I'm trying to get this working using SendMessage, but for some reason it doesn't work. Relevant code is (in C#, but tried Java with jnative as well), trying this on Vista

    [DllImport("user32.dll", CharSet=CharSet.Auto)]
    public static extern int SendMessage(IntPtr A_0, int A_1, int A_2,  int  A_3);

    static int WM_CLOSE = 0x10;
    static int WM_LBUTTONDOWN = 0x201;
    static int WM_LBUTTONUP = 0x202;

    public static void click(IntPtr hWnd, int x, int y)
    {
        SendMessage(hWnd, WM_LBUTTONDOWN, 1, ((x << 0x10) ^ y));
        SendMessage(hWnd, WM_LBUTTONUP, 0, ((x << 0x10) ^ y));
    }

    public static void close(IntPtr hWnd)
    {
        SendMessage(hWnd, WM_CLOSE, 0, 0);
    }

The close works fine, but the click doesn't do anything.