Display *dpy;               /* the X display */
GdkWindow *gdkWindow;       /* the GDK window wrapped around your X window */
GtkIMContext *im_context;   /* the context for the keyboard input method */

/*
 * the following three atoms are needed to get virtual keyboard input
 */
Atom hildon_com, hildon_utf, hildon_cls;

...                         /* set up your hildon / gtk program */
dpy = ...;                  /* open the display */

/*
 * now create the atoms we need
 */
hildon_com = XInternAtom(dpy, "_HILDON_IM_COM", TRUE);
hildon_utf = XInternAtom(dpy, "_HILDON_IM_INSERT_UTF8", TRUE);
hildon_cls = XInternAtom(dpy, "_HILDON_IM_CLOSE", TRUE);

/*
 * create and map your X and GDK windows, then show the keyboard (im_context)
 */
...
gdkWindow = ...;            /* see snippet 3 on how this is done */
...

/*
 * now add support for the hildon ClientMessage events to your event handler
 */
while (!quit)
{
  while (gtk_events_pending())
    gtk_main_iteration();

  XNextEvent(dpy, &event);
  switch(event.type)
  {
    case ClientMessage:
      if (event.xclient.message_type == but_hildon_cls)      /* keyboard closed */
      {
        hildon_gtk_im_context_hide(im_context);
        gtk_im_context_reset(im_context);
        g_object_unref(im_context);
        im_context = NULL;
      }
      else if (event.xclient.message_type == but_hildon_utf) /* keyboard input */
      {
        XEvent kev = event;                                  /* create new event */
        KeySym sym = XStringToKeysym(&event.xclient.data.b[4]); /* read the key */

        if (!sym) sym = event.xclient.data.b[4];             /* fall back to input */

        kev.type = KeyPress;                                 /* keyboard event */
        kev.xkey.root = ev->window;
        kev.xkey.subwindow = None;
        kev.xkey.time = CurrentTime;
        kev.xkey.x = kev.xkey.y = kev.xkey.x_root = kev.xkey.y_root = 1;
        kev.xkey.same_screen = TRUE;
        kev.xkey.keycode = XKeysymToKeycode(dpy, sym);      /* convert to key code */

        if (isupper(ev->data.b[4]))                         /* upper case letter? */
            kev.xkey.state = ShiftMask;                     /* yes: we need shift */
        else
            kev.xkey.state = 0;

        XSendEvent(dpy, win, TRUE, KeyPressMask, &kev);

        kev.type = KeyRelease;                              /* key release event */
        XSendEvent(dpy, win, TRUE, KeyReleaseMask, &kev);
      }
      else if (event.xclient.message_type == but_hildon_com)/* special key/event */
      {
        switch (event.xclient.data.b[4])
        {
          case 0:                                          /* return / enter */
            ... /* send XK_Return (or handle specially) */
            break;
          case 1:                                          /* tab */
            ... /* send XK_Tab (or handle specially) */
            break;
          case 2:                                         /* backspace */
            ... /* send XK_BackSpace (or handle specially) */
            break;
          case 4:                                        /* state change */
              break;
          case 7:                                        /* special char */
              break;
          default:
              printf("Unknown IM event data %d\n",
                        (int) event.xclient.data.b[4]);
        }
      }
      break;

    case KeyPress:
      ...
      break;

    ...
  }
}