getting GDK_GRAB_NOT_VIEWABLE for keyboard grab

[Thura <thurahlaing06 gmail com>]

I am trying to grab keyboard for my application window, and getting return
value "3" (GDK_GRAB_NOT_VIEWABLE)  ...
Any clue?

Here is my code.

gtk_window_fullscreen (GTK_WINDOW(object->window));
gtk_widget_show_all (GTK_WIDGET(object->window));

int retval = gdk_keyboard_grab (object->window->window, FALSE,
GDK_CURRENT_TIME);