This function returns the position you need to pass to move() to keep this
window in its current position. This means that the meaning of the
returned value varies with window gravity.
If you haven't changed the window gravity, its gravity will be
GDK2.GRAVITY_NORTH_WEST. This means that get_position() gets the position
of the top-left corner of the window manager frame for the window. move()
sets the position of this same top-left corner.
get_position() is not 100% reliable because X does not specify a way to
obtain the geometry of the decorations placed on a window by the window
manager. Thus GTK+ is using a "best guess" that works with most window
managers.
Moreover, nearly all window managers are historically broken with respect
to their handling of window gravity. So moving a window to its current
position as returned by get_position() tends to result in moving the window
slightly. Window managers are slowly getting better over time.
If a window has gravity GDK2.GRAVITY_STATIC the window manager frame is not
relevant, and thus get_position() will always produc accurate results.
However you can't use static gravity to do things like place a window in a
corner of the screen, because static gravity ignores the window manager
decorations.
If you are saving and restoring your application's window positions, you
should know that it's impossible for applications to do this without
getting it somewhat wrong because applications do not have sufficient
knowledge of window manager state.
GTK2.Window()->get_modal()