widget mapping & event windows

[Tristan Van Berkom <vantr touchtunes com>]

Hi all,
    I'm writing a GTK_NO_WINDOW type widget that uses a input only
window, and I was looking at some examples:
    - GtkButton
    - GtkRange

Both hook into the `map'/`unmap' vfuncs to show/hide their
event windows.

Both assert `g_return_if_fail(GTK_IS_BUTTON(button))' (or range
respectivly) in their `->map()'/`->unmap()' functions.

Is there any sence in that ?

Is there any reason why I should do the same ?

Cheers,
                                    -Tristan