how to implement a modal window

[Neo Liu <Neo Liu Sun COM>]

Gurus,

I want to implement below behavior

1.main window has a button.
2.when the button is pressed, a new modal window pops up.

However, it seems neither gtk_window_set_modal nor gtk_grab_add does help.

What's the right way to use that? Is there any sample code that I can 
refer to?

thanks in advance and best regards,

ln