void gtk_entry_set_visibility ( GtkEntry* entry, gboolean visible )
Sets whether the contents of the entry are visible or not.
When visibility is set to
FALSE, characters are displayed
as the invisible char, and will also appear that way when
the text in the entry widget is copied elsewhere.
By default, GTK+ picks the best invisible character available in the current font, but it can be changed with gtk_entry_set_invisible_char().
Note that you probably want to set
inform input methods about the purpose of this entry,
in addition to setting visibility to