Gets the filename for the icon. If the %GTK_ICON_LOOKUP_USE_BUILTIN
flag was passed to gtk_icon_theme_lookup_icon(), there may be no
filename if a builtin icon is returned; in this case, you should
use gtk_icon_info_get_builtin_pixbuf().
the filename for the icon, or %NULL
if gtk_icon_info_get_builtin_pixbuf() should be used instead.
The return value is owned by GTK+ and should not be modified
or freed.
Gets the filename for the icon. If the %GTK_ICON_LOOKUP_USE_BUILTIN flag was passed to gtk_icon_theme_lookup_icon(), there may be no filename if a builtin icon is returned; in this case, you should use gtk_icon_info_get_builtin_pixbuf().