Re: Question about entry callbacks

[Havoc Pennington <hp redhat com>]

Vicki Stanfield <vicki dialupnet com> writes:
> I am trying to create a callback for an entry widget. When a string
> is typed in, I want the callback to be called. I assume that I can
> use the entry widget which is passed in with the gtk_entry_get_text
> function to get the string. The problem is that when I try to compile,
> I get an error which doesn't make sense to me. The code is based on the
> example at http://www.gtk.org/tutorial/sec-textentries.html
> 
> My call looks like this:
> 
> entry_widget = gtk_entry_new_with_max_length(35);
> gtk_signal_connect_object (GTK_OBJECT(entry_widget), "activate",
>     GTK_SIGNAL_FUNC(GetAccountName), entry_widget);

The warning you get is because the last arg to connect_object has to
be cast to GtkObject with the GTK_OBJECT() macro.

Though, rather than adding that cast, I would suggest abandoning all
use of gtk_signal_connect_object(). It is an evil, confusing,
nonsensical function that causes endless confusion judging by
questions on this list. Just pretend it does not exist and you will be
happier. ;-) It is purely a way to save typing; it is never required
in order to achieve a given result.
 
> void GetAccountName(GtkWidget *widget, GtkWidget *entry_widget)

With connect_object, the callback should be:
 void GetAccountName (gpointer user_data, GtkWidget *widget_emitting_signal)

With plain connect(), the args are in their normal order:
 void GetAccountName (GtkWidget *widget_emitting_signal, gpointer user_data)

i.e. connect_object basically just swaps the args. It also requires
the user data to be a GtkObject, but there is no rational reason for
that.

Though the order changes, the first and last args to a callback are always the
object that emitted the signal (in this case the entry) and the user
data passed to connect() or connect_object().

If a signal has any additional args, such as the event arg to
button_press_event, then those args go in the middle between the
emitting object and user data.

Havoc