Re: [gtk-list] [gtkmm] signal handlers vs. virtual functions

[Tero Pulkkinen <terop students cc tut fi>]

Davide Rossetti <rossetti@apemaia.roma1.infn.it> writes:
> hi gtk-- users, 
> I have a mothodological question:  
> when is "good" to override X_impl() virtual functions in gtk-- widgets ?  
> 
> 2) for personalised widget classes, subclassed from stock gtk-- widget
>    classes, there are two options available:
> 	2.1) use connect_to_method(X, this, handle_X_method);
> 	2.2) override X_impl().

I'd prefer X_impl() most times when you've already derived from some
widget. Then for widgets that you just *use*, you need to use
connect_to_* technique.

=> virtual functions are better and easier to use, but sometimes you must
   use connect's to communicate between two widgets.

for example,

class mywindow : public Gtk_Window {
public:
	gint destroy_event_impl(GdkEventAny*)  { ... }
};

Doing this with connect_to_* functions would be silly.

but the following:

class mywindow : public Gtk_Window {
  Gtk_Button b;
public:
  mywindow() : b("test") { connect_to_method(b.clicked, this, &foomethod); }
  void foomethod() { ... }
}

Here, its obvious to use connect_to_method, since that way you dont need 
to derive from Gtk_Button just for catching events..

> (2.2) can give problems: either it is a do nothing function [is it
> true?] or there is 'meat' inside and you have to call the
> Super::X_impl() right inside your X_impl() [and you have to
> remember/know when to call it before or after your processing]

Yes, when you override virtual functions in gtk--, usually its good
to call the default implementation. I dont see it as a problem, just
a common use of virtual functions.

-- 
-- Tero Pulkkinen -- terop@modeemi.cs.tut.fi --