Re: Button in Gtk

["Brian J. Tarricone" <bjt23 cornell edu>]

Ajax John wrote:
> I want to know what is the difference does it make when a Button is
> decleared as
> GtkWidget *button;
> GtkButton *button;
>
> I'm confused which one to used in my program.
> In simple words when should I declare my button as Gtkwidget * and as
> GtkButton *.

There's no difference; it's merely a matter of convention and/or 
convenience.  Most functions in gtk that you'll use after creating a 
widget (of any type, not just GtkButton) will take a GtkWidget pointer. 
 Also, most (all?) of the widget _new() functions will return GtkWidget 
pointers.  So you can either do things like this:

GtkWidget *box = /* box created somehow */
GtkButton *button = GTK_WIDGET(gtk_button_new());
gtk_widget_show(GTK_WIDGET(button));
gtk_box_pack_start(GTK_BOX(box), GTK_WIDGET(button), FALSE, FALSE, 0);

or you can do things like this:

GtkWidget *box = /* ... */
GtkWidget *button = gtk_button_new();
gtk_widget_show(button);
gtk_box_pack_start(GTK_BOX(box), button, FALSE, FALSE, 0);

As you can see, declaring all your widgets as GtkWidget* rather than 
their actual type saves you a bit of typing.  This way seems to be 
standard practice.

Of course, there might be situations where you use the widget a lot both 
as a GtkWidget and as it's actual type, so you might want to just keep 
around another variable pointing to the same object:

GtkWidget *box = /* ... */
GtkWidget *widget = gtk_button_new();
GtkButton *button = GTK_BUTTON(widget);
gtk_button_set_foo(button, foo);
gtk_button_set_bar(button, bar);
gtk_button_set_baz(button, baz);
gtk_widget_show(widget);
gtk_box_pack_start(GTK_BOX(box), widget, FALSE, FALSE, 0);

(Though I rarely actually do this myself.)  It's really up to you; it 
makes no difference to the actual functioning of the program.  Just be 
sure to use the class-cast macros when needed and you'll be fine.

        -brian