Re: Quick question on Glib style/design

[Jan Kratochvil <rcpt-gtk-devel-list AT gnome org jankratochvil net>]

Hi,

On Wed, 04 Aug 2004 04:21:31 +0200, muppet wrote:
...
> not quite.  notice that most gtk+ constructors return GtkWidget*?

I do not much understand why. GLib functions expect C type of the most far
ancestor type they need to access to be as general as possible. They usually
return the most far descendant class they create. Just why GTK+ has a style
where the constructor gtk_button_new() returns (GtkWidget *) and not its native
class (GtkButton *)? It is not much systematic this way.

It looks dangerous to me to cast a return value of a function to some
descendant class as I need to know the inner behavior of the constructor to be
allowed to cast it.


>   GtkWidget * foo;
>   GtkContainer * container;
> 
>   container = (GtkContainer*) gtk_window_new (GTK_WINDOW_TOPLEVEL);

It would be more correct to cast by
    container = GTK_CONTAINER (gtk_window_new (GTK_WINDOW_TOPLEVEL));

to get the proper class hierarchy checking.


Regards,
Lace

-- 
Jan Kratochvil; Captive: free r/w NTFS Filesystem; http://www.jankratochvil.net/