[563] in The GTK GIMP ToolKit mailing list archive
[gtk-list] Re: More tutorial
daemon@ATHENA.MIT.EDU (Ian Main)
Tue Jul 29 13:46:11 1997
Date: Tue, 29 Jul 1997 10:46:55 -0700 (PDT)
From: Ian Main <slow@intergate.bc.ca>
To: Gtk+ mailing list <gtk-list@redhat.com>
In-Reply-To: <Pine.SOL.3.92.970729181703.23335A-100000@korillov.dtek.chalmers.se>
Resent-From: gtk-list@redhat.com
Reply-To: gtk-list@redhat.com
On Tue, 29 Jul 1997, Martin Norb{ck wrote:
> On Tue, 29 Jul 1997, Ian Main wrote:
>
> > /* this is a callback function. the data arg is ignored..
> > * More on callbacks below. */
> > void hello (gpointer *data)
> > {
> > g_print ("Hello World\n");
> > }
> [SNIP]
> > * defined above. */
> > gtk_signal_connect (GTK_OBJECT (button), "clicked",
> > GTK_SIGNAL_FUNC (hello), NULL);
> One little comment.
> The clicked signal has declaration:
> void GtkButton::Clicked( GtkButton* button );
> which means that the callback really should have type
> void hello( GtkButton* button, gpointer* data );
> where the button argument is the button that sent the signal.
>
> Since you are not using the data in this example there is nothing to worry
> about, but if you try to use it you will probably get an error.
>
> Since the C calling convention allows any number of arguments to any function,
> the above code will work. The type checker can't check this either, because
> the hello function is casted anyway, so it's a bit of a problem really.
>
> ----- BEGIN FLAME PROTECTION -----
> I hope I am right; I gathered this information by reading the source code. If I
> am wrong could someone please tell me, because that may fix some of the bugs
> in my programs!
> ----- END FLAME PROTECTION -----
>
> /norpan
>
> Signature left blank
Nope, your right. I just did it from memory, and figured it'd be better
to have the callback function declared properly so it makes a better
template.
Thanks to everyone for your suggestions so far :) I'm incorporating the
changes..
Ian
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