Re: Reference to a C++ object in GTK+ callbacks

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

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On 12/14/2005 11:19 AM, Stephen Pollei wrote:
> On 12/13/05, Daryl Lee <dlee altaregos com> wrote:
>
> > > Are you sure that is the right style for that callback?
> > > static void
> > > rocket_cb(GtkWidget *widget, GdkEventExpose *event, gpointer data)
> > > {
> > >        class city_node *city=static_cast<class city_node *>(data);
> > >        global_game.rocket_up(*city);
> > >        city->update_targets();
> > >        each_tick(NULL);
> > > }
> >
> > C++ functions do, indeed, have to be "static" to be used as GTK+
> > callbacks.
>
> Untrue I just removed the static keyword from 8 of my callbacks and
> then recompiled, worked just fine. As Andy Grebe of apogeelabs said
> "... function needs to have the correct format".
> That I bet was the problem. That I label a lot of my callbacks with
> "static", I just consider good style.
> diff -u1 gtk_main.cc-save gtk_main.cc > static-out.diff
>
> The only c++ problem I can see is if you had overloaded functions; I
> can't think of how you'd select which one you meant.

IIRC, I believe the functions only have to be static in this case if
they're actually C++ class methods.  Plain old C global functions don't
need to be static, though if they're only used in that one module,
there's no reason *not* to make them static, and it's good practice to
do so.

        -brian

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