Re: g_signal_connect_swapped

[Michael 'Mickey' Lauer <mickeyl linuxtogo org>]

Richard Riley wrote:
> "Matt Hoosier" <matt hoosier gmail com> writes:

> > On 11/25/06, Richard <rileyrg googlemail com> wrote:
> > > Could someone explain the reason for this function
> > >
> > > "g_signal_connect_swapped"
> > >
> > > I have read the manual here:
> > >
> > > http://www.gtk.org/tutorial/x159.html
> > >
> > > where it says:
> > >
> > > ,----
> > > | g_signal_connect_swapped() is the same as g_signal_connect() except that
> > > | the instance on which the signal is emitted and data will be swapped
> > > | when calling the handler. So when using this function to connect
> > > | signals, the callback should be of the form
> > > |
> > > |
> > > | void callback_func( gpointer   callback_data,
> > > |                     ... /* other signal arguments */
> > > |                     GtkWidget *widget);
> > > |
> > > | where the object is usually a widget.
> > > `----
> > >
> > > Could anyone express this a little clearer? I (as a gtk beginner) can
> > > see no reason for it.
> >
> > This just means that the "widget" and "callback_data" pointers will be
> > pushed onto the call stack in the opposite order from their ordering
> > if hooked up with g_signal_connect(). If you're designing your own
> > callback function, this probably isn't useful; just use
> > g_signal_connnect() with a callback that has GObject* and gpointer
> > parameters [in that order].

> I can see the order has changed - it was the reason I was looking for. I
> don't currently see the point. Maybe it will become clearer as I learn
> more.

The point is being able to connect a signal to a method that you
didn't write, but one that's already defined. If you wouldn't have
g_signal_connect_after you'd need to create methods that do nothing
but modify argument order.

-- 
Michael 'Mickey' Lauer | IT-Freelancer | http://www.vanille-media.de