Re: connect_notify()

[Matthias Kaeppler <nospam digitalraid com>]

Martin Schulze wrote:
> Am 07.03.2005 11:35:55 schrieb(en) Matthias Kaeppler:
>
> > Hello,
> >
> > I want a context menu to popup when the user right-clicks on a tree
> > view. So I looked up signal_button_press_event() and I was told to
> > either derive my own view from TreeView (I don't want that) and
> > override
> > the default handler, or use connect_notify() instead.
> > Well, what does this mysterious function do? Googling for it turned
> > out
> > that it has something to do with coverting non-void return types to
> > void
> > return types of the signal handler (though I don't understand why  this
> >
> > is needed at all).
> >
> > Anyway, if I use this function to connect my own signal handler (as
> > usual with sigc::mem_fun), the compiler complains about mismatching
> > return types (the errors message is pretty long-winded, STL style,  you
> >
> > don't want to see it I guess...).
> > Instead of posting the error message from g++, here's the code which
> > caused it:
> >
> > // m_view is a TreeView
> >
> > m_view.signal_button_press_event().connect_notify( sigc::mem_fun(
> > *this,
> > &FileBrowser::on_rmb_clicked ) );
> >
> > // ...
> >
> > void FileBrowser::on_rmb_clicked()
> > {
> >     // ...
> > }
> >
> > I don't get what's wrong here.
>
>
> The function signature of your callback function does not match the  
> function signature of the signal. It should look as follows:
>
> void on_rmb_clicked(GdkEventButton* event)
>
> for connect_notify() or
>
> bool on_rmb_clicked(GdkEventButton* event)
>
> for connect().
>
> Like you already found out, the connect_notify() variant adds the  
> boolean return value for you in such a way that the internal handling  
> of an event is suppressed (which means a value of false, I think).
>
> Regards,
>
>  Martin
>
>
> > --
> > Matthias Kaeppler
> >
> > _______________________________________________
> > gtkmm-list mailing list
> > gtkmm-list gnome org
> > http://mail.gnome.org/mailman/listinfo/gtkmm-list

Ah, I see.
Thanks a lot Martin.

Regards,
Matthias Kaeppler