Re: [gtkmm] Gtk::DrawingArea help required

[ej <e j virgin net>]

Timothy M. Shead wrote:

> ej wrote:
>
> > The button signal handler works fine when I comment out the expose 
> > event handler connect line, but
> > with that line the program fails to compile with the following :
> >
> > ejames sonata:/data/My_NEAT/StockDB/helloworld> g++ -o picture  
> > main.cpp Picture.cpp `pkg-config gtkmm-2.0 --cflags --libs`
> > Picture.cpp: In constructor `Picture::Picture()':
> > Picture.cpp:24: error: no matching function for call to `
> >   Glib::SignalProxy1<bool, GdkEventExpose*>::connect(SigC::Slot0<void>)'
> > /opt/gnome/include/gtkmm-2.0/glibmm/signalproxy.h:136: error: 
> > candidates are:
> >   SigC::Connection Glib::SignalProxy1<R, P1>::connect(const 
> > SigC::Slot1<R,
> >   P1>&, bool) [with R = bool, P1 = GdkEventExpose*]
>
>
> The signature of event handlers is dictated by the signal; in this 
> case, you have to provide a function that takes GdkEventExpose* and 
> returns bool:
>
> bool Picture::on_expose_event(GdkEventExpose*)
> {
>     std::cout << "expose event generated" << std::endl;
> }
>
> Cheers,
> Tim
Thanks Tim.
I had a look at the docs for Gtk::Button and Gtk::widget and I've 
twigged about the signatures that event handlers need.
Out of interest, can anyone out there explain why the Button event can 
make do with a void handler with no args, but the expose
event needs a boolean function taking a GDKEventExpose* ?

My next step...work out how to draw in my DrawingArea... :-)

Cheers,
EJ