Re: C++-classes.

[Jeff Franks <jcf tpg com au>]

David Larsson wrote:

> > GtkClass::GtkClass()
> > {
> >   button = gtk_button_new();
> >
> >   gtk_signal_connect(GTK_OBJECT(button),
> >    
> "clicked", GTK_SIGNAL_FUNC(&GtkClass::Test), 0);       // C++ doesn't use NULL. It's a C macro.
>  
>
> > }
> >    
>
> Ah, then I came up to another problem. If you then want to modify the "calling" class variable, for example 
> the GtkWidget *button.
>
> If you do a:
>
> void GtkClass::Test()
> {
>  gtk_widget_hide(button);
>  // or a GtkClass::button?
>  // or even call another method in GtkClass?
> }
>
> it doesn't seem to work. How can i fix this?
>  
Pass the pointer you want passed to the callback as the user data:

Solution one:

GtkClass::GtkClass()
{
   button = gtk_button_new();

   gtk_signal_connect(GTK_OBJECT(button), "clicked", GTK_SIGNAL_FUNC(&GtkClass::Test), button);
}

void GtkClass::Test(GtkWidget* widget, GtkWidget *button)
{
 gtk_widget_hide(button);
}

Solution two: looks cleaner as it swaps the widget and user_data arguments.

GtkClass::GtkClass()
{
   button = gtk_button_new();

   gtk_signal_connect_swapped(GTK_OBJECT(button), "clicked", GTK_SIGNAL_FUNC(&GtkClass::Test), button);
}

void GtkClass::Test(GtkWidget *button)
{
 gtk_widget_hide(button);
}

Jeff Franks