Re: Gtk::Widget as virtual base

[jyotirmoy bhattacharya <jmoy matecon gmail com>]

Thanks for your interest.

> Maybe you can resolve most of this ambiguitys with using virtual
> inheritance.  The problem is,  that  
>[  keyword diamond inheritance ]
> for doing this, both classes you inherit from should use virtual
> inhertitance from Gtk::Widget. I guess this is not the case for
> Gtk::HBox, so using virtual inheritance for vwwidget only doesn't >help.
Why dosen't gtkmm make Gtk::Widget a virtual base of widgets
like Gtk::Hbox? I can't think of any programs that
might by broken by such a change but being a gtkmm newbie
I really don't know.

> Maybe there is an easier way to do what you want to do ...
The workaround that I am using at present is

class vwidget
{
  public:
    virtual void magic()=0;
    virtual Gtk::Widget *get_widget()=0;
};

class mywidget: public vwidget
{
  public:
    void magic() {x=1;}
    Gtk::Widget *get_widget() {return &box;}
  private:
    int x;
    Gtk::Hbox box;
};

But besides being inelegant, this is a maintenance problem
since the actual class corresponding to mywidget is displayed
by using a large hierarchy of widgets and everytime I change
the root of that hierarchy I have to remember to update 
get_widget(). If I forget to do so the mistake is not caught during
compilation and leads to obscure runtime errors.