Re: HScale on_button_press_event blocking

[Robert Pearce <rob bdt-home demon co uk>]

On Wed, 9 May 2007, Patrick Schweiger <pschweiger symmetricom com> wrote 
:
> On Tue, 2007-05-08 at 20:43 -0400, Jeremy Harmon wrote:
>
> > bool seekBar::on_button_press_event(GdkEventButton *event)
> > {
> >         m_isSeeking = true;
> >      return false;
> > }
>
> instead of returning false, try calling the super class' implementations
> to get the behavior they implement:

Just in case this seems bizarre or contrary to the documentation, I 
think it's worth adding a few comments.

When the GTK / GTKmm documentation says you return false to let other 
handlers operate, it refers to the way GTK itself hooks up a "list" of 
on-event call-backs. This ties several (possibly user-defined) functions 
to one GTK event. Each function can return true to say "I have now 
completely dealt with this event", or false to let other callbacks have 
their say.

However, when you _override_ a GTKmm class's existing handler, you are 
effectively replacing that function both in C++ terms and, consequently, 
in the GTK callback list. Thus if you want the super-class's 
functionality, your replacement virtual method must call its parent's 
version. This is normal behaviour for C++ (and other OO languages).

I hope that adds clarity and not confusion!
--
Rob Pearce                       http://www.bdt-home.demon.co.uk

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