Re: Correct signal handler to overload in a treeview to STOP the selection from changing

[Bob Caryl <bob fis-cal com>]

Bob Caryl wrote:

> Huston, Bob wrote:
>
> > I have a treeview derived class, in which when a branch in the tree 
> > is displayed I display a
> > notebook derived class showing many GUI controls for information 
> > gathering. When
> > the user selects a different branch in the tree, I save off the 
> > currently displayed notebook information
> > and display a new notebook for the new branch that is selected.
> >  
> > I accomplish this by overloading the on_cursor_changed signal handler 
> > in the tree view class.
> >  
> > The issue I am having is that when I am switching notebooks being 
> > displayed I validate any and all
> > information on the current notebook, if the information is valid, I 
> > want to warn the user via and keep the
> > tree from switching views.  
> > I am not switching the notebooks when this occurs, however the tree 
> > is still switching which branch is selected.
> >  
> > My code basically is this:
> >  
> > void CMyTreeView::on_cursor_changed()
> > {
> >     // save/validate the current notebook:
> >     if ( !SaveCurrentNotebook())
> >         return;
> >  
> >     // put up the new notebook
> >     .....
> >     return Gtk::TreeView::on_cursor_changed();
> > }
> >  
> > I need to know how to either return from this handler so that the 
> > selection doesn't change, or a different handler
> > to overload to do my processing prior to the selection change 
> > occurs.  I thought that by not allowing the
> > parent tree view class's version of on_cursor_changed to be called 
> > that this would happen.
> >  
> > --Bob
> >  
> >
> > ------------------------------------------------------------------------
> >
> > _______________________________________________
> > gtkmm-list mailing list
> > gtkmm-list gnome org
> > http://mail.gnome.org/mailman/listinfo/gtkmm-list
> >  
>
> Hey Bob,
>
> I could not find a signal directly relating to the Gtk::TreeView to 
> which you could connect in order to prevent the TreeView from changing 
> rows in response to a mouse click (and remember, a row can also be 
> changed with the arrow keys on the keyboard).  However, you might 
> consider connecting to "Gtk::Main::signal_key_snooper" and looking for 
> a "GDK_BUTTON_PRESS" event (see GdkEventButton 
> http://www.gtk.org/api/2.6/gdk/gdk-Event-Structures.html#GdkEventButton 
> <http://www.gtk.org/api/2.6/gdk/gdk-Event-Structures.html#GdkEventButton>).  
> You can compare the GdkWindow pointer to the GdkWindow corresponding 
> to your Gtk::TreeView in your connected callback slot to determine 
> whether or not to allow the cursor to change depending on the 
> validation of your controls in your notebook page.
>
> Connection code looks like this:
>
> Gtk::Main::signal_key_snooper().connect(sigc::mem_fun(*this,&<your 
> class name here>::<your callback slot name here>));
>
> I don't know if this will actually work, but I do know that you can 
> choose to go ahead a propagate the event or not in your callback.  If 
> you do propagate it, you must be sure to prevent catching that event a 
> second (and third and fourth and so forth) time.
>
> Hope this might help.
>
> Bob Caryl
>
> _______________________________________________
> gtkmm-list mailing list
> gtkmm-list gnome org
> http://mail.gnome.org/mailman/listinfo/gtkmm-list
>  
Hey Bob,

Well, I wish now I had taken the time to test my theory.  It doesn't 
work.  Apparently this signal is triggered *only* by keyboard input (as 
its name implies).  Sorry.

Bob Caryl

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