Re: file selection interacting with drawing area

[Paul Davis <pjdavis engineering uiowa edu>]

Amadeus W. M. wrote:

> On Sun, 14 May 2006 11:25:13 -0600, Timothy M. Shead wrote:
>
>  
>
> > On Sun, 2006-05-14 at 12:42 -0400, Amadeus W. M. wrote:
> >    
> >
> > > I have an unusual problem. I have a window (MainWindow) which contains a
> > > drawing area (Darea) and some buttons. The user can draw various things
> > > with the mouse. E.g. a segment is being drawn/updated continuously when
> > > the user moves the mouse with button 1 pressed. The final position of the
> > > segment is recorded when button 1 is released, so there is an
> > > on_Darea_button_release() callback, which also draws the segment.
> > >
> > > Enter the file selection dialog. When the user selects a file by
> > > double-clicking, the dialog terminates upon the second button PRESS. The
> > > event immediately following the second button press is a button RELEASE,
> > > but that's now caught by the Darea, because the file selector is gone.
> > > Bad things happen: the Darea, of course, tries to store and draw a segment,
> > > because on_Darea_button_release() has been called.
> > >
> > > What do I do?
> > >
> > > I'm thinking about introducing a
> > >
> > > bool loading_file;
> > >
> > > which is set to 1 when the file chooser is being popped up,
> > > and inspected within on_Darea_button_release(): only draw/store the
> > > segment if and only if loading_file=0; if loading_file happens to be 1,
> > > set it to 0. Something like this:
> > >
> > > bool on_Darea_button_release(GdkEventButton * ev)
> > > {
> > >
> > >    if(loading_file){
> > >       loading_file=0;
> > >       return 0;
> > >    }
> > >
> > >    // if we've survived...
> > >
> > >    // set the segment from ev->x, ev->y.
> > >    Darea.queue_draw(); 
> > >    return 0;
> > > }
> > >
> > > This seems awkward and prone to error though. Is there a more natural/Gtk
> > > way?
> > >      
> > I wouldn't make this conditional on the file dialog, since other
> > dialog(s) added later may cause the same problem.  
> >    
>
> That's exactly why I didn't like it.
>
> You just need to keep
>  
>
> > track of whether you caught a button press event, and ignore the button
> > release if you didn't - add an on_Darea_button_press() handler and set a
> > flag there - then test it in on_Darea_button_release().
> >
> >    
>
> Yes, it's more robust to set the bool flag to 1 in
> on_Darea_button_press_event(), rather than make it contingent upon the
> file selection dialog. Then, in on_Darea_button_release_event(), just
> return if the flag is not 1. But I can't avoid the flag thing, can I?
>
>  
You could set the sensitivity of your widget to button_press events in 
your load file method.

But the more I think about this, the more I'm unsure if it'd work.

I'd go with the flag.

> Thanks!
>
>
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