Re: Gtk::ProgressBar is not being updated inside a for statement

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

On Fri, 11 Sep 2009 02:08:24 +0300 "sledge" wrote:
> 
> > void wait(double seconds){
> >  clock_t end_wait;
> >  end_wait = clock () + end_wait * CLOCKS_PER_SEC ;
> >  while (clock() < end_wait) {}
> > }
> > 
> > for(int i=1; i<=max_time; i++){
> > 
> >               wait(1); //Waits one second
> > 
> >               myProgressBar.set_fraction(i/max_time); //it updates the 
> > GUI until it has returned to the main window loop
> > 
> >                while(Gtk::Main::events_pending()) //this should update 
> > the progress bar in GUI on each iteration in this for statement, but it 
> > doesn't
> > 
> >                Gtk::Main::iteration();//I tried both arguments, false 
> > and true, none of them worked, same result... it gets updated when it 
> > exits the function that uses this for statement
> > }
> 
> You should put the                Gtk::Main::iteration() inside the while loop:
> 
> while(Gtk::Main::events_pending()) 
> {
>    Gtk::Main::iteration();
> }
> 
Looks like it already is inside the while - there's no semicolon on the line with the while. Granted the braces would make that clearer (which is why the "MISRA" guidelines for safety-critical C require them) or at the very least some indentation, but they're redundant in this case.

No, as somebody else has posted, the problem is 
            myProgressBar.set_fraction(i/max_time); 
will only ever pass 0 or 1 because it's doing an integer divide. Change it to 
            myProgressBar.set_fraction ( (float)i / (float)max_time );

That said, stuffing a Gtk::Main::iteration(); call into your code is ALWAYS a sign of bad programming, even if it's the only solution you can find to a problem you've lumbered yourself with due to a bad architectural decision three years and two projects ago. The right way to do the job here is to start a timer event so the GTK main-loop will call your update function regularly. The update function won't contain a for loop, or a while loop, or any Gtk::Main:: method calls, and there won't be a function called wait either.