Re: interrupting a big loop

[Allin Cottrell <cottrell wfu edu>]

On Wed, 19 May 2004, Tristan Van Berkom wrote:

> Allin Cottrell wrote:
> > When my (gtk) app is engaged in a time-consuming loop process, I'd
> > like to offer the user the chance of breaking out if he/she loses
> > interest.  The pseudo-code is something like:
> >
> > for (i=0; i<LARGE_NUMBER; i++) {
> >    if (break_condition()) break;
> >    /* do something complicated */
> > }
> >
> > where "break_condition()" checks whether a particular quit key has
> > been pressed or quit button has been clicked.
> >
> > My puzzle is over how exactly to link the break_condition() function
> > with the appropriate callback associated with the keystroke or
> > button-click.  Do I need something like g_main_context_iteration()?
>
>     If you take this approach (which is less complicated than using threads,
> and IMO preferable when possible), yes.
>
> You'll need to:
>
> for (i=0; i<LARGE_NUMBER; i++) {
>      /* process Gtk events
>       */
>      while (gtk_events_pending())
>          gtk_main_iteration();
>
>      /* It is possible that your callback
>       * `on_cancel_button_clicked()' was called
>       * during `gtk_main_iteration()'.
>       */
>      if (should_stop == TRUE) break;
>
>      /* do something complicated */
> }

Thank you, this is just the sort of thing I was groping for.  I have
one more question.

>      /* It is possible that your callback
>       * `on_cancel_button_clicked()' was called
>       * during `gtk_main_iteration()'.
>       */
>      if (should_stop == TRUE) break;

What's the best way of implementing this?  Make "should_stop" a global
boolean that is initially set to FALSE, and is set TRUE within the
cancel button callback?  Or can one avoid a global?

Allin Cottrell