Re: progressbar updates

[Tim Evans <t evans aranz com>]

Felix Natter wrote:

> "Brian J. Tarricone" <bjt23 cornell edu> writes:
>
>
> > the progress bar is only updated when the gtk main loop is run, which
> > only happens when any functions you are running give control back to the
> > main loop.
>
>
> Ok, but isn't then the clean reason to start a subthread?
>
> I get problems in the main thread when I access the progressbar
> (set_fraction) and statusbar (push/pop) from the subthread (=> display
> problems...). How can I synchronize this?

You can safely pass messages from the subthread to the main/gui thread 
using g_idle_add:

  typedef struct {
     GtkWidget *progress_bar;
     gdouble fraction;
  } ProgressBarSetFraction;

  gboolean idle_progress_bar_set_fraction (gpointer data)
  {
      ProgressBarSetFraction *p = data;
      gtk_progress_bar_set_fraction (p->progress_bar, p->fraction);
      g_free (p);
      return FALSE;
  }

  int main (void)
  {
      ...
      g_thread_init (NULL);
      ...
  }

In subthread:

    ProgressBarSetFraction *p;

    p = g_new (ProgressBarSetFraction, 1);
    p->progress_bar = ...;
    p->fraction = 0.5;
    g_idle_add (gtk_progress_bar_set_fraction, p);

Note that the above code assumes that you do *not* call 
gdk_threads_init.  If you did, you would need to add 
gdk_thread_enter/leave inside the idle function and all other idle and 
timeout functions.

--
Tim Evans
Applied Research Associates NZ
http://www.aranz.com/