Re: hello & threads

["david::" <voiser gmail com>]

Perfect, it works perfect with g_timeout_add.

thanks for your time, Tim


On Sat, 15 Jan 2005 12:55:03 +0000, Tim Müller <zen18864 zen co uk> wrote:
> On Saturday 15 January 2005 12:27, david:: wrote:
>
> > well i have a problem with an application i'm writing. I have 2
> > threads. The first one creates an empty window with a button and calls
> > gtk_main(). The second one does this:
> >
> > void  secondThread(){
> >
> >   char str[100];
> >   int i=0;
> >
> >   while(TRUE) {
> >
> >     // here i create a string
> >     sprintf(str, "%d\n", i++);
> >
> >     // and here I change the button label
> >     if (window != NULL)
> >       gtk_button_set_label(GTK_BUTTON(button), str);
> >
> >     // once a second
> >     g_usleep(1000000);
> >   }
> > }
> >
> > well the thread is quite simple. But when i launch the program the
> > button changes its label 3 or 4 times and then becomes blank.
> >
> > I well, i have been using gtk for a time and i have never had this
> > problem. can you tell me what i am doing wrong??
>
> Don't use Gtk or Gdk functions from any thread that's not the main GUI thread.
> If you do, you'll have to use locks (see http://www.gtk.org/faq/ for
> details), but I really don't recommend this.
>
> In your case, you could do somthing like:
>
> static gboolean
> change_label (gchar *str)
> {
>  if (window != NULL)
>   gtk_button_set_label (GTK_BUTTON (button), str);
>  g_free (str);
>  return FALSE; /* only once */
> }
>
>  .....
>
>  // change label here
>  g_idle_add ((GSourceFunc) change_label, g_strdup (str));
>
>  ....
>
> change_label will be called as soon as possible from the context of the main
> thread.
>
> I assume this is just a simple example. Because if not, you don't need threads
> at all, just do something like:
>
> static gboolean
> update_button (gpointer the_button)
> {
>  static gint i; /* 0 */
>  gchar *str;
>
>  str = g_strdup_printf ("%d", i++);
>  gtk_button_set_label (GTK_BUTTON (the_button), str);
>  g_free (str);
>
>  return TRUE; /* call again */
> }
>
> and then .....
>
>       .... set up window etc....
>
>       button = gtk_button_new ( .... );
>
>       g_timeout_add (1 * 1000, update_button, button);
>
>      gtk_main ();
>
> That way the function update_button() will be called once per second (until
> you return FALSE).
>
> Cheers
>  -Tim