Redraw from other thread

enki · **Joined:** Thu Sep 10, 2009 2:01 pm **Posts:** 2

Hi everybody!
I need help about redrawing two widgets -- a DrawingArea and a HScale. I've got a timer in a parallel thread that increments the scroll value every 300 milliseconds. I also have a callback function that draw a different "plot" in the drawarea whenever the scale value changes.
Now the problem: after changing the value with gtk_range_set_value I queue the redraw of the two widgets with gtk_widget_queue_draw, than I call the gdk_window_process_updates on the main window to effectively redraw everything. Things goes fine until I get the error "<unknown>: Fatal IO error 11 (Resource temporarily unavailable) on X server :0.0.", and the program exits. I really don't know what's the matter. Here's the interested part of the code:

Code:

void scroll_timer(union sigval unused)
{
   int v, limit;

   v=gtk_range_get_value(GTK_RANGE(scale));
   limit=gtk_adjustment_get_upper(gtk_range_get_adjustment(GTK_RANGE(scale)));
   if(v==limit)
      v=0;
   else
      v++;
   gtk_range_set_value(GTK_RANGE(scale),v);

   gtk_widget_queue_draw(scale);
   gtk_widget_queue_draw(drawarea);
   gdk_window_process_updates(gtk_widget_get_window(mainwindow),TRUE);
}

tadeboro · **Posted:** Thu Sep 10, 2009 10:10 pm

Hello and welcome to the GTK+ forums.

This is probably caused because you're using GTK+ functions from more than single thread without locking global lock, which causes race condition at certain point.

I wrote a blog post some time ago about threads and GTK+ which you may find useful: http://tadeboro.blogspot.com/2009/06/multi-threaded-gtk-applications.html.

Tadej

enki · **Joined:** Thu Sep 10, 2009 2:01 pm **Posts:** 2

Fantastic! Great!!!
Really thanks! You solved perfectly my problem, and you're blog is very very very usefull.

Note: I lost all my afternoon only because I was linking the program to gthread instead of gthread-2.0. :? Everything goes fine now!

Thanks again
Edoardo

GTK+ Forums

Redraw from other thread

Who is online