Widgets and GThreads.

["Claudio Saavedra V." <csaavedra alumnos utalca cl>]

Hi

I am writing a GTK+-2.0 code that is supposed to change the label of a GtkButton
constantly in a thread diferent than the main, while the button is usefull.

The next is the code i have until now:

-- code --

#include <stdio.h>
#include <gtk/gtk.h>
#include <stdlib.h>
#include "gthread.h"

static void
print_something (GtkWidget *widget, 
                 gpointer data)
{
        g_print ("this is the window thread\n");
}

static void
destroy (GtkWidget *widget,
         gpointer   data)
{
        gtk_main_quit ();
}

void *
thread_pipe_socket (GtkButton *button)
{
        GError *error = G_IO_ERROR_NONE;
        GIOStatus *status;
        gint len;
        GString *buffer = g_string_new ("");
        GIOChannel *channel;
        FILE *foo;
        gchar **new_label;

        /* numbers is a program that generates numbers, sends it to the stdout
           and sleep 1 second. */

        foo = popen ("./numbers", "r");
        channel = g_io_channel_unix_new (fileno (foo));
        
        if(error){
                g_print("(%i) %s\n", error->code, error->message);
                return;
        }

        if (channel != NULL) {
                g_print ("Socket ready\n");
                while (g_io_channel_read_line_string 
                       (channel, buffer, &len, &error) == G_IO_STATUS_NORMAL){
                        g_print ("%s", buffer->str);
                        new_label = g_strsplit (buffer->str, "\n", -1);
                        gtk_button_set_label (button, new_label[0]);
                        g_strfreev (new_label [0]);
                }
        }
}       

int
main (int  argc,
      char *argv[])
{
        GtkWidget *window;
        GtkWidget *button;
        pthread_t thread;

        g_thread_init (NULL);

        gtk_init (&argc, &argv);

        window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
        
        g_signal_connect (G_OBJECT (window), "delete_event", 
                          G_CALLBACK (destroy), NULL);
        
        g_signal_connect (G_OBJECT (window), "destroy", 
                          G_CALLBACK (destroy), NULL);
        
        button = gtk_button_new_with_label ("This is one thread");
        
        g_signal_connect (G_OBJECT (button), "clicked",
                          G_CALLBACK (print_something), NULL);

        gtk_container_add (GTK_CONTAINER (window), button);

        gtk_widget_show_all (window);

        pthread_create (&thread, NULL, thread_pipe_socket, button);

        gdk_threads_enter ();
        gtk_main ();
        gdk_threads_leave ();

        return 0;

}

-- code --

This works fine, the label is changed when a new number gets in the channel.

However, if i click in the button repeatedly, the button looses the label. I
guess that this is because the widget is being accesed in a wrong way (not
locking it) by gtk_button_set_label.

How can i lock a widget? i have seen some examples for locking variables but
none of them seems to work fine with widgets that are modified by the main loop.

Is that really the problem? or am i missing something important?

I am very lost so please, any hint will help me.

Thanks.

Claudio


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--
Claudio Saavedra Valdés
http://csv.no-ip.org
mailto:csaavedra_at_alumnos_dot_utalca_dot_cl
Ingeniería Civil en Computación
UTALCA - Chile.





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