Hello! Here ‘s a fairly simple example of how to create single instance Applications with LibUnique and Gtk +. I took the example in the documentation and changed it to demonstrate how to pass a parameter to the active instance.
How to compile:
gcc -o uniquesample uniquesample.c `pkg-config --cflags gtk+-2.0 unique-1.0 --libs gtk+-2.0 unique-1.0`How to run it, first launch first instance:
# ./uniquesample
Then, launch the others:
# ./uniquesample "One App to rule them All"
Here’s the code:
#include gtk/gtk.h
#include unique/unique.h
static UniqueResponse
message_received_cb (UniqueApp *app,
                     UniqueCommand command,
                     UniqueMessageData *message,
                     guint time_,
                     gpointer user_data)
{
  UniqueResponse res;
/* get text payload from the unique message data*/
  gchar *texto = unique_message_data_get_text (message);
/* Get the label widget */
  GtkLabel *label = GTK_LABEL (user_data);
switch (command)
  {
    case UNIQUE_ACTIVATE:
      {
        gtk_label_set_text (GTK_LABEL (label), texto);
        res = UNIQUE_RESPONSE_OK;
        break;
      }
    default:
      res = UNIQUE_RESPONSE_OK;
      break;
  }
return res;
}
static gboolean
delete_event_cb (GtkWidget *widget, GdkEvent *event, gpointer data)
{
  gtk_main_quit ();
}
int
main (int argc, char *argv[])
{
  gtk_init (&argc, &argv);
/* Create the UniqueApp Instance */
  UniqueApp *app = unique_app_new ("home.myapp", NULL);
/* check if there already is an instance running */
  if (unique_app_is_running (app))
  {
    if (argc > 1)
    {
      /* build a message with the first command line argument */
      UniqueMessageData *message = unique_message_data_new();
      unique_message_data_set_text (message, argv[1], -1);
/* send the message, we don't care about the response */
      unique_app_send_message (app, UNIQUE_ACTIVATE, message);
unique_message_data_free (message);
      g_object_unref (app);
    }
  }
  else
  {
    /* this is the first instance */
    GtkWidget *window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
    GtkWidget *label = gtk_label_new ("UNIQUE INSTANCE");
/* Makes app "watch" a window.
     * Every watched window will receive startup notification changes automatically
     */
    unique_app_watch_window (app, GTK_WINDOW (window));
/* connect to the signal so we can handle commands and responses
     * We are passing the label widget here as user data */
    g_signal_connect (G_OBJECT (app), "message-received",
                      G_CALLBACK (message_received_cb), label);
g_signal_connect (G_OBJECT (window), "delete_event",
                      G_CALLBACK (delete_event_cb), NULL);
gtk_widget_set_size_request (GTK_WIDGET (window), 300, 200);
gtk_container_add (GTK_CONTAINER (window), label);
    gtk_widget_show_all(window);
gtk_main ();
g_object_unref (app);
  }
return 0;
}
