true_

All this function does it to return true.

This can be useful for example if you want to inhibit the deletion of a window. Of course you should not do this as the user expects a reaction from clicking the close icon of the window...

A persistent window

#include <gtk/gtk.h>

int
main (int argc, char **argv)
{
 GtkWidget *win, *but;
 const char *text = "Close yourself. I mean it!";

 gtk_init (&argc, &argv);

 win = gtk_window_new (GTK_WINDOW_TOPLEVEL);
 g_signal_connect (win,
                   "delete-event",
                   G_CALLBACK (gtk_true),
                   NULL);
 g_signal_connect (win, "destroy",
                   G_CALLBACK (gtk_main_quit),
                   NULL);

 but = gtk_button_new_with_label (text);
 g_signal_connect_swapped (but, "clicked",
                           G_CALLBACK (gtk_object_destroy),
                           win);
 gtk_container_add (GTK_CONTAINER (win), but);

 gtk_widget_show_all (win);

 gtk_main ();

 return 0;
}