gtk+에서 사소한 질문.. ㅡ+ㅡ

예제:

#include <gtk/gtk.h>

#define DEF_STATUS_CONTEXT      "status"

gboolean delete_event_cb(GtkWidget *widget, GdkEvent *event, gpointer data);
void destroy_cb(GtkWidget *widget, gpointer data);
void pressed_cb(GtkWidget *widget, gpointer data);

GtkWidget *appwin;
GtkWidget *button;
GtkWidget *status;

guint def_status_context = -1;

int
main(int argc, char *argv[])
{
  GtkWidget *box;

  gtk_init(&argc, &argv);

  appwin = gtk_window_new(GTK_WINDOW_TOPLEVEL);
  gtk_widget_show(appwin);

  g_signal_connect(G_OBJECT(appwin), "delete-event",
                   G_CALLBACK(delete_event_cb), NULL);
  g_signal_connect(G_OBJECT(appwin), "destroy",
                   G_CALLBACK(destroy_cb), NULL);

  box = gtk_vbox_new(0, 0);
  gtk_widget_show(box);

  button = gtk_button_new_with_label("Hello, world");

  g_signal_connect(G_OBJECT(button), "pressed",
                   G_CALLBACK(pressed_cb), NULL);

  gtk_widget_show(button);
  gtk_box_pack_start(GTK_BOX(box), button, 1, 1, 0);

  status = gtk_statusbar_new();
  gtk_widget_show(status);
  def_status_context = gtk_statusbar_get_context_id(GTK_STATUSBAR(status),
                                                    DEF_STATUS_CONTEXT);

  gtk_box_pack_end(GTK_BOX(box), status, 0, 1, 0);
  gtk_container_add(GTK_CONTAINER(appwin), box);

  gtk_main();

  return 0;
}


gint
status_printf(const char *format, ...)
{
  va_list argptr;
  static gchar buf[LINE_MAX];
  gint ret;

  g_assert(def_status_context != -1);

  va_start(argptr, format);
  ret = g_vsnprintf(buf, LINE_MAX, format, argptr);
  va_end(argptr);

  gtk_statusbar_pop(GTK_STATUSBAR(status), def_status_context);
  gtk_statusbar_push(GTK_STATUSBAR(status), def_status_context, buf);

  return ret;
}


gboolean
delete_event_cb(GtkWidget *widget, GdkEvent *event, gpointer data)
{
  g_print("event: delete-event\n");
  return FALSE;
}


void
destroy_cb(GtkWidget *widget, gpointer data)
{
  g_print("event: destroy\n");
  return gtk_main_quit();
}


void
pressed_cb(GtkWidget *widget, gpointer data)
{
  static int count = 0;
  status_printf("event: pressed %d", ++count);
}