#include <gtk/gtk.h>

int main (int argc,
    gchar **argv)
{
  GtkWidget *window, *entry;
  GtkStyleContext *style;

  gtk_init (&argc, &argv);

  window = gtk_window_new (GTK_WINDOW_TOPLEVEL);

  entry = gtk_entry_new ();

  style = gtk_widget_get_style_context (GTK_WIDGET (entry));
  gtk_style_context_add_class (style, GTK_STYLE_CLASS_ERROR);

  gtk_container_add (GTK_CONTAINER (window), entry);
  gtk_widget_show_all (window);

  gtk_main ();
  return 0;
}
