gtk2/demos/gtk-demo/theming_style_classes.c

/* CSS Theming/Style Classes
 *
 * GTK+ uses CSS for theming. Style classes can be associated
 * with widgets to inform the theme about intended rendering.
 *
 * This demo shows some common examples where theming features
 * of GTK+ are used for certain effects: primary toolbars,
 * inline toolbars and linked buttons.
 */

#include <gtk/gtk.h>

static GtkWidget *window = NULL;

GtkWidget *
do_theming_style_classes (GtkWidget *do_widget)
{
  GtkWidget *grid;
  GtkBuilder *builder;
  GError *err = NULL;

  if (!window)
    {
      window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
      gtk_window_set_screen (GTK_WINDOW (window),
                             gtk_widget_get_screen (do_widget));
      gtk_window_set_title (GTK_WINDOW (window), "Style Classes");
      gtk_container_set_border_width (GTK_CONTAINER (window), 12);
      g_signal_connect (window, "destroy",
                        G_CALLBACK (gtk_widget_destroyed), &window);

      builder = gtk_builder_new ();
      gtk_builder_add_from_resource (builder, "/theming_style_classes/theming.ui", NULL);
      if (err)
        {
          g_error ("ERROR: %s\n", err->message);
          return NULL;
        }

      grid = (GtkWidget *)gtk_builder_get_object (builder, "grid");
      gtk_widget_show_all (grid);
      gtk_container_add (GTK_CONTAINER (window), grid);
      g_object_unref (builder);
    }

  if (!gtk_widget_get_visible (window))
    {
      gtk_widget_show (window);
    }
  else
    {
      gtk_widget_destroy (window);
      window = NULL;
    }

  return window;
}