The following C code creates a big window with just a button.  On some themes,
the button is extremely slow to draw, update or resize.  For example, it is
really bad with the "Smokey Blue" on RH9.  It may be useful to see what is
making some themes so slow.

#include <gtk/gtk.h>

int main(int argc, char **argv)
{
    GtkWidget *window, *button, *label;
    gtk_init (&argc, &argv);
    window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
    gtk_window_set_default_size (GTK_WINDOW (window), 800, 800);
    button = gtk_button_new ();
    label = gtk_label_new ("big button");
    gtk_container_add (GTK_CONTAINER (button), label);
    gtk_container_add (GTK_CONTAINER (window), button);
    gtk_widget_show_all (window);
    g_signal_connect (G_OBJECT (window), "delete_event",
                      G_CALLBACK (gtk_main_quit), 0);
    gtk_main();
    return 0;
}