问删除GtkButton的图像填充(内边框)？

EN

#include <gtk/gtk.h>

static void destroy (GtkWidget *widget, gpointer data){
    gtk_main_quit();
}

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

    GtkWidget *window;
    GtkWidget *button;
    GtkStyle *style;

    gtk_init(&argc, &argv);

    /* window */
    window = gtk_window_new(GTK_WINDOW_TOPLEVEL); 
    gtk_window_set_title(GTK_WINDOW (window), "my Program");
    gtk_widget_set_usize(window,200,150);
    gtk_window_set_position(GTK_WINDOW (window),GTK_WIN_POS_CENTER);
    gtk_signal_connect (GTK_OBJECT (window), "destroy", GTK_SIGNAL_FUNC(destroy),NULL);

    /* Create a new button (NO GLOW) */
    button = gtk_button_new_with_label ("Exit");
    /*-------------------------------------------------------------*/
    style = gtk_widget_get_style(button);
    style->bg[GTK_STATE_PRELIGHT] = style->bg[GTK_STATE_NORMAL];
    gtk_widget_set_style(button, style);
    /*-------------------------------------------------------------*/
    gtk_container_add (GTK_CONTAINER (window), button);
    gtk_signal_connect (GTK_OBJECT (button), "clicked", GTK_SIGNAL_FUNC (destroy), NULL);


    gtk_widget_show(button);
    gtk_widget_show(window);
    gtk_main();

    return 0;
}