static void
get_iter_bounds(GtkTextBuffer *buffer, GtkTextIter *start, GtkTextIter *end)
{
  GtkTextMark *insert_mark;
  if(!gtk_text_buffer_get_selection_bounds(buffer, start, end))
  {
    insert_mark = gtk_text_buffer_get_insert(buffer);
    gtk_text_buffer_get_iter_at_mark(buffer, start, insert_mark);
    *end = *start;
  }
}

static void
bold_toggled(GtkToggleButton *button, GtkWidget *text_view)
{
  GtkTextIter start;
  GtkTextIter end;
  GtkTextBuffer *buffer;

  buffer = gtk_text_view_get_buffer(GTK_TEXT_VIEW(text_view));
  gtk_widget_grab_focus(text_view);

  get_iter_bounds(buffer, &start, &end);

  if(gtk_toggle_button_get_active(button))
  {
    gtk_text_buffer_apply_tag_by_name(buffer, "strong", &start, &end);
  }
  else
  {
    gtk_text_buffer_remove_tag_by_name(buffer, "strong", &start, &end);
  }

}