children = children->next)
children = next) {  next = children->next;
static void columns_forall(GtkContainer *container, gboolean include_internals,                           GtkCallback callback, gpointer callback_data){    Columns *cols;    ColumnsChild *child;    GList *children;    g_return_if_fail(container != NULL);    g_return_if_fail(IS_COLUMNS(container));    g_return_if_fail(callback != NULL);    cols = COLUMNS(container);    for (children = cols->children;         children && (child = children->data);         children = children->next)	if (child->widget)	    callback(child->widget, callback_data);}