Changes

* about the third parameter

** the key <code>state</code> determines when the page background is recalculated. <code>state=repeat</code> ensures that the page background is always recalculated (useful if you want to use a variable that depends on the current page, such as its number with {{cmd|realpageno}}).

** <code>state=stop</code> doesn't recalculate, and stops the automatic recalculation.