Minimum version: Midgard 1.4 (Bifrost)
Walks the style tree starting at the style record with id root to a level of maxlevel deep. for each style the user defined function func is called. Parameters to this function will be: id, the id of the style currently being walked, level , the level of descendance from the root level, &xparam, a variable passed through by the user. If order is FALSE, each style will be processed after all its children. If set to TRUE, each style will be processed before its children.
Returns TRUE if successful. Returns FALSE on failure.