[xsl] Counting indent level

[Nicholas Orr <nick@xxxxxxxxxxx>]

G'day all,

I've got some XML that contains a list of items and groups, and each  
group could contain either more items or more groups like so :

<catalog>
	<item />
	<group>
		< group >
		< item />
		< item />
		< group >
			< group >
				< item />
etc

So groups can contain either items or more groups or nothing.  Items  
only exist at the root (catalog) of this part of the tree or inside  
groups.  I'm outputting a single list of all of the items and group  
currently using this :

<xsl:for-each select="item|descendant::group|descendant::group/item">

The reason for that is that a item node might also contain child nodes  
that are also called <item> nodes that I don't want.  I only want a  
item node that has it's immediate parent a group node.  (There may be  
an easier way to do that...)

How do I count the "indent" level - so how many parent "groups" each  
item or group has, right back up to the catalog node?  Eg in the  
example above, it would be 0 for the first item and group, 1 for the  
next 4 etc.

I can change the for-each that I'm using, although it has to remain in  
the same order, so I can't process them out of order.

Is the easiest way to count back up the tree for each one, or is there  
a way to build that into the for-each?  If I use count, how do I count  
the path back up to the catalog node?

Thanks in advance,
Nick