[Therion] Orientation of symbol fills

[Bruce]

>Can someone please tell me how to change the orientation that an area
fill symbol is drawn using? I am trying to make my flowstone fill
indicate the direction it flows in.

Not really an answer I'm afraid, but my understanding is that it is buried
in the metapost code.  I've often wanted my flowstone areas to flow in the
right direction as well.

If you study the metapost for this symbol (and a few of the others) it would
be quite straight forward to deduce how to rotate it - the obvious
shortcoming being that all of the flows for any one compilation will flow in
the rotated direction.

What is needed to achieve individually rotated fills is to completely
re-write the symbol allowing an optional user attribute (-attr rotate 0
deg).
There was a similar discussion on area symbol scales a while back, most of
which I did not find with a quick search, but there is some early and only
slightly relevant discussion here.

http://article.gmane.org/gmane.comp.gis.therion/727/match=area+scale
http://article.gmane.org/gmane.comp.gis.therion/635/match=area+scale

You might get some clues if you scroll down to 'area block' here
 http://therion.speleo.sk/wiki/doku.php?id=metapost&s[]=area&s[]=block
#cave_symbol_size_and_density_examples 

Now after looking at the code briefly I might backtrack a little.  It seems
that only the path of the perimeter of an area entity(or line entity) is
passed to the metapost symbol code. (compared to points which have position,
rotation, scale and alignment parsed) This suggests to me that this is the
only parameter that can be individually changed within any one compilation
for an entity of type area or type line.
Perhaps the controlling therion code needs to be changed to allow either the
entity area to have optional extra variables parsed to it (preferable), or a
new entity 'areaX' needs to be devised???  Most area symbols would probably
need modification to accommodate this feature.

If non-user-definable variables are easier, my vote would go with rotation
and scale.

Have I guessed right?
Is this something that could be included without too much difficulty?
Bruce