While we're on the plot window...



   embedding ability specific to TCL, or could it
   theoretically be done with other toolkits?  Will I

One thing you might look at is the TeXmacs.   Maxima has an interface
with that, which is interesting.   Needs some work, but it does
typesetting of the math.   I also will be putting an interface into
xmaxima that displays properly typeset output.	  

Displaying a plot window inside another application is easy enough:

If you are doing it under X windows at least then for example
do
xwininfo 
to find the id of the window you are interested in.
suppose it has id  0x100001a

% wish -use 0x100001a -f foo.tcl
where
foo.tcl is
=======
label .l -text {hello world}
pack .l
=====
will put that window into the one you specified which perhaps
belongs to another application.   The plotting stuff is all in
the files: plotting.tcl
In the xmaxima.tcl you want the stuff starting at
## source plotting.tcl
down to
## endsource plotting.tcl


       -use id                                                          
       Specifies that the main window for the 
       application is to be embedded  in  the 
       window whose identifier is id, instead 
       of being  created  as  an  independent 
       toplevel window.  Id must be specified 
       in the same way as the value  for  the 
       -use option for toplevel widgets (i.e. 
       it has a form like  that  returned  by 
       the winfo id command).