dw:redisplay-helper-stream

[shirley@parc.xerox.com (Mark Shirley)]

    I'm trying to write something similar to dw:format-graph-from-root but
with a different layout algorithm.  The key element I need is a way to figure
out the bounding box for some text and graphical output before actually
writing those things to the output stream.  For instance, I need a "helper"
stream that produces no output, but records the motions of the cursor and the
bounding boxes of graphics calls.

    By casting about with the document examiner and :Find Symbol, I've found
dw:redisplay-helper-stream which looks to be the right thing, but I can't find
a description of how to use it (and we don't have source for most of the
useful bits).

    Has anyone done this or does anybody know whether this is the right place
for me to be looking?  Is there some other approach I've missed?
 Thanks,
    Mark Shirley