Remote Use of UMASS Scheme Under X-Windows

This document was prepared using UMASS Scheme running remotely under
X-Windows, so it is possible!

(1) You will of course require an X-server on your machine - I am using
an X-server running under Linux. I can't help you set up this server.

(2) You should remotely log in to one of the delux machines (DecStations),
NOT to the el machines (Alphas).

(3) To run any X-application on your machine do

    setenv DISPLAY <mymachine>:0.0

where <mymachine> is the net address of your machine. If you use the ppp
connection, then you will be told the name as the link is established,
for example  cmpsci3.

(4) The Poplog system  on which UMASS  Scheme is based  is optimised for  high
bandwidth Ethernet  (or  other fast  LAN)  connections, not  for  low-bandwith
telephone connections, so care  is required in  using the system.  Essentially
the problem is  that, under  X-Windows, every time  you do  something on  your
machine, such as uncover a part of a hidden window, the remote machine can  be
called upon to restore  what you see,  and indeed this is  the default way  in
which X-windows works. Moreover the X-protocol (which is what is passed  along
the lines) is based on a lot of very low level operations (unlike HTML).  This
makes X very versatile, but at a price.

So, something that  to you seems  simple, like moving  or uncovering a  window
(strictly speaking it's  a widget in  X-terminology) involves quite  a lot  of
traffic. The  designers of  the  POPLOG X-window  interface system  opted  for
extensive use of widgets - one per file being edited, and so have ensured that
a lot of traffic on the line is created when you do apparently simple things.

(4) So,  bearing this  in  mind, the  major problem  is  that events  such  as
clicking the mouse are queued. So you can get far ahead of the X-system if you
are not careful. If nothing seems to  be happening, you probably need to  wait
while queued operations are performed.