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<TITLE>The Answer Guy 28: Tools for converting X output to java </TITLE>
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<H4>"Linux Gazette...<I>making Linux just a little more fun!</I>"
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<H1 align="center"><A NAME="answer">
<img src="../gx/dennis/qbubble.gif" alt="" border="0" align="middle">
<a href="./lg_answer28.html">The Answer Guy</a>
<img src="../gx/dennis/bbubble.gif" alt="" border="0" align="middle">
</A></H1> <BR>
<H4 align="center">By James T. Dennis,
<a href="mailto:answerguy@ssc.com">answerguy@ssc.com</a><BR>
Starshine Technical Services,
<A HREF="http://www.starshine.org/">http://www.starshine.org/</A> </H4>
<p><hr><p>
<H3><img src="../gx/dennis/qbub.gif" alt="(?)" width="50" height="28"
align="left" border="0">Tools for converting X output to java</H3>
<p><strong>From Sheldon E. Newhouse on Tue, 31 Mar 1998 on the [linuxprog]
<a href="http://linux-lists.home.ml.org">mailing list</a></strong></p>
<P><strong>Are there any tools available to convert
standard C code with X displays to java displays? Basically, we have a
long program which is written in C and does low level X output. We would
like to port it so that the number crunching part works on a back-end
server and users can view output on java clients. The part of the program
that does the display is fairly short, but intimately connected with the
X libraires. Any ideas or references would be appreciated.
<br><br>
TIA,
<br>-sen</strong></p>
<blockquote><img src="../gx/dennis/bbub.gif" width="50" height="28" alt="(!)"
align="left" border="0">I'm not sure about a "Java X Server" per
se. However there has been some work done on execution of remote X
applications through a web browser interface.
<br><br>
I have yet to use any of this stuff (I barely use X) --- so I can only
rely on hearsay and a bit of web searching.
<br><br>
The first technology to consider is the latest release of X Windows
itself. There was an initiative by the X Consortium (*)
called "Broadway" --- this eventually became the widely accepted
code name (possibly widely excepted as well -- but we won't get into that)
for the entire X11R6.3 release.
<br>
<ul><li>(Formerly at <A HREF="http://www.x.org">http://www.x.org</A>
this now appears to be part of The Open Group at
<A HREF="http://www.opengroup.org/">http://www.opengroup.org/</A>)
</ul>
<br>
Since I don't know most of the details it's probably best for me to
just refer you to some online articles that discuss it:
<br>
<dl>
<dt>Broadway/Xweb FAQ
<dd><A HREF="http://www.broadwayinfo.com/bwfaq.htm"
>http://www.broadwayinfo.com/bwfaq.htm</A>
<dt>Can X Survive on the Internet? By Brad Weinert
<dd><A HREF="http://www.sigs.com/publications/docs/xspot/9609/xspot9609.d.execbrief.html">http://www.sigs.com/publications/docs/xspot/9609/xspot9609.d.execbrief.html</A>
<dt>X Is Dead, Long Live X
<dd><A HREF="http://www.sigs.com/publications/docs/xspot/9603i/xspot9603.d.edit.html">http://www.sigs.com/publications/docs/xspot/9603/xspot9603.d.edit.html</A>
</dl>
<ul>
<li>Both of these articles at sigs.com seem to be
a bit out of date, now that ``Broadway'' has been
released. However they offer a pretty quick
preview of what X Web is supposed to be.
</ul>
<br>
Note that the constraint of this approach is that it seems to require
that you actually have an X Server on the clients. This is great if
you have just about any sort of Linux/Unix clients --- but may be
prohibitive if you intend for Windows (NT, '95, or 3.x) or MacOS
clients to access your applications.
<br><br>
You might be able to deploy the MI/X server (a freely available X Server
for Windows and MacOS) but I don't know if it supports the X11R6.x
"Broadway" features. You can find out more about MI/X at
<A HREF="http://tnt.microimages.com/freestuf/mix/"
>http://tnt.microimages.com/freestuf/mix/</A> and read MicroImages
Inc.'s FAQ at <A HREF="http://tnt.microimages.com/freestuf/mix/mix-faq.htm"
>http://tnt.microimages.com/freestuf/mix/mix-faq.htm</A>.
<br><br>
A quick perusal of that suggests that it won't support the Broadway
set of extensions (since the FAQ says that it doesn't support LBX --
the "low bandwidth X" which is apparently a key part of Broadway).
<br><br>
I don't know what commercial X Servers for Windows or the Mac will
help --- but I needn't spend any more space on that issue since I
you don't specify that as a requirement. Hummingbird's Exceed
(<A HREF="http://www.unipres.com/hbird/exceed/"
>http://www.unipres.com/hbird/exceed/</A>) is a likely candidate.
<br><br>
Another approach might be to provide your clients with VNC ---
which was listed in Linux Weekly News
(<A HREF="http://www.eklektix.com/lwn/">http://www.eklektix.com/lwn/</A>)
a few weeks ago. This has nothing to do with Java and almost nothing
to do with X Windows. However it does allow you to view X Windows
displays from Windows and Mac clients and vice versa --- using an
alternative to the X communications protocols.
<br><br>
The potential advantage is that it sounds much easier to install and
configure than a Windows or MacOS X server. Take a look at at the
"Olivetti and Oracle Research Laboratories"
(<A HREF="http://www.orl.co.uk/vnc/">http://www.orl.co.uk/vnc/</A>)
for more on that. Another advantage of this over MI/X would be that it
is open source available under the GPL --- MI/X is free to use but the
sources are not available.
<br><br>
The two approaches that are more directly suggested by your
question are:
<br><blockquote>
An Xlib to Java awt cross compiler (or class or library)
</blockquote><br>
... or:
<br><blockquote>
An X Server for the Java virtual machine (a class that implements
Xlib).
</blockquote><br>
I suspect that both of these are feasible --- though the performance
costs of the latter may not make it palatable and I'm sure that the
portability issues in each would be significant.
<br><br>
Despite my search engine efforts I was unable to find any information
on any work being done on either approach. However, I'm not an expert
in Java and I don't keep up on it much. So, maybe someone else here
will help us out.
<br><br>
I did look in several likely places at
<A HREF="http://www.developer.com/directories/"
>http://www.developer.com/directories/</A>
(formerly the Gamelan archives). The closest I found is a JXTerm ---
allegedly an 'xterm' in Java. This includes telnet and cut and paste
features. There are several Java terminal emulators including VT100,
VT220, ANSI-BBS, TN3270 and TN5250 applets.
<br><br>
Meanwhile I've been hearing snippets of SCO's
(<A HREF="http://www.sco.com/">http://www.sco.com/</A>)
"Tarantella" for the last year or so. This apparently does act as
an X Windows to Java gateway, providing a sort of "web desktop" or
"webtop" as their marketing copy refers to it. It appears that you'd
have to install a SCO OpenServer system to either run your application
or to act as a gateway between your applications server and your clients.
(I doubt sincerely that SCO will make Tarantella available for Linux
--- and it doesn't seem to be written <em>in</em> Java). I'm really curious
as to how this works.
<br><br>
(While I was writing this I installed a new copy of the Netscape
RPM from my Red Hat CD -- this is a new system that I just built
from parts, it's running S.u.S.E. -- started an X session, started
Navigator, pointed my browswer at
<A HREF="http://tarantella.sco.com/">http://tarantella.sco.com/</A> and
tried to access their demo. It gets to some point before showing
my anything like X or it's "webtop" with some complaint about a
Java Security violation in some class or another. Exiting and
retrying got me further along. Hint: don't try 'Tarantella'
during your first Navigator session. Eventually I was able to
get it running ...err... walking ...err... limping along.
It might be faster over a T1 or an ethernet -- I happen to be
using the 28.8 PPP connection at the moment).
<br><br>
If you're curious, go try the demo yourself. You can also find a
set of slides from a presentation by Andy Bovington (?) on:
<br><dl>
<dt>Controlling X/Motif apps from Java and Javascript.
<dd><A HREF="http://www.sco.com/forum97/tarantella/presentations/bov/"
>http://www.sco.com/forum97/tarantella/presentations/bov/</A>
</dl><br>
In typical "big company" fashion SCO doesn't tell you how much this
product costs. They expect you to fill out a survey and have their
sales critters call you.
<br><br>
I suspect that this circumlocution may result in more converts to
open source software than all of the other "freedom" arguments we can
muster.
<br><br>
Meanwhile, my wife, Heather, found a couple of promising links
(she's the <em>real</em> search engine wiz in the family).
<br><br>
Here's the most promising:
<br><dl>
<dt>Eugene O'Neil's XTC, the X Tool Collection
<dd><A HREF="http://www.cs.umb.edu/~eugene/XTC/"
>http://www.cs.umb.edu/~eugene/XTC/</A>
</dl><br>
... which appears to be at the early alpha stages but, in his own
words:
<br><blockquote>
... is an implementation of the X Window Protocol, written in pure
Java. It does not require any native C libraries, such as Xlib:
instead, it is intended as a complete replacement for Xlib, written
from the ground up to be flexible, object-oriented, and
multi-threaded.
</blockquote><br>
(Wow!)
<br><br>
There was also some work done by a Mr. Igor Boukanov at:
<br><dl>
<dt>Pure Java X client
<dd><A HREF="http://asfys3.fi.uib.no/~boukanov/java.doc/lib.x.html"
>http://asfys3.fi.uib.no/~boukanov/java.doc/lib.x.html</A>
</dl><br>
By far the best technical information I found on X Windows in my
search was:
<br>
<dl>
<dt>Kenton Lee's: Technical X Window System and Motif WWW Sites
<dd><A HREF="http://www.rahul.net/kenton/xsites.html"
>http://www.rahul.net/kenton/xsites.html</A>
</dl><br>
Kenton has the best set of links on the subject, and apparently has
written articles for 'X Advisor Magazine' and several others.
</blockquote>
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<H5 align="center"><a href="http://www.linuxgazette.com/ssc.copying.html"
>Copyright ©</a> 1998, James T. Dennis <BR>
Published in <I>Linux Gazette</I> Issue 28 May 1998</H5>
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