Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!wuarchive!decwrl!ucbvax!agate!saturn!golding
From: golding@saturn.ucsc.edu (Richard A. Golding)
Newsgroups: comp.os.os2
Subject: Re: X Server for OS/2?
Message-ID: <10806@saturn.ucsc.edu>
Date: 19 Feb 90 07:58:56 GMT
References: <6119@umd5.umd.edu> <993@fiver.UUCP>
Organization: U.C. Santa Cruz, CIS/CE.
Lines: 64

In article <993@fiver.UUCP>, palowoda@fiver.UUCP (Bob Palowoda) writes:
>   Hmm, this is interesting. Can OS/2 or PM act as a client also? I was
> wondering if a OS/2 application can be run over a network similar to
> X.  Or does PM have some sort of extension that one can build an external
> user interface?

Having worked both on the internals of PM and on X servers, I think I
can comment.

OS/2 generally isn't intended as a network operating system, but rather
as a single-user operating system which can, with difficulty, access
some remote services.  This is a near-inversion of the X/Athena model
of computing, where the local workstation is used mostly just for
display and perhaps some light computation or file storage, and remote
systems are used for heavy-duty computation.

Obviously an X server can be built to run under PM.  The simplest way
(and the way most layered X products seem to start out) is to simply
put an X server in a PM window.  PM provides most of the necessary
input events, and the X server can paint whatever bits it needs to.
However, you can't just compile the MIT X11Rx sample server and tweak
it a bit to get such a server.  The MIT server assumes (among other
things) large linear address spaces, sockets (though X11R4 includes
streams support, I believe), and Unix-style signals.

A more sophisticated X server, where the X clients' windows are put in
separate PM windows, is virtually out of the question.  PM doesn't
support the richness of window types (how do you treat the
TRANSIENT_FOR hint?) that X does, and it doesn't have the mechanics to
support ICCCM-compliant applications (e.g. PM isn't very flexible in
its focus model.)  PM would have to serve as the X window manager,
which leads to interesting questions about mapping/unmapping windows
and reparenting support, as well as questions as to how well the X
selections model can work with the PM clipboard (for they are very
different.)  (For non-X types:  an X window manager is different from
the window system.  The window system implements windows.  The window
manager handles borders and things like resizing windows.  The toolkit
provides widgets and application-building tools.  The session
manager... and so on.)

I'd also guess that it will be quite a while before PM can support any
of the X extensions -- SHAPES certainly seems out of the question at
present, and OS/2 doesn't have memory models (in version 1.x) that can
support  PEX or VEX.  (This is particularly sad since so many DOS
machines get sold specifically because they will support cheap video
hardware.)

In short, I think that PM and X are two quite different beasts.  It
shouldn't be too hard to support PM under X, since PM provides so many
fewer services; given that several different interfaces to X already
exist (Xlib, Xt (using Athena, Motif, or ATT Open Look), CLX, Xview,
InterViews, Andrew) I don't think there are any doubts that PM would
work.  (Note that Motif is *not* PM under X; Motif is a widget set
which contains, among other things, widgets similar in function to the
the PM controls.  It is, however, based on Xt.)  The reverse, however,
seems more problematic.

-richard
-----------
Richard A. Golding, Crucible (work) and UC Santa Cruz CIS Board (grad student)
Internet:  golding@cis.ucsc.edu   Work: {uunet|ucscc}!cruc!golding
Post: Baskin Centre for CE & IS, Appl. Sci. Bldg., UC, Santa Cruz CA 95064
  or: 519 California St., Santa Cruz, CA 95060
  or: Crucible, 1717 Seabright #1, Santa Cruz CA 95062