Xref: utzoo comp.unix.aux:1346 comp.windows.x:14453
Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uwm.edu!gem.mps.ohio-state.edu!tut.cis.ohio-state.edu!snorkelwacker!think!kulla!barmar
From: barmar@kulla (Barry Margolin)
Newsgroups: comp.unix.aux,comp.windows.x
Subject: Re: can I display Mac applications remotely using X?
Message-ID: <31012@news.Think.COM>
Date: 20 Oct 89 21:47:03 GMT
References: <650@studsys.mu.edu> <1989Oct20.183825.6061@csmil.umich.edu>
Sender: news@Think.COM
Followup-To: comp.unix.aux
Organization: Thinking Machines Corporation, Cambridge MA, USA
Lines: 38

In article <1989Oct20.183825.6061@csmil.umich.edu> holtz@zurich.csmil.umich.edu (Brian Holtz) writes:
>I've heard that there's an X server that runs under Mac OS; would this
>be a way to have regular Mac applications display remotely on other
>workstations?  Is there _any_ way to do such a thing?

No.  An X server allows applications on other machines to display in
windows on the server machine.

In order to allow ordinary Mac applications to display remotely, the
low-level managers and toolboxes that access the screen directly would have
to be reimplemented using X operations.  This is a large, difficult
conversion, often requiring some redesign of the display manager because of
changes in underlying assumptions.  Symbolics spent a couple of years doing
this to their Lisp Machine window system so that it would work in the
MacIvory and UX400S co-processor environments.  Console drivers written for
hardwired displays generally assume that they can access the console
atomically, and that reading/writing bitmaps from/to the display is a cheap
operation, and applications often make similar assumptions.  This is not
the case when the display is at the other end of a network connection.
Routines that normally run at interrupt level now must make calls to
network stream interfaces, and handle all the myriad exceptional cases that
may be involved.

Consider the way screen fonts are handled.  The Mac keeps lots of bitmaps
around, and simply copies them to the screen; in System 7.0 it will keep
outlines around, compute bitmaps as needed, and copy them to the screen.
In X, however, the performant way to display characters is to send
character data to the server, allowing it to look up bitmaps from its own
fonts.  This means that the available fonts depend on the server you're
using; you may get strange results if you write a file directly on a Mac,
and then look at it again while using an X server on a Sun.  Symbolics's
decision was to make both styles of text output available, at the choice of
the application that creates a window.  They also provide a way to convert
Symbolics font files into X font files.
Barry Margolin, Thinking Machines Corp.

barmar@think.com
{uunet,harvard}!think!barmar