From:	"M. Schulter" <mschulter AT value DOT net>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Emacs M-! and graphics mode
Date:	10 Apr 1998 22:45:30 GMT
Organization:	Value Net Internetwork Services Inc.
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Message-ID:	<6gm7ea$r6t$1@vnetnews.value.net>
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To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

Eli Zaretskii <eliz AT is DOT elta DOT co DOT il> wrote:

: But as far as I understand your situation, you are running graphics
: programs via `M-!'.  If so, this is incorrect usage: M-! is meant to
: run programs that don't grab the screen; it is meant for programs
: which input and output text via the normal stdio functions.

Hello, there.

Curiously, with version 19.31, I discovered what appears to be a very
useful exception to this rule in 1996. Before reporting my unusual
experience, I should start with an _important warning_ for anyone who
might try something similar with a graphics application using an Emacs
Shell Command (M-!).

-------------------------------------------------------------------------
CAUTION: This is a report of an _exceptional_ success for something I
wouldn't expect to succeed. Readers of this newsgroup should _not_ assume
that it would necessarily work for your favorite graphics application or
utility. At the least, I would urge that anyone trying a similar
experiment should be prepared for the system to lock up or crash,
requiring a reboot.
-------------------------------------------------------------------------

For some reason -- although I didn't expect it to work, for the reason you
give -- I found that I can run a free DOS command-line graphics viewer
called PICEM as a Shell Command (M-!) without any problem.

Why this works, I have no idea; but the screen (Hercules Graphics
Card Plus, 720x348x2) changes to graphics mode when PICEM loads, and after
viewing a PCX or GIF file, pressing <Esc> in PICEM returns smoothly to
Emacs and text mode.

This "unexpected feature" is _very_ helpful in designing PostScript
artwork within Emacs, which is how I discovered it. This is a constant
process of shifting between editing in Emacs and previewing the PostScript
drawing with Image Alchemy PS (a commercial PostScript interpreter which
translates the code into PCX or GIF) and PICEM (which displays the PCX or
GIF on screen).

In fact, using a batch file to run Image Alchemy PS and then PICEM, and a
Shell Command macro to start the patch file, I can edit a PostScript file
in Emacs and then just press F7, say, whenever I want a preview. It takes
just one keystroke to go into preview mode in PICEM, and another (after
scrolling around the preview in graphics mode with the arrow keys) to
return to editing in Emacs.

Simply running an automated Shell Command, rather than suspending Emacs,
is obviously must faster and also more fun <grin> -- but I'm not sure why
it should work in this special case to shift from text to graphics mode
and back again.

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