Path: csiph.com!usenet.pasdenom.info!weretis.net!feeder4.news.weretis.net!storethat.news.telefonica.de!telefonica.de!news-1.dfn.de!news.dfn.de!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail
From: Helge Blischke <h.blischke@acm.org>
Newsgroups: comp.lang.postscript
Subject: Re: Make ghostscript signal an /interrupt error when it received a SIGINT
Followup-To: comp.lang.postscript
Date: Tue, 30 Apr 2013 18:35:23 +0200
Lines: 55
Message-ID: <auaa6dFmu6pU1@mid.individual.net>
References: <a167181f-d7b2-4457-94e0-21239c955b6a@googlegroups.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7Bit
X-Trace: individual.net 9XW19Z7U84AbX1f2mLztRwkRpzBDAYY1dPqQufaZZBM5zYN9Us
Cancel-Lock: sha1:kV3/dMfLNyuMyIP5pdLkSlk2Yi4=
User-Agent: KNode/0.99.01
Xref: csiph.com comp.lang.postscript:1374

luser- -droog wrote:

> With my Mandelbrot explorer
> (https://code.google.com/p/xpost/downloads/detail?name=mandel2.ps), I'd
> like to be able to interrupt the drawing and return to the menu if the
> resolution is too high and it's taking too long.
> 
> The PLRM, 1ed, says
> 
>> interrupt  (error)
> 
>> processes an external request to interrupt execution of a PostScript
>> program. When the interpreter receives an interrupt request, it executes
>> interrupt as if it were an error (i.e. it looks up the name 'interrupt'
>> in errordict). Execution of interrupt is sandwiched between execution of
>> two objects being interpreted in normal sequence.
> 
>> The precise nature of an external interrupt request depends on the en-
>> vironment in which the PostScript interpreter is running. In typical
>> environments, receipt of a control-C character from a serial communi-
>> cation channel gives rise to the interrupt error. This permits a user to
>> explicitly abort a PostScript computation. The default definition of
>> interrupt executes a stop.
> 
> 
> I tried wrapping the drawing functions in a stopped context.
> 
> % The Main Loop
> % - draw the object according to currrent parameters
> % - enter menu loop
> % - showpage
> {
>     {
>         createtable findmaxmin sketch flushpage
>     } stopped clear
>     menu
>     showpage
> } loop
> 
> But ctrl-C just kills the whole interpreter.
> 
> Is there a special mode or flag to enable /interrupt errors with GS?

Looking (not too deeply) into the Ghostscript sources reveals: 
it seems that capturing signals like this is mainly restricted to
events associated with the PostScript input (currentfile and friends).
I guess it is not trivial to enhance gs to treat CTRL-C as an interrupt 
error without fidling around with the kernel of ghostscript's ps interpreter
ans how it is hooked up to the operating system (to be precise: the OS 
abstraction level).

So I'd suggest you file a feature request at bugs.ghostscript.com.

Helge