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From: friesen@psivax.UUCP (Stanley Friesen)
Newsgroups: net.unix-wizards
Subject: Re: Eighth Edition and job control (was Re: UNIX Futures)
Message-ID: <1124@psivax.UUCP>
Date: Tue, 22-Apr-86 11:24:55 EST
Article-I.D.: psivax.1124
Posted: Tue Apr 22 11:24:55 1986
Date-Received: Thu, 24-Apr-86 05:49:06 EST
References: <3289@sun.UUCP> <57700002@hpcvlo.UUCP>
Reply-To: friesen@psivax.UUCP (Stanley Friesen)
Organization: Pacesetter Systems Inc., Sylmar, CA
Lines: 53

In article <1918@ism780c.UUCP> tim@ism780c.UUCP (Tim Smith) writes:
>In article <1106@psivax.UUCP> friesen@psivax.UUCP (Stanley Friesen) writes:
>>
>>	Actually, under UNIX the way to do this is have the windowing
>>system send some standard signal, say SIGWINCH, to the process whose
>>window is being changed. The default action for this signal would of
>>course be to *ignore* it.
>
>I don't think that this is equivalent to what I want.  I want there to
>be two types of procs: those that know about windows, and those that
>don't.  Those that do would be told about window changes, probably
>with a signal.  Those that don't would not know that they are on
>a windowing system.  Their window would look like a terminal.

	EXACTLY, that is why the default action for SIGWINCH is
*ignore*, that way a program that doesn't care need not even know
about it! By simply doing nothing it gets nothing, it doesn't even
really recieve the signal, it gets thrown away by the kernel. Thus the
manager program(the multiplexor or meta-shell) need not know which
programs want to know about changes, it can just send the signal
all the time and let the processes that want to know arrange, by
explicit action, to catch and process the signal. In short arranging
to catch SIGWINCH is equivalent to notifying the kernel "I want to
know about window changes".

> When
>the user does something like change the size of the window, that would
>not change the logical size of the window, just the physical size.

	Certainly.
>
>[ by the way, I am assuming a windowing system that keeps track of what
>  is obscured by other windows, not one that requires procs to redraw
>  their own screens.  Thus, the only window changes that a proc should
>  care about are size changes ( and deletions... ) ]
>
	Absolutely. Well, deleting a window attached to a running
process should be *rare*, maybe this should send a SIGHUP, since it is
logically equivalent to unplugging a terminal.

>Note that under this scheme I should be able to take vi or rogue, and
>run them with no changes at all.

	And under mine as well, if it is implemented correctly. As I
said, a process that doesn't care simply does nothing and the kernel
silently and transparently ignores SIGWINCH. The program never even
knows it has been sent.
-- 

				Sarima (Stanley Friesen)

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