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From: whm@arizona.UUCP (Bill Mitchell)
Newsgroups: net.emacs
Subject: Re: "interruptable" screen updates
Message-ID: <21483@arizona.UUCP>
Date: Mon, 11-Feb-85 03:43:30 EST
Article-I.D.: arizona.21483
Posted: Mon Feb 11 03:43:30 1985
Date-Received: Tue, 12-Feb-85 04:49:30 EST
References: <21482@arizona.UUCP>
Distribution: net
Organization: Dept of CS, U of Arizona, Tucson
Lines: 37

A few minutes ago I wrote:
> 
> Namely, in #264, if I initiated an action that would take some non-trivial
> amount of real-time, such as a partial redraw of the screen at 1200 baud,
> and I then hit another key that caused another screen update, the first
> update would soon stop and the latter screen update would be performed.  In
> the new version, it seems that the first update is completed before
> the second one is started.  When using emacs-rnews, this often doubles or
> triples the real-time required to move through a number of non-interesting
> articles.

I suddenly couldn't bear emacs-rnews with this new behavior so I had 
to get to the bottom of the problem before I could continue reading my
news.

It turns out that the new "gentty" system is the culprit.  There seems to
be a macro OUTCHRPEND(fd) which provides the number of output characters
pending on file descriptor fd.  In gentty.h, OUTCHRPEND is defined to be
0 for all flavors of terminal drivers and has associated comments such
as "don't know how to do this yet".  Nonetheless, OUTCHRPEND is only used
in one place in display.c and if you replace the expression:

	OUTCHRPEND(fileno(stdin))

with the #264 code, which reads:

	(stdout->_ptr - stdout->_base)

things work like they used to.

My T2.00 tape is about a month old so it wouldn't be surprising if Unipress
has corrected this bogon in the meantime.

					Back to the reading the news,
					Bill Mitchell
					whm.arizona@csnet-relay
					{ihnp4,noao,mcnc,utah-cs}!arizona!whm