Path: utzoo!mnetor!uunet!husc6!mit-eddie!uw-beaver!cornell!batcomputer!braner
From: braner@batcomputer.tn.cornell.edu (braner)
Newsgroups: comp.sys.atari.st
Subject: IDLE - replaces NITE
Message-ID: <3167@batcomputer.tn.cornell.edu>
Date: 13 Dec 87 13:56:51 GMT
Reply-To: braner@tcgould.tn.cornell.edu (braner)
Organization: Cornell Theory Center, Cornell University, Ithaca NY
Lines: 45
Summary: this one is benign

[]

A long time ago the utility "NIGHT" was posted.  It blanked the screen
after a few minutes with no activity, and unblanked it upon a keypress
or a mouse movement or BIOS text output to the screen.

NIGHT had serious bugs.  NITE fixed some, but it blanks the screen by
the same method: switching to external video sync.  If there are no
external sync signals, there are no vertical blanks, no picture---and
no VBL interrupts.  But many operations in the ST rely on those VBL
interrupts.  Leaving the ST on for long periods with NIGHT active leads
to strange behavior and a need for a reboot.

Here is IDLE, an alternative to NITE.  It should not cause any problems,
since all it does is shift the video RAM pointer 32K below the normal
location.  Since that area is normally all zeros, setting the video
palette right will display it as all black.  IDLE checks to see that
that piece of RAM is all zeros, and if it is not, it leaves the video
pointer as it was, and reverses the colors instead.  The check for
nonzeros is done slowly, so strange things _might_ show on the screen
for up to 20 seconds.  But not to worry: IDLE does _not_ write to the
video RAM.

I have only tested IDLE with a monochrome monitor, but it is supposed
to work with color too.

- Moshe Braner

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