Direct screen writes (Re: Graphic characters in Norton Utilities SYS-V)

[Rick Richardson]

In article <R4:49J at xds13.ferranti.com> peter at ficc.ferranti.com (Peter da Silva) writes:
>> In other cases, direct screen writes are of tremendous value.
>> People find it convenient to lean on the arrow keys to move
>> around, and expect to stop on a dime when they see where they
>> want to be.

>There are many programs that provide this facility over even slow serial
>ports, by either doing heuristics to determine when to do updates, or by
>simply abandoning the current update of the screen image so long as input
>is pending.

This is true (and where I got on this boat by pointing out that ETI
implements jump-scroll for you).  The point is that jump scroll
doesn't allow you to lean on arrow keys.  Jump scroll, no matter
how you implement it, is visually annoying.  You cannot train
your eyes on just one spot on the screen in order to scan for
the context you are looking for.

When it comes to human engineering, there is no substitute for
a fast scroll capability.  Mere mortal users expect it, and
it is one of the first 'features' they look for.

As my little test program shows, this is not gratuitous optimization.
It is clearly a desirable optimization.  The optimization allows
region scrolling to keep up with the repeat rate from the keyboard
(typically 20-30 per second) in a visually pleasing manner.

Pipe dreams like 'it should be in the device driver' don't help
todays users.  Wizbang search features aren't a substitute (though
needed) since it is most natural to use the eye as a pattern recognizer.

The Norton *implementation* may have been buggy in that there was
no way to disable it (or perhaps it should have defaulted 'off',
with a manner to enable it).


-Rick

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