🚀 go-pugleaf

pas@lcs.mit.edu (Paul A. Selkirk) writes:
>Does anyone know of a bulletproof way for a TSR to tell whether DOS (assume
>2.x or 3.x) is idling in the command interpreter, or executing a program?

not off hand...
 
>For the record, I am writing a screen-saver TSR that will only trigger when DOS
>is idling.  There are dozens of screen-savers, but I need one that won't kill
>a lengthy graphics program.  (Ever try generating the Mandelbrot set on a 4.77 
>MHz XT with no FPU?  I thought so.)

How about this, run the screen saver off of the timer interrupt.  If
the correct amount of time has passed, then change the pallette to all
black (if EGA or VGA) or do a memory copy of the screen and blank it 
(if < EGA).  While the screen is blank, the screen saver won't stop
any program that's currently running, but will latch on to the
keyboard or mouse interrupt.  And, of course, when the keyboard/mouse
interrupt is caught, you simply restore the screen by restoring the
palette (if >= EGA), or copy the screen back into video memory (if
< EGA).

This sounds like it might be a more elegant solution and you won't
have to worry about losing that Mandlebrot you've been generating for
the last xx hours...and probably just as important, it won't stop that
Mandlebrot while it's generating.  The only thing that could hurt this
is that if a program decides to modify the palette while the screen is
blanked.  I don't know EGA very well, but I bet there's probably a way
to intercept incoming commands to change the palette, and what you'd
do is intercept that and change what you've saved the palette as
appropiately.

TrevorB


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