🚀 go-pugleaf

In article <718222072.F00001@monly.wlink.nl.monly.wlink.nl> Martijn.Dijksterhuis@p6.f17.n512.z2.wlink.nl (Martijn Dijksterhuis) writes:
>
>Together with some friends of mine i'm writing a program that is in dire need of a smooth scrolling routine for the 0x13Hex VGA (320x200x256) mode.
>

First of all, what kind of images are you trying to scroll.  If you wanted you
could switch your program to Mode X (check other forums or Dr. Dobbs Journal
for details) and then you could manipulate the Start Address High and Start
Address Low to create a smooth scroll.  If you don't want to do this there is
another possiblity.  If you are able to blank your screen before the scroll
starts (just for a brief moment, less than a second probably) and are able to
do the same after the scroll then you could try the following.  First turn off
the video refresh so your monitor will blank, then switch the video mode to
Mode X, load the second page of memory in (it won't quite work like Mode X but
you can probably figure out the addressing you need), and then turn on video
refresh.  You theoretically then have the current image on your monitor and
then by manipulating the Start Address High and Start Address Low registers you
can scroll the second page of memory onto the screen.  I advise that you now
blank the screen again.  Copy the second page of memory to the first (in Mode X
again of course) and set the Start Address High and Start Address Low registers
to the first page.  This will make a VERY smooth scroll if done correctly and
when you are complete with the scroll the video card is like it was before you
started to scroll.
     Hope this helps.  Write me a email message and let me know.

Chris Hall
hallch@handel.colostate.edu <- email address