Johnny Billquist schreef op 3-7-2020 om 13:24:
On 2020-07-03 13:19, Johnny Billquist wrote:
On 2020-07-03 13:14, Lars Brinkhoff wrote:
Johnny Billquist wrote:
I am not at all sure I agree with that... I think you too should look
at the VT100 technical manual and see how soft scrolling is done, as
an example of a place where the hardware emulation can actually become
rather tricky...
Now I'm curious. If you have a title and a page number, I will take a
look.
I posted this last night, but here it comes again:
You really should check out of smooth scrolling on the VT100 is
accomplished...
(http://www.bitsavers.org/pdf/dec/terminal/vt100/EK-VT100-TM-003_VT100_Technical_Manual_Jul82.pdf,
page 4-97, section 4.7.9 - "Split Screen Smooth Scrolling". Emulating
those hardware tricks are not going to be easy...
Oh, and just for the people who don't want to read a lot of
documentation, the smooth scrolling is essentially done by the
terminal by changing where the source of the video signal generation
picks up font information, so that you actually start scanning at a
specific line of the font definition for characters at the video
generation stage. And then you do additional trickery so that you
start scanning the next line data as well, so that compared to the
line above, this line is generated using data from two lines, and your
picking up font definition lines with offsets, and then you need a bit
of special casing for the first and last lines of the region.
I hope that made sense... :-)
Johnny
The plain English description of "how it works" in the manual should be
used in every advanced programming class.
"Now, class, program this in SNOBOL or your own favorite programming
language." :-)
/Wilm
_______________________________________________
Simh mailing list
[email protected]
http://mailman.trailing-edge.com/mailman/listinfo/simh
