[Simh] MAME and simh

[Johnny Billquist]

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

-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
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