[C64] [Apple2] [C128] Add Faster text routines.

[tschak909]

The C64, Apple2, and C128 targets need faster routines.

You can see an example of accelerated text output in:
https://github.com/tschak909/platoterm64/blob/master/src/atari/fast_text.s

can somebody adapt this for the above targets?

The fast text routine has flags for:

• double size/normal size
• transparent background mode/normal
• normal/erase mode

[rhalkyard]

It was a rainy day, so I had a go at porting the Atari fast text routines to the C64 :). feature/c64-fasttext in my fork of the repo.

It's very much a first pass and probably fairly naive - I'm a newcomer to the 6502 - but according to some very rudimentary benchmarking in the VICE monitor, it's taken us down from ~10000 to ~3000 cycles per character drawn.

No color support yet (though it should be fairly easy to drop in, since we could piggyback on a lot of the same offset-calculation logic) and due to the awkward bitmap layout, X-axis boundary checks aren't as straightforward (I've left them out for now), but it's a start.

It shouldn't be too difficult to adapt the same code to the C128 - and given the overhead involved in accessing VDC RAM, I imagine we'll see an even greater benefit there.

[tschak909]

eeeeeeeeexcellent :)

[rhalkyard]

I've added a C128 version (for both 640x480i and 640x200p modes) to the same branch. Lots of room for improvement, I'm sure, and I haven't benchmarked it yet, but combined with the ethernet interface, it feels positively speedy :)

[tschak909]

That is awesomesauce, god I have to try on a real 128 :)

[rhalkyard]

You really do! The interlaced mode is a bit demanding on monitors, but on my Sony PVM, it's sharp as a tack.

The VDC is very flexible (if somewhat buggy and chaotic and slow), but there isn't much software out there that makes good use of it, but I recently heard of a demo that squeezes interlaced 800x600 video out of it. If I run out of things to do this winter, I might have a go at adapting that code into a TGI driver, so we can show an unadulterated 512x512 PLATO screen without any scaling or anything.

The problem is, especially when going beyond the officially-documented text and 640x200 graphics modes, results are very dependent on the monitor and the particular revision of the VDC hardware, and emulation is a bit hit-or-miss - my 128DCR and CRT monitor renders a noticeably different (and much better-looking) 640x480 display compared to what I get in VICE. So, the more people trying it out on different real 128s, the better!

[rhalkyard]

Ugh, I lost a drive on my main development machine and my work-in-progress source for this was one of the casualties. Might be a little while before I can get everything back together :/

[tschak909]

No worries, anything I can do to help?

-Thom

[rhalkyard]

Thanks; it's mostly a matter of fishing through the last copy of the code I've got (in my c64-fasttext branch) and trying to figure out what works and what doesn't. IIRC I had the fast text routines and color text working for the C64, and the 128 version was well along the way - fast text was working and color was very broken but sort of working.