[Coco] Text/Background Screen Inversion

[Brendan Donahe]

I see - so I think the problem here would be that unless you are launching
a BASIC program from SDCX.BAS, this may not work permanently.  In other
words, other ML programs/games will likely alter $FF22 for their own
purposes.  That said, one _could_ do something like this:

if CoCo1or2 AND 64kRAM {
  copy BASIC ROMs to upper RAM and switch to all RAM mode (there are short
ML routines out there that do this; I have one if you need it)
  patch the copy in RAM to have bit 5 of $FF22 set properly (I think
someone would have to take a look at the Color Basic/Extended Color Basic
Unravelled books to figure out the places where $FF22 are altered and patch
those.)
}

Given that this is not a complete solution and may still get lost when
launching other (non-BASIC) programs, I'm not sure it achieves your goal.

Brendan

On Thu, Feb 3, 2022 at 2:21 PM <michaelkline704 at gmail.com> wrote:

> Hi Brendan,
>
> I was remembering that when I used a programme called "ColorKit", it would
> invert the video. For which, I liked a lot better. Easier to read. It would
> be an idea for use with the CoCo 2. On, my CoCo 3, I use the pallet
> commands to give myself a black background with a yellow/white looking
> foreground (CMP). I add those changes to SDCX.BAS. Some other changes are
> ">>" for the "OK" prompt and a printer baud change that I make in the
> Autoexec. I'm also considering combining AUTOEXEC.BAS and SDCX.BAS, to
> speed up the auto load... just a hair 😊.
>
> Thus/then I am curious if someone had written a simple (probably ML)
> programme that does the inversion and keeps it running in the background.
> Again, the idea would be for the CoCo 1/2. SDCX.BAS would run such a
> programme if it determined that the CoCo is a 1 or 2.
>
> Michael
> -----------
>
> -----Original Message-----
> From: Coco <coco-bounces at maltedmedia.com> On Behalf Of Brendan Donahe
> Sent: 03 February 2022 13:43
> To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
> Subject: Re: [Coco] Text/Background Screen Inversion
>
> Michael,
>
> While what Alex describes is certainly the most straightforward approach,
> I'd think it would also be possible to (on a 64k CoCo 1 or 2, at least), be
> able to patch a copy of the BASIC ROM in RAM for use within all your
> BASIC-only programs.  I'm not sure which system(s) you're targeting or in
> what software you want to preserve your reverse-video.  The problem is that
> even with a BASIC patch, other ML software you might launch from BASIC
> likely overwrites that video mode setting and would not preserve the bit
> change you wrote to the VDG control register.  $FF22 bit 5, in particular,
> would be of interest to you - see page 50 of
> https://www.lomont.org/software/misc/coco/Lomont_CoCoHardware.pdf.
>
> If you want it permanent without copying the ROM to RAM and patching BASIC
> or in various software packages, a hardware solution would be best.
> Assuming we're talking about the CoCo 1 or 2, you can invert the sense of
> the INV pin on the 6847 VDG with a hardware hack.  This was a common
> modification back-in-the-day.
>
> Hope this helps,
> Brendan
>
> On Sat, Jan 29, 2022 at 6:47 PM Alex Evans <varmfskii at gmail.com> wrote:
>
> > Not really. When the CoCo is at the Ok prompt, it resets the display
> > features.
> > You can poke to invert the colors and/or switch to orange instead of
> > green, and it will stay that way as long as your program is running.
> >
> >
> > On Sat, Jan 29, 2022 at 3:14 PM <michaelkline704 at gmail.com> wrote:
> >
> > > Is there a poke(s) or a ML programme that would invert the screen
> > > background and text colours to a dark green background / light green
> > > text and leave
> > it
> > > that way until you power cycled?
> > >
> > >
> > >
> > > Michael
> > >
> > >
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