[Coco] Text/Background Screen Inversion

[michaelkline704 at gmail.com]

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
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-----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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