Been a while since posting my progress...
Properly emulating a mid-1980s RGB CRT is challenging. These displays had a very poor dot pitch, often .38 - .66, but had many interesting characteristics that dramatically enhanced 320x200 resolution or lower DOS games. A VGA or EGA display of that era looked worse. Sure, they were sharper, but they weren't visually powerful, either, unlike the RGB displays, and this is a big reason why RGB tubes were used in arcade machines of the time. They simply looked better.
These screenshots were taken from within Retroarch using their screenshot function, so the entire border was not captured, but believe me, when I'm playing DOS games it feels like I'm sitting in front of a full machine, as I have an overlay of the monitor, desktop and room with the dosbox window in the middle--or wherever I would want it, depending on the overlay I use. Refer to my older screenshots in this thread for comparison, but I think I'm getting close now to what a true old-era RGB monitor should look like:
Here's the overlay playing a VGA game:
This is done using Retroarch's 32-bit Dosbox core version 1.7.3(64-bit core doesn't work with external midi devices for some reason, nor MUNT) and many customizations to some shaders. I'm willing to share if anyone wants to give a try:
https://mega.nz/file/aNk0SRpJ#EhD0V6WIlRiodkb … umPCssvPb_kAER0
You drop that into Retroarch and then go from there. This isn't for a Retroarch noob to simply install and run--knowledge is required here of both Retroarch and Dosbox.
Basically, the gist is you put a batch file in your Dos directory named "poo.bat" or whatever you want to name it--I have one for VGA/EGA dos games and another for Tandy ones(because they use different mode settings in Dosbox options), and then Retroarch will call up the .cfg file in the /config/DOSBox subfolder which contains instructions on what shaders to use and how to resize the screen to fit within the overlay. So you copy those contents into the new config for whatever new .bat you make and it will launch into the DOSBox environment. You then navigate in dos via the command line to launch whatever in the sandboxed DOS subdirectory that has all your games.
One of my Retroarch config files also completely scrubs the keyboard of hotkeys within Retroarch itself so you can type and use the function keys(with the exception of F11 in mine which exits but I may change and F1).
The RGB emulation still isn't perfect, but it is getting close! I'm not satisfied with a little bit of bright pixel spots in the dark areas but note that the screenshots aren't 100% accurate because I am emulating the full 60 hz refresh rate which means there are two scanline passes for each frame, odd/even, so when I capture a screenshot it isn't capturing both passes in the shot.
You MUST run Retroarch in fullscreen mode. Borderless window will NOT work with RGB emulation because your framerate will drop to 59.xx instead of a solid 60 hz, which produces a staggered delay and induces jitter in the image.
I'd like to get this working on the newer Retroarch versions but the last time I tried to port to 1.9x was a nightmare because it wasn't accepting the .cfg parameters for image size to fit within the overlay bezel, among other issues. It became too much of a pain to bother with.