Yes, fork the entire repo, make your changes either in the web interface or via command line (don’t worry about number of commits; I’ll just squash it down to one anyway), create a pull request comparing your fork to the main repo.
I’ll merge it in whenever I see it come up.
Ok, I think I did it 
Do I need to click “merge pull request”?
Ah, I see: it was making a PR to your own repo from a branch. Weird.
Anyway, I was able to make the PR to the main repo from your branch and then merged it, as well. So, congrats, you’re in https://github.com/libretro/slang-shaders/commit/e38e31d142ffdedfadb78212729201622e91f6e9
lol glad you were able to figure it out. Thanks!
I discovered you can switch out the masks in the Mame_hlsl and decided to try torture myself and see what I could do with a shadow mask. (I had to make my own as the one provided caused artifacts.) Here is a comparison of my work in progress with default venom, mask set to 3. Last one is Dreamcast so you can see how it works with higher res games. I scaled the images down and it looks like it cause some uneven scanlines that aren’t present in 4k.
Okay so it’s in there now, but I can’t get it to load. Should I replace “shaders_slang” in the filepath with “…” ?
This is what it currently looks like:
shader0 = “shaders_slang/misc/grade.slang”
Should it be this instead?
shader0 = “…/misc/grade.slang”
I have some notes at the top before all the shader code but that shouldn’t be a problem, right?
EDIT: Okay yeah that’s what needed to happen. Works fine after making that change, I’ll do another pull request and hopefully won’t screw that up this time 
That mask isn’t looking right IMO, I suggest using either regular Lottes stretched dot mask or the guest-dr-venom slotmask pattern. I think the vertical lines in that mask make it look somewhat strange.
@Nesguy I agree. the mame_hlsl shader has a scaneline Y offset that I put at the minimum value above 0. It gives the scanlines a 3D effect that is interesting. The negative is the masking can wonky. I’m hoping I can find a balance.
Yeah that’s a lot better IMO as far as the mask is concerned. Sharpness still seems high but it’s tough finding that sweet spot where the pixel edges are soft but high contrast edges stay sharp. I tried looking at mame_hlsl to see if it has some kind of reverse-blur sharpening but it was annoying to use. Too many settings and I couldn’t figure out how to get it to blur the right way (dark pixels at edges become brighter instead of light pixels becoming darker). I think this is the result of doing gamma correction before blurring.
It’s an odd shader for sure. It looks like some aspects aren’t working as their is a bloom pass in the folder that doesn’t work in slang but does in GLSL.
That’s because the updated slang version is based on MAME’s bgfx shader backend version, which doesn’t have bloom, while the GLSL version is still based on MAME’s HLSL shader backend version, which does have bloom but also has some other issues.
Very nice. I think this setup is the best image for the least hassle on 31khz CRTs.
I’m not able to set a wider horizontal resolution and 240p vertical at 120hz, so this is the best I can get. I followed your tips on another topic. Thank you.
Same settings like above but with Blargg composite filter. I chosen a heavy dithered game like Comix Zone.
