Why is there a _<color code> suffix in SnacksBackdrop highlight group name?

[okuuva]

I was banging my head against a wall when trying to link the SnacksBackdrop highlight group in order to change it's color without having to use a hard coded color value. The problem was that it didn't seem to take effect. After some digging I discovered that Snacks actually adds _<color code> (or _T) to the group name:

snacks.nvim/lua/snacks/win.lua

Line 924 in 5e00b0a

local group = ("SnacksBackdrop_%s"):format(bg and bg:sub(2) or "T")

I get using a separate hlgroup for transparency but doesn't having a color code included in the hlgroup name kinda defeat the purpose? Or is my googlefu just off and I'm missing something here? I've never run across hlgroups with underscores in the name before, hence the confusion.

And if anybody runs across this discussion later on, I did come up with the following workaround to the original problem:

styles = {
  zen = {
    backdrop = {
      transparent = false, -- works even with transparent = true but then it'll tint the backdrop with the hlgroup as well
      win = {
        wo = { winhighlight = "Normal:SnacksBackdrop" },
      },
    },
  },
}

[folke]

_T is for transparent

[okuuva]

Yeah that much I could figure out, but why is the regular group SnacksBackdrop_0d0d0d, or SnacksBackdrop_000000, or SnacksBackdrop_<whatever you happen to set the backdrop color to be>? Why not just SnacksBackdrop? The suffix makes it impossible to theme, unless I'm still missing something obvious here.

[folke]

It depends on the blend value of the backdrop

[okuuva]

Ah, so is it creating a new hlgroup for all the different backdrops? So if you set the backdrop setting for one component it creates a new hlgroup for it based on the bg and/or blend?

[folke]

Yes indeed

[okuuva]

Ok, got it! It makes sense now that I think about it. I was just confused because README only mentions SnacksBackdrop hlgroup and trying to make changes to that group didn't have any effect no matter what I tried.

So right now that plain hlgroup isn't defined or used anywhere. Is there any backdrop setting (existing or possibly new one that could be added) where using the plain group would make sense? It'd make theming a lot easier.