Hardcoding background color can be problematic

[Ptival]

The following create a couple of issues:

https://github.com/uvm-plaid/uvmhs/blob/a0ac0d780499d2a47906a10896c5d601d45b9903/src/UVMHS/Lib/Parser/ParserContext.hs#L48

1. For users with a dark terminal, the foreground text is often white or close, resulting in almost zero contrast between background and foreground.
2. Regardless of user background/foreground terminal, this also plays poorly with the current defaults, say for keywords.

In this screenshot, both effects can be seen, the double quotes, as well as the let keyword, are barely legible.

I feel like this ought to be configured via PrettyParams, so that users can at least override it.

[davdar]

Yes I've been meaning to support this!

I think we should do the following:

• add to the PrettyParams datatype in UVMS/Lib/Pretty/Doc.hs a new parameter; suggestions for the name of the parameter welcome, but first candidates that come to mind are annotationFormat, metaFormat and auxiliaryFormat.
• give a default value that is BG grayLight
• define helper function after ppLineNumFmt and ppLineNum that wrap around this parameter, the way those functions do for lineNumberFormat
• change the code you reference in this issue to use that helper function.

Additionally, I'd love a solution that automatically scrapes an environment variable to determine whether or not the terminal is in light or dark mode (there is an env variable for this, right?) I'm not sure the right place to put this logic, here are some options that come to mind:

• unsafe IO (io_UNSAFE) in the definition of prettyParams₀ (this is I think my preference)
• there is initUVMHS in UVMHS/Core/IO.hs; we could put it there
• we could scrape this env variable every time we print (again using unsafe IO), but unclear where to put it... oh, ppRenderWith in UVMHS/Lib/Pretty/RenderANSI.hs may be a good candidate; it's already scraping a global flag for enabling/disabling color...
• just like gv_PPRINT_COLOR is a magic global variable that changes the behavior of ppRenderWith, we could have gv_PPRINT_DARKMODE that does the same. The advantage of this is you could override its value in code, e.g., if you wanted to hardcode output for light/dark mode and not pull the value from an environment variable (which should be its initial value).

[davdar]

Oh, and I left this implied but forgot to write it down... once we have good support for switching between light/dark mode, we'll want a good default prettyParams₀ for dark mode.