Better support for background transparency (hi Normal ctermbg=NONE)

[oblitum]

Despite liking the choice of colours, they better not be exactly the same (comment foreground colour and OverLength background colour are the same):

I'm using https://github.com/whatyouhide/vim-lengthmatters which highlights long lines using OverLength.

UPDATE

This happens because I use transparent background by setting hi! Normal ctermbg=NONE in the .vimrc.

[romainl]

Are you using Apprentice in a 8/16color terminal?

That plugin works in 256color (see first screenshot) and GUI (see second screenshot) because the Normal background color is set. But in 8/16color it is set to NONE, which fools your plugin (see third screenshot).

256color

GUI

8/16color

[oblitum]

no, it's 256.

[romainl]

Check your $TERM inside Vim, as well as the value of t_Co:

:echo $TERM
:echo &t_Co

[oblitum]

$TERM -> screen-256color
&t_Co -> 256

[oblitum]

Your explanation above should then provide the answer to the behaviour I'm having, this is my setup:

" Colorscheme {{{
colors apprentice
"colors seoul256-light
hi! link Conceal Normal
hi! Normal ctermbg=NONE
hi! NonText ctermbg=NONE
" }}}

I do that on purpose to get transparent background.

[romainl]

You are using Vim in tmux?

It looks fine, here:

[oblitum]

I've just checked that commenting out NONE settings made it work as expected. It's indeed nice but, I can't exchange it for losing the background transparency. I'll change the issue title.

[romainl]

It appears to be a flaw in vim-lengthmatters's design, not in Apprentice's design.

The author wrongly assumes the value is a color (say 250 or #bcbcbc or maybe fg) but forgets it could perfectly be NONE, in which case he should pick another (default?) color.

I will certainly not change anything in Apprentice to address bugs in other plugins. You should contact the author via his plugin's issue tracker.

[oblitum]

Ah, my bad. Sorry to bother then, if the issue is there then that's OK, I thought it was colorscheme's fault. I'll check how to fix this there then, I've done two pull-requests on vim-lengthmatters lately, let's go for the 3rd.

[oblitum]

Do you have an advice on what should be picked to play nice with Apprentice?

[romainl]

You shouldn't adapt vim-lengthmatters to fit Apprentice (or any other specific colorscheme) or vice-versa.

That plugin obviously needs fallback values but how to define them is a potentially difficult matter.

One elegant but relatively complex way could be to calculate those values from existing ones but that also could lead to weird cornercases… What if we get NONE and NONE?

A simpler but not very elegant way could be to define arbitrary defaults, possibly based on &background.

[oblitum]

I'm going to set this on my .vimrc, since I'm already deviating from Apprentice default, Lengthmatters also provide options for setting OverLength colours so I'll try to set them to Apprentice colours before I override them with NONE.