Themes with highlight groups using "links" to other groups do not propagate colors to SwiftUI properly

[s-daveb]

I think I figured out why another bug where some themes do not propagate their theme colors to VimR, such as dracula.

I noticed color changes are propagated from In NvimView+Resize.swift, line 129

autocmd ColorScheme * call rpcnotify(\(channel), 'autocommand', 'colorscheme', get(nvim_get_hl(0, {'id': hlID('Normal')}), 'fg', -1), get(nvim_get_hl(0, {'id': hlID('Normal')}), 'bg', -1), get(nvim_get_hl(0, {'id': hlID('Visual')}), 'fg', -1), get(nvim_get_hl(0, {'id': hlID('Visual')}), 'bg', -1), get(nvim_get_hl(0, {'id': hlID('Directory')}), 'fg', -1), get(nvim_get_hl(0, {'id': hlID('TablineSel')}), 'bg', -1), get(nvim_get_hl(0, {'id': hlID('TablineSel')}), 'fg', -1))

But when I try to get those specific groups in neovim:

echo get(nvim_get_hl(0, {'id': hIID('TablineSel')}, 'fg') 
['bold': vitrue, 'cterm': {'bold': vitrue}, 'link': 'Normal'})

echo get(nvim_get_hl(0, {'id': hIID('TablineFill')}, 'fg') 
({'link': 'DraculaBgDark'})

Because some themes define highlight groups that pull their values from other groups ("link" to other groups), when using the existing code, get(nvim_get_hl(0, {'id': hlID('TablineFill')}), 'bg', -1), the result with these highlight groups is always -1.

Reading up on highlight groups in the neovim docs, they suggest using something more like synIDattr(synIDtrans(hlID('TablineFill')),'bg').

Trying it in my clients, I get:

echo synIDattr(synIDtrans(hlID('TablineFill')),'bg')
#21222c

echo synIDattr(synIDtrans(hlID('TablineFill')),'fg')

This is a lot better, returning with hex color codes starting with #, but it results in empty strings when there is no value set, which could affect how existing code handles missing color codes.

I'm working on a pull-request that changes how the colors are grabbed, without changing how their error handling ( value of -1 ) works; but I wanted to also have this issue to explain the problem.

[georgeharker]

I think I use a couple of plugins which do the link decode in lua. Take a look at lualine source - I think it decodes highlights to get the separators right in a highlight module. GeorgeOn May 28, 2024, at 6:36 AM, S David @.**> wrote: I think I figured out why another bug where some themes do not propagate their theme colors to VimR, such as dracula. I noticed color changes are propagated from In NvimView+Resize.swift, line 129 autocmd ColorScheme call rpcnotify((channel), 'autocommand', 'colorscheme', get(nvim_get_hl(0, {'id': hlID('Normal')}), 'fg', -1), get(nvim_get_hl(0, {'id': hlID('Normal')}), 'bg', -1), get(nvim_get_hl(0, {'id': hlID('Visual')}), 'fg', -1), get(nvim_get_hl(0, {'id': hlID('Visual')}), 'bg', -1), get(nvim_get_hl(0, {'id': hlID('Directory')}), 'fg', -1), get(nvim_get_hl(0, {'id': hlID('TablineSel')}), 'bg', -1), get(nvim_get_hl(0, {'id': hlID('TablineSel')}), 'fg', -1)) But when I try to get those specific groups in neovim: echo get(nvim_get_hl(0, {'id': hIID('TablineSel')}, 'fg') ['bold': vitrue, 'cterm': {'bold': vitrue}, 'link': 'Normal'})

echo get(nvim_get_hl(0, {'id': hIID('TablineFill')}, 'fg') ({'link': 'DraculaBgDark'}) When using the existing code, get(nvim_get_hl(0, {'id': hlID('TablineFill')}), 'bg', -1), the result with these highlight groups is always -1, becaus ethese specific groups have their values "linked" to other highlight groups. Looking at the neovim documentation, they suggest using something more like synIDattr(synIDtrans(hlID('TablineFill')),'bg'). Trying it in my clients, I get: echo synIDattr(synIDtrans(hlID('TablineFill')),'bg')

21222c

echo synIDattr(synIDtrans(hlID('TablineFill')),'fg') This is a lot better, with hex color codes starting with #, but it results in empty strings when there is no value set, which could affect how existing code handles missing color codes. I'm working on a pull-request, but I wanted to also have this issue to explain the problem.

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[s-daveb]

@georgeharker That's not a bad suggestion, but where possible, it's probably best to let the neovim runtime do all the hard work.

I found that using the builtin funtionss as such follows all links automatically:

synIDattr(synIDtrans(hlID(<GroupName>)), <fg|bg>) " -> returns '#rrggbb' or ''

I got the following vimscript function to behave like get() when the result is not found

function! GetHiColor(hlID, component)
  let color = synIDattr(synIDtrans(hlID(a:hlID)), a:component)
  if empty(color)
    return -1
  else
    return str2nr(color[1:], 16) "removes leading # and converts hex string to its int value
  endif
endfunction

echo GetHiColor('TabLineFill', 'bg')   " -> 2171436
echo get(nvim_get_hl(0, {'id': hlID('TabLineFill')}), 'bg', -1)  " -> -1