My C++ language server ccls implements a semantic highlightingfeatures through the non-standard messages$ccls/publishSemanticHighlight and$ccls/publishSkippedRanges, supported by both emacs-cclsand vscode-ccls.

For years, my primary editor was Emacs. In 2018, I created emacs-ccls(a fork of emacs-cquery) and enjoyed its rainbow semantic highlighting.My setup also relied heavily on two features:

• Bolding and underlining variables of static duration storage
• Italicizing member functions and variables

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(setq ccls-sem-highlight-method 'font-lock)
(ccls-use-default-rainbow-sem-highlight)

My elisp skills have gotten a bit rusty since I haven't been codingin it for a while. Switching to Neovim presented a challenge: it lackedthe rainbow highlighting I loved.

Thankfully, Neovim supports "semantic tokens" from LSP 3.16, astandardized approach adopted by many editors.

I've made changes to ccls (available on abranch) to support semantic tokens. This basically adapts the$ccls/publishSemanticHighlight code to supporttextDocument/semanticTokens/full andtextDocument/semanticTokens/range.

While semantic tokens do not differentiate symbols, we can definecustom modifiers to achieve similar results.

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tokenModifiers: {
  "declaration", "definition", ...

  "id0", "id1", ... "id9",
}

ccls assigns the same modifier ID to tokens belonging to the samesymbol. For different symbols, it attempts to assign unique IDs. Whilewe have only 10 predefined IDs (each linked to a specific color),there's a chance that two symbols might share the same ID. However, thisis uncommon and generally acceptable.

For a token with type variable, Neovim's built-in LSPplugin assigns it a highlight group@lsp.typemod.variable.id$i.cpp where $i is aninteger between 0 and 9. We can customize a foreground color for eachmodifier ID. The complete Lua code follows:

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local func_colors = {
  '#e5b124', '#927754', '#eb992c', '#e2bf8f', '#d67c17',
  '#88651e', '#e4b953', '#a36526', '#b28927', '#d69855',
}
local type_colors = {
  '#e1afc3', '#d533bb', '#9b677f', '#e350b6', '#a04360',
  '#dd82bc', '#de3864', '#ad3f87', '#dd7a90', '#e0438a',
}
local param_colors = {
  '#e5b124', '#927754', '#eb992c', '#e2bf8f', '#d67c17',
  '#88651e', '#e4b953', '#a36526', '#b28927', '#d69855',
}
local var_colors = {
  '#429921', '#58c1a4', '#5ec648', '#36815b', '#83c65d',
  '#419b2f', '#43cc71', '#7eb769', '#58bf89', '#3e9f4a',
}
local all_colors = {
  class = type_colors,
  enumMember = var_colors,
  field = var_colors,
  ['function'] = func_colors,
  parameter = param_colors,
  struct = type_colors,
  variable = var_colors
}
for type, colors in pairs(all_colors) do
  for i = 1,#colors do
    vim.api.nvim_set_hl(0, string.format('@lsp.typemod.%s.id%s.cpp', type, i-1), {fg=colors[i]})
  end
end

vim.cmd([[
hi @lsp.mod.classScope.cpp gui=italic
hi @lsp.mod.static.cpp gui=bold
hi @lsp.typemod.variable.namespaceScope.cpp gui=bold,underline
]], {})

Using this setup, let's examine the C++ code above:

This is quite appealing, but I need assistance to get code lensworking.

emacs-ccls

When this feature branch is merged, Emacs users can just remove thefollowing two lines:

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(setq ccls-sem-highlight-method 'font-lock)
(ccls-use-default-rainbow-sem-highlight)

TODO: How to change lsp-semantic-token-modifier-faces tosupport rainbow semantic tokens in lsp-mode and emacs-ccls?

vscode-ccls

Help is needed to remove $ccls/publishSemanticHighlightto use the built-in semantic tokens support. Unfortunately, vscode-cclsis not actively maintained, and I lack the expertise to maintain theplugin of an editor I do not commonly use.