User borders around LSP floating windows

Question

In neovim, these keymaps (from nvim-lspconfig) show diagnostics from LSP servers on a floating window:

vim.keymap.set('n', '<leader>le', vim.diagnostic.open_float, opts)
vim.keymap.set('n', '[d', vim.diagnostic.goto_prev, opts)
vim.keymap.set('n', ']d', vim.diagnostic.goto_next, opts)

The floating window uses highlight group :h hl-NormalFloat. I set its background to be equal to :h hl-Normal so it looks like a transparent window. The problem is: now I can't distinguish between the floating window and the main window.

I could reset the background color of NormalFloat to something distinguishable than Normal, but that would not work properly with the highlighting colors of the diagnostic messages. Adding a border around the floating would be the best solution. How do I do that?

Answer 1

Since version 5.0, neovim supports adding borders to floating windows. :h lsp integrates it, too. But not by default; we have to enable it. The following configuration would do so.

local _border = "single"

vim.lsp.handlers["textDocument/hover"] = vim.lsp.with(
  vim.lsp.handlers.hover, {
    border = _border
  }
)

vim.lsp.handlers["textDocument/signatureHelp"] = vim.lsp.with(
  vim.lsp.handlers.signature_help, {
    border = _border
  }
)

vim.diagnostic.config{
  float={border=_border}
}

The border of the floating windows uses FloatBorder highlight group. So we will have to define it for optimum readability/visibility.

highlight FloatBorder  ctermfg=NONE ctermbg=NONE cterm=NONE

The document for border can be found in :h nvim_open_win (search for /\v<border:), which is used in configuring LSP diagnostics (see :h vim.diagnostic.config()) and LSP handlers (see :h vim.lsp.handlers.hover() and :h vim.lsp.handlers.signature_help()).

 

P.S. The floating window of :LSPInfo does not use the configuration of the diagnostic or handlers. It's provided by the plugin nvim-lspconfig, which provides a separate configuration for its border, which can be activated by this code:

require('lspconfig.ui.windows').default_options = {
  border = _border
}