nvim/pack/acp/opt/nvim-lspconfig/lua/lspconfig/ui/windows.lua

-- The following is extracted and modified from plenary.vnim by
-- TJ Devries. It is not a stable API, and is expected to change
--
local function apply_defaults(original, defaults)
  if original == nil then
    original = {}
  end

  original = vim.deepcopy(original)

  for k, v in pairs(defaults) do
    if original[k] == nil then
      original[k] = v
    end
  end

  return original
end

local win_float = {}

win_float.default_options = {
  winblend = 15,
  percentage = 0.9,
}

function win_float.default_opts(options)
  options = apply_defaults(options, win_float.default_options)

  local width = math.floor(vim.o.columns * options.percentage)
  local height = math.floor(vim.o.lines * options.percentage)

  local top = math.floor(((vim.o.lines - height) / 2) - 1)
  local left = math.floor((vim.o.columns - width) / 2)

  local opts = {
    relative = 'editor',
    row = top,
    col = left,
    width = width,
    height = height,
    style = 'minimal',
    border = {
      { ' ', 'NormalFloat' },
      { ' ', 'NormalFloat' },
      { ' ', 'NormalFloat' },
      { ' ', 'NormalFloat' },
      { ' ', 'NormalFloat' },
      { ' ', 'NormalFloat' },
      { ' ', 'NormalFloat' },
      { ' ', 'NormalFloat' },
    },
  }

  return opts
end

--- Create window that takes up certain percentags of the current screen.
---
--- Works regardless of current buffers, tabs, splits, etc.
--@param col_range number | Table:
--                  If number, then center the window taking up this percentage of the screen.
--                  If table, first index should be start, second_index should be end
--@param row_range number | Table:
--                  If number, then center the window taking up this percentage of the screen.
--                  If table, first index should be start, second_index should be end
function win_float.percentage_range_window(col_range, row_range, options)
  options = apply_defaults(options, win_float.default_options)

  local win_opts = win_float.default_opts(options)
  win_opts.relative = 'editor'

  local height_percentage, row_start_percentage
  if type(row_range) == 'number' then
    assert(row_range <= 1)
    assert(row_range > 0)
    height_percentage = row_range
    row_start_percentage = (1 - height_percentage) / 2
  elseif type(row_range) == 'table' then
    height_percentage = row_range[2] - row_range[1]
    row_start_percentage = row_range[1]
  else
    error(string.format("Invalid type for 'row_range': %p", row_range))
  end

  win_opts.height = math.ceil(vim.o.lines * height_percentage)
  win_opts.row = math.ceil(vim.o.lines * row_start_percentage)

  local width_percentage, col_start_percentage
  if type(col_range) == 'number' then
    assert(col_range <= 1)
    assert(col_range > 0)
    width_percentage = col_range
    col_start_percentage = (1 - width_percentage) / 2
  elseif type(col_range) == 'table' then
    width_percentage = col_range[2] - col_range[1]
    col_start_percentage = col_range[1]
  else
    error(string.format("Invalid type for 'col_range': %p", col_range))
  end

  win_opts.col = math.floor(vim.o.columns * col_start_percentage)
  win_opts.width = math.floor(vim.o.columns * width_percentage)

  local bufnr = options.bufnr or vim.api.nvim_create_buf(false, true)
  local win_id = vim.api.nvim_open_win(bufnr, true, win_opts)
  vim.api.nvim_win_set_buf(win_id, bufnr)

  vim.cmd 'setlocal nocursorcolumn ts=2 sw=2'

  return {
    bufnr = bufnr,
    win_id = win_id,
  }
end

return win_float