neovim/runtime/lua/vim/highlight.lua

local api = vim.api

local highlight = {}

---@private
function highlight.create(higroup, hi_info, default)
  local options = {}
  -- TODO: Add validation
  for k, v in pairs(hi_info) do
    table.insert(options, string.format("%s=%s", k, v))
  end
  vim.cmd(string.format([[highlight %s %s %s]], default and "default" or "", higroup, table.concat(options, " ")))
end

---@private
function highlight.link(higroup, link_to, force)
  vim.cmd(string.format([[highlight%s link %s %s]], force and "!" or " default", higroup, link_to))
end


--- Highlight range between two positions
---
---@param bufnr number of buffer to apply highlighting to
---@param ns namespace to add highlight to
---@param higroup highlight group to use for highlighting
---@param rtype type of range (:help setreg, default charwise)
---@param inclusive boolean indicating whether the range is end-inclusive (default false)
---@param priority number indicating priority of highlight (default 50)
function highlight.range(bufnr, ns, higroup, start, finish, rtype, inclusive, priority)
  rtype = rtype or 'v'
  inclusive = inclusive or false
  priority = priority or 50

  -- sanity check
  if start[2] < 0 or finish[1] < start[1] then return end

  local region = vim.region(bufnr, start, finish, rtype, inclusive)
  for linenr, cols in pairs(region) do
    local end_row
    if cols[2] == -1 then
      end_row = linenr + 1
      cols[2] = 0
    end
    api.nvim_buf_set_extmark(bufnr, ns, linenr, cols[1], {
      hl_group = higroup,
      end_row = end_row,
      end_col = cols[2],
      priority = priority,
      strict = false
    })
  end

end

local yank_ns = api.nvim_create_namespace('hlyank')
--- Highlight the yanked region
---
--- use from init.vim via
---   au TextYankPost * lua vim.highlight.on_yank()
--- customize highlight group and timeout via
---   au TextYankPost * lua vim.highlight.on_yank {higroup="IncSearch", timeout=150}
--- customize conditions (here: do not highlight a visual selection) via
---   au TextYankPost * lua vim.highlight.on_yank {on_visual=false}
---
-- @param opts dictionary with options controlling the highlight:
--              - higroup   highlight group for yanked region (default "IncSearch")
--              - timeout   time in ms before highlight is cleared (default 150)
--              - on_macro  highlight when executing macro (default false)
--              - on_visual highlight when yanking visual selection (default true)
--              - event     event structure (default vim.v.event)
function highlight.on_yank(opts)
  vim.validate {
    opts = { opts,
    function(t) if t == nil then return true else return type(t) == 'table' end end,
    'a table or nil to configure options (see `:h highlight.on_yank`)',
  }}
  opts = opts or {}
  local event = opts.event or vim.v.event
  local on_macro = opts.on_macro or false
  local on_visual = (opts.on_visual ~= false)

  if (not on_macro) and vim.fn.reg_executing() ~= '' then return end
  if event.operator ~= 'y' or event.regtype == '' then return end
  if (not on_visual) and event.visual then return end

  local higroup = opts.higroup or "IncSearch"
  local timeout = opts.timeout or 150

  local bufnr = api.nvim_get_current_buf()
  api.nvim_buf_clear_namespace(bufnr, yank_ns, 0, -1)

  local pos1 = vim.fn.getpos("'[")
  local pos2 = vim.fn.getpos("']")

  pos1 = {pos1[2] - 1, pos1[3] - 1 + pos1[4]}
  pos2 = {pos2[2] - 1, pos2[3] - 1 + pos2[4]}

  highlight.range(bufnr, yank_ns, higroup, pos1, pos2, event.regtype, event.inclusive, 200)

  vim.defer_fn(
    function()
      if api.nvim_buf_is_valid(bufnr) then
        api.nvim_buf_clear_namespace(bufnr, yank_ns, 0, -1)
      end
    end,
    timeout
  )
end

return highlight