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wezterm.on(event_name, callback)

Since: Version 20201031-154415-9614e117

The functionality described in this section requires version 20201031-154415-9614e117 of wezterm, or a more recent version.

This function follows the html/javascript naming for defining event handlers.

wezterm.on causes your specified callback to be called when event_name is emitted. Events can be emitted by wezterm itself, or through code/configuration that you specify.

wezterm.on can register multiple callbacks for the same event; internally an ordered list of callbacks is maintained for each event. When the event is emitted, each of the registered callbacks is called in the order that they were registered.

The callback will receive the following parameters: - a window object that represents the active gui window. - a pane object that represents the active pane.

If a callback returns false it will prevent any callbacks that were registered after it from being triggered for the current event. Some events have a defined default action; returning false will prevent that default action from being taken for the current event.

There is no way to de-register an event handler. However, since the Lua state is built from scratch when the configuration is reloaded, simply reloading the configuration will clear any existing event handlers.

See wezterm.action_callback for a helper to define a custom action callback.

Predefined Events

See Window Events for a list of pre-defined events.

Custom Events

You may register handlers for arbitrary events for which wezterm itself has no special knowledge. It is recommended that you avoid event names that are likely to be used future versions of wezterm in order to avoid unexpected behavior if/when those names might be used in future.

The wezterm.emit function and the EmitEvent key assignment can be used to emit events.

Example: opening whole scrollback in vim

In the following example, a key is assigned to capture the entire scrollback and visible area of the active pane, write it to a file and then open that file in the vim editor:

local wezterm = require 'wezterm'
local io = require 'io'
local os = require 'os'
local act = wezterm.action

wezterm.on('trigger-vim-with-scrollback', function(window, pane)
  -- Retrieve the text from the pane
  local text = pane:get_lines_as_text(pane:get_dimensions().scrollback_rows)

  -- Create a temporary file to pass to vim
  local name = os.tmpname()
  local f =, 'w+')

  -- Open a new window running vim and tell it to open the file
    act.SpawnCommandInNewWindow {
      args = { 'vim', name },

  -- Wait "enough" time for vim to read the file before we remove it.
  -- The window creation and process spawn are asynchronous wrt. running
  -- this script and are not awaitable, so we just pick a number.
  -- Note: We don't strictly need to remove this file, but it is nice
  -- to avoid cluttering up the temporary directory.

return {
  keys = {
      key = 'E',
      mods = 'CTRL',
      action = act.EmitEvent 'trigger-vim-with-scrollback',