docs: pane:get_metadata

refs: #2460

docs/config/lua/pane/get_metadata.md

@@ -0,0 +1,74 @@
+# `pane:get_metadata()`
+
+*Since: nightly builds only*
+
+Returns metadata about a pane. The return value depends on the instance of the
+underlying pane. If the pane doesn't support this method, `nil` will be returned.
+Otherwise, the value is a lua table with the metadata contained in table fields.
+
+To consume this value, it is recommend to use logic like this to obtain a table
+value even if the pane doesn't support this method:
+
+```lua
+local meta = pane:get_metadata() or {}
+```
+
+The following metadata keys may be present:
+
+## password_input
+
+A boolean value that is populated only for local panes.
+It is set to true if it appears as though the local PTY is
+configured for password entry (local echo disabled, canonical
+input mode enabled).
+
+This example demonstrates how to change the color scheme
+to exaggerate when a password is being input:
+
+```lua
+local wezterm = require 'wezterm'
+
+wezterm.on('update-status', function(window, pane)
+  local meta = pane:get_metadata() or {}
+  local overrides = window:get_config_overrides() or {}
+  if meta.password_input then
+    overrides.color_scheme = 'Red Alert'
+  else
+    overrides.color_scheme = nil
+  end
+  window:set_config_overrides(overrides)
+end)
+
+return {}
+```
+
+## is_tardy
+
+A boolean value that is populated only for multiplexer client panes.
+It is set to true if wezterm is waiting for a response from the multiplexer
+server.
+
+This can be used in conjunction with `since_last_response_ms` below.
+
+## since_last_response_ms
+
+An integer value that is populated only for multiplexer client panes.
+It is set to the number of elapsed milliseconds since the most recent
+response from the multiplexer server.
+
+This example shows how to put mux latency information into the status area:
+
+```lua
+local wezterm = require 'wezterm'
+
+wezterm.on('update-status', function(window, pane)
+  local meta = pane:get_metadata() or {}
+  if meta.is_tardy then
+    local secs = meta.since_last_response_ms / 1000.0
+    window:set_right_status(string.format('tardy: %5.1fs⏳', secs))
+  end
+end)
+
+return {}
+```
+