Mode Line Idle

Simple delayed text evaluation for the mode-line.

This package provides a convenient way to defer text evaluation in a way that can be easily integrated into existing mode-line's without requiring a minor mode or configuration.

Available via melpa.

Motivation

To be able to add useful information into the mode-line without slowing down Emacs performance.

While delaying updates is not so difficult, having multiple timers can become awkward when mixed in with the mode-lines configuration.

Instead of avoiding expensive information in the mode-line, it can be calculated when idle.

Usage

To use mode-line-idle you will need to set mode-line-format using eval (examples below).

The function signature is:

(mode-line-idle delay content default-text &rest keywords)

delay

The number of seconds to delay evaluation once Emacs is idle.

content

The text to evaluate which can be a tree that gets converted into a string, this takes on a similar for to mode-line-format (more on this below).

default-text

The text to show before the value has been computed.

Optional Keyword Arguments

:interrupt (boolean)

When non-nil, evaluating the string will be interrupted on key input.

This is intended for long running operations, to prevent them locking Emacs if the user begins typing while the operation is running.

Interruption uses the same behavior as quit, see with-no-input documentation for details.

:literal (boolean)

When non-nil, replace % with %% to prevent mode-line-format from interpreting the character.

Examples

Simple example showing a delayed evaluated block in the mode line.

(defvar my-date '(:eval (current-time-string)))
(setq-default mode-line-format
  (list "Example " '(:eval (mode-line-idle 1.0 my-date "?"))))

The block to evaluate can be included inline as well.

(setq-default mode-line-format
  (list "Example " '(:eval (mode-line-idle 1.0 '(:eval (current-time-string)) "?"))))

As with mode-line-format, propertize is supported.

(defvar my-date '(:propertize (:eval (current-time-string)) face warning))
(setq-default mode-line-format
  (list "Example " '(:eval (mode-line-idle 1.0 my-date "?"))))

Two timers, with different faces.

(defvar my-date '(:eval (current-time-string)))
(defvar my-word '(:eval (count-words (point-min) (point-max))))
(setq-default mode-line-format
  (list "Example " '(:eval (list
                             "Date: "
                             (mode-line-idle 1.0 my-date "...")
                             " Word Count: "
                             (mode-line-idle 3.0 my-word "?" :interrupt t)))))

Utility Functions

(mode-line-idle-force-update &optional delay-in-seconds)

Calculate pending mode-line-idle items immediately.

When delay-in-seconds nil or omitted - update everything. Otherwise skip items with an idle time over this value.

Installation

This package can be installed from melpa.

(use-package mode-line-idle
  :commands (mode-line-idle))