GNU-devel ELPA - pulsar

Copyright (C) 2022-2024 Free Software Foundation, Inc.

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, with the Front-Cover Texts being “A GNU Manual,” and with the Back-Cover Texts as in (a) below. A copy of the license is included in the section entitled “GNU Free Documentation License.”

(a) The FSF’s Back-Cover Text is: “You have the freedom to copy and modify this GNU manual.”

This is a small package that temporarily highlights the current line after a given function is invoked. The affected functions are defined in the user option pulsar-pulse-functions and the effect takes place when either pulsar-mode (buffer-local) or pulsar-global-mode is enabled.

By default, Pulsar does not try to behave the same way for a function’s aliases. If those are not added explicitly to the pulsar-pulse-functions, they will not have a pulse effect. However, the user option pulsar-resolve-pulse-function-aliases can be set to a non-nil value to change this behaviour, meaning that Pulsar will cover a function’s aliases even if those are not explicitly added to the pulsar-pulse-functions.

Pulsar can also produce an effect over a specific region. This is useful to, for example, highlight the area covered by text that is pasted in the buffer. The user option pulsar-pulse-region-functions defines a list of functions that are region-aware in this regard. The default value covers copyring, pasting, and undoing/redoing.

The pulse effect also happens whenever there is a change to the window layout. This includes the selection, addition, deletion, resize of windows in a frame. Users who do not want this to happen can set the user option pulsar-pulse-on-window-change to a nil value.

The overall duration of the highlight is determined by a combination of pulsar-delay and pulsar-iterations. The latter determines the number of blinks in a pulse, while the former sets their delay in seconds before they fade out. The applicable face is specified in pulsar-face.

To disable the pulse but keep the temporary highlight, set the user option pulsar-pulse to nil. The current line will remain highlighted until another command is invoked.

The user option pulsar-inhibit-hidden-buffers controls whether Pulsar is active in hidden buffers. These are buffers that users normally do not interact with and are not displayed in the interface of the various buffer-switching commands. When this user option is nil, pulsar-mode will work in those buffers as well.

To highlight the current line on demand, use the pulsar-pulse-line command. When pulsar-pulse is non-nil (the default), its highlight will pulse before fading away. Whereas the pulsar-highlight-line command never pulses the line: the highlight stays in place as if pulsar-pulse is nil.

The command pulsar-pulse-region pulses the active region. The effect of the pulse is controlled by the aforementioned user options, namely, pulsar-delay, pulsar-iterations, pulsar-face.

A do-what-I-mean command is also on offer: pulsar-highlight-dwim. It highlights the current line line like pulsar-highlight-line. If the region is active, it applies its effect there. The region may also be a rectangle (internally they differ from ordinary regions).

To help users differentiate between the pulse and highlight effects, the user option pulsar-highlight-face controls the presentation of the pulsar-highlight-line and pulsar-highlight-dwim commands. By default, this variable is the same as pulsar-face.

Pulsar depends on the built-in pulse.el library.

Why the name “pulsar”? It sounds like “pulse” and is a recognisable word. Though if you need a backronym, consider “Pulsar Unquestionably Luminates, Strictly Absent the Radiation”.

Remember to read the doc string of each of these variables.

(require 'pulsar)

;; Check the default value of `pulsar-pulse-functions'.  That is where
;; you add more commands that should cause a pulse after they are
;; invoked

(setq pulsar-pulse t)
(setq pulsar-delay 0.055)
(setq pulsar-iterations 10)
(setq pulsar-face 'pulsar-magenta)
(setq pulsar-highlight-face 'pulsar-yellow)

(pulsar-global-mode 1)

;; OR use the local mode for select mode hooks

(dolist (hook '(org-mode-hook emacs-lisp-mode-hook))
  (add-hook hook #'pulsar-mode))

;; pulsar does not define any key bindings.  This is just a sample that
;; respects the key binding conventions.  Evaluate:
;;
;;     (info "(elisp) Key Binding Conventions")
;;
;; The author uses C-x l for `pulsar-pulse-line' and C-x L for
;; `pulsar-highlight-line'.
;;
;; You can replace `pulsar-highlight-line' with the command
;; `pulsar-highlight-dwim'.
(let ((map global-map))
  (define-key map (kbd "C-c h p") #'pulsar-pulse-line)
  (define-key map (kbd "C-c h h") #'pulsar-highlight-line))

Beside pulsar-pulse-line, Pulsar defines a few functions that can be added to hooks that are provided by other packages.

There are two functions to recenter and then pulse the current line: pulsar-recenter-top and pulsar-recenter-center (alias pulsar-recenter-middle).

There also exists pulsar-reveal-entry which displays the hidden contents of an Org or Outline heading. It can be used in tandem with the aforementioned recentering functions.

Example use-cases:

;; integration with the `consult' package:
(add-hook 'consult-after-jump-hook #'pulsar-recenter-top)
(add-hook 'consult-after-jump-hook #'pulsar-reveal-entry)

;; integration with the built-in `imenu':
(add-hook 'imenu-after-jump-hook #'pulsar-recenter-top)
(add-hook 'imenu-after-jump-hook #'pulsar-reveal-entry)

Pulsar is meant to be a collective effort. Every bit of help matters.

Author/maintainer

Protesilaos Stavrou.

Contributions to the code or manual

Abdelhak Bougouffa, Aymeric Agon-Rambosson, Bahman Movaqar, Daniel Mendler, Ivan Popovych, JD Smith, Maxim Dunaevsky, Ryan Kaskel, shipmints, ukiran03.

Ideas and user feedback

Anwesh Gangula, Diego Alvarez, Duy Nguyen, Matthias Meulien, Mark Barton, Petter Storvik, Ronny Randen, Rudolf Adamkovič, Toon Claes, and users djl, kb.

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