--- /dev/null
+ ;;; beacon.el --- Highlight the cursor whenever the window scrolls -*- lexical-binding: t; -*-
+
+ ;; Copyright (C) 2015 Free Software Foundation, Inc.
+
+ ;; Author: Artur Malabarba <emacs@endlessparentheses.com>
+ ;; URL: https://github.com/Malabarba/beacon
+ ;; Keywords: convenience
+ ;; Version: 0.1
+ ;; Package-Requires: ((seq "1.9"))
+
+ ;; This program is free software; you can redistribute it and/or modify
+ ;; it under the terms of the GNU General Public License as published by
+ ;; the Free Software Foundation, either version 3 of the License, or
+ ;; (at your option) any later version.
+
+ ;; This program is distributed in the hope that it will be useful,
+ ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+ ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ ;; GNU General Public License for more details.
+
+ ;; You should have received a copy of the GNU General Public License
+ ;; along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+ ;;; Commentary:
+
+ ;; This is a global minor-mode. Turn it on everywhere with:
+ ;; ┌────
+ ;; │ (beacon-mode 1)
+ ;; └────
+ ;;
+ ;; Whenever the window scrolls a light will shine on top of your cursor so
+ ;; you know where it is.
+ ;;
+ ;; That’s it.
+ ;;
+ ;;
+ ;; 1 Customizations
+ ;; ════════════════
+ ;;
+ ;; • The appearance of the beacon is configured by `beacon-size' and
+ ;; `beacon-color'.
+ ;;
+ ;; • The duration is configured by `beacon-blink-duration' and
+ ;; `beacon-blink-delay'.
+ ;;
+ ;; • To customize /when/ the beacon should blink at all, configure
+ ;; `beacon-blink-when-window-scrolls',
+ ;; `beacon-blink-when-window-changes', and
+ ;; `beacon-blink-when-point-moves'.
+ ;;
+ ;; • To prevent the beacon from blinking only on some major-modes,
+ ;; configure `beacon-dont-blink-major-modes'. For specific buffers, you
+ ;; can do `(setq-local beacon-mode nil)'. For even more refined
+ ;; control, configure `beacon-dont-blink-predicates'
+ ;;
+ ;; • Beacon can also push the mark for you whenever point moves a long
+ ;; distance. For this, configure `beacon-push-mark'.
+
+ ;;; Code:
+
+ (require 'seq)
+
+ (defgroup beacon nil
+ "Customization group for beacon."
+ :group 'emacs
+ :prefix "beacon-")
+
+ (defvar beacon--timer nil)
+
+ (defcustom beacon-push-mark nil
+ "Should the mark be pushed before long movements?
+ If nil, `beacon' will not push the mark.
+ Otherwise this should be a number, and `beacon' will push the
+ mark whenever point moves more than that many lines."
+ :type '(choice integer (const nil)))
+
+ (defcustom beacon-blink-when-point-moves nil
+ "Should the beacon blink when moving a long distance?
+ If nil, don't blink due to plain movement.
+ If non-nil, this should be an integer, which is the minimum
+ movement distance (in lines) that triggers a beacon blink."
+ :type '(choice integer (const nil)))
+
+ (defcustom beacon-blink-when-buffer-changes t
+ "Should the beacon blink when changing buffer?"
+ :type 'boolean)
+
+ (defcustom beacon-blink-when-window-scrolls t
+ "Should the beacon blink when the window scrolls?"
+ :type 'boolean)
+
+ (defcustom beacon-blink-when-window-changes t
+ "Should the beacon blink when the window changes?"
+ :type 'boolean)
+
+ (defcustom beacon-blink-duration 0.3
+ "Time, in seconds, that the blink should last."
+ :type 'number)
+
+ (defcustom beacon-blink-delay 0.3
+ "Time, in seconds, before starting to fade the beacon."
+ :type 'number)
+
+ (defcustom beacon-size 40
+ "Size of the beacon in characters."
+ :type 'number)
+
+ (defcustom beacon-color 0.5
+ "Color of the beacon.
+ This can be a string or a number.
+
+ If it is a number, the color is taken to be white or
+ black (depending on the current theme's background) and this
+ number is a float between 0 and 1 specifing the brightness.
+
+ If it is a string, it is a color name or specification,
+ e.g. \"#666600\"."
+ :type '(choice number color))
+
+ (defcustom beacon-dont-blink-predicates nil
+ "A list of predicates that prevent the beacon blink.
+ These predicate functions are called in order, with no
+ arguments, before blinking the beacon. If any returns
+ non-nil, the beacon will not blink."
+ :type 'hook)
+
+ (add-hook 'beacon-dont-blink-predicates (lambda () (bound-and-true-p hl-line-mode)))
+ (add-hook 'beacon-dont-blink-predicates #'window-minibuffer-p)
+
+ (defcustom beacon-dont-blink-major-modes '(magit-status-mode)
+ "A list of major-modes where the beacon won't blink.
+ Whenever the current buffer satisfies `derived-mode-p' for
+ one of the major-modes on this list, the beacon will not
+ blink."
+ :type '(repeat symbol))
+
+ \f
+ ;;; Overlays
+ (defvar beacon--ovs nil)
+
+ (defconst beacon-overlay-priority (/ most-positive-fixnum 2)
+ "Priotiy used on all of our overlays.")
+
+ (defun beacon--make-overlay (length &rest properties)
+ "Put an overlay at point with background COLOR."
+ (let ((ov (make-overlay (point) (+ length (point)))))
+ (overlay-put ov 'beacon t)
+ ;; Our overlay is very temporary, so we take the liberty of giving
+ ;; it a high priority.
+ (overlay-put ov 'priority beacon-overlay-priority)
+ (overlay-put ov 'window (selected-window))
+ (while properties
+ (overlay-put ov (pop properties) (pop properties)))
+ (push ov beacon--ovs)
+ ov))
+
+ (defun beacon--colored-overlay (color)
+ "Put an overlay at point with background COLOR."
+ (beacon--make-overlay 1 'face (list :background color)))
+
+ (defun beacon--ov-put-after-string (overlay colors)
+ "Add an after-string property to OVERLAY.
+ The property's value is a string of spaces with background
+ COLORS applied to each one.
+ If COLORS is nil, OVERLAY is deleted!"
+ (if (not colors)
+ (when (overlayp overlay)
+ (delete-overlay overlay))
+ (overlay-put overlay 'beacon-colors colors)
+ (overlay-put overlay 'after-string
+ (propertize
+ (mapconcat (lambda (c) (propertize " " 'face (list :background c)))
+ colors
+ "")
+ 'cursor 1000))))
+
+ (defun beacon--after-string-overlay (colors)
+ "Put an overlay at point with an after-string property.
+ The property's value is a string of spaces with background
+ COLORS applied to each one."
+ ;; The after-string must not be longer than the remaining columns
+ ;; from point to right window-end else it will be wrapped around.
+ (let ((colors (seq-take colors (- (window-width) (current-column)))))
+ (beacon--ov-put-after-string (beacon--make-overlay 0) colors)))
+
+ (defun beacon--ov-at-point ()
+ (car (or (seq-filter (lambda (o) (overlay-get o 'beacon))
+ (overlays-in (point) (point)))
+ (seq-filter (lambda (o) (overlay-get o 'beacon))
+ (overlays-at (point))))))
+
+ (defun beacon--vanish ()
+ "Turn off the beacon."
+ (when (timerp beacon--timer)
+ (cancel-timer beacon--timer))
+ (mapc #'delete-overlay beacon--ovs)
+ (setq beacon--ovs nil))
+
+ \f
+ ;;; Colors
+ (defun beacon--int-range (a b)
+ "Return a list of integers between A inclusive and B exclusive.
+ Only returns `beacon-size' elements."
+ (let ((d (/ (- b a) beacon-size))
+ (out (list a)))
+ (dotimes (_ (1- beacon-size))
+ (push (+ (car out) d) out))
+ (nreverse out)))
+
+ (defun beacon--color-range ()
+ "Return a list of background colors for the beacon."
+ (let* ((bg (color-values (face-attribute 'default :background)))
+ (fg (cond
+ ((stringp beacon-color) (color-values beacon-color))
+ ((< (color-distance "black" bg)
+ (color-distance "white" bg))
+ (make-list 3 (* beacon-color 65535)))
+ (t (make-list 3 (* (- 1 beacon-color) 65535))))))
+ (apply #'cl-mapcar (lambda (r g b) (format "#%04x%04x%04x" r g b))
+ (mapcar (lambda (n) (butlast (beacon--int-range (elt fg n) (elt bg n))))
+ [0 1 2]))))
+
+ \f
+ ;;; Blinking
+ (defun beacon--shine ()
+ "Shine a beacon at point."
+ (let ((colors (beacon--color-range)))
+ (save-excursion
+ (while colors
+ (if (looking-at "$")
+ (progn
+ (beacon--after-string-overlay colors)
+ (setq colors nil))
+ (beacon--colored-overlay (pop colors))
+ (forward-char 1))))))
+
+ (defun beacon--dec ()
+ "Decrease the beacon brightness by one."
+ (pcase (beacon--ov-at-point)
+ (`nil (beacon--vanish))
+ ((and o (let c (overlay-get o 'beacon-colors)) (guard c))
+ (beacon--ov-put-after-string o (cdr c)))
+ (o
+ (delete-overlay o)
+ (save-excursion
+ (while (progn (forward-char 1)
+ (setq o (beacon--ov-at-point)))
+ (let ((colors (overlay-get o 'beacon-colors)))
+ (if (not colors)
+ (move-overlay o (1- (point)) (point))
+ (forward-char -1)
+ (beacon--colored-overlay (pop colors))
+ (beacon--ov-put-after-string o colors)
+ (forward-char 1))))))))
+
+ (defun beacon-blink ()
+ "Blink the beacon at the position of the cursor."
+ (interactive)
+ (beacon--vanish)
+ (unless (or (not beacon-mode)
+ (run-hook-with-args-until-success 'beacon-dont-blink-predicates)
+ (seq-find #'derived-mode-p beacon-dont-blink-major-modes))
+ (beacon--shine)
+ (setq beacon--timer
+ (run-at-time beacon-blink-delay
+ (/ beacon-blink-duration 1.0 beacon-size)
+ #'beacon--dec))))
+
+ \f
+ ;;; Movement detection
+ (defvar beacon--window-scrolled nil)
+ (defvar beacon--previous-place nil)
+ (defvar beacon--previous-mark-head nil)
+ (defvar beacon--previous-window nil)
+
+ (defun beacon--movement-> (delta)
+ "Return non-nil if latest point movement is > DELTA.
+ If DELTA is nil, return nil."
+ (and delta
+ (markerp beacon--previous-place)
+ (equal (marker-buffer beacon--previous-place)
+ (current-buffer))
+ (> (abs (- (point) beacon--previous-place))
+ delta)
+ (> (count-screen-lines (min (point) beacon--previous-place)
+ (max (point) beacon--previous-place))
+ delta)))
+
+ (defun beacon--maybe-push-mark ()
+ "Push mark if it seems to be safe."
+ (when (and (not mark-active)
+ (beacon--movement-> beacon-push-mark))
+ (let ((head (car mark-ring)))
+ (when (and (eq beacon--previous-mark-head head)
+ (not (equal head beacon--previous-place)))
+ (push-mark beacon--previous-place)))))
+
+ (defun beacon--post-command ()
+ "Blink if point moved very far."
+ (cond
+ ((not (markerp beacon--previous-place))
+ (beacon--vanish))
+ ;; Blink for switching windows.
+ ((and beacon-blink-when-window-changes
+ (not (eq beacon--previous-window (selected-window))))
+ (beacon-blink))
+ ;; Blink for scrolling.
+ ((and beacon-blink-when-window-scrolls
+ beacon--window-scrolled
+ (equal beacon--window-scrolled (selected-window)))
+ (beacon-blink))
+ ;; Blink for movement
+ ((beacon--movement-> beacon-blink-when-point-moves)
+ (beacon-blink))
+ ;; Even if we don't blink, vanish any previous beacon.
+ (t (beacon--vanish)))
+ (beacon--maybe-push-mark)
+ (setq beacon--window-scrolled nil)
+ (unless (window-minibuffer-p)
+ (setq beacon--previous-mark-head (car mark-ring))
+ (setq beacon--previous-place (point-marker))
+ (setq beacon--previous-window (selected-window))))
+
+ (defun beacon--window-scroll-function (win _start-pos)
+ "Blink the beacon or record that window has been scrolled.
+ If invoked during the command loop, record the current window so
+ that it may be blinked on post-command. This is because the
+ scrolled window might not be active, but we only know that at
+ `post-command-hook'.
+
+ If invoked outside the command loop, `post-command-hook' would be
+ unreliable, so just blink immediately."
+ (if this-command
+ (setq beacon--window-scrolled win)
+ (setq beacon--window-scrolled nil)
+ (beacon-blink)))
+
+ \f
+ ;;; Minor-mode
+ (defcustom beacon-lighter
+ (cond
+ ((char-displayable-p ?💡) " 💡")
+ ((char-displayable-p ?Λ) " Λ")
+ (t " *"))
+ "Lighter string used on the mode-line."
+ :type 'string)
+
+ ;;;###autoload
+ (define-minor-mode beacon-mode
+ nil nil beacon-lighter nil
+ :global t
+ (if beacon-mode
+ (progn
+ (add-hook 'window-scroll-functions #'beacon--window-scroll-function)
+ (add-hook 'post-command-hook #'beacon--post-command)
+ (add-hook 'pre-command-hook #'beacon--vanish))
+ (remove-hook 'window-scroll-functions #'beacon--window-scroll-function)
+ (remove-hook 'post-command-hook #'beacon--post-command)
+ (remove-hook 'pre-command-hook #'beacon--vanish)))
+
+ (provide 'beacon)
+ ;;; beacon.el ends here
