Display History in Emacs Buffer

display_history.el

;; Copyright (C) 2024 PSD Authors
;;
;; This program is free software: you can redistribute it and/or modify
;; it under the terms of the GNU Affero 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 Affero General Public License for more details.
;;
;; You should have received a copy of the GNU Affero General Public License
;; along with this program.  If not, see <https://gnu.org>.

;; 1. Basic Settings and Language Selection
(setq system-time-locale "en_US.UTF-8")
(setq display-time-interval 1) ;; ENSURES THE CLOCK UPDATES EVERY SECOND
(display-time-mode 1)

;; 2. Appearance Definition
(defface mode-line-clock-face
  '((t :foreground "yellow" :weight bold))
  "Yellow face for the clock and date in the modeline.")

;; 3. Logging and Buffer Functions
(defun log-current-time-to-history ()
  "Adds the current time to the *display-history* buffer and keeps the last 1000 lines."
  (let ((current-time-string (format-time-string "%H:%M:%S | %Y.%m.%d | Week %V | %A | %Z")))
    (with-current-buffer (get-buffer-create "*display-history*")
      (let ((inhibit-read-only t))
        (save-excursion
          (goto-char (point-max))
          (insert (concat "[" current-time-string "]\n"))
          ;; Limit buffer size to 1000 lines for performance
          (when (> (count-lines (point-min) (point-max)) 1000)
            (goto-char (point-min))
            (forward-line (- (count-lines (point-min) (point-max)) 1000))
            (delete-region (point-min) (point))))))))

(defun display-history ()
  "Displays the time history buffer on the screen."
  (interactive)
  (display-buffer (get-buffer-create "*display-history*")))

;; 4. Modeline Format
(setq display-time-string-forms
      '((propertize (format-time-string "%H:%M:%S | %Y.%m.%d | Week %V | %A | %Z") 
                    'face 'mode-line-clock-face)))

;; 5. Start Timers
;; Clear existing timers for a clean start
(cancel-function-timers 'log-current-time-to-history)

(run-at-time t 1 (lambda ()
                   (log-current-time-to-history)
                   (force-mode-line-update t))) ;; 't' parameter forces update across all windows

;; 6. Shortcut Configuration: Control + F12
(global-set-key (kbd "C-<f12>") 'display-history)