init.el

;; -*- coding: utf-8; lexical-binding: t; -*-

;;; Code:

;; Without this comment emacs25 adds (package-initialize) here
;; (package-initialize)

(let* ((minver "26.1"))
  (when (version< emacs-version minver)
    (error "Emacs v%s or higher is required" minver)))

(setq user-init-file (or load-file-name (buffer-file-name)))
(setq user-emacs-directory (file-name-directory user-init-file))

(defvar my-debug nil "Enable debug mode.")

(setq *is-a-mac* (eq system-type 'darwin))
(setq *win64* (eq system-type 'windows-nt))
(setq *cygwin* (eq system-type 'cygwin) )
(setq *linux* (or (eq system-type 'gnu/linux) (eq system-type 'linux)) )
(setq *unix* (or *linux* (eq system-type 'usg-unix-v) (eq system-type 'berkeley-unix)) )
(setq *emacs28* (>= emacs-major-version 28))

;; don't GC during startup to save time
(unless (bound-and-true-p my-computer-has-smaller-memory-p)
  (setq gc-cons-percentage 0.6)
  (setq gc-cons-threshold most-positive-fixnum))

;; {{ emergency security fix
;; https://bugs.debian.org/766397
(with-eval-after-load 'enriched
  (defun enriched-decode-display-prop (start end &optional param)
    (list start end)))
;; }}

(setq *no-memory* (cond
                   (*is-a-mac*
                    ;; @see https://discussions.apple.com/thread/1753088
                    ;; "sysctl -n hw.physmem" does not work
                    (<= (string-to-number (shell-command-to-string "sysctl -n hw.memsize"))
                        (* 4 1024 1024)))
                   (*linux* nil)
                   (t nil)))

(defconst my-emacs-d (file-name-as-directory user-emacs-directory)
  "Directory of emacs.d.")

(defconst my-site-lisp-dir (concat my-emacs-d "site-lisp")
  "Directory of site-lisp.")

(defconst my-lisp-dir (concat my-emacs-d "lisp")
  "Directory of personal configuration.")

;; Light weight mode, fewer packages are used.
(setq my-lightweight-mode-p (and (boundp 'startup-now) (eq startup-now t)))

(defun require-init (pkg &optional maybe-disabled)
  "Load PKG if MAYBE-DISABLED is nil or it's nil but start up in normal slowly."
  (when (or (not maybe-disabled) (not my-lightweight-mode-p))
    (load (file-truename (format "%s/%s" my-lisp-dir pkg)) t t)))

(defun my-add-subdirs-to-load-path (lisp-dir)
  "Add sub-directories under LISP-DIR into `load-path'."
  (let* ((default-directory lisp-dir))
    (setq load-path
          (append
           (delq nil
                 (mapcar (lambda (dir)
                           (unless (string-match "^\\." dir)
                             (expand-file-name dir)))
                         (directory-files lisp-dir)))
           load-path))))

;; @see https://www.reddit.com/r/emacs/comments/3kqt6e/2_easy_little_known_steps_to_speed_up_emacs_start/
;; Normally file-name-handler-alist is set to
;; (("\\`/[^/]*\\'" . tramp-completion-file-name-handler)
;; ("\\`/[^/|:][^/|]*:" . tramp-file-name-handler)
;; ("\\`/:" . file-name-non-special))
;; Which means on every .el and .elc file loaded during start up, it has to runs those regexps against the filename.
(let* ((file-name-handler-alist nil))

  (require-init 'init-autoload)
  ;; `package-initialize' takes 35% of startup time
  ;; need check https://github.com/hlissner/doom-emacs/wiki/FAQ#how-is-dooms-startup-so-fast for solution
  (require-init 'init-modeline)
  (require-init 'init-utils)
  (require-init 'init-file-type)
  (require-init 'init-elpa)

  ;; make all packages in "site-lisp/" loadable right now because idle loader
  ;; are not used and packages need be available on the spot.
  (when (or my-lightweight-mode-p my-disable-idle-timer)
    (my-add-subdirs-to-load-path (file-name-as-directory my-site-lisp-dir)))

  ;; Any file use flyspell should be initialized after init-spelling.el
  (require-init 'init-spelling t)
  (require-init 'init-ibuffer t)
  (require-init 'init-bookmark)
  (require-init 'init-ivy)
  (require-init 'init-windows)
  (require-init 'init-javascript t)
  (require-init 'init-org t)
  (require-init 'init-python t)
  (require-init 'init-lisp t)
  (require-init 'init-yasnippet t)
  (require-init 'init-cc-mode t)
  (require-init 'init-linum-mode)
  (require-init 'init-git)
  (require-init 'init-gtags t)
  (require-init 'init-clipboard)
  (require-init 'init-ctags t)
  (require-init 'init-gnus t)
  (require-init 'init-lua-mode t)
  (require-init 'init-term-mode)
  (require-init 'init-web-mode t)
  (require-init 'init-company t)
  (require-init 'init-chinese t) ;; cannot be idle-required
  ;; need statistics of keyfreq asap
  (require-init 'init-keyfreq t)
  (require-init 'init-httpd t)

  ;; projectile costs 7% startup time

  ;; don't play with color-theme in light weight mode
  ;; color themes are already installed in `init-elpa.el'
  (require-init 'init-theme)

  ;; essential tools
  (require-init 'init-essential)
  ;; tools nice to have
  (require-init 'init-misc t)
  (require-init 'init-emms t)

  (require-init 'init-emacs-w3m t)
  (require-init 'init-shackle t)
  (require-init 'init-dired t)
  (require-init 'init-writting t)
  (require-init 'init-hydra) ; hotkey is required everywhere
  ;; use evil mode (vi key binding)
  (require-init 'init-evil) ; init-evil dependent on init-clipboard

  ;; ediff configuration should be last so it can override
  ;; the key bindings in previous configuration
  (when my-lightweight-mode-p
    (require-init 'init-ediff))

  ;; @see https://github.com/hlissner/doom-emacs/wiki/FAQ
  ;; Adding directories under "site-lisp/" to `load-path' slows
  ;; down all `require' statement. So we do this at the end of startup
  ;; NO ELPA package is dependent on "site-lisp/".
  (unless my-disable-idle-timer
    (my-add-subdirs-to-load-path (file-name-as-directory my-site-lisp-dir)))

  (require-init 'init-no-byte-compile t)

  (unless my-lightweight-mode-p
    ;; @see https://www.reddit.com/r/emacs/comments/4q4ixw/how_to_forbid_emacs_to_touch_configuration_files/
    ;; See `custom-file' for details.
    (setq custom-file (concat my-emacs-d "custom-set-variables.el"))
    (if (file-exists-p custom-file) (load custom-file t t))

    ;; my personal setup, other major-mode specific setup need it.
    ;; It's dependent on *.el in `my-site-lisp-dir'
    (my-run-with-idle-timer 1 (lambda () (load "~/.custom.el" t nil)))))


;; @see https://www.reddit.com/r/emacs/comments/55ork0/is_emacs_251_noticeably_slower_than_245_on_windows/
;; Emacs 25 does gc too frequently
;; (setq garbage-collection-messages t) ; for debug
(defun my-cleanup-gc ()
  "Clean up gc."
  (setq gc-cons-threshold  67108864) ; 64M
  (setq gc-cons-percentage 0.1) ; original value
  (garbage-collect))

(run-with-idle-timer 4 nil #'my-cleanup-gc)

(message "*** Emacs loaded in %s with %d garbage collections."
           (format "%.2f seconds"
                   (float-time (time-subtract after-init-time before-init-time)))
           gcs-done)
;;; Local Variables:
;;; no-byte-compile: t
;;; End:
(put 'erase-buffer 'disabled nil)