Don't use post-command-hook to notify the changes of elscreen for display's performance

[aki-s]

Just repeating forward-char makes texts invisible by too much of requests to redraw display.

Emacs 26.3 on Darwin.

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elscreen.el L.573

(defun elscreen-set-screen-modified ()
  (elscreen-set-conf-list 'modified-inquirer nil)
  (add-hook 'post-command-hook 'elscreen-run-screen-update-hook)) ;; <-- Don't

Using idel-timer with mutex would be the best answer.

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Because this issue can be observed in random buffer (After window layout is changed (e.g. split window)?),
there may exist the other problem which mistakenly
calls elscreen-set-screen-modified by judging from incorrect internal state.

My assumption is that post-command-hook is not cleared properly by concurrency issue after elscreen-run-screen-update-hook is added.

[aki-s]

It looks just overwriting existing methods could resolve this issue.

  ;; <override elscreen.el>
  (defvar elscreen--update-unlock-idle-timer nil)
  (defun elscreen--unlock-update-lock()
    (setq elscreen--update-unlock-idle-timer nil))
  (defun elscreen-run-screen-update-hook ()
    "Override function of elscreen.el to prevent huge performance issue of redisplay."
    (unless elscreen--update-unlock-idle-timer
      (setq elscreen--update-unlock-idle-timer
            (run-with-idle-timer 1 nil #'elscreen--unlock-update-lock))
      (when elscreen-frame-confs
        (elscreen-notify-screen-modification-suppress
         (run-hooks 'elscreen-screen-update-hook)))
      (remove-hook 'post-command-hook 'elscreen-run-screen-update-hook)
      ))
  (defun elscreen-set-screen-modified ()
    "Override function of elscreen.el to prevent huge performance issue of redisplay."
    (unless elscreen--update-unlock-idle-timer
      (elscreen-set-conf-list 'modified-inquirer nil)
      (add-hook 'post-command-hook 'elscreen-run-screen-update-hook)))
  ;; </override elscreen.el>