elisp to "dim" faces except in the current window - work in progress

dimmer.el

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(setq face-remapping-alist nil)

(with-selected-window (get-buffer-window "*eshell*")
  (setq face-remapping-alist nil)
  (redraw-display))


;; ======================================================================

(defvar dimmer-face-remaps (make-hash-table))

(defvar dimmer-last-buffer nil)

(defvar dimmer-percent 0.80)

(defvar dimmer-invert nil)

(defun dimmer-face-color (f pct &optional invert)
  (when-let ((fg (face-foreground f)))
    (if invert
        (apply 'color-rgb-to-hex
               (mapcar (lambda (x) (- 1 (* (- 1 x) pct)))
                       (color-name-to-rgb fg)))
        (apply 'color-rgb-to-hex
               (mapcar (lambda (x) (* x pct))
                       (color-name-to-rgb fg))))))

;; (dimmer-face-color 'default 0.1 t)
;; (dimmer-face-color 'hiwin-face 0.5)

(defun dimmer-dim-window (name pct &optional invert)
  (let ((win (get-buffer-window name))
        (cookies nil))
    (unless (gethash win dimmer-face-remaps)
      (with-selected-window win
        (puthash win
                 (dolist (f (face-list) cookies)
                   (when-let ((c (dimmer-face-color f pct invert)))
                     (setq cookies
                           (cons (face-remap-add-relative f :foreground c) cookies))))
                 dimmer-face-remaps)))))

(defun dimmer-restore-window (name)
  (let ((win (get-buffer-window name)))
    (when-let ((cookies (gethash win dimmer-face-remaps)))
      (with-selected-window win
        (dolist (c cookies)
          (face-remap-remove-relative c)))
      (remhash win dimmer-face-remaps))))

;; (dimmer-dim-window "hiwin.el" 0.70)
;; (gethash (get-buffer-window "*eshell*") dimmer-face-remaps)
;; (dimmer-restore-window "hiwin.el")

;;;###autoload
(defun dimmer-activate ()
  (interactive)
  (add-hook 'post-command-hook 'dimmer-command-hook))

;;;###autoload
(defun dimmer-deactivate ()
  (interactive)
  (remove-hook 'post-command-hook 'dimmer-command-hook)
  (dimmer-delete-all))

(defun fih ()
  (message (concat "focus in: " (buffer-name (window-buffer (selected-window))))))

(defun foh ()
  (message (concat "focus out: " (buffer-name (window-buffer (selected-window))))))

;; (add-hook 'focus-in-hook 'fih)
;; (add-hook 'focus-out-hook 'foh)

(defun dimmer-command-hook ()
  (unless (eq (current-buffer) dimmer-last-buffer)
    (let ((current (current-buffer))
          (previous dimmer-last-buffer))
      (setq dimmer-last-buffer current)
      (when current
        (dimmer-restore-window (buffer-name current)))
      (when previous
        (dimmer-dim-window (buffer-name previous) dimmer-percent dimmer-invert)))))