[Optimize] just update the face of the buffer name in `after-change-functions'.

`doom-modeline--buffer-file-name' may consume lots fof CPU if it's called too frequently.

Refer to #32 (comment).

Author: seagle0128

doom-modeline-segments.el

@@ -305,6 +305,7 @@ Uses `all-the-icons-material' to fetch the icon."
 (advice-add #'org-narrow-to-element :after #'doom-modeline-update-buffer-file-state-icon)
 (advice-add #'org-narrow-to-subtree :after #'doom-modeline-update-buffer-file-state-icon)
 (advice-add #'org-edit-src-save :after #'doom-modeline-update-buffer-file-state-icon)
+(advice-add #'symbol-overlay-rename :after #'doom-modeline-update-buffer-file-state-icon)
 
 (when (>= emacs-major-version 26)
   (add-variable-watcher
@@ -340,7 +341,6 @@ mouse-1: Previous buffer\nmouse-3: Next buffer"
 (add-hook 'find-file-hook #'doom-modeline-update-buffer-file-name)
 (add-hook 'after-revert-hook #'doom-modeline-update-buffer-file-name)
 (add-hook 'after-save-hook #'doom-modeline-update-buffer-file-name)
-(add-hook 'after-change-functions #'doom-modeline-update-buffer-file-name)
 (add-hook 'clone-indirect-buffer-hook #'doom-modeline-update-buffer-file-name)
 (add-hook 'evil-insert-state-exit-hook #'doom-modeline-update-buffer-file-name)
 (advice-add #'not-modified :after #'doom-modeline-update-buffer-file-name)
@@ -350,10 +350,10 @@ mouse-1: Previous buffer\nmouse-3: Next buffer"
 (advice-add #'undo :after #'doom-modeline-update-buffer-file-name)
 (advice-add #'undo-tree-undo-1 :after #'doom-modeline-update-buffer-file-name)
 (advice-add #'undo-tree-redo-1 :after #'doom-modeline-update-buffer-file-name)
-(advice-add #'symbol-overlay-rename :after #'doom-modeline-update-buffer-file-name)
 (advice-add #'popup-create :after #'doom-modeline-update-buffer-file-name)
 (advice-add #'popup-delete :after #'doom-modeline-update-buffer-file-name)
 (advice-add #'org-edit-src-save :after #'doom-modeline-update-buffer-file-name)
+(advice-add #'symbol-overlay-rename :after #'doom-modeline-update-buffer-file-name)
 
 (with-no-warnings
   (if (boundp 'after-focus-change-function)
@@ -375,6 +375,15 @@ mouse-1: Previous buffer\nmouse-3: Next buffer"
            (if buffer-file-name
                (doom-modeline-update-buffer-file-name))))))))
 
+;; Optimize: just update the face of the buffer name in `after-change-functions', since
+;; `doom-modeline--buffer-file-name' may consume lots fof CPU if it's called too frequently.
+(defun doom-modeline-update-buffer-file-name-face (&rest _)
+  "Update the face of buffer file name in mode-line."
+  (when (and doom-modeline--buffer-file-name (buffer-modified-p))
+    (setq doom-modeline--buffer-file-name
+          (propertize doom-modeline--buffer-file-name 'face 'doom-modeline-buffer-modified))))
+(add-hook 'after-change-functions #'doom-modeline-update-buffer-file-name-face)
+
 (defsubst doom-modeline--buffer-mode-icon ()
   "The icon of the current major mode."
   (when (and doom-modeline-icon doom-modeline-major-mode-icon)