Change minibuffer color when NOT in minibuffer AND minibuffer active

Question

I frequently click on another application when I'm doing something in the minibuffer, and then I've forgotten I was in the minibuffer when I come back to emacs. I would like to highlight the minibuffer when it's active, but I'm in another emacs window. I have a solution that almost works.

(let ((bufs '(("0" . nil) ("1" . nil))))
  (defun tg/minibuf-conspicuous-when-active-hook ()
    (dolist (buf bufs)
      (if (and (not (minibufferp)) (active-minibuffer-window))
          (with-current-buffer (get-buffer (concat " *Minibuf-" (car buf) "*"))
            ;;(message "1-- %s %s" (car buf) bufs)
            (setcdr buf (face-remap-add-relative 'default :background "#355E3B")))
        (when (cdr buf)
          (with-current-buffer (get-buffer (concat " *Minibuf-" (car buf) "*"))
            ;;(message "2-- %s %s" (car buf) bufs)
            (face-remap-remove-relative (cdr buf))))))))
    (add-hook 'buffer-list-update-hook 'tg/minibuf-conspicuous-when-active-hook)
    (add-hook 'window-configuration-change-hook 'tg/minibuf-conspicuous-when-active-hook)

The reason I need both buffer-list-update-hook and window-configuration-change-hook is because there are some cases where buffer-list-update-hook is never called. This works if I move to another window within emacs and then back to the minibuffer. However, if I click on another application and then back, the minibuffer gets stuck on the new color I've set until I cancel. I can see from the debug messages that it is calling face-remap-remove-relative, but for some reason, it doesn't seem to work. In fact, I can replace that line with the following, and it works as expected.

            (face-remap-add-relative 'default :background "#000000")

Is there something I need to do to make it apply face-remap-remove-relative? Is there a simpler way to do this?

Answer 1

Minibuffer is selected

Minibuffer is DE-selected

(require 'hi-lock)

(defcustom my-minibuf-active-and-selected-face 'hi-green ; You can set this to nil
  "The face specification used by when minibuffer is active and selected.
It may contain any value suitable for a `face' text property,
including a face name, a list of face names, a face attribute
plist, etc."
  :type '(choice (face)
                 (repeat :tag "List of faces" face)
                 (plist :tag "Face property list"))
  :group 'display)

(defcustom my-minibuf-active-and-deselected-face 'hi-salmon
  "The face specification used by when minibuffer is active and de-selected.
It may contain any value suitable for a `face' text property,
including a face name, a list of face names, a face attribute
plist, etc."
  :type '(choice (face)
                 (repeat :tag "List of faces" face)
                 (plist :tag "Face property list"))
  :group 'display)

;; current remapping cookie for  buffer-face-mode
(defvar-local my-minibuf-face-remapping nil)

(defun my-minibuf-update-mapping (face)
  ;; Remove existing mapping
  (when my-minibuf-face-remapping
    (face-remap-remove-relative my-minibuf-face-remapping)
    (setq my-minibuf-face-remapping nil))
  ;; Add new mapping
  (setq my-minibuf-face-remapping
        (face-remap-add-relative 'default face))
  ;; Update
  (force-window-update (current-buffer)))

(defun my-minibuf-selected-or-deselected-function (w)
  (cond
   ;; Minibuffer has been selected
   ((and (eq w (minibuffer-window))
         (eq w (selected-window)))
    (my-minibuf-update-mapping my-minibuf-active-and-selected-face))
   ;; Minibuffer has been deselected
   ((and (eq w (minibuffer-window))
         (not (eq w (selected-window))))
    (with-selected-window (minibuffer-window)
      (my-minibuf-update-mapping my-minibuf-active-and-deselected-face)))))

(add-hook 'minibuffer-setup-hook
          (defun install-minibuf-selected-or-deselected-function ()
            (add-hook 'window-selection-change-functions
                      'my-minibuf-selected-or-deselected-function nil t)))