Clean up the face setting section; font scaling does not work well

README.org

@@ -483,19 +483,19 @@ Emacs]] for how to setup fonts properly.  It boils down to two rules:
    with respect to the height of the face (those heights default to 1.0 for no
    scaling).
 The code in listing [[lst:configure-face-attributes]] implements those rules.
-Listing [[lst:set-default-face-height]] shows that font scaling is easy in case of
-proper initialization of all face heights.  To adjust the font size in the
-current or future frames, invoke src_emacs-lisp{(set-default-face-height)}.  To
-adjust the font size in the current buffer, type:
+Listing [[lst:face-setting-functions]] shows that font scaling is easy in case of
+proper initialization of all face heights in a frame.  To adjust the font size
+in windows, invoke src_emacs-lisp{(set-default-face-height)}.  To adjust the
+font size in the current buffer, type:
 1. {{{kbd(s-=)}}} to invoke src_emacs-lisp[:results silent]{(text-scale-adjust
    +1)}.
 2. {{{kbd(s--)}}} to invoke src_emacs-lisp[:results silent]{(text-scale-adjust
    -1)}.
 3. {{{kbd(s-0)}}} to invoke src_emacs-lisp[:results silent]{(text-scale-adjust
    0)}.
-Listing [[lst:fix-gtk-color-for-invert-default-face]],
-[[lst:shadow-org-font-lock-faces]], and [[lst:shadow-emacs-font-lock-faces]] show a
-tweaks to improve visibility without theming:
+Listing [[lst:face-setting-functions]], [[lst:shadow-org-font-lock-faces]], and
+[[lst:shadow-emacs-font-lock-faces]] show tweaks to improve visibility without
+theming:
 1. Fixing the =gtk= background color of the already loaded =region= face.
 2. Toggling between a dark and light background by means of
    src_emacs-lisp{(invert-default-face)}.
@@ -526,11 +526,12 @@ selects a fixed pitch face for =magit-mode= and =progmode= buffers.
     (set-face-attribute 'variable-pitch nil :family "DejaVu Sans"))))
 #+end_src
 
-#+caption[Implement =set-default-face-height=]:
-#+caption: Implement =set-default-face-height=.
-#+name: lst:set-default-face-height
+#+caption[Implement =face= setting functions]:
+#+caption: Implement =face= setting functions.
+#+name: lst:face-setting-functions
 #+begin_src emacs-lisp -n :results silent
 (with-eval-after-load 'emacs
+  ;; Neither `set-default-face-height' nor `text-scale-adjust' work well.
   (defun set-default-face-height ()
     "Set the default face height in all current and future frames.
 
@@ -543,29 +544,12 @@ Scale all other faces with a height that is a real number."
            (height (string-to-number
                     (completing-read prompt choices nil 'require-match))))
       (message "Setting the height of the default face to %s" height)
-      (set-face-attribute 'default nil :height height))))
-#+end_src
-
-#+caption[Fix a `gtk' color and implement =invert-default-face=]:
-#+caption: Fix a `gtk' color and implement =invert-default-face=.
-#+name: lst:fix-gtk-color-for-invert-default-face
-#+begin_src emacs-lisp -n :results silent
-(with-eval-after-load 'emacs
-  (defun fix-gtk-region-face-background-color ()
-    (when (featurep 'gtk)
-      (set-face-attribute
-       'region nil
-       :background (cdr (assoc (face-attribute 'default :background)
-                               '(("white" . "LightGoldenrod2")
-                                 ("black" . "blue3")))))))
+      (set-face-attribute 'default nil :height height)))
 
   (defun invert-default-face ()
     "Invert the default face."
     (interactive)
-    (invert-face 'default)
-    (fix-gtk-region-face-background-color))
-
-  (fix-gtk-region-face-background-color))
+    (invert-face 'default)))
 #+end_src
 
 #+caption[Shadow Org font-lock faces to improve the readability]:
@@ -638,15 +622,15 @@ verse and quote blocks are fontified using the `org-verse' and
 (defun set-buffer-variable-pitch-face ()
   "Set a variable width (proportional) font in current buffer."
   (interactive)
-  (setq buffer-face-mode-face 'variable-pitch)
-  (buffer-face-mode))
+  (let ((buffer-face-mode-face 'variable-pitch))
+    (buffer-face-mode)))
 
 ;; Use monospaced font faces in current buffer
 (defun set-buffer-fixed-pitch-face ()
   "Set a fixed width (monospace) font in current buffer."
   (interactive)
-  (setq buffer-face-mode-face 'fixed-pitch)
-  (buffer-face-mode))
+  (let ((buffer-face-mode-face 'fixed-pitch))
+    (buffer-face-mode)))
 
 (add-hook 'magit-mode-hook #'set-buffer-fixed-pitch-face)
 (add-hook 'prog-mode-hook #'set-buffer-fixed-pitch-face)