Add a section to tweak the look by shadowing face definitions

README.org

@@ -257,6 +257,88 @@ the ~custom-file~ as [[info:emacs#Saving Customizations][saving customizations (
     (add-to-list 'initial-frame-alist '(width . 180)))
 #+end_src
 
+**  [[info:emacs#Faces][Text faces or look (info)]]
+:PROPERTIES:
+:CUSTOM_ID: sec:text-faces-or-look
+:END:
+
+Section [[#sec:text-faces-or-styles][text faces or styles (info)]] tells that this setup does not use theming.
+However, it relies on shadowing the definition of faces in order to improve
+visibility.  The last item in the page on [[https://orgmode.org/worg/org-contrib/babel/examples/fontify-src-code-blocks.html#org5c4406f][fontifying source code blocks]]
+describes this method.  Section [[#sec:text-faces-or-styles][text faces or styles (info)]] also defines the
+function src_emacs-lisp{(my-invert-default-face)} to toggle between a dark and a
+light background.
+
+#+caption[Improve the visibility of faces in =faces.el=]:
+#+caption: Improve the visibility of faces in =faces.el=.
+#+name: lst:tweak-faces-faces-early
+#+begin_src emacs-lisp
+  ;; Shadow the definition in faces.el:
+  (defface region
+    '((((class color) (min-colors 88) (background dark))
+       :background "blue3" :extend t)
+      (((class color) (min-colors 88) (background light) (type gtk))
+       :distant-foreground "gtk_selection_fg_color"
+       :background "LightGoldenrod2" :extend t)
+      (((class color) (min-colors 88) (background light) (type ns))
+       :distant-foreground "ns_selection_fg_color"
+       :background "ns_selection_bg_color" :extend t)
+      (((class color) (min-colors 88) (background light))
+       :background "LightGoldenrod2" :extend t)
+      (((class color) (min-colors 16) (background dark))
+       :background "blue3" :extend t)
+      (((class color) (min-colors 16) (background light))
+       :background "LightGoldenrod2" :extend t)
+      (((class color) (min-colors 8))
+       :background "blue" :foreground "white" :extend t)
+      (((type tty) (class mono))
+       :inverse-video t)
+      (t :background "gray" :extend t))
+    "My basic face for highlighting the region.")
+#+end_src
+
+#+caption[Improve the visibility of faces in =org-faces.el=]:
+#+caption: Improve the visibility of faces in =org-faces.el=.
+#+name: lst:tweak-org-faces-early
+#+begin_src emacs-lisp
+  ;; Shadow the definition in org-faces.el:
+  (defface org-block
+    ;; https://emacs.stackexchange.com/questions/9600/
+    ;; how-can-i-override-a-pre-defined-face-for-light-and-dark-backgrounds
+    `((((background dark))
+       :inherit (fixed-pitch)
+       ,@(and (>= emacs-major-version 27) '(:extend t))
+       :background "#444444")
+      (t
+       :inherit (fixed-pitch)
+       ,@(and (>= emacs-major-version 27) '(:extend t))
+       :background "#FFFFD0"))
+    "My face used for text inside various blocks.
+
+  It is always used for source blocks.  You can refine what face
+  should be used depending on the source block language by setting,
+  `org-src-block-faces', which takes precedence.
+
+  When `org-fontify-quote-and-verse-blocks' is not nil, text inside
+  verse and quote blocks are fontified using the `org-verse' and
+  `org-quote' faces, which inherit from `org-block'.")
+#+end_src
+
+#+caption[Improve the visibility of faces in =sh-script.el=]:
+#+caption: Improve the visibility of faces in =sh-script.el=.
+#+name: lst:tweak-sh-script-faces-early
+#+begin_src emacs-lisp
+  ;; Shadow the definition in sh-script.el:
+  (defface sh-heredoc
+    '((((class color) (background dark))
+       (:foreground "yellow"))
+      (((class color) (background light))
+       (:foreground "magenta"))
+      (t
+       (:weight bold)))
+    "My face to show a here-document.")
+#+end_src
+
 * [[info:emacs#Package Installation][Install the selected packages (info)]]
 :PROPERTIES:
 :CUSTOM_ID: sec:install-selected-packages
@@ -2515,7 +2597,7 @@ on tables by means of =org-narrow-to-table=.
   (define-key ctl-x-map (kbd "n t") #'org-narrow-to-table)
   (define-key ctl-x-map (kbd "C-n") #'narrow-or-widen-dwim)
 #+end_src
-** [[info:emacs#Faces][Text faces (or styles)]]
+** [[info:emacs#Faces][Text faces or styles (info)]]
 :PROPERTIES:
 :CUSTOM_ID: sec:text-faces-or-styles
 :END:
@@ -2532,8 +2614,7 @@ The code in listing [[lst:configure-face-attributes]] source implements those ru
 In case of proper initialization of all face heigths, font scaling is easy as
 listing [[lst:my-set-default-face-height]] shows.  Finally, the code in listing
 [[lst:my-invert-default-face]] allows swapping the foreground and background colors
-of the default face on all frames and the code in listing [[lst:custom-set-faces]]
+of the default face on all frames.
-improves the visibility of some default faces.
 
 #+caption[Configure =face-attributse=]:
 #+caption: Configure =face-attributes=.
@@ -2587,16 +2668,6 @@ improves the visibility of some default faces.
       (invert-face 'default)))
 #+end_src
 
-#+caption[Improve the visibility of some default faces]:
-#+caption: Improve the visibility of some default faces.
-#+name: lst:custom-set-faces
-#+begin_src emacs-lisp
-  (with-eval-after-load 'faces
-    (custom-set-faces
-     '(region ((((class color) (min-colors 88) (background light) (type gtk))
-                :background "lightgoldenrod2")))))
-#+end_src
-
 ** [[https://jblevins.org/log/rainbow-mode][Visualize color codes and names]]
 :PROPERTIES:
 :CUSTOM_ID: sec:rainbow-mode