bug#54059: 29.0.50; Feature request: alpha channel for font lock colors

[Jose A Ortega Ruiz]

As discussed in bug#53890, it'd be nice to be able to customize face
colors with an alpha channel component.  I guess this could be done
by accepting as valid color strings of the form "#RRGGBBAA", and then
have the ability of specifying an opacity everywhere a color can be used
in a face definition (foreground, background, underline, boxes...).

Cheers,
jao


In GNU Emacs 29.0.50 (build 21, x86_64-pc-linux-gnu, cairo version 1.16.0)
 of 2022-02-17 built on rivendell
Repository revision: 246f627a4125d8b3ae5e88748a439f3f594340b5
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12101003
System Description: Debian GNU/Linux bookworm/sid

Configured using:
 'configure --prefix=/usr/local/stow/emacs --with-x-toolkit=no
 --with-imagemagick'

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ
IMAGEMAGICK JPEG JSON LCMS2 LIBOTF LIBSELINUX LIBSYSTEMD LIBXML2
M17N_FLT MODULES NOTIFY INOTIFY OLDXMENU PDUMPER PNG RSVG SECCOMP SOUND
THREADS TIFF X11 XDBE XIM XPM ZLIB

Important settings:
  value of $LANG: en_GB.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Circe Channel

Minor modes in effect:
  global-git-commit-mode: t
  magit-auto-revert-mode: t
  circe-lagmon-mode: t
  pdf-occur-global-minor-mode: t
  telega-root-auto-fill-mode: t
  telega-active-locations-mode: t
  telega-patrons-mode: t
  telega-mode-line-mode: t
  cursor-intangible-mode: t
  global-diff-hl-mode: t
  eshell-vterm-mode: t
  eshell-syntax-highlighting-global-mode: t
  shell-dirtrack-mode: t
  winner-mode: t
  global-auto-revert-mode: t
  corfu-global-mode: t
  corfu-mode: t
  marginalia-mode: t
  mct-minibuffer-mode: t
  persistent-scratch-autosave-mode: t
  global-so-long-mode: t
  display-battery-mode: t
  jao-minibuffer-mode: t
  minibuffer-electric-default-mode: t
  minibuffer-depth-indicate-mode: t
  repeat-mode: t
  savehist-mode: t
  recentf-mode: t
  save-place-mode: t
  override-global-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  show-paren-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  column-number-mode: t

Load-path shadows:
/home/jao/lib/elisp/org-static-blog/org-static-blog hides 
/home/jao/.emacs.d/elpa.29/org-static-blog-20220110.739/org-static-blog
/home/jao/etc/emacs/site/custom hides 
/usr/local/stow/emacs/share/emacs/29.0.50/lisp/custom
/home/jao/.emacs.d/elpa.29/transient-20220216.2303/transient hides 
/usr/local/stow/emacs/share/emacs/29.0.50/lisp/transient

Features:
(shadow sort mailalias bbdb-message mail-extr vc-mtn vc-hg vc-bzr vc-src
vc-sccs vc-svn vc-cvs vc-rcs magit-extras forge-list forge-commands
forge-semi forge-bitbucket buck forge-gogs gogs forge-gitea gtea
forge-gitlab glab forge-github ghub-graphql treepy gsexp ghub
forge-notify forge-revnote forge-pullreq forge-issue forge-topic yaml
bug-reference forge-post forge-repo forge forge-core forge-db closql
emacsql-sqlite emacsql emacsql-compiler autoload paredit cal-persia
tabify link-hint avy ido bash-completion em-unix em-script em-prompt
em-ls em-hist em-pred em-glob em-extpipe em-cmpl em-basic em-banner
magit-bookmark magit-submodule magit-obsolete magit-blame magit-stash
magit-reflog magit-bisect magit-push magit-pull magit-fetch magit-clone
magit-remote magit-commit magit-sequence magit-notes magit-worktree
magit-tag magit-merge magit-branch magit-reset magit-files magit-refs
magit-status magit magit-repos magit-apply magit-wip magit-log
which-func magit-diff git-commit log-edit add-log magit-core
magit-autorevert magit-margin magit-transient magit-process with-editor
magit-mode magit-git magit-section magit-utils executable copyright
hlint-refactor display-fill-column-indicator smartscan smerge-mode diff
mm-archive quail pdf-sync pdf-annot facemenu pdf-outline pdf-links
pdf-history shr-color textsec uni-scripts idna-mapping ucs-normalize
uni-confusable textsec-check url-http url-gw url-cache url-auth
org-duration org-agenda org-appear cdlatex texmathp image-file
image-converter cal-iso cal-move emojify apropos tar-mode arc-mode
archive-mode ht network-stream circe-display-images circe-lagmon
lui-track circe lui-irc-colors irc lcs lui-logging lui-format
circe-compat slack slack-company slack-unread slack-websocket
slack-thread-event slack-room-event slack-star-event
slack-reaction-event slack-reply-event slack-typing slack-slash-commands
slack-message-event slack-event slack-dialog-edit-element-buffer
slack-dialog-buffer slack-dialog slack-stars-buffer
slack-search-result-buffer slack-thread-message-compose-buffer
slack-file-list-buffer slack-file-info-buffer slack-all-threads-buffer
slack-message-buffer slack-user-profile-buffer slack-pinned-items-buffer
slack-pinned-item slack-thread-message-buffer slack-room-info-buffer
slack-room-buffer slack-message-share-buffer slack-message-edit-buffer
slack-room-message-compose-buffer slack-message-compose-buffer
slack-message-attachment-preview-buffer slack-action slack-star
slack-reminder slack-search slack-message-reaction slack-message-editor
slack-message-sender slack-message-notification slack-buffer
slack-message-formatter slack-thread slack-im slack-channel slack-group
slack-conversations slack-create-message slack-attachment
slack-selectable slack-bot-message slack-user-message slack-file
slack-message slack-message-faces slack-unescape slack-block
slack-mrkdwn slack-usergroup slack-reaction slack-modeline slack-room
slack-counts slack-user slack-bot slack-dnd-status slack-emoji
slack-image slack-request slack-log request lui flyspell ispell
slack-team slack-team-ws slack-util websocket mule-util pdf-occur
ibuf-ext ibuffer ibuffer-loaddefs tablist tablist-filter
semantic/wisent/comp semantic/wisent semantic/wisent/wisent
semantic/util-modes semantic/util semantic semantic/tag semantic/lex
semantic/fw mode-local cedet pdf-isearch pdf-misc bigml bml-logs bml
bml-misc bml-whizzml bml-clojure bml-clj-tests bml-python bml-skels
bml-utils whizzml-skeletons skeleton whizzml-mode lice sieve sieve-mode
sieve-manage sasl sasl-anonymous sasl-login sasl-plain jao-mpc
jao-random-album jao-lyrics jao-mpris telega-obsolete telega
telega-tdlib-events telega-webpage visual-fill-column telega-root
telega-info telega-chat telega-modes telega-company telega-user
telega-notifications telega-voip telega-msg telega-tme telega-sticker
telega-i18n telega-vvnote bindat telega-ffplay telega-media telega-sort
telega-filter telega-ins telega-folders telega-inline telega-tdlib
telega-util rainbow-identifiers dired-aux telega-server telega-core
cursor-sensor telega-customize emacsbug sendmail jao-mullvad bluetooth
enwc enwc-backend json-mode json-snatcher js cc-mode cc-fonts cc-guess
cc-menus cc-cmds cc-styles cc-align cc-engine cc-vars cc-defs
virtualenvwrapper gud ediprolog pie haskell-doc inf-haskell
haskell-decl-scan haskell haskell-completions haskell-load
haskell-commands highlight-uses-mode haskell-modules haskell-sandbox
haskell-navigate-imports haskell-repl haskell-svg haskell-collapse
hideshow haskell-debug haskell-interactive-mode
haskell-presentation-mode haskell-compile haskell-hoogle haskell-process
haskell-session haskell-mode haskell-cabal haskell-utils
haskell-font-lock haskell-indentation haskell-string
haskell-sort-imports haskell-lexeme haskell-align-imports
haskell-complete-module haskell-ghc-support flymake-proc flymake
warnings dabbrev haskell-customize geiser-guile info-look geiser-repl
geiser-compile geiser-debug geiser-image geiser-company geiser-doc
geiser-menu geiser-edit etags fileloop xref project geiser-completion
geiser-autodoc geiser-eval geiser-connection geiser-syntax scheme
geiser-impl help-fns radix-tree geiser-log geiser-popup view
geiser-custom geiser-base geiser idris-mode idris-commands
idris-hole-list idris-ipkg-mode idris-tree-info idris-warnings-tree
idris-info idris-repl idris-highlight-input idris-prover inferior-idris
idris-warnings idris-log idris-events idris-simple-indent idris-syntax
idris-common-utils idris-settings idris-keys idris-core idris-compat
prop-menu package-lint finder lisp-mnt edit-list git-modes
gitignore-mode gitconfig-mode conf-mode gitattributes-mode git-link
git-timemachine diff-hl log-view pcvs-util vc-dir ewoc vc
jao-eshell-here eshell-autojump em-dirs esh-var eshell-up git-ps1-mode
eshell-vterm em-term eshell-syntax-highlighting em-alias vterm tramp
tramp-loaddefs trampver tramp-integration files-x tramp-compat
parse-time ls-lisp face-remap term disp-table ehelp vterm-module
term/xterm xterm saveplace-pdf-view consult-notmuch org-capture
org-refile jao-notmuch notmuch notmuch-tree notmuch-jump notmuch-hello
notmuch-show notmuch-print notmuch-crypto notmuch-mua notmuch-message
notmuch-draft notmuch-maildir-fcc notmuch-address notmuch-company
notmuch-parser notmuch-wash coolj notmuch-query goto-addr icalendar
notmuch-tag notmuch-lib notmuch-version notmuch-compat pcase hl-line
mm-view mml-smime smime dig bbdb-anniv bbdb-com crm bbdb bbdb-site
timezone randomsig message yank-media rfc822 mml mml-sec mm-decode
mm-bodies mm-encode mail-parse rfc2231 rfc2047 rfc2045 ietf-drums
mailabbrev gmm-utils mailheader socks gnutls nsm rmc elpher ol-eww
jao-eww-session eww xdg url-queue shr pixel-fill kinsoku svg dom puny
mm-url gnus nnheader gnus-util mail-utils range mm-util mail-prsvr
markdown-toc dash s markdown-mode htmlize jao-org-links jao-maildir
jao-doc-view let-alist doc-view pdf-tools pdf-view pdf-cache pdf-info tq
pdf-util pdf-macs image-mode exif ol-info ol-bbdb ol-eshell esh-mode
eshell esh-cmd esh-ext esh-opt esh-proc esh-io esh-arg esh-module
esh-groups esh-util jao-org-notes ob-shell shell ob-scheme ob-python
python ob-org ob-ocaml ob-makefile ob-haskell ob-gnuplot ob-clojure
ob-calc calc-store calc-trail calc-ext calc calc-loaddefs rect calc-macs
ob-prolog prolog smie align poly-org polymode poly-lock polymode-base
polymode-weave polymode-export polymode-compat polymode-methods
polymode-core polymode-classes eieio-custom eieio-base color org-tempo
tempo ox-texinfo ox-latex ox-html table ox-ascii ox-publish ox
org-element avl-tree generator org-fragtog jao-afio winner autorevert
filenotify autoinsert embark-consult embark ffap thingatpt
consult-recoll jao-compilation consult bookmark corfu marginalia mct
orderless imenu find-dired dired-x dired dired-loaddefs wgrep grep
compile text-property-search jka-compr persistent-scratch so-long
cal-china lunar solar cal-dst cal-bahai cal-islam cal-hebrew holidays
hol-loaddefs vc-git diff-mode vc-dispatcher appt diary-lib
diary-loaddefs jao-tracking tracking shorten jao-notify alert log4e
notifications gntp battery jao-minibuffer minibuf-eldef mb-depth
jao-recoll diminish jao-light-theme jao-themes pinentry epa-file epa
derived epg rfc6068 epg-config transient cus-edit pp cus-load repeat
edmacro kmacro jao-sleep dbus xml server savehist recentf tree-widget
wid-edit saveplace gnu-elpa-keyring-update use-package
use-package-ensure use-package-delight use-package-diminish
use-package-bind-key bind-key use-package-core cl-extra help-mode org ob
ob-tangle ob-ref ob-lob ob-table ob-exp org-macro org-footnote org-src
ob-comint org-pcomplete pcomplete comint ansi-color ring org-list
org-faces org-entities noutline outline easy-mmode org-version
ob-emacs-lisp ob-core ob-eval org-table oc-basic bibtex iso8601
time-date ol org-keys oc org-compat advice org-macs org-loaddefs
format-spec find-func cal-menu calendar cal-loaddefs finder-inf tex-site
rx info package browse-url url url-proxy url-privacy url-expand
url-methods url-history url-cookie url-domsuf url-util mailcap
url-handlers url-parse auth-source cl-seq eieio eieio-core cl-macs
eieio-loaddefs password-cache json map url-vars seq gv subr-x byte-opt
bytecomp byte-compile cconv cl-loaddefs cl-lib iso-transl tooltip eldoc
paren electric uniquify ediff-hook vc-hooks lisp-float-type elisp-mode
mwheel term/x-win x-win term/common-win x-dnd tool-bar dnd fontset image
regexp-opt fringe tabulated-list replace newcomment text-mode lisp-mode
prog-mode register page tab-bar menu-bar rfn-eshadow isearch easymenu
timer select scroll-bar mouse jit-lock font-lock syntax font-core
term/tty-colors frame minibuffer cl-generic cham georgian utf-8-lang
misc-lang vietnamese tibetan thai tai-viet lao korean japanese eucjp-ms
cp51932 hebrew greek romanian slovak czech european ethiopic indian
cyrillic chinese composite emoji-zwj charscript charprop case-table
epa-hook jka-cmpr-hook help simple abbrev obarray cl-preloaded nadvice
button loaddefs faces cus-face macroexp files window text-properties
overlay sha1 md5 base64 format env code-pages mule custom widget keymap
hashtable-print-readable backquote threads dbusbind inotify lcms2
dynamic-setting system-font-setting font-render-setting cairo x
multi-tty make-network-process emacs)

Memory information:
((conses 16 3066710 423763)
 (symbols 48 87841 297)
 (strings 32 536937 72151)
 (string-bytes 1 22947420)
 (vectors 16 218965)
 (vector-slots 8 6623590 267119)
 (floats 8 12574 3188)
 (intervals 56 253600 31977)
 (buffers 992 99))

-- 
Tact is the ability to tell a man he has an open mind when he has a
hole in his head.