Achieve XDG compliance

… sort of.  Emacs apps will stuff all manner of transient state under
user-emacs-directory by default, so full XDG compliance would probably
involve customizing them all to instead use ~/.cache but 🤷

1 files changed, 368 insertions, 0 deletions

diff --git a/.config/emacs/gnus/init.el b/.config/emacs/gnus/init.el
new file mode 100644
index 0000000..ab5b7f3
--- /dev/null
+++ b/.config/emacs/gnus/init.el
@@ -0,0 +1,368 @@
+;;; -*- lexical-binding: t -*-
+
+;;; Externalities.
+
+;; user-full-name       from /etc/passwd; set with chfn(1).
+;; user-mail-address    from EMAIL variable; set with ~/.profile,
+;;                      ~/.xsessionrc, DE's convention-du-jour.
+
+;; ~/.authinfo.gpg:
+;;      machine imap.gmail.com login LOGIN password PASSWORD port 993
+;;      machine smtp.gmail.com login LOGIN password PASSWORD port 587
+
+;;; Þe Olde Setq.
+(setq gnus-select-method
+      '(nnimap "gmail"
+               (nnimap-address "imap.gmail.com")
+               (nnimap-server-port 993)
+               (nnmail-expiry-target "nnimap+gmail:[Gmail]/Trash")
+               (nnmail-expiry-wait immediate))
+      gnus-secondary-select-methods
+      '((nntp "archive.lwn.net")
+        (nntp "news.gmane.io"))
+
+      smtpmail-smtp-server "smtp.gmail.com"
+      smtpmail-smtp-service 587
+
+      ;; Archival of sent messages.
+      gnus-gcc-mark-as-read t
+      ;; The next setting makes the previous one useless; keeping both
+      ;; for now because I'm not sure which I'll settle for.
+      gnus-message-archive-group nil
+
+      ;; Groups.
+      gnus-group-uncollapsed-levels 2
+
+      ;; Summary.
+      gnus-summary-line-format "%*%U%R  %-16,16&user-date; %B%-23,23f  %s\n"
+      gnus-summary-dummy-line-format "                     ╭                          %S\n"
+      gnus-summary-make-false-root 'dummy
+      gnus-sum-thread-tree-root "╭ "
+      gnus-sum-thread-tree-false-root "┬ "
+      gnus-sum-thread-tree-single-indent "  "
+      gnus-sum-thread-tree-indent " "
+      gnus-sum-thread-tree-single-leaf "╰► "
+      gnus-sum-thread-tree-leaf-with-other "├► "
+      gnus-sum-thread-tree-vertical "│"
+      gnus-thread-sort-functions
+      '(gnus-thread-sort-by-number
+        (not gnus-thread-sort-by-most-recent-date))
+      gnus-user-date-format-alist '(((gnus-seconds-today)
+                                     . "%H:%M")
+                                    ((+ 86400 (gnus-seconds-today))
+                                     . "Yesterday %H:%M")
+                                    ((* 6 86400)
+                                     . "%a %H:%M")
+                                    ((gnus-seconds-month)
+                                     . "%a %d")
+                                    ((gnus-seconds-year)
+                                     . "%b %d")
+                                    (t
+                                     . "%F"))
+      ;; Articles.
+      gnus-cite-parse-max-size nil
+      gnus-header-face-alist
+      '(("From" nil gnus-header-from)
+        ("Subject" nil gnus-header-subject)
+        ("Date" nil eighters-date)
+        ("Newsgroups:.*," nil gnus-header-newsgroups)
+        ("" gnus-header-name gnus-header-content))
+      gnus-sorted-header-list
+      (list
+       ;; What, when.
+       "^Subject:" "^Summary:" "^Keywords:" "^Date:"
+       ;; Who.
+       "^From:" "^Organization:" "^Followup-To:" "^To:" "^Cc:" "^Newsgroups:")
+      gnus-treat-display-smileys nil
+      ;; Do not fill anything; let visual-line-mode wrap text.
+      ;;; NB: for format=flowed, there is no setting to say "un-fill
+      ;;; flowed lines", so we *enable* filling, setting an absurd
+      ;;; line length limit, in order to un-fill flowed lines.
+      fill-flowed-display-column most-positive-fixnum
+      mm-fill-flowed t
+      ;;; More long-line-folding settings.
+      gnus-article-unfold-long-headers t
+      gnus-treat-fill-article nil
+      gnus-treat-fill-long-lines nil
+      gnus-treat-fold-headers nil)
+
+;;; Window configurations.
+
+(defvar my/gnus-side-by-side-threshold 160)
+
+(gnus-add-configuration
+ '(article
+   (if (>= (frame-width) my/gnus-side-by-side-threshold)
+       '(horizontal 1.0
+                    (summary 1.0 point)
+                    (article 80))
+     '(vertical 1.0
+                (summary 0.25 point)
+                (article 1.0)))))
+
+(dolist (buf-name '(forward reply reply-yank))
+  (gnus-add-configuration
+   `(,buf-name
+     (if (>= (frame-width) my/gnus-side-by-side-threshold)
+         '(vertical 1.0
+                    (summary 0.25)
+                    (horizontal 1.0
+                                (article 0.5)
+                                (message 1.0 point)))
+       '(vertical 1.0
+                  (summary 0.2)
+                  (article 0.2)
+                  (message 1.0 point))))))
+
+;;; Summary tweaks.
+
+(defun my/gnus-toggle-article-wrap ()
+  (interactive)
+  (with-current-buffer gnus-article-buffer
+    (visual-line-mode 'toggle)))
+
+(defun my/gnus-summary-tweak-keys ()
+  (keymap-local-set "C-c d v" 'my/gnus-toggle-article-wrap))
+
+(add-hook 'gnus-summary-mode-hook 'my/gnus-summary-tweak-keys)
+
+;; message-subject-re-regexp is used both in Gnus summary buffers to
+;; detect and elide similar subjects in a thread, and by message mode
+;; when replying, to determine what to strip from the subject.
+;;
+;; Some MUAs add cruft to the subject, turning "Re: bug#123: foobar"
+;; into "RE: [External] : Re: bug#1234: foobar", which Debbugs will
+;; then turn into "bug#1234: [External] : Re: bug#1234: foobar".
+;;
+;; The only way I can find to tell the Gnus summary code to
+;; canonicalize all that cruft away is by tweaking this regexp, but
+;; setting its global value causes message-mode to elide stuff it
+;; shouldn't when crafting subjects.  Therefore, chase down the best
+;; Gnus hook for the job, and set the regexp locally.
+(defun my/gnus-reply-prefixes ()
+  (mapcan (lambda (prefix) (list prefix (upcase prefix) (capitalize prefix)))
+          '("re" "aw" "sv" "fw" "fwd")))
+
+(setq my/gnus-summary-normalize-subject
+      (rx-to-string
+       `(seq bol
+             (+ (or (seq word-start (or ,@(my/gnus-reply-prefixes)) word-end)
+                    (seq "bug#" (+ digit))
+                    (seq "[" (or "External" "SPAM UNSURE") "]"))
+                (? (* space) ":") (* space)))))
+
+(add-hook 'gnus-summary-generate-hook
+          (lambda ()
+            (setq-local message-subject-re-regexp
+                        my/gnus-summary-normalize-subject)))
+
+(let* ((initials (mapconcat (lambda (s) (substring s 0 1))
+                            (split-string user-full-name)
+                            nil))
+       (sent-prefix (format "%s → " initials)))
+  (setq gnus-summary-to-prefix sent-prefix
+        gnus-summary-newsgroup-prefix sent-prefix))
+
+;;; Article tweaks.
+
+(defun my/gnus-article-eschew-tables ()
+  ;; I set shr-fill-text to nil because I prefer letting
+  ;; visual-line-mode manage wrapping.  Unfortunately, many HTML
+  ;; emails rely on <table>s for layouts, and rendering can get ugly.
+  ;; Work around this by treating <table> & children as any other
+  ;; <div>.
+  (make-local-variable 'shr-external-rendering-functions)
+  (pcase-dolist (`(,tag . ,shr-function)
+                 '((table . shr-tag-div)
+                   (thead . shr-tag-div)
+                   (tbody . shr-tag-div)
+                   (tr    . shr-tag-ul)
+                   (th    . shr-tag-li)
+                   (td    . shr-tag-li)))
+    (setf (alist-get tag shr-external-rendering-functions) shr-function)))
+
+(defun my/gnus-article-has-html ()
+  ;; Hard to tell the difference between
+  ;; * the variable `gnus-article-mime-handles',
+  ;; * the function `gnus-article-mime-handles',
+  ;; * the variable `gnus-article-mime-handle-alist'.
+  ;;
+  ;; Stealing debbugs.el's patch-finding logic.
+  (seq-some
+   (lambda (handle)
+     (string= (mm-handle-media-type (cdr handle)) "text/html"))
+   (gnus-article-mime-handles)))
+
+(defun my/gnus-article-should-wrap ()
+  (save-excursion
+    (message-goto-body)
+    (let ((should-wrap nil)
+          (has-html (my/gnus-article-has-html)))
+      (while-let (((not should-wrap))
+                  ((not (eobp)))
+                  (current-line (thing-at-point 'line)))
+        (setq should-wrap
+              (and
+               ;; The line is bigger than the target width.
+               (> (length current-line)
+                  (window-width (get-buffer-window gnus-article-buffer)))
+               ;; The line is not boring (citation, diff addition/removal).
+               (not (string-match-p "\\`[>+-]" current-line))
+               ;; Lines that start with spaces are boring, except in
+               ;; HTML parts: those are choked with <table> tags that
+               ;; shr left-pads with spaces.
+               ;; NB: HAS-HTML is a naive heuristic: we are assuming
+               ;; that "any text/html part is present" means "we are
+               ;; looking at this text/html part".
+               (or (not (string-match-p "\\` " current-line)) has-html)))
+        (forward-line))
+      should-wrap)))
+
+(defun my/gnus-article-wrap-maybe ()
+  ;; Enable visual-line-mode when it helps, i.e. when the message has
+  ;; long lines that are not part of citations nor patches.
+  (with-current-buffer gnus-article-buffer
+   (visual-line-mode
+    (unless (my/gnus-article-should-wrap) -1))))
+
+;; Article setup is tricky.  In order, `gnus-article-prepare'
+;;
+;; (1) calls `gnus-article-setup-buffer', which
+;;     (a) calls `gnus-article-mode', which runs
+;;         gnus-article-mode-hook,
+;;     (b) sets truncate-lines from gnus-article-truncate-lines,
+;;
+;; (2) calls `gnus-display-mime', which may end up calling `mm-shr';
+;;     this can call `shr-tag-table', which turns truncate-lines on
+;;     unconditionally.
+;;
+;; (3) runs gnus-article-prepare-hook.
+;;
+;; Gnus will only run (1a) once, and skip that step when it re-uses
+;; the same *Article* buffer for subsequent articles.  So for our
+;; purposes, we need to
+;;
+;; (Ⅰ) hack the shr rendering functions in mode-hook, before `mm-shr'
+;;     gets to work.
+;; (Ⅱ) call `visual-line-mode' (if needed) in prepare-hook, after
+;;     truncate-lines has been set.
+
+(add-hook 'gnus-article-mode-hook 'my/gnus-article-eschew-tables)
+(add-hook 'gnus-article-prepare-hook 'my/gnus-article-wrap-maybe)
+
+;;; MIME display.
+(defun my/mm-display-markdown-inline (handle)
+  (mm-display-inline-fontify handle 'markdown-mode))
+
+(with-eval-after-load 'mm-decode
+  ;; bug-gnu-emacs:<jwvzfsnntlq.fsf-monnier+emacs@gnu.org>
+  (setf (alist-get "text/markdown" mm-inline-media-tests nil nil 'equal)
+        '(my/mm-display-markdown-inline)))
+
+;;; Key bindings.
+;;
+;; m            compose
+;;
+;; Group buffer:
+;;
+;; L            list all groups
+;; RET          view unread mail in group
+;; C-u RET      view all mail in group
+;; g            refresh
+;; G G          search group
+;;
+;; Summary buffer:
+;;
+;; B m          move message to group
+;; / N          fetch new
+;; M-g          refresh (expire, move, fetch new, show unread)
+;; C-u M-g      refresh (expire, move, fetch new, show all)
+;; C-u g        show raw, undecoded message source; g to decode
+;; T h          collapse (hide) thread
+;; T s          expand (show) thread
+;; T k, C-M-k   mark thread as read
+;; M-1 T k      mark thread as unread
+;; r            reply
+;; R            reply (quoting)
+;; S w          reply-all
+;; S W          reply-all (quoting)
+;; C-c C-f      forward
+;; d            mark read
+;; M-u          clear marks (≡ mark unread)
+;; E            expire
+;; #            toggle mark for next action
+;; M-#, M P u   unmark for next action
+;;
+;;      Draft summary buffer:
+;;
+;;      D e     edit draft
+;;
+;; Article buffer:
+;;
+;; o            save attachment at point
+;; K b          add button for inlined MIME part
+;;
+;; Composing:
+;;
+;; C-c C-c      send
+;; C-c C-a      attach
+;; C-c C-f s    change the subject (append "was:")
+;;
+;;; FAQ.
+;;
+;; - how to see *all mails*, not just unread?
+;;      - C-u RET
+;;
+;; - how to do something on a bunch of mail matching a pattern?
+;;      - M P R     ; mark all mails with subjects matching regexp
+;;      - M-& <x>   ; do <x> on all marked mails
+;;
+;; - how to delete mail?
+;;      - E to mark as expired
+;;      - C-u M-g to refresh
+;;
+;; - how to remove groups deleted on the IMAP server?
+;;      - b to iterate over "bogus" groups and remove them
+;;
+;; - how to list most-recent mails on top?
+;;      - cf. gnus-thread-sort-functions
+;;
+;; - how to close a mail without going back to the group list?
+;;      - = to make summary full-screen
+;;
+;; - how to get contact completion?
+;;      - install ebdb from GNU ELPA
+;;      - or just use message-mail-alias-type
+;;
+;; - how to refresh?
+;;      - summary buffer:
+;;          - / N (fetch new)
+;;          - M-g (expire, move, fetch & redisplay)
+;;      - group buffer: g
+;;
+;; - what do all those letters mean?
+;;   (info "(gnus) Marking Articles")
+;;      - O     old ≡ read during previous session
+;;      - R     just read
+;;      - r     manually marked as read
+;;      - A     answered
+;;      - E     expirable
+;;      - G     cancelled (e.g. moved somewhere else)
+;;      - .     unseen
+;;
+;; - how to subscribe to mailing lists?
+;;      - to browse an NNTP server, either
+;;          - hit B in the group buffer, then nntp *some server*
+;;          - or add (nntp "*some server*") to gnus-secondary-methods
+;;      - over the list: u
+;;
+;;; TODO.
+;;
+;; - gnus-summary-line-format (📎 for attachments)
+;;
+;; - how to archive mails and news locally?
+;;
+;; - describe-key is mostly useless in article mode:
+;;   > X runs the command gnus-article-read-summary-keys
+;;
+;; - detect possibly missing attachments from keywords