Make Gnus leverage visual-line-mode

Set shr-fill-text to nil; this automatically causes eww to enable
visual-line-mode.

For Gnus, the dance is a bit more involved.  Not 100% happy with where
I landed, but at least I gave myself an escape hatch by rebinding C-c
d v in summary buffers.

Also,

* lift size restriction when fontifying citations: it mostly only ever
causes fontification failures when people review big patches,
* tweak header order slightly,
* align shr heading faces with eighters-title-* faces.

1 files changed, 85 insertions, 10 deletions

diff --git a/.gnus b/.gnus
index 8472771..37a17af 100644
--- a/.gnus
+++ b/.gnus
@@ -56,6 +56,7 @@
                                     (t
                                      . "%F"))
       ;; Articles.
+      gnus-cite-parse-max-size nil
       gnus-header-face-alist
       '(("From" nil gnus-header-from)
         ("Subject" nil gnus-header-subject)
@@ -67,20 +68,26 @@
        ;; What, when.
        "^Subject:" "^Summary:" "^Keywords:" "^Date:"
        ;; Who.
-       "^From:" "^Followup-To:" "^To:" "^Cc:" "^Newsgroups:" "^Organization:")
-      gnus-treat-display-smileys nil)
+       "^From:" "^Organization:" "^Followup-To:" "^To:" "^Cc:" "^Newsgroups:")
+      gnus-treat-display-smileys nil
+      ;; Do not fill anything; let visual-line-mode wrap text.
+      gnus-article-unfold-long-headers t
+      gnus-treat-fill-article nil
+      gnus-treat-fill-long-lines nil
+      gnus-treat-fold-headers nil)
+
+;;; Summary tweaks.
+
+(defun my/gnus-toggle-article-wrap ()
+  (interactive)
+  (with-current-buffer gnus-article-buffer
+    (visual-line-mode 'toggle)))
 
 (add-hook 'gnus-summary-mode-hook
           (lambda ()
             (setq fill-column 120)
-            (my/centered-mode)))
-(add-hook 'gnus-article-mode-hook
-          (lambda ()
-            (setq fill-column 80
-                  my/centered-set-right-margin t)
-            (my/centered-mode)))
-
-;;; Summary tweaks.
+            (my/centered-mode)
+            (keymap-local-set "C-c d v" 'my/gnus-toggle-article-wrap)))
 
 ;; message-subject-re-regexp is used both in Gnus summary buffers to
 ;; detect and elide similar subjects in a thread, and by message mode
@@ -119,6 +126,74 @@
   (setq gnus-summary-to-prefix sent-prefix
         gnus-summary-newsgroup-prefix sent-prefix))
 
+;;; Article tweaks.
+
+(defun my/gnus-article-has-html ()
+  (seq-some
+   (lambda (handle)
+     (and (listp handle)
+          (string= (mm-handle-media-type 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) fill-column)
+               ;; The line is not boring (citation, diff addition/removal).
+               (not (string-match-p "\\`[>+-]" current-line))
+               ;; Lines that start with spaces are boring, unless this
+               ;; is an HTML part: 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)))
+
+;; Keep article buffer centered; enable visual-line-mode when it helps
+;; (long lines that are not part of citations nor patches).
+;;
+;; Use article-prepare hook instead of article-mode hook to ensure
+;; visual-line-mode will be set and effectively clear truncate-lines.
+;;
+;; The sequence goes like this: gnus-article-prepare first calls
+;; gnus-article-setup-buffer, which
+;;
+;; (1) sets truncate-lines from gnus-article-truncate-lines,
+;; (2) calls gnus-article-mode, which runs gnus-article-mode-hook.
+;;
+;; But then gnus-article-prepare calls gnus-display-mime, which may
+;; end up calling mm-shr, which *might* end up calling shr-tag-table,
+;; which unconditionally turns truncate-lines back on.
+;;
+;; Then gnus-article-prepare runs gnus-article-prepare-hook: that's
+;; our cue to run visual-line-mode, which will set truncate-lines back
+;; *off*.
+;;
+;; eww does not have this problem because it checks shr-fill-text &
+;; turns visual-line-mode "late enough"; though the display of tables
+;; remains less than ideal since rows are wrapped.  Ideally
+;; shr-tag-table should switch to an alternative layout when
+;; shr-fill-text is nil.
+
+(defun my/gnus-article-setup ()
+  (setq fill-column 80
+        my/centered-set-right-margin t)
+  (my/centered-mode)
+  (when (my/gnus-article-should-wrap)
+    (visual-line-mode)))
+
+(add-hook 'gnus-article-prepare-hook 'my/gnus-article-setup)
+
 ;;; Key bindings.
 ;;
 ;; m            compose