[PATCH v2 1/1] emacs: notmuch-show-header-line: allow format strings and functions

Subject: [PATCH v2 1/1] emacs: notmuch-show-header-line: allow format strings and functions

Date: Mon, 16 May 2022 03:20:39 +0100

To: notmuch@notmuchmail.org

Cc: jao

From: jao

If a string value is assigned to notmuch-show-header-line, it's used
as a format string to be passed passed to format-spec with `%s`
substituted by the message's subject.  If a function is given, it's
called with the subject as argument, and its return value used as
header line.

As before, t means displaying the subject and nil not using any header
line.

Signed-off-by: jao <jao@gnu.org>
---
 emacs/notmuch-show.el | 37 ++++++++++++++++++++++++++++++-------
 1 file changed, 30 insertions(+), 7 deletions(-)

diff --git a/emacs/notmuch-show.el b/emacs/notmuch-show.el
index 7c1f02c9..79599480 100644
--- a/emacs/notmuch-show.el
+++ b/emacs/notmuch-show.el
@@ -85,8 +85,26 @@ visible for any given message."
   :group 'notmuch-show)
 
 (defcustom notmuch-show-header-line t
-  "Show a header line with the current message's subject."
-  :type 'boolean
+  "Show a header line in notmuch show buffers.
+
+If t (the default), the header line will contain the current
+message's subject.
+
+If a string, this value is interpreted as a format string to be
+passed to `format-spec` with `%s` as the substitution variable
+for the message's subject.  E.g., to display the subject trimmed
+to a maximum of 80 columns, you could use \"%>-80s\" as format.
+
+If you assign to this variable a function, the function will be
+called with the subject as argument and its return value used as
+the header line.
+
+Finally, if this variabale is set to nil, no header is
+displayed."
+  :type '(choice (const :tag "No header" ni)
+                 (const :tag "Subject" t)
+                 (string :tag "Format")
+		 (function :tag "Function"))
   :group 'notmuch-show)
 
 (defcustom notmuch-show-relative-dates t
@@ -1351,11 +1369,16 @@ If no messages match the query return NIL."
        (lambda () (notmuch-show-set-prop :orig-tags (notmuch-show-get-tags))))
       ;; Set the header line to the subject of the first message.
       (when notmuch-show-header-line
-	(setq header-line-format
-	      (replace-regexp-in-string "%" "%%"
-					(notmuch-sanitize
-					 (notmuch-show-strip-re
-					  (notmuch-show-get-subject))))))
+        (let* ((s (replace-regexp-in-string "%" "%%"
+                                            (notmuch-sanitize
+                                             (notmuch-show-strip-re
+                                              (notmuch-show-get-subject)))))
+               (h (cond ((stringp notmuch-show-header-line)
+                         (format-spec notmuch-show-header-line `((?s . ,s))))
+			((functionp notmuch-show-header-line)
+			 (funcall notmuch-show-header-line s))
+			(notmuch-show-header-line s))))
+          (setq header-line-format h)))
       (run-hooks 'notmuch-show-hook)
       (if state
 	  (notmuch-show-apply-state state)
-- 
2.36.1

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