From 2d022f1756b559bf0bba374420d421103c344cbb Mon Sep 17 00:00:00 2001
From: "Dirk-Jan C. Binnema" <djcb@djcbsoftware.nl>
Date: Sun, 7 Jun 2026 19:53:30 +0300
Subject: [PATCH] mu4e: cite region in reply

When replying to a message with some part selected / marked, cite only
that part.

Implements ancient feature-request, issue #44.
---
 NEWS.org             |  3 +++
 mu4e/mu4e-compose.el | 50 ++++++++++++++++++++++++++++++--------------
 mu4e/mu4e.texi       |  3 ++-
 3 files changed, 39 insertions(+), 17 deletions(-)

diff --git a/NEWS.org b/NEWS.org
index 4286e2fa..159afedb 100644
--- a/NEWS.org
+++ b/NEWS.org
@@ -45,6 +45,9 @@
      a buffer with a tabulated list of the mu4e links in your ~org-agenda-files~
      (1.14.2).
 
+   - When replying to message with a region marked, cite only the marked region.
+     A very only feature-request, finally implemented.
+
 *** scm
 
    - added new ~--eval~ command-line option, so you can do e.g.
diff --git a/mu4e/mu4e-compose.el b/mu4e/mu4e-compose.el
index 70cd0711..2a15c12a 100644
--- a/mu4e/mu4e-compose.el
+++ b/mu4e/mu4e-compose.el
@@ -325,19 +325,28 @@ buffers; lets remap its faces so it uses the ones for mu4e."
     (message-cite-original-without-signature)
     (delete-region (point-min) (point-max))))
 
-(defun mu4e--compose-cite (msg)
-  "Return a cited version of the ORIG message MSG (a string).
-This function uses `message-cite-function', and its settings apply."
-  (with-temp-buffer
-    (insert (mu4e-view-message-text msg))
-    (goto-char (point-min))
-    (push-mark (point-max))
-    (let ((message-signature-separator "^-- *$")
-          (message-signature-insert-empty-line t))
-      (funcall message-cite-function))
-    (pop-mark)
-    (goto-char (point-min))
-    (buffer-string)))
+(defun mu4e--compose-cite (msg &optional region)
+  "Return a cited version of the message MSG (a string).
+If REGION is non-nil, cite it instead of MSG' body. This function
+uses `message-cite-function', and its settings apply."
+  (let ((orig (mu4e--compose-message-text msg)))
+    (with-temp-buffer
+      (insert orig)
+      (goto-char (point-min))
+
+      ;; if have a region, replace the body with it.
+      (save-excursion
+        (when (and region (re-search-forward "\n\n" nil 'noerror))
+          (delete-region (point) (point-max))
+          (insert region)))
+
+      (push-mark (point-max))
+      (let ((message-signature-separator "^-- *$")
+            (message-signature-insert-empty-line t))
+        (funcall message-cite-function))
+      (pop-mark)
+      (goto-char (point-min))
+      (buffer-string))))
 
 ;;; Interactive functions
 
@@ -365,15 +374,24 @@ SWITCH-FUNCTION is ignored."
 (defun mu4e-compose-reply-to (&optional to wide)
   "Reply to the message at point.
 Optional TO can be the To: address for the message. If WIDE is
-non-nil, make it a \"wide\" reply (a.k.a. \"reply-to-all\")."
+non-nil, make it a \"wide\" reply (a.k.a. \"reply-to-all\").
+
+The original message body is cited (as per
+`message-cite-function'). If some region in the view buffer is
+selected, that region is used instead of the original message
+body for citing.'"
   (interactive)
-  (let ((parent (mu4e-message-at-point)))
+  (let ((parent (mu4e-message-at-point))
+        (region (when (and (eq major-mode 'mu4e-view-mode)
+                           (use-region-p))
+                  (buffer-substring-no-properties
+                   (region-beginning) (region-end)))))
     (mu4e--draft-with-parent
      'reply parent
      (lambda ()
        (with-current-buffer (mu4e--message-call #'message-reply to wide)
          (message-goto-body)
-         (insert (mu4e--compose-cite parent))
+         (insert (mu4e--compose-cite parent region))
          ;; include matching MIME parts from the parent
          (mu4e--reply-insert-mime-parts parent)
          (current-buffer))))))
diff --git a/mu4e/mu4e.texi b/mu4e/mu4e.texi
index 5c7e35cf..1a9de451 100644
--- a/mu4e/mu4e.texi
+++ b/mu4e/mu4e.texi
@@ -1819,7 +1819,8 @@ reply''.
 
 By default, the reply will cite the message being replied to. If you do not want
 that, you can set (or @code{let}-bind) @code{message-cite-function} to
-@code{mu4e-message-cite-nothing}.
+@code{mu4e-message-cite-nothing}. When you have a region selected while
+replying, only the selected part is cited.
 
 See @ref{(message) Reply} and @ref{(message) Wide Reply} for further details.