From 8df69384f3951356dfb539e2cf72d905f82d00ae Mon Sep 17 00:00:00 2001
From: Lars Ingebrigtsen <larsi@gnus.org>
Date: Sat, 7 May 2022 13:19:49 +0200
Subject: [PATCH] Allow dabbrev to ignore binary buffers

* doc/emacs/abbrevs.texi (Dynamic Abbrevs): Document it.
* lisp/dabbrev.el (dabbrev-ignored-buffer-names)
(dabbrev-ignored-buffer-regexps): Link to it.
(dabbrev-ignored-buffer-modes): New user option (bug#19392).
(dabbrev--filter-buffer-modes): New function.
(dabbrev--select-buffers, dabbrev--make-friend-buffer-list): Use it.
---
 doc/emacs/abbrevs.texi |  5 ++++-
 etc/NEWS               |  7 +++++++
 lisp/dabbrev.el        | 40 ++++++++++++++++++++++++++++++----------
 3 files changed, 41 insertions(+), 11 deletions(-)

diff --git a/doc/emacs/abbrevs.texi b/doc/emacs/abbrevs.texi
index 9f339a03577..07f66ec10ac 100644
--- a/doc/emacs/abbrevs.texi
+++ b/doc/emacs/abbrevs.texi
@@ -411,10 +411,13 @@ away in the buffer to search for an expansion.
 
 @vindex dabbrev-check-all-buffers
 @vindex dabbrev-check-other-buffers
+@vindex dabbrev-ignored-buffer-modes
   After scanning the current buffer, @kbd{M-/} normally searches other
 buffers.  The variables @code{dabbrev-check-all-buffers} and
 @code{dabbrev-check-other-buffers} can be used to determine which
-other buffers, if any, are searched.
+other buffers, if any, are searched.  Buffers that have major modes
+derived from any of the modes in @code{dabbrev-ignored-buffer-modes}
+are ignored.
 
 @vindex dabbrev-ignored-buffer-names
 @vindex dabbrev-ignored-buffer-regexps
diff --git a/etc/NEWS b/etc/NEWS
index a2f7f038524..2e7a1d86386 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -734,6 +734,13 @@ script that was used in ancient South Asia.  A new input method,
 
 * Changes in Specialized Modes and Packages in Emacs 29.1
 
+** dabbrev
+
++++
+*** New user option 'dabbrev-ignored-buffer-modes'.
+Buffers with major modes in this list will be ignored.  By default,
+this includes "binary" buffers like 'archive-mode' and 'image-mode'.
+
 ** Package
 
 +++
diff --git a/lisp/dabbrev.el b/lisp/dabbrev.el
index 220a2f52e92..adbfca01a30 100644
--- a/lisp/dabbrev.el
+++ b/lisp/dabbrev.el
@@ -225,18 +225,28 @@ or matched by `dabbrev-ignored-buffer-regexps'."
 
 (defcustom dabbrev-ignored-buffer-names '("*Messages*" "*Buffer List*")
   "List of buffer names that dabbrev should not check.
-See also `dabbrev-ignored-buffer-regexps'."
+See also `dabbrev-ignored-buffer-regexps' and
+`dabbrev-ignored-buffer-modes'."
   :type '(repeat (string :tag "Buffer name"))
   :group 'dabbrev
   :version "20.3")
 
 (defcustom dabbrev-ignored-buffer-regexps nil
   "List of regexps matching names of buffers that dabbrev should not check.
-See also `dabbrev-ignored-buffer-names'."
+See also `dabbrev-ignored-buffer-names' and
+`dabbrev-ignored-buffer-modes'."
   :type '(repeat regexp)
   :group 'dabbrev
   :version "21.1")
 
+(defcustom dabbrev-ignored-buffer-modes
+  '(archive-mode image-mode tar-mode)
+  "Inhibit looking for abbreviations in buffers derived from these modes.
+See also `dabbrev-ignored-buffer-names' and
+`dabbrev-ignored-buffer-regexps'."
+  :type '(repeat symbol)
+  :version "29.1")
+
 (defcustom dabbrev-check-other-buffers t
   "Should \\[dabbrev-expand] look in other buffers?
 nil: Don't look in other buffers.
@@ -632,19 +642,29 @@ See also `dabbrev-abbrev-char-regexp' and \\[dabbrev-completion]."
   "Return a list of other buffers to search for a possible abbrev.
 The current buffer is not included in the list.
 
-This function makes a list of all the buffers returned by `buffer-list',
-then discards buffers whose names match `dabbrev-ignored-buffer-names'
-or `dabbrev-ignored-buffer-regexps'.  It also discards buffers for which
-`dabbrev-friend-buffer-function', if it is bound, returns nil when called
-with the buffer as argument.
-It returns the list of the buffers that are not discarded."
+This function makes a list of all the buffers returned by
+`buffer-list', then discards buffers whose names match
+`dabbrev-ignored-buffer-names' or
+`dabbrev-ignored-buffer-regexps', and major modes that match
+`dabbrev-ignored-buffer-modes'.  It also discards buffers for
+which `dabbrev-friend-buffer-function', if it is bound, returns
+nil when called with the buffer as argument.  It returns the list
+of the buffers that are not discarded."
   (dabbrev-filter-elements
-   buffer (buffer-list)
+   buffer (dabbrev--filter-buffer-modes)
    (and (not (eq (current-buffer) buffer))
 	(not (dabbrev--ignore-buffer-p buffer))
 	(boundp 'dabbrev-friend-buffer-function)
 	(funcall dabbrev-friend-buffer-function buffer))))
 
+(defun dabbrev--filter-buffer-modes ()
+  (seq-filter (lambda (buffer)
+                (not (apply
+                      #'provided-mode-derived-p
+                      (buffer-local-value 'major-mode buffer)
+                      dabbrev-ignored-buffer-modes)))
+              (buffer-list)))
+
 (defun dabbrev--try-find (abbrev reverse n ignore-case)
   "Search for ABBREV, backwards if REVERSE, N times.
 If IGNORE-CASE is non-nil, ignore case while searching.
@@ -779,7 +799,7 @@ of the start of the occurrence."
 	  (setq list
 		(append list
 			(dabbrev-filter-elements
-			 buffer (buffer-list)
+			 buffer (dabbrev--filter-buffer-modes)
 			 (and (not (memq buffer list))
 			      (not (dabbrev--ignore-buffer-p buffer)))))))
       ;; Remove the current buffer.
-- 
2.39.2