GNU bug report logs - #75993
Special mode-class for diff-mode

Message received at submit <at> debbugs.gnu.org:

Received: (at submit) by debbugs.gnu.org; 1 Feb 2025 17:36:58 +0000
From debbugs-submit-bounces <at> debbugs.gnu.org Sat Feb 01 12:36:58 2025
Received: from localhost ([127.0.0.1]:59863 helo=debbugs.gnu.org)
	by debbugs.gnu.org with esmtp (Exim 4.84_2)
	(envelope-from <debbugs-submit-bounces <at> debbugs.gnu.org>)
	id 1teHQQ-0002pr-8U
	for submit <at> debbugs.gnu.org; Sat, 01 Feb 2025 12:36:58 -0500
Received: from lists.gnu.org ([2001:470:142::17]:46872)
 by debbugs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256)
 (Exim 4.84_2) (envelope-from <juri@HIDDEN>) id 1teHQN-0002pa-IY
 for submit <at> debbugs.gnu.org; Sat, 01 Feb 2025 12:36:55 -0500
Received: from eggs.gnu.org ([2001:470:142:3::10])
 by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256)
 (Exim 4.90_1) (envelope-from <juri@HIDDEN>) id 1teHQG-0000ay-Km
 for bug-gnu-emacs@HIDDEN; Sat, 01 Feb 2025 12:36:49 -0500
Received: from relay9-d.mail.gandi.net ([217.70.183.199])
 by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256)
 (Exim 4.90_1) (envelope-from <juri@HIDDEN>) id 1teHQE-0004fi-W9
 for bug-gnu-emacs@HIDDEN; Sat, 01 Feb 2025 12:36:48 -0500
Received: by mail.gandi.net (Postfix) with ESMTPSA id 5C029442A0
 for <bug-gnu-emacs@HIDDEN>; Sat,  1 Feb 2025 17:36:40 +0000 (UTC)
From: Juri Linkov <juri@HIDDEN>
To: bug-gnu-emacs@HIDDEN
Subject: Special mode-class for diff-mode
Organization: LINKOV.NET
X-Debbugs-Cc: Stefan Monnier <monnier@HIDDEN>
Date: Sat, 01 Feb 2025 19:33:03 +0200
Message-ID: <87wme9in8w.fsf@HIDDEN>
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/31.0.50 (x86_64-pc-linux-gnu)
MIME-Version: 1.0
Content-Type: text/plain
X-GND-State: clean
X-GND-Score: 0
X-GND-Cause: gggruggvucftvghtrhhoucdtuddrgeefvddrtddtgdduvdefhecutefuodetggdotefrodftvfcurfhrohhfihhlvgemucfitefpfffkpdcuggftfghnshhusghstghrihgsvgenuceurghilhhouhhtmecufedtudenucenucfjughrpefhvffuohffkfgfgggtsehttdertddtredtnecuhfhrohhmpefluhhrihcunfhinhhkohhvuceojhhurhhisehlihhnkhhovhdrnhgvtheqnecuggftrfgrthhtvghrnhepjefggfdttdfhleetjeekjeeugedvkefgudffgfdthedvtdekteevhefgffejueetnecukfhppeeluddruddvledrleeirdeltdenucevlhhushhtvghrufhiiigvpedtnecurfgrrhgrmhepihhnvghtpeeluddruddvledrleeirdeltddphhgvlhhopehmrghilhdrghgrnhguihdrnhgvthdpmhgrihhlfhhrohhmpehjuhhriheslhhinhhkohhvrdhnvghtpdhnsggprhgtphhtthhopedupdhrtghpthhtohepsghughdqghhnuhdqvghmrggtshesghhnuhdrohhrgh
X-GND-Sasl: juri@HIDDEN
Received-SPF: pass client-ip=217.70.183.199; envelope-from=juri@HIDDEN;
 helo=relay9-d.mail.gandi.net
X-Spam_score_int: -25
X-Spam_score: -2.6
X-Spam_bar: --
X-Spam_report: (-2.6 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_LOW=-0.7,
 RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001,
 RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001,
 SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no
X-Spam_action: no action
X-Spam-Score: 0.7 (/)
X-Debbugs-Envelope-To: submit
X-BeenThere: debbugs-submit <at> debbugs.gnu.org
X-Mailman-Version: 2.1.18
Precedence: list
List-Id: <debbugs-submit.debbugs.gnu.org>
List-Unsubscribe: <https://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, 
 <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe>
List-Archive: <https://debbugs.gnu.org/cgi-bin/mailman/private/debbugs-submit/>
List-Post: <mailto:debbugs-submit <at> debbugs.gnu.org>
List-Help: <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=help>
List-Subscribe: <https://debbugs.gnu.org/cgi-bin/mailman/listinfo/debbugs-submit>, 
 <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=subscribe>
Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org
Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org>
X-Spam-Score: -0.3 (/)

Tags: patch

Visiting a diff file and trying to copy lines with 'w' (diff-kill-ring-save)
does something unexpected since view-mode overrides 'w' with
'View-scroll-page-backward-set-page-size' for non-nil 'view-read-only'.

Here is the fix like for all modes that use single-letter keys:

diff --git a/lisp/vc/diff-mode.el b/lisp/vc/diff-mode.el
index 77807fc4f35..b88dd4bf736 100644
--- a/lisp/vc/diff-mode.el
+++ b/lisp/vc/diff-mode.el
@@ -1550,6 +1550,7 @@ diff-mode-read-only
 (defvar whitespace-style)
 (defvar whitespace-trailing-regexp)
 
+(put 'diff-mode 'mode-class 'special)
 ;;;###autoload
 (define-derived-mode diff-mode fundamental-mode "Diff"
   "Major mode for viewing/editing context diffs.