From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED.blaine.gmane.org!not-for-mail From: Eli Zaretskii Newsgroups: gmane.emacs.bugs Subject: bug#38049: C mode fontification broken with reposition-window Date: Wed, 06 Nov 2019 19:13:44 +0200 Message-ID: <83zhh9exmf.fsf@gnu.org> References: <8736f4k8mi.fsf@mail.linkov.net> <20191105210737.GA6303@ACM> Injection-Info: blaine.gmane.org; posting-host="blaine.gmane.org:195.159.176.226"; logging-data="47220"; mail-complaints-to="usenet@blaine.gmane.org" Cc: 38049@debbugs.gnu.org, juri@linkov.net To: Alan Mackenzie Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane.org@gnu.org Wed Nov 06 18:15:13 2019 Return-path: Envelope-to: geb-bug-gnu-emacs@m.gmane.org Original-Received: from lists.gnu.org ([209.51.188.17]) by blaine.gmane.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1iSOtk-000C9b-HZ for geb-bug-gnu-emacs@m.gmane.org; Wed, 06 Nov 2019 18:15:12 +0100 Original-Received: from localhost ([::1]:33476 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iSOtj-00043N-CF for geb-bug-gnu-emacs@m.gmane.org; Wed, 06 Nov 2019 12:15:11 -0500 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:43824) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iSOtc-00043F-Lt for bug-gnu-emacs@gnu.org; Wed, 06 Nov 2019 12:15:05 -0500 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iSOtb-0004RF-Jx for bug-gnu-emacs@gnu.org; Wed, 06 Nov 2019 12:15:04 -0500 Original-Received: from debbugs.gnu.org ([209.51.188.43]:60611) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1iSOtZ-0004O6-TP; Wed, 06 Nov 2019 12:15:01 -0500 Original-Received: from Debian-debbugs by debbugs.gnu.org with local (Exim 4.84_2) (envelope-from ) id 1iSOtZ-00041T-Na; Wed, 06 Nov 2019 12:15:01 -0500 X-Loop: help-debbugs@gnu.org Resent-From: Eli Zaretskii Original-Sender: "Debbugs-submit" Resent-CC: bug-gnu-emacs@gnu.org, bug-cc-mode@gnu.org Resent-Date: Wed, 06 Nov 2019 17:15:01 +0000 Resent-Message-ID: Resent-Sender: help-debbugs@gnu.org X-GNU-PR-Message: followup 38049 X-GNU-PR-Package: emacs,cc-mode Original-Received: via spool by 38049-submit@debbugs.gnu.org id=B38049.157306044915370 (code B ref 38049); Wed, 06 Nov 2019 17:15:01 +0000 Original-Received: (at 38049) by debbugs.gnu.org; 6 Nov 2019 17:14:09 +0000 Original-Received: from localhost ([127.0.0.1]:41199 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1iSOsi-0003zn-Oh for submit@debbugs.gnu.org; Wed, 06 Nov 2019 12:14:09 -0500 Original-Received: from eggs.gnu.org ([209.51.188.92]:34511) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1iSOsg-0003zB-Kd for 38049@debbugs.gnu.org; Wed, 06 Nov 2019 12:14:07 -0500 Original-Received: from fencepost.gnu.org ([2001:470:142:3::e]:52363) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1iSOsa-00035a-Pe; Wed, 06 Nov 2019 12:14:00 -0500 Original-Received: from [176.228.60.248] (port=3417 helo=home-c4e4a596f7) by fencepost.gnu.org with esmtpsa (TLS1.2:RSA_AES_256_CBC_SHA1:256) (Exim 4.82) (envelope-from ) id 1iSOsa-0000Zi-3M; Wed, 06 Nov 2019 12:14:00 -0500 In-reply-to: <20191105210737.GA6303@ACM> (message from Alan Mackenzie on Tue, 5 Nov 2019 21:07:37 +0000) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.51.188.43 X-BeenThere: bug-gnu-emacs@gnu.org List-Id: "Bug reports for GNU Emacs, the Swiss army knife of text editors" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane.org@gnu.org Original-Sender: "bug-gnu-emacs" Xref: news.gmane.org gmane.emacs.bugs:171037 Archived-At: > Date: Tue, 5 Nov 2019 21:07:37 +0000 > From: Alan Mackenzie > Cc: 38049@debbugs.gnu.org > > (i) reposition-window narrows to (2758 3940) in > repos-count-screen-lines. > (ii) This latter function uses vertical-motion to count the lines. > (iii) vertical-motion triggers jit-lock fontification. > (iv) This calls (eventually) c-font-lock-fontify-region. > (v) c-font-lock-fontify-region attempts to examine buffer text before > the start of the jit-lock chunk to find syntactic context. > (vi) This is outside the visible region, so Emacs raises an exception. > (vii) The exception is caught and discarded by an unwind-protect in > c-font-lock-fontify-region. > (viii) The jit-lock chunk remains unfontified. > > As Stefan M has sometimes remarked, narrowing is often not a good idea. Narrowing is part of life. Why can't c-font-lock-fontify-region be fixed so as not to signal an error in these cases? If we do, will that fix the original problem? > It would seem undesirable for the vertical-motion in (iii) to trigger > font-locking, since it is merely trying to count lines. vertical-motion calls functions from the display engine, which fontifies the text it traverses. It doesn't only count lines, it also counts columns in canonical character width units (i.e. actually in pixels). So it cannot possibly avoid fontifications because fontification might affect how many pixels characters take on display. Fontifications can also affect the line count, if some fontification code actually puts display properties on the fontified text -- something that you rarely if ever see, but Lisp programs can rightfully expect that. So this idea: > Perhaps there should be a macro `without-fontifying' which could be > wrapped around this call to vertical-motion, if there isn't such a > thing anyway. cannot fly, sorry. Let's try to fix the problem in c-font-lock-fontify-region instead, okay?