X-Loop: help-debbugs@HIDDEN Subject: bug#18417: 24.3.93; posn-at-point confused by fill-column-indicator Resent-From: Dmitry <dgutov@HIDDEN> Original-Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> Resent-CC: bug-gnu-emacs@HIDDEN Resent-Date: Sat, 06 Sep 2014 09:44:02 +0000 Resent-Message-ID: <handler.18417.B.140999661216037 <at> debbugs.gnu.org> Resent-Sender: help-debbugs@HIDDEN X-GNU-PR-Message: report 18417 X-GNU-PR-Package: emacs X-GNU-PR-Keywords: To: 18417 <at> debbugs.gnu.org X-Debbugs-Original-To: bug-gnu-emacs@HIDDEN Received: via spool by submit <at> debbugs.gnu.org id=B.140999661216037 (code B ref -1); Sat, 06 Sep 2014 09:44:02 +0000 Received: (at submit) by debbugs.gnu.org; 6 Sep 2014 09:43:32 +0000 Received: from localhost ([127.0.0.1]:60321 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.80) (envelope-from <debbugs-submit-bounces <at> debbugs.gnu.org>) id 1XQCWp-0004Aa-UH for submit <at> debbugs.gnu.org; Sat, 06 Sep 2014 05:43:32 -0400 Received: from eggs.gnu.org ([208.118.235.92]:48722) by debbugs.gnu.org with esmtp (Exim 4.80) (envelope-from <raaahh@HIDDEN>) id 1XQCWm-0004AK-T6 for submit <at> debbugs.gnu.org; Sat, 06 Sep 2014 05:43:29 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from <raaahh@HIDDEN>) id 1XQCWc-0005Zy-Sr for submit <at> debbugs.gnu.org; Sat, 06 Sep 2014 05:43:23 -0400 X-Spam-Checker-Version: SpamAssassin 3.3.2 (2011-06-06) on eggs.gnu.org X-Spam-Level: X-Spam-Status: No, score=0.0 required=5.0 tests=BAYES_40,FREEMAIL_FROM, T_DKIM_INVALID autolearn=disabled version=3.3.2 Received: from lists.gnu.org ([2001:4830:134:3::11]:42371) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from <raaahh@HIDDEN>) id 1XQCWc-0005Zu-Pd for submit <at> debbugs.gnu.org; Sat, 06 Sep 2014 05:43:18 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50443) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from <raaahh@HIDDEN>) id 1XQCWX-0007WY-Vw for bug-gnu-emacs@HIDDEN; Sat, 06 Sep 2014 05:43:18 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from <raaahh@HIDDEN>) id 1XQCWT-0005YY-7W for bug-gnu-emacs@HIDDEN; Sat, 06 Sep 2014 05:43:13 -0400 Received: from mail-lb0-x22d.google.com ([2a00:1450:4010:c04::22d]:46251) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from <raaahh@HIDDEN>) id 1XQCWS-0005YK-V5 for bug-gnu-emacs@HIDDEN; Sat, 06 Sep 2014 05:43:09 -0400 Received: by mail-lb0-f173.google.com with SMTP id c11so14805231lbj.32 for <bug-gnu-emacs@HIDDEN>; Sat, 06 Sep 2014 02:43:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=sender:from:to:subject:date:message-id:mime-version:content-type; bh=rOzdAPJCs4G4VLjlet7633i1LtIY+gCIfhcZcGV/zrQ=; b=DjbQWR9oK1OdQDOhE2/h+46x6oyzRcc2VKdziQQ6Vs0GQMkvoIdk5smhQOkN+I0HcM o+KSPRFtVej7Rd6j49B6UTTAWhqQWTVPlCoGOTgzqjW90K8vRzq42vT+xs0+wPUQrI9n C6d8nHJd6RSvQ9ZESMEL+Uh4qKINIZlhmDXKJCLPKneahnVoWAME6PV5fUP1DGGVM/1S 6MkB+3ZZq7hRZXRijP28fycimOhUO4hi6CTaw2/ELo9qYue+fbD1wTrZGAAJdfMJJVQB BUTQPIbR76191z4xWAEbIQ9kjx8+/+CK1ETlxEjhYtMTgdzyy5RMPcLXGS1GKWbkypDV eudQ== X-Received: by 10.112.219.71 with SMTP id pm7mr16040346lbc.3.1409996587157; Sat, 06 Sep 2014 02:43:07 -0700 (PDT) Received: from axl ([178.252.98.87]) by mx.google.com with ESMTPSA id k7sm1471768lak.22.2014.09.06.02.43.05 for <bug-gnu-emacs@HIDDEN> (version=TLSv1.2 cipher=RC4-SHA bits=128/128); Sat, 06 Sep 2014 02:43:06 -0700 (PDT) From: Dmitry <dgutov@HIDDEN> Date: Sat, 06 Sep 2014 13:43:00 +0400 Message-ID: <86sik513vf.fsf@HIDDEN> MIME-Version: 1.0 Content-Type: text/plain X-detected-operating-system: by eggs.gnu.org: Error: Malformed IPv6 address (bad octet value). X-detected-operating-system: by eggs.gnu.org: Error: Malformed IPv6 address (bad octet value). X-Received-From: 2001:4830:134:3::11 X-Spam-Score: -4.0 (----) X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <http://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <http://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: <http://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: -4.0 (----) 1. Download, put inside load-path and require fill-column-indicator.el, from https://github.com/alpaker/Fill-Column-Indicator. 2. Open an empty buffer, add a newline inside it. 3. Toggle fcm-mode on. Notice the indicator at the end of the empty line. 4. With point at the beginning of that line, evaluate (posn-col-row (posn-at-point (point))) and see it evaluate to (71 . 0). The problem is probably not in posn-col-row, because (posn-x-y (posn-at-point (point))) also returns a large non-zero value in car. In GNU Emacs 24.3.93.3 (x86_64-unknown-linux-gnu, GTK+ Version 3.10.8) of 2014-09-05 on axl Repository revision: 117482 monnier@HIDDEN Windowing system distributor `The X.Org Foundation', version 11.0.11501000 System Description: Ubuntu 14.04.1 LTS
Content-Disposition: inline Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-Mailer: MIME-tools 5.503 (Entity 5.503) Content-Type: text/plain; charset=utf-8 X-Loop: help-debbugs@HIDDEN From: help-debbugs@HIDDEN (GNU bug Tracking System) To: Dmitry <dgutov@HIDDEN> Subject: bug#18417: Acknowledgement (24.3.93; posn-at-point confused by fill-column-indicator) Message-ID: <handler.18417.B.140999661216037.ack <at> debbugs.gnu.org> References: <86sik513vf.fsf@HIDDEN> X-Gnu-PR-Message: ack 18417 X-Gnu-PR-Package: emacs Reply-To: 18417 <at> debbugs.gnu.org Date: Sat, 06 Sep 2014 09:44:02 +0000 Thank you for filing a new bug report with debbugs.gnu.org. This is an automatically generated reply to let you know your message has been received. Your message is being forwarded to the package maintainers and other interested parties for their attention; they will reply in due course. Your message has been sent to the package maintainer(s): bug-gnu-emacs@HIDDEN If you wish to submit further information on this problem, please send it to 18417 <at> debbugs.gnu.org. Please do not send mail to help-debbugs@HIDDEN unless you wish to report a problem with the Bug-tracking system. --=20 18417: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=3D18417 GNU Bug Tracking System Contact help-debbugs@HIDDEN with problems
X-Loop: help-debbugs@HIDDEN Subject: bug#18417: 24.3.93; posn-at-point confused by fill-column-indicator Resent-From: Eli Zaretskii <eliz@HIDDEN> Original-Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> Resent-CC: bug-gnu-emacs@HIDDEN Resent-Date: Sun, 07 Sep 2014 17:23:01 +0000 Resent-Message-ID: <handler.18417.B18417.141011054615292 <at> debbugs.gnu.org> Resent-Sender: help-debbugs@HIDDEN X-GNU-PR-Message: followup 18417 X-GNU-PR-Package: emacs X-GNU-PR-Keywords: To: Dmitry <dgutov@HIDDEN> Cc: 18417 <at> debbugs.gnu.org Reply-To: Eli Zaretskii <eliz@HIDDEN> Received: via spool by 18417-submit <at> debbugs.gnu.org id=B18417.141011054615292 (code B ref 18417); Sun, 07 Sep 2014 17:23:01 +0000 Received: (at 18417) by debbugs.gnu.org; 7 Sep 2014 17:22:26 +0000 Received: from localhost ([127.0.0.1]:32968 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.80) (envelope-from <debbugs-submit-bounces <at> debbugs.gnu.org>) id 1XQgAT-0003yZ-Hr for submit <at> debbugs.gnu.org; Sun, 07 Sep 2014 13:22:26 -0400 Received: from mtaout28.012.net.il ([80.179.55.184]:48293) by debbugs.gnu.org with esmtp (Exim 4.80) (envelope-from <eliz@HIDDEN>) id 1XQgAR-0003yJ-B6 for 18417 <at> debbugs.gnu.org; Sun, 07 Sep 2014 13:22:24 -0400 Received: from conversion-daemon.mtaout28.012.net.il by mtaout28.012.net.il (HyperSendmail v2007.08) id <0NBJ00I00K3H5000@HIDDEN> for 18417 <at> debbugs.gnu.org; Sun, 07 Sep 2014 20:21:00 +0300 (IDT) Received: from HOME-C4E4A596F7 ([87.69.4.28]) by mtaout28.012.net.il (HyperSendmail v2007.08) with ESMTPA id <0NBJ00GGXK701320@HIDDEN>; Sun, 07 Sep 2014 20:21:00 +0300 (IDT) Date: Sun, 07 Sep 2014 20:22:22 +0300 From: Eli Zaretskii <eliz@HIDDEN> In-reply-to: <86sik513vf.fsf@HIDDEN> X-012-Sender: halo1@HIDDEN Message-id: <837g1fcpm9.fsf@HIDDEN> References: <86sik513vf.fsf@HIDDEN> X-Spam-Score: 1.0 (+) X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <http://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <http://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: <http://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: 1.0 (+) > From: Dmitry <dgutov@HIDDEN> > Date: Sat, 06 Sep 2014 13:43:00 +0400 > > 1. Download, put inside load-path and require fill-column-indicator.el, > from https://github.com/alpaker/Fill-Column-Indicator. > 2. Open an empty buffer, add a newline inside it. > 3. Toggle fcm-mode on. Notice the indicator at the end of the empty > line. ^^^^^^^^ I assume you meant "fci-mode". > 4. With point at the beginning of that line, evaluate > > (posn-col-row (posn-at-point (point))) > > and see it evaluate to (71 . 0). > > The problem is probably not in posn-col-row, because (posn-x-y > (posn-at-point (point))) also returns a large non-zero value in car. This was previously reported and discussed here: http://lists.gnu.org/archive/html/emacs-devel/2013-07/msg00445.html My correspondent there expressed interest in fixing this, but I never heard from him about this since then, although I pointed him at posn-at-point as the most probable culprit. Anyway, I'm not going to lose sleep over this, sorry. The recipe in effect invokes undefined behavior in posn-at-point, because fci-mode uses a zero-length (a.k.a. "empty") overlay to place, in a very convoluted way, a stretch of whitespace followed by an image, before the newline. Since "at point" means "before point", and the recipe asks for coordinates at the newline position, it is not clear whether the reported coordinates should or shouldn't include the stretch glyph. The result you see is the consequence of the implementation details of the functions that simulate display in order to compute screen coordinates at a given buffer position. Since the buffer position of the newline is not "covered" by the empty overlay, Emacs happily stops when it reaches the newline, oblivious to the fact that on the way it produced the stretch glyph of a very large width. If someone wants to work on this, patches will be welcome, of course.
X-Loop: help-debbugs@HIDDEN Subject: bug#18417: 24.3.93; posn-at-point confused by fill-column-indicator Resent-From: Dmitry Gutov <dgutov@HIDDEN> Original-Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> Resent-CC: bug-gnu-emacs@HIDDEN Resent-Date: Sun, 07 Sep 2014 18:56:01 +0000 Resent-Message-ID: <handler.18417.B18417.141011614924160 <at> debbugs.gnu.org> Resent-Sender: help-debbugs@HIDDEN X-GNU-PR-Message: followup 18417 X-GNU-PR-Package: emacs X-GNU-PR-Keywords: To: Eli Zaretskii <eliz@HIDDEN> Cc: 18417 <at> debbugs.gnu.org Received: via spool by 18417-submit <at> debbugs.gnu.org id=B18417.141011614924160 (code B ref 18417); Sun, 07 Sep 2014 18:56:01 +0000 Received: (at 18417) by debbugs.gnu.org; 7 Sep 2014 18:55:49 +0000 Received: from localhost ([127.0.0.1]:33001 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.80) (envelope-from <debbugs-submit-bounces <at> debbugs.gnu.org>) id 1XQhcq-0006Hb-P7 for submit <at> debbugs.gnu.org; Sun, 07 Sep 2014 14:55:49 -0400 Received: from mail-lb0-f179.google.com ([209.85.217.179]:40739) by debbugs.gnu.org with esmtp (Exim 4.80) (envelope-from <raaahh@HIDDEN>) id 1XQhcm-0006HI-Tf for 18417 <at> debbugs.gnu.org; Sun, 07 Sep 2014 14:55:46 -0400 Received: by mail-lb0-f179.google.com with SMTP id p9so3175856lbv.10 for <18417 <at> debbugs.gnu.org>; Sun, 07 Sep 2014 11:55:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=sender:message-id:date:from:user-agent:mime-version:to:cc:subject :references:in-reply-to:content-type:content-transfer-encoding; bh=f+f0mLF8g/TU64SJX2pywmYpC9CLYEQS582iXHYJj/w=; b=HZBIGiwBmLPT6IDTPS93QGkPY2adzvasvOv1e+PH+perUOKxLSlZE2xfH6W2J4sRoK kCOLRS/wlNKclE7cmIr/6dDvRj4R2XeD2/amUNbZ8NFrVgafSlgR/l0vf4FuAUjw7UZt AMoB4pmD9M7ztlaTSvV8slRs7hVR8av0qgaa+aoM1zyQBmUcNrMzCo6T5lz8uTIVVN/3 F7SdXQu9350pdfALXE2Xb6XcZ7s3RmVkW4I3xBUbQZUGf8OTGKqANI84HbR0WKIWKEs1 N3GPEVINLD3rllM0q5rswCZR/50BWEM1wX1Nte2+CnNDR+nDs8BUou+qzPvs/az5YDbO H8iA== X-Received: by 10.112.140.200 with SMTP id ri8mr3425383lbb.84.1410116138504; Sun, 07 Sep 2014 11:55:38 -0700 (PDT) Received: from [192.168.1.3] ([178.252.98.87]) by mx.google.com with ESMTPSA id b1sm2656348lah.34.2014.09.07.11.55.36 for <multiple recipients> (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 07 Sep 2014 11:55:37 -0700 (PDT) Message-ID: <540CAA26.8070303@HIDDEN> Date: Sun, 07 Sep 2014 22:55:34 +0400 From: Dmitry Gutov <dgutov@HIDDEN> User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.0 MIME-Version: 1.0 References: <86sik513vf.fsf@HIDDEN> <837g1fcpm9.fsf@HIDDEN> In-Reply-To: <837g1fcpm9.fsf@HIDDEN> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Score: -0.7 (/) X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <http://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <http://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: <http://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: -0.7 (/) On 09/07/2014 09:22 PM, Eli Zaretskii wrote: > I assume you meant "fci-mode". Yes, sorry. > Anyway, I'm not going to lose sleep over this, sorry. Fair enough. fci-mode does some pretty complex stuff. > The recipe in > effect invokes undefined behavior in posn-at-point, because fci-mode > uses a zero-length (a.k.a. "empty") overlay to place, in a very > convoluted way, a stretch of whitespace followed by an image, before > the newline. If it's a problem, would you maybe suggest a better way to implement this feature, for the Fill-Column-Indicator author?
X-Loop: help-debbugs@HIDDEN Subject: bug#18417: 24.3.93; posn-at-point confused by fill-column-indicator Resent-From: Eli Zaretskii <eliz@HIDDEN> Original-Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> Resent-CC: bug-gnu-emacs@HIDDEN Resent-Date: Sun, 07 Sep 2014 19:44:02 +0000 Resent-Message-ID: <handler.18417.B18417.141011903428689 <at> debbugs.gnu.org> Resent-Sender: help-debbugs@HIDDEN X-GNU-PR-Message: followup 18417 X-GNU-PR-Package: emacs X-GNU-PR-Keywords: To: Dmitry Gutov <dgutov@HIDDEN> Cc: 18417 <at> debbugs.gnu.org Reply-To: Eli Zaretskii <eliz@HIDDEN> Received: via spool by 18417-submit <at> debbugs.gnu.org id=B18417.141011903428689 (code B ref 18417); Sun, 07 Sep 2014 19:44:02 +0000 Received: (at 18417) by debbugs.gnu.org; 7 Sep 2014 19:43:54 +0000 Received: from localhost ([127.0.0.1]:33012 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.80) (envelope-from <debbugs-submit-bounces <at> debbugs.gnu.org>) id 1XQiNO-0007Sf-Gn for submit <at> debbugs.gnu.org; Sun, 07 Sep 2014 15:43:54 -0400 Received: from mtaout21.012.net.il ([80.179.55.169]:48420) by debbugs.gnu.org with esmtp (Exim 4.80) (envelope-from <eliz@HIDDEN>) id 1XQiNL-0007SN-1m for 18417 <at> debbugs.gnu.org; Sun, 07 Sep 2014 15:43:52 -0400 Received: from conversion-daemon.a-mtaout21.012.net.il by a-mtaout21.012.net.il (HyperSendmail v2007.08) id <0NBJ00E00Q659000@HIDDEN> for 18417 <at> debbugs.gnu.org; Sun, 07 Sep 2014 22:43:44 +0300 (IDT) Received: from HOME-C4E4A596F7 ([87.69.4.28]) by a-mtaout21.012.net.il (HyperSendmail v2007.08) with ESMTPA id <0NBJ00E4JQSV9S10@HIDDEN>; Sun, 07 Sep 2014 22:43:44 +0300 (IDT) Date: Sun, 07 Sep 2014 22:43:49 +0300 From: Eli Zaretskii <eliz@HIDDEN> In-reply-to: <540CAA26.8070303@HIDDEN> X-012-Sender: halo1@HIDDEN Message-id: <83zjebb4i2.fsf@HIDDEN> References: <86sik513vf.fsf@HIDDEN> <837g1fcpm9.fsf@HIDDEN> <540CAA26.8070303@HIDDEN> X-Spam-Score: 1.0 (+) X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <http://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <http://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: <http://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: 1.0 (+) > Date: Sun, 07 Sep 2014 22:55:34 +0400 > From: Dmitry Gutov <dgutov@HIDDEN> > CC: 18417 <at> debbugs.gnu.org > > > The recipe in > > effect invokes undefined behavior in posn-at-point, because fci-mode > > uses a zero-length (a.k.a. "empty") overlay to place, in a very > > convoluted way, a stretch of whitespace followed by an image, before > > the newline. > > If it's a problem, would you maybe suggest a better way to implement > this feature, for the Fill-Column-Indicator author? I could try, but right now I don't feel I understand all the subtle details and reasons that led to such an implementation. There are 2 special characters, u+e000 and u+e001, each one has a display-table setting to display it as something else, then there's an empty overlay with an after-string made of these special characters that has a display property with :align-to, followed by an image... And I'm not sure I listed all of the "features". (The 'cursor' property I omitted intentionally, because I believe I know why they are needed.) Why each one of these is needed?
X-Loop: help-debbugs@HIDDEN Subject: bug#18417: 24.3.93; posn-at-point confused by fill-column-indicator Resent-From: Alp Aker <alptekin.aker@HIDDEN> Original-Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> Resent-CC: bug-gnu-emacs@HIDDEN Resent-Date: Sun, 07 Sep 2014 19:53:01 +0000 Resent-Message-ID: <handler.18417.B18417.141011956329551 <at> debbugs.gnu.org> Resent-Sender: help-debbugs@HIDDEN X-GNU-PR-Message: followup 18417 X-GNU-PR-Package: emacs X-GNU-PR-Keywords: To: Eli Zaretskii <eliz@HIDDEN> Cc: 18417 <at> debbugs.gnu.org, Dmitry Gutov <dgutov@HIDDEN> Received: via spool by 18417-submit <at> debbugs.gnu.org id=B18417.141011956329551 (code B ref 18417); Sun, 07 Sep 2014 19:53:01 +0000 Received: (at 18417) by debbugs.gnu.org; 7 Sep 2014 19:52:43 +0000 Received: from localhost ([127.0.0.1]:33020 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.80) (envelope-from <debbugs-submit-bounces <at> debbugs.gnu.org>) id 1XQiVu-0007gY-W5 for submit <at> debbugs.gnu.org; Sun, 07 Sep 2014 15:52:43 -0400 Received: from mail-wi0-f182.google.com ([209.85.212.182]:50075) by debbugs.gnu.org with esmtp (Exim 4.80) (envelope-from <alptekin.aker@HIDDEN>) id 1XQiVs-0007gE-HE for 18417 <at> debbugs.gnu.org; Sun, 07 Sep 2014 15:52:41 -0400 Received: by mail-wi0-f182.google.com with SMTP id z2so1650797wiv.9 for <18417 <at> debbugs.gnu.org>; Sun, 07 Sep 2014 12:52:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; bh=CVRgEOtTsD3yYvKLvRJtDpWHWSnbLMnVHRJjGAIdA8M=; b=qt6l9BJNVM11SOaJyC6rvHUJCtxCOt0lwfJiyRF6+8LxQjFOh2GHlFtMb0ZJx51CHX 1gTDwyLkZ9uN+1uUETk4PMcdZVPpjbR7diOEMvEHG1ISLZFO+GLRWKsRZJHS4PbjqbeA VHOvH87jQGEZxOKN4rvsk7EkGzNthVpVt28UbE8hznhaNNvPslolUkLBmZqRnOR/xPLs W6SSvm28vroNRXWWUFe2YzpnWC2Oky86cfrbtzlqdKPiY1J39oaqvAmVM6pho8DWuyRQ oO596EqaA5zi6DKyYi0JZee+JvfCrvWHNa+In41izmIEbvI/4zC9RTEVoUKUw5nBYbC7 6Pug== MIME-Version: 1.0 X-Received: by 10.180.36.236 with SMTP id t12mr18089157wij.38.1410119554696; Sun, 07 Sep 2014 12:52:34 -0700 (PDT) Received: by 10.217.39.84 with HTTP; Sun, 7 Sep 2014 12:52:34 -0700 (PDT) In-Reply-To: <83zjebb4i2.fsf@HIDDEN> References: <86sik513vf.fsf@HIDDEN> <837g1fcpm9.fsf@HIDDEN> <540CAA26.8070303@HIDDEN> <83zjebb4i2.fsf@HIDDEN> Date: Sun, 7 Sep 2014 15:52:34 -0400 Message-ID: <CACxch4pJF1HhtpRM_CXOJfRw_F1ytFkkzEPqUJ=i8gz8Zo3_rQ@HIDDEN> From: Alp Aker <alptekin.aker@HIDDEN> Content-Type: multipart/alternative; boundary=e89a8f64672f260ad305027f0bb0 X-Spam-Score: -0.7 (/) X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <http://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <http://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: <http://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: -0.7 (/) --e89a8f64672f260ad305027f0bb0 Content-Type: text/plain; charset=UTF-8 > There are 2 special characters, u+e000 and u+e001, each one has a > display-table setting to display it as something else, then there's an > empty overlay with an after-string made of these special characters > that has a display property with :align-to, followed by an image... > And I'm not sure I listed all of the "features". (The 'cursor' > property I omitted intentionally, because I believe I know why they > are needed.) Why each one of these is needed? At least some of that is cruft, as at one point I was trying to support all of v22, v23, and v24, and there were various differences in the behavior of overlay-strings (as well as the 'cursor property) among those versions. I'll try to simplify the implementation and see if I can come up with something that doesn't trigger any UB in the display engine. --e89a8f64672f260ad305027f0bb0 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable <div dir=3D"ltr"><div>> There are 2 special characters, u+e000 and u+e00= 1, each one has a<br>> display-table setting to display it as something = else, then there's an<br>> empty overlay with an after-string made o= f these special characters<br>> that has a display property with :align-= to, followed by an image...<br>> And I'm not sure I listed all of th= e "features".=C2=A0 (The 'cursor'<br>> property I omit= ted intentionally, because I believe I know why they<br>> are needed.)= =C2=A0 Why each one of these is needed?<br><br></div>At least some of that = is cruft, as at one point I was trying to support all of v22, v23, and v24,= and there were various differences in the behavior of overlay-strings (as = well as the 'cursor property) among those versions.=C2=A0 I'll try = to simplify the implementation and see if I can come up with something that= doesn't trigger any UB in the display engine.<br></div> --e89a8f64672f260ad305027f0bb0--
X-Loop: help-debbugs@HIDDEN Subject: bug#18417: 24.3.93; posn-at-point confused by fill-column-indicator Resent-From: Eli Zaretskii <eliz@HIDDEN> Original-Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> Resent-CC: bug-gnu-emacs@HIDDEN Resent-Date: Sun, 07 Sep 2014 19:57:01 +0000 Resent-Message-ID: <handler.18417.B18417.141011981729954 <at> debbugs.gnu.org> Resent-Sender: help-debbugs@HIDDEN X-GNU-PR-Message: followup 18417 X-GNU-PR-Package: emacs X-GNU-PR-Keywords: To: Alp Aker <alptekin.aker@HIDDEN> Cc: 18417 <at> debbugs.gnu.org, dgutov@HIDDEN Reply-To: Eli Zaretskii <eliz@HIDDEN> Received: via spool by 18417-submit <at> debbugs.gnu.org id=B18417.141011981729954 (code B ref 18417); Sun, 07 Sep 2014 19:57:01 +0000 Received: (at 18417) by debbugs.gnu.org; 7 Sep 2014 19:56:57 +0000 Received: from localhost ([127.0.0.1]:33028 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.80) (envelope-from <debbugs-submit-bounces <at> debbugs.gnu.org>) id 1XQia1-0007n4-8M for submit <at> debbugs.gnu.org; Sun, 07 Sep 2014 15:56:57 -0400 Received: from mtaout21.012.net.il ([80.179.55.169]:49071) by debbugs.gnu.org with esmtp (Exim 4.80) (envelope-from <eliz@HIDDEN>) id 1XQiZz-0007mr-F9 for 18417 <at> debbugs.gnu.org; Sun, 07 Sep 2014 15:56:56 -0400 Received: from conversion-daemon.a-mtaout21.012.net.il by a-mtaout21.012.net.il (HyperSendmail v2007.08) id <0NBJ00E00QWDAC00@HIDDEN> for 18417 <at> debbugs.gnu.org; Sun, 07 Sep 2014 22:56:49 +0300 (IDT) Received: from HOME-C4E4A596F7 ([87.69.4.28]) by a-mtaout21.012.net.il (HyperSendmail v2007.08) with ESMTPA id <0NBJ00ED3REO9S30@HIDDEN>; Sun, 07 Sep 2014 22:56:49 +0300 (IDT) Date: Sun, 07 Sep 2014 22:56:54 +0300 From: Eli Zaretskii <eliz@HIDDEN> In-reply-to: <CACxch4pJF1HhtpRM_CXOJfRw_F1ytFkkzEPqUJ=i8gz8Zo3_rQ@HIDDEN> X-012-Sender: halo1@HIDDEN Message-id: <83y4tvb3w9.fsf@HIDDEN> References: <86sik513vf.fsf@HIDDEN> <837g1fcpm9.fsf@HIDDEN> <540CAA26.8070303@HIDDEN> <83zjebb4i2.fsf@HIDDEN> <CACxch4pJF1HhtpRM_CXOJfRw_F1ytFkkzEPqUJ=i8gz8Zo3_rQ@HIDDEN> X-Spam-Score: 1.0 (+) X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <http://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <http://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: <http://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: 1.0 (+) > Date: Sun, 7 Sep 2014 15:52:34 -0400 > From: Alp Aker <alptekin.aker@HIDDEN> > Cc: Dmitry Gutov <dgutov@HIDDEN>, 18417 <at> debbugs.gnu.org > > > There are 2 special characters, u+e000 and u+e001, each one has a > > display-table setting to display it as something else, then there's an > > empty overlay with an after-string made of these special characters > > that has a display property with :align-to, followed by an image... > > And I'm not sure I listed all of the "features". (The 'cursor' > > property I omitted intentionally, because I believe I know why they > > are needed.) Why each one of these is needed? > > At least some of that is cruft, as at one point I was trying to support all of > v22, v23, and v24, and there were various differences in the behavior of > overlay-strings (as well as the 'cursor property) among those versions. That was my guess, yes. > I'll try to simplify the implementation and see if I can come up > with something that doesn't trigger any UB in the display engine. Thank you.
X-Loop: help-debbugs@HIDDEN Subject: bug#18417: 24.3.93; posn-at-point confused by fill-column-indicator Resent-From: Alp Aker <alptekin.aker@HIDDEN> Original-Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> Resent-CC: bug-gnu-emacs@HIDDEN Resent-Date: Mon, 08 Sep 2014 03:12:01 +0000 Resent-Message-ID: <handler.18417.B18417.141014590411437 <at> debbugs.gnu.org> Resent-Sender: help-debbugs@HIDDEN X-GNU-PR-Message: followup 18417 X-GNU-PR-Package: emacs X-GNU-PR-Keywords: To: Eli Zaretskii <eliz@HIDDEN> Cc: 18417 <at> debbugs.gnu.org, Dmitry <dgutov@HIDDEN> Received: via spool by 18417-submit <at> debbugs.gnu.org id=B18417.141014590411437 (code B ref 18417); Mon, 08 Sep 2014 03:12:01 +0000 Received: (at 18417) by debbugs.gnu.org; 8 Sep 2014 03:11:44 +0000 Received: from localhost ([127.0.0.1]:33140 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.80) (envelope-from <debbugs-submit-bounces <at> debbugs.gnu.org>) id 1XQpMm-0002yP-2M for submit <at> debbugs.gnu.org; Sun, 07 Sep 2014 23:11:44 -0400 Received: from mail-wi0-f170.google.com ([209.85.212.170]:34374) by debbugs.gnu.org with esmtp (Exim 4.80) (envelope-from <alptekin.aker@HIDDEN>) id 1XQpMi-0002y7-TT for 18417 <at> debbugs.gnu.org; Sun, 07 Sep 2014 23:11:41 -0400 Received: by mail-wi0-f170.google.com with SMTP id cc10so1953684wib.5 for <18417 <at> debbugs.gnu.org>; Sun, 07 Sep 2014 20:11:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; bh=sVLpMD3AN4+xhUXa//q5ox5t+Bz/LYalbKJuuPnsQqM=; b=htTyRhBS07snyHtXsYVRByGJxhtwIRP58KnE5aUz5bYJ+PcPnsn3c6u2LISQZdYPJh PGm6L1cWFssOsDTzruiNX8HpCVMdAbw8ptlhgBHcFYPjKLwZ1GZj2JvCZ3emXMOx5ixI Z96B2qGBnm+zYhY6omn6R+L3CuSsmjDMwSQEPDQQuflzQ4w0BTTtd2YcKUf9KhjmmZ2W DdPMEz3KH2mUPHclG+T08hRKqNm7KoYO9I4O3zcdxFXlM+Pvf2ZzDPOPYHU4fFLoygVb xYGRrfyY0IBaAZQoCtEc3pOzPQH9pOnPgVZ+rH4s9XeUwy4e4WIPMs5353TCMV78HZ6O el8w== MIME-Version: 1.0 X-Received: by 10.180.36.236 with SMTP id t12mr19779856wij.38.1410145895210; Sun, 07 Sep 2014 20:11:35 -0700 (PDT) Received: by 10.217.39.84 with HTTP; Sun, 7 Sep 2014 20:11:35 -0700 (PDT) In-Reply-To: <837g1fcpm9.fsf@HIDDEN> References: <86sik513vf.fsf@HIDDEN> <837g1fcpm9.fsf@HIDDEN> Date: Sun, 7 Sep 2014 23:11:35 -0400 Message-ID: <CACxch4rNSrMXZAm9h_AB+p0k+hpAE3+p_RWHV=zyXxM_GEOVKQ@HIDDEN> From: Alp Aker <alptekin.aker@HIDDEN> Content-Type: multipart/alternative; boundary=e89a8f64672f2a642c0502852dc8 X-Spam-Score: -0.7 (/) X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <http://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <http://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: <http://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: -0.7 (/) --e89a8f64672f2a642c0502852dc8 Content-Type: text/plain; charset=UTF-8 > The recipe in effect invokes undefined behavior in posn-at-point, > because fci-mode uses a zero-length (a.k.a. "empty") overlay to > place, in a very convoluted way, a stretch of whitespace followed > by an image, before the newline. [snip] > Since the buffer position of the newline is not "covered" by the > empty overlay, Emacs happily stops when it reaches the newline, > oblivious to the fact that on the way it produced the stretch > glyph of a very large width. I'm not sure it's due to the overlay having zero length. Here's a minimal recipe that provokes the same behavior using a overlay of length 1 (covering the newline): (progn (delete-all-overlays) (goto-char (point-min)) (insert "\n") (setq o (make-overlay 1 2) s (propertize " " 'display '(space :align-to 10) 'cursor t)) (overlay-put o 'before-string s) (goto-char (point-min)) (setq col (car (posn-col-row (posn-at-point (point))))) (message (concat "Current column: " (number-to-string col)))) --e89a8f64672f2a642c0502852dc8 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable <div dir=3D"ltr"><div>> The recipe in effect invokes undefined behavior = in posn-at-point,<br>> because fci-mode uses a zero-length (a.k.a. "= ;empty") overlay to<br>> place, in a very convoluted way, a stretch= of whitespace followed<br>> by an image, before the newline.<br>[snip]<= br>> Since the buffer position of the newline is not "covered"= by the<br>> empty overlay, Emacs happily stops when it reaches the newl= ine,<br>> oblivious to the fact that on the way it produced the stretch<= br>> glyph of a very large width.<br><br></div>I'm not sure it's= due to the overlay having zero length.=C2=A0 Here's a minimal recipe t= hat provokes the same behavior using a overlay of length 1 (covering the ne= wline):<br><br>(progn<br>=C2=A0 (delete-all-overlays)<br>=C2=A0 (goto-char = (point-min))<br>=C2=A0 (insert "\n")<br>=C2=A0 (setq o (make-over= lay 1 2)<br>=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 s (propertize "= "<br>=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 'displa= y '(space :align-to 10)<br>=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0 'cursor t))<br>=C2=A0 (overlay-put o 'before-string s)<br= >=C2=A0 (goto-char (point-min))<br>=C2=A0 (setq col (car (posn-col-row (pos= n-at-point (point)))))<br>=C2=A0 (message (concat "Current column: &qu= ot; (number-to-string col))))<br><br><div><br></div></div> --e89a8f64672f2a642c0502852dc8--
X-Loop: help-debbugs@HIDDEN Subject: bug#18417: 24.3.93; posn-at-point confused by fill-column-indicator Resent-From: Eli Zaretskii <eliz@HIDDEN> Original-Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> Resent-CC: bug-gnu-emacs@HIDDEN Resent-Date: Tue, 09 Sep 2014 14:39:02 +0000 Resent-Message-ID: <handler.18417.B18417.141027350715596 <at> debbugs.gnu.org> Resent-Sender: help-debbugs@HIDDEN X-GNU-PR-Message: followup 18417 X-GNU-PR-Package: emacs X-GNU-PR-Keywords: To: Alp Aker <alptekin.aker@HIDDEN> Cc: 18417 <at> debbugs.gnu.org, dgutov@HIDDEN Reply-To: Eli Zaretskii <eliz@HIDDEN> Received: via spool by 18417-submit <at> debbugs.gnu.org id=B18417.141027350715596 (code B ref 18417); Tue, 09 Sep 2014 14:39:02 +0000 Received: (at 18417) by debbugs.gnu.org; 9 Sep 2014 14:38:27 +0000 Received: from localhost ([127.0.0.1]:35464 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.80) (envelope-from <debbugs-submit-bounces <at> debbugs.gnu.org>) id 1XRMYs-00043O-7g for submit <at> debbugs.gnu.org; Tue, 09 Sep 2014 10:38:26 -0400 Received: from mtaout28.012.net.il ([80.179.55.184]:44548) by debbugs.gnu.org with esmtp (Exim 4.80) (envelope-from <eliz@HIDDEN>) id 1XRMYm-000433-UM for 18417 <at> debbugs.gnu.org; Tue, 09 Sep 2014 10:38:22 -0400 Received: from conversion-daemon.mtaout28.012.net.il by mtaout28.012.net.il (HyperSendmail v2007.08) id <0NBN00J001U1WM00@HIDDEN> for 18417 <at> debbugs.gnu.org; Tue, 09 Sep 2014 17:36:55 +0300 (IDT) Received: from HOME-C4E4A596F7 ([87.69.4.28]) by mtaout28.012.net.il (HyperSendmail v2007.08) with ESMTPA id <0NBN00INX1XI2H20@HIDDEN>; Tue, 09 Sep 2014 17:36:55 +0300 (IDT) Date: Tue, 09 Sep 2014 17:38:24 +0300 From: Eli Zaretskii <eliz@HIDDEN> In-reply-to: <CACxch4rNSrMXZAm9h_AB+p0k+hpAE3+p_RWHV=zyXxM_GEOVKQ@HIDDEN> X-012-Sender: halo1@HIDDEN Message-id: <8338c0c10f.fsf@HIDDEN> References: <86sik513vf.fsf@HIDDEN> <837g1fcpm9.fsf@HIDDEN> <CACxch4rNSrMXZAm9h_AB+p0k+hpAE3+p_RWHV=zyXxM_GEOVKQ@HIDDEN> X-Spam-Score: 1.0 (+) X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <http://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <http://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: <http://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: 1.0 (+) > Date: Sun, 7 Sep 2014 23:11:35 -0400 > From: Alp Aker <alptekin.aker@HIDDEN> > Cc: Dmitry <dgutov@HIDDEN>, 18417 <at> debbugs.gnu.org > > > The recipe in effect invokes undefined behavior in posn-at-point, > > because fci-mode uses a zero-length (a.k.a. "empty") overlay to > > place, in a very convoluted way, a stretch of whitespace followed > > by an image, before the newline. > [snip] > > Since the buffer position of the newline is not "covered" by the > > empty overlay, Emacs happily stops when it reaches the newline, > > oblivious to the fact that on the way it produced the stretch > > glyph of a very large width. > > I'm not sure it's due to the overlay having zero length. Here's a minimal > recipe that provokes the same behavior using a overlay of length 1 (covering > the newline): You are right, the length of the overlay is not the issue here. I mentioned that for completeness, but my wording could indeed mislead into thinking that the zero length is the culprit. The actual problem is that overlays with before-strings and after-strings never "cover" (as in "conceal" or "hide") anything. The buffer contents is still there, so Emacs gives you the coordinates of the buffer position on the display, not of the first glyph produced from the overlay string. Btw, the same will happen with cursor positioning if you remove the 'cursor' property from the overlay string, and for the same reason.
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