From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Eli Zaretskii Newsgroups: gmane.emacs.bugs Subject: bug#27544: 25.1; Visualization of Unicode bidirectional marks Date: Sat, 01 Jul 2017 15:16:51 +0300 Message-ID: <83o9t4pd1o.fsf@gnu.org> References: Reply-To: Eli Zaretskii NNTP-Posting-Host: blaine.gmane.org X-Trace: blaine.gmane.org 1498911491 24179 195.159.176.226 (1 Jul 2017 12:18:11 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sat, 1 Jul 2017 12:18:11 +0000 (UTC) Cc: 27544@debbugs.gnu.org To: Itai Berli Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane.org@gnu.org Sat Jul 01 14:18:07 2017 Return-path: Envelope-to: geb-bug-gnu-emacs@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1dRHLh-00060W-RT for geb-bug-gnu-emacs@m.gmane.org; Sat, 01 Jul 2017 14:18:05 +0200 Original-Received: from localhost ([::1]:54147 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dRHLn-0007aB-0O for geb-bug-gnu-emacs@m.gmane.org; Sat, 01 Jul 2017 08:18:11 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:38204) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dRHLh-0007Zt-71 for bug-gnu-emacs@gnu.org; Sat, 01 Jul 2017 08:18:06 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dRHLe-0004rF-14 for bug-gnu-emacs@gnu.org; Sat, 01 Jul 2017 08:18:05 -0400 Original-Received: from debbugs.gnu.org ([208.118.235.43]:44297) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1dRHLd-0004r7-TR for bug-gnu-emacs@gnu.org; Sat, 01 Jul 2017 08:18:01 -0400 Original-Received: from Debian-debbugs by debbugs.gnu.org with local (Exim 4.84_2) (envelope-from ) id 1dRHLd-0007O1-LB for bug-gnu-emacs@gnu.org; Sat, 01 Jul 2017 08:18:01 -0400 X-Loop: help-debbugs@gnu.org Resent-From: Eli Zaretskii Original-Sender: "Debbugs-submit" Resent-CC: bug-gnu-emacs@gnu.org Resent-Date: Sat, 01 Jul 2017 12:18:01 +0000 Resent-Message-ID: Resent-Sender: help-debbugs@gnu.org X-GNU-PR-Message: followup 27544 X-GNU-PR-Package: emacs X-GNU-PR-Keywords: Original-Received: via spool by 27544-submit@debbugs.gnu.org id=B27544.149891143228339 (code B ref 27544); Sat, 01 Jul 2017 12:18:01 +0000 Original-Received: (at 27544) by debbugs.gnu.org; 1 Jul 2017 12:17:12 +0000 Original-Received: from localhost ([127.0.0.1]:46974 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1dRHKq-0007N1-H2 for submit@debbugs.gnu.org; Sat, 01 Jul 2017 08:17:12 -0400 Original-Received: from eggs.gnu.org ([208.118.235.92]:47152) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1dRHKp-0007Mn-04 for 27544@debbugs.gnu.org; Sat, 01 Jul 2017 08:17:11 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dRHKg-0004c8-GX for 27544@debbugs.gnu.org; Sat, 01 Jul 2017 08:17:05 -0400 Original-Received: from fencepost.gnu.org ([2001:4830:134:3::e]:56203) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dRHKg-0004c4-Cs; Sat, 01 Jul 2017 08:17:02 -0400 Original-Received: from 84.94.185.246.cable.012.net.il ([84.94.185.246]:2502 helo=home-c4e4a596f7) by fencepost.gnu.org with esmtpsa (TLS1.2:RSA_AES_256_CBC_SHA1:256) (Exim 4.82) (envelope-from ) id 1dRHKf-0000bo-P1; Sat, 01 Jul 2017 08:17:02 -0400 In-reply-to: (message from Itai Berli on Sat, 1 Jul 2017 14:48:21 +0300) 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: 208.118.235.43 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:134072 Archived-At: > From: Itai Berli > Date: Sat, 1 Jul 2017 14:48:21 +0300 > > A default should be something that aligns with the expectations of a > casual user; you cannot expect a casual user to start writing elisp > code or tinkering with `glyphless-char-display-control`. > > And how can we know what a casual user would expect? Thank you for describing your expectations. However, to change the defaults, we'd need to hear from more than one user. If we find that the majority thinks the default should be changed, we will eventually do that, as we do with any other default. > 1. We can follow established standards, particularly if we claim to > conform to them, as Emacs does to the Unicode standard. The Unicode > bidi algorithm 8.0.0 specifications state the following about LRM, RLM > and ALM (section 2.6 Implicit Directional Marks): > > they do not display or have any other semantic effect > and again, in the same section: > > they do not appear in the display The UBA also allows to retain these characters, including display them, see section 5.2 there. This is how Emacs behaves, again in line with general Emacs feature of allowing users to see what's in the buffer. > 4. We can see how Emacs implements similar constructs. The bidi marks > are control sequences that can be inserted into the editor using `C-x > 8 RET `. Let's see how other control sequences are > handled by this mechanism. If you try to insert, say, the characters > Null character (U+0000), Bell character (U+0007) and Escape character > (U+001B) using this method, we'll get: There are control characters other than those which you tried, for which Emacs does use the same display method as for bidi controls: try ZWJ (U+200D) or ARABIC NUMBER SIGN (U+0600) -- all the characters of Unicode General Category "Cf" that don't have an established graphic image are by default displayed as thin spaces. This is explained in the doc string of glyphless-char-display-control.