From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Eli Zaretskii Newsgroups: gmane.emacs.bugs Subject: bug#23594: 25.0.94; Display errors on Linux tty Date: Sun, 22 May 2016 18:27:42 +0300 Message-ID: <838tz26rkh.fsf@gnu.org> References: <20160521104720.GA2987@acm.fritz.box> <83k2in72de.fsf@gnu.org> <20160521190110.GB2987@acm.fritz.box> <83d1of6xe5.fsf@gnu.org> <20160522093813.GA2136@acm.fritz.box> Reply-To: Eli Zaretskii NNTP-Posting-Host: plane.gmane.org X-Trace: ger.gmane.org 1463930903 19594 80.91.229.3 (22 May 2016 15:28:23 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Sun, 22 May 2016 15:28:23 +0000 (UTC) Cc: 23594@debbugs.gnu.org To: Alan Mackenzie Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane.org@gnu.org Sun May 22 17:28:12 2016 Return-path: Envelope-to: geb-bug-gnu-emacs@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1b4VIa-0008Se-9G for geb-bug-gnu-emacs@m.gmane.org; Sun, 22 May 2016 17:28:12 +0200 Original-Received: from localhost ([::1]:43360 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1b4VIZ-0007sJ-Ai for geb-bug-gnu-emacs@m.gmane.org; Sun, 22 May 2016 11:28:11 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:41851) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1b4VIS-0007sC-D9 for bug-gnu-emacs@gnu.org; Sun, 22 May 2016 11:28:05 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1b4VIQ-00015x-BZ for bug-gnu-emacs@gnu.org; Sun, 22 May 2016 11:28:03 -0400 Original-Received: from debbugs.gnu.org ([208.118.235.43]:48846) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1b4VIQ-00015s-7h for bug-gnu-emacs@gnu.org; Sun, 22 May 2016 11:28:02 -0400 Original-Received: from Debian-debbugs by debbugs.gnu.org with local (Exim 4.84_2) (envelope-from ) id 1b4VIQ-0005Kp-3n for bug-gnu-emacs@gnu.org; Sun, 22 May 2016 11:28:02 -0400 X-Loop: help-debbugs@gnu.org Resent-From: Eli Zaretskii Original-Sender: "Debbugs-submit" Resent-CC: bug-gnu-emacs@gnu.org Resent-Date: Sun, 22 May 2016 15:28:02 +0000 Resent-Message-ID: Resent-Sender: help-debbugs@gnu.org X-GNU-PR-Message: followup 23594 X-GNU-PR-Package: emacs X-GNU-PR-Keywords: Original-Received: via spool by 23594-submit@debbugs.gnu.org id=B23594.146393087820497 (code B ref 23594); Sun, 22 May 2016 15:28:02 +0000 Original-Received: (at 23594) by debbugs.gnu.org; 22 May 2016 15:27:58 +0000 Original-Received: from localhost ([127.0.0.1]:32950 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1b4VIL-0005KX-Ml for submit@debbugs.gnu.org; Sun, 22 May 2016 11:27:57 -0400 Original-Received: from eggs.gnu.org ([208.118.235.92]:50857) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1b4VIL-0005KJ-1h for 23594@debbugs.gnu.org; Sun, 22 May 2016 11:27:57 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1b4VIB-0000wk-MV for 23594@debbugs.gnu.org; Sun, 22 May 2016 11:27:51 -0400 Original-Received: from fencepost.gnu.org ([2001:4830:134:3::e]:49768) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1b4VIB-0000vb-JS; Sun, 22 May 2016 11:27:47 -0400 Original-Received: from 84.94.185.246.cable.012.net.il ([84.94.185.246]:2226 helo=home-c4e4a596f7) by fencepost.gnu.org with esmtpsa (TLS1.2:RSA_AES_128_CBC_SHA1:128) (Exim 4.82) (envelope-from ) id 1b4VI9-0001Nf-KE; Sun, 22 May 2016 11:27:46 -0400 In-reply-to: <20160522093813.GA2136@acm.fritz.box> (message from Alan Mackenzie on Sun, 22 May 2016 09:38:13 +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: 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:118534 Archived-At: > Date: Sun, 22 May 2016 09:38:13 +0000 > Cc: 23594@debbugs.gnu.org > From: Alan Mackenzie > > On Sat, May 21, 2016 at 10:09:38PM +0300, Eli Zaretskii wrote: > > > > This bug exists since we started showing the 'decomposition' of > > > > characters in Emacs 24.1. With LF, we send a literal LF character > > > > to the screen. > > That's only half the story. The literal LF doesn't seem to be the > problem. What do you mean by "literal LF"? A newline ends a line, and is never displayed at all, the display engine "swallows" it so it disappears without a trace, and instead instructs the terminal to move to the next line. > Rather, it's got a 'composition text-property attached to it. > The string we're trying to display is > > #(" decomposition: (10) ('\n')\n" 24 25 (composition (0 1 [9 10 9]))) > ^ > | > 24 > > What is this composition trying to do? The [9 10 9] is [\t \n \t]. It tries to prevent the character from being composed with surrounding ones, so that we could display there combining marks and other similar stuff. > Under X-Windows, the same string is displayed, this time successfully. > The call > (inseert #(" decomposition: .... [9 10 9]))) > works on X-Windows, the "\n" with the composition property being > displayed as a square box. Why is that a "success", exactly? Is the user supposed to guess that the box represents a LF? > > > OK. The next question is is it easy to fix? > > > Yes. We should not send control characters to that buffer. > > It seems to me there is a bug in the display engine here: the same > string which is displayed successfully in X-Windows goes badly wrong on > a Linux tty. > > Comments? IMO, there's no such thing as a successful display of an unadorned LF (or any other control character), on any kind of terminal. What would be the graphics for that?