From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Eli Zaretskii Newsgroups: gmane.emacs.devel Subject: Re: how reliable is rendering of complex scripts? Date: Fri, 02 Oct 2015 10:30:17 +0300 Message-ID: <83pp0x7mnq.fsf@gnu.org> References: <20151002.073900.472512461.wl@gnu.org> Reply-To: Eli Zaretskii NNTP-Posting-Host: plane.gmane.org X-Trace: ger.gmane.org 1443773933 5103 80.91.229.3 (2 Oct 2015 08:18:53 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Fri, 2 Oct 2015 08:18:53 +0000 (UTC) Cc: Kenichi Handa , emacs-devel@gnu.org To: Werner LEMBERG Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Fri Oct 02 10:18:38 2015 Return-path: Envelope-to: ged-emacs-devel@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 1ZhvY1-0001Jq-5m for ged-emacs-devel@m.gmane.org; Fri, 02 Oct 2015 10:18:33 +0200 Original-Received: from localhost ([::1]:58015 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZhvY0-0000v2-04 for ged-emacs-devel@m.gmane.org; Fri, 02 Oct 2015 04:18:32 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:34821) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZhunY-0000mF-He for emacs-devel@gnu.org; Fri, 02 Oct 2015 03:30:33 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZhunU-0002wt-9T for emacs-devel@gnu.org; Fri, 02 Oct 2015 03:30:32 -0400 Original-Received: from mtaout20.012.net.il ([80.179.55.166]:51455) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZhunU-0002wF-13; Fri, 02 Oct 2015 03:30:28 -0400 Original-Received: from conversion-daemon.a-mtaout20.012.net.il by a-mtaout20.012.net.il (HyperSendmail v2007.08) id <0NVL009000LR0400@a-mtaout20.012.net.il>; Fri, 02 Oct 2015 10:30:25 +0300 (IDT) Original-Received: from HOME-C4E4A596F7 ([84.94.185.246]) by a-mtaout20.012.net.il (HyperSendmail v2007.08) with ESMTPA id <0NVL008VT0UPUX40@a-mtaout20.012.net.il>; Fri, 02 Oct 2015 10:30:25 +0300 (IDT) In-reply-to: <20151002.073900.472512461.wl@gnu.org> X-012-Sender: halo1@inter.net.il X-detected-operating-system: by eggs.gnu.org: Solaris 10 X-Received-From: 80.179.55.166 X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Original-Sender: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.devel:190654 Archived-At: (CC'ing Handa-san, who wrote most of the relevant display code in Emacs, and also the m17n shaping engine libraries.) > Date: Fri, 02 Oct 2015 07:39:00 +0200 (CEST) > From: Werner LEMBERG > > I wonder how reliable emacs displays complex scripts like Devanagari > or Arabic. AFAIK, no one has ever performed a study about this, let alone repeated it when the relevant standards changed. > For example, the maintainers of the HarfBuzz library did extensive > comparisons of the rendering results with the MS engine to iron out > zillions of small buglets in OpenType handling. At least on MS-Windows, Emacs uses the MS engine directly, so some of similar buglets should not affect us on Windows. > AFAIK, Emacs relies on the m17n libraries, at least on GNU/Linux (no > idea about other environments), controlling the OpenType handling > (partially?) with Lisp code That is correct. And while the shaping engines, like libm17n-flt and Uniscribe, are beyond the scope of Emacs maintenance, the supporting Lisp and C code is on our table. However, we currently lack a maintainer in that area (have been lacking for a long time), so I guess we are not up to speed with the latest developments. I'm talking first and foremost about the definitions of character-composition patterns, which tell Emacs which sequences of characters should be rendered as a single grapheme cluster. There's a lot to do in this area for various languages. > are there test suites to compare the results? There's a test suite for bidirectional display, but it only tests the reordering of characters for display, not the shaping. There's nothing else, AFAIK. If you, or someone else, can work on adding one, that'd be great.