From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Richard Wordingham via "Bug reports for GNU Emacs, the Swiss army knife of text editors" Newsgroups: gmane.emacs.bugs Subject: bug#20140: 24.4; M17n shaper output rejected Date: Sun, 13 Feb 2022 21:11:52 +0000 Message-ID: <20220213211152.03e2990a@JRWUBU2> References: <20150318222040.4066e6e9@JRWUBU2> <87r18jk5nr.fsf@gnus.org> <83v8xv2icg.fsf@gnu.org> <20220205225251.08a0faab@JRWUBU2> <83sfsmpmxb.fsf@gnu.org> Reply-To: Richard Wordingham Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="37038"; mail-complaints-to="usenet@ciao.gmane.io" Cc: 20140@debbugs.gnu.org, larsi@gnus.org To: Eli Zaretskii Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Sun Feb 13 22:13:10 2022 Return-path: Envelope-to: geb-bug-gnu-emacs@m.gmane-mx.org Original-Received: from lists.gnu.org ([209.51.188.17]) by ciao.gmane.io with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1nJMBB-0009TB-Sm for geb-bug-gnu-emacs@m.gmane-mx.org; 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a=rsa-sha256; c=relaxed/relaxed; d=ntlworld.com; s=meg.feb2017; t=1644786713; bh=lCt54f8LeGalCZnBHvkBJuN4mS0KamwLhiy+VBo24Q8=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=Vp60P5ik2u5044CdLoO+x01Z8bbR+qc4ZolXzrfgsj7aJrqM5OjEvfweA82dRyh13 Om/FbD2I4IkIATr9gx9r0VAajUgTE8pBE0PPUKOF0nu6J+MmX9uSbpO+LFxpAAXGXC y5yBkQaIF6Qh4vv9DkJjGdjXJUlhnBsuoxzS9XNDlcMo7O0kN45zK9HjR275Wezt6F mtWvhrl6llK7L8ym/qG1+BXzmUgX59L7vwq5hMvXftvseWDII7q17t6pWf/HepzMYB yTQpwVtw0x+tk+XQUqkdeT+9SYzn0zlR4HCmqeOiz9p5cwHMjKuTr335OZFs69sorm EroBr3nCocUUg== In-Reply-To: <83sfsmpmxb.fsf@gnu.org> X-Mailer: Claws Mail 3.17.5 (GTK+ 2.24.32; x86_64-pc-linux-gnu) X-CMAE-Envelope: MS4xfBtyEVtWvmM6z8lLrCjo36SULrVxB90yUS8eMKa0hHuwbtVf3drxAOgl379qTcQUt5ng74dS0SqneuuRikTL81RBbdhwGfeFrP8fN5T3cd15z7nvSeEd omolTchML6Pxv33hj7Hby3/EYxFgv/3h6zLjtY1CHv0eZagGWlyzY55lKatGDOM9eD50lgnpll7qJNwAOWirdG+5/SnwqCLAnr9z/3Hv0xmJIWcyVXr9xSbY hGDrc/pQ2PGAwFwg99Rq6w== X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list 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-mx.org@gnu.org Original-Sender: "bug-gnu-emacs" Xref: news.gmane.io gmane.emacs.bugs:226841 Archived-At: On Sun, 13 Feb 2022 21:49:04 +0200 Eli Zaretskii wrote: > > Date: Sat, 5 Feb 2022 22:52:51 +0000 > > From: Richard Wordingham > > Cc: Lars Ingebrigtsen , 20140@debbugs.gnu.org > > > > Sad to see that Khaled Hosny's suggestion not to use composition > > rules seems not to have been taken. > > Btw, the _only_ reason Handa-san and now myself were able to implement > something like the forward/backward-char-intrusive commands is that we > DO control which parts of text are composed and which aren't. If we > were to follow HarfBuzz developers' advice, and were to hand all the > text to HarfBuzz for shaping, we would need the HarfBuzz cooperation > to implement such features in the editor. You mean the more sophisticated mechanisms which position the cursor intelligently. Those two commands you named work by completely ignoring the composition mechanism. Correct me if I am wrong, but for Arabic, is not Emacs restricted to typewriter-like fonts? There would be a similar problem with the use of Tai Khuen or other tunnelling fonts for Northern Thai if you used the current mechanism for advancing character by character. Tunnelling fonts write parts of one cluster under the next. The Tai Khuen fonts I've seen do this by relying on characteristics of Tai Khuen spelling. The rules don't hold for Northern Thai, and consequently the subscript portions of successive orthographic syllables can overwrite one another. A sophisticated font could check for clashes, but that needs the orthographic syllables to be passed to the shaper together. Richard.