From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Eli Zaretskii Newsgroups: gmane.emacs.help Subject: Re: Display of decomposed characters Date: Fri, 19 Mar 2021 18:44:25 +0200 Message-ID: <835z1ndrfa.fsf@gnu.org> References: <83v9csplwq.fsf@gnu.org> <83wnx5n1zw.fsf@gnu.org> <831rea3ymg.fsf@gnu.org> <0077B374-A65D-412D-B1A5-4ADDD50D41A7@gmail.com> <83pn0k825c.fsf@gnu.org> <8335wsh5f3.fsf@gnu.org> <3FBB9207-645C-479C-B540-C2BBD7BF6954@gmail.com> Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="9020"; mail-complaints-to="usenet@ciao.gmane.io" To: help-gnu-emacs@gnu.org Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Fri Mar 19 17:45:59 2021 Return-path: Envelope-to: geh-help-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 1lNIG6-0002DK-LP for geh-help-gnu-emacs@m.gmane-mx.org; Fri, 19 Mar 2021 17:45:58 +0100 Original-Received: from localhost ([::1]:41534 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lNIG5-0008Aa-Ll for geh-help-gnu-emacs@m.gmane-mx.org; Fri, 19 Mar 2021 12:45:57 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:55136) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lNIEf-0008AP-3g for help-gnu-emacs@gnu.org; Fri, 19 Mar 2021 12:44:29 -0400 Original-Received: from fencepost.gnu.org ([2001:470:142:3::e]:38120) by eggs.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lNIEe-0001x1-Sn for help-gnu-emacs@gnu.org; Fri, 19 Mar 2021 12:44:28 -0400 Original-Received: from 84.94.185.95.cable.012.net.il ([84.94.185.95]:4995 helo=home-c4e4a596f7) by fencepost.gnu.org with esmtpsa (TLS1.2:RSA_AES_256_CBC_SHA1:256) (Exim 4.82) (envelope-from ) id 1lNIEe-0001WR-85 for help-gnu-emacs@gnu.org; Fri, 19 Mar 2021 12:44:28 -0400 In-Reply-To: <3FBB9207-645C-479C-B540-C2BBD7BF6954@gmail.com> (message from Philipp on Fri, 19 Mar 2021 17:37:31 +0100) X-BeenThere: help-gnu-emacs@gnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Users list for the GNU Emacs text editor List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Original-Sender: "help-gnu-emacs" Xref: news.gmane.io gmane.emacs.help:128455 Archived-At: > From: Philipp > Date: Fri, 19 Mar 2021 17:37:31 +0100 > Cc: help-gnu-emacs@gnu.org > > >>>> What if Emacs ignored font lookup for combining characters and always picked the font of the previous base character? > >>> > >>> What would that produce if the font of the previous character didn't > >>> have a glyph for the accent? The accent will disappear, or maybe will > >>> be displayed as "tofu", right? Does that sound like a good strategy? > >> > >> Can't the shaping engine produce fake compositions in that case? > > > > What do you mean by "fake compositions"? what would they entail, and > > which glyphs would they use? > > For example, the shaping engine could use U+00A8 (assuming it's available in the font), but place it on top of the base glyph, without horizontal shift. First, we were talking about the case where U+00A8 is NOT available in the font. (If it _is_ available, then this whole discussion is pointless, because things already work well in that case.) > (At least that would be a possibility; I don't know whether Harfbuzz actually does that.) > That would still produce suboptimal results, but probably slightly better ones. I don't understand what you are describing here. If the font does have U+00A8, what you describe already happens. If the font doesn't have the glyph, what can the shaper do? The horizontal shift happens because we use U+00A8 from a different font. Placing a glyph from a different font on top of a base glyph is in general an impossible task, because different fonts have different ways of describing the points where the accents shall be placed on top of base characters. > The optimal approach (for this case) would still be to try out composition before font selection, and use that if it works. I tried to explain why that's not possible, but I guess I failed miserably. > I should note that Emacs is not alone in producing suboptimal results in this case; other GUI programs on that systems appear to either perform the fake composition I mentioned before, or no composition at all (placing the base and combining characters next to each other). Which should tell us something about the issue and the ways it can and cannot be solved.