From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED.blaine.gmane.org!not-for-mail From: Eli Zaretskii Newsgroups: gmane.emacs.devel Subject: Re: Question about display engine Date: Sat, 10 Aug 2019 14:30:25 +0300 Message-ID: <83ftm98dgu.fsf@gnu.org> References: <83k1bpasic.fsf@gnu.org> <20190807155738.yviofsumjjhqueci@Ergus> <83imr9ar9f.fsf@gnu.org> <0975890b-37b4-428d-f6e5-5dcf894fb6be@gmx.at> <83ftmdapxm.fsf@gnu.org> <20190808083804.ta3evocyb4hirywj@Ergus> <20190808145015.2qaxwzwf4ws2i3er@Ergus> Injection-Info: blaine.gmane.org; posting-host="blaine.gmane.org:195.159.176.226"; logging-data="147756"; mail-complaints-to="usenet@blaine.gmane.org" Cc: spacibba@aol.com, emacs-devel@gnu.org To: martin rudalics Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Sat Aug 10 13:31:16 2019 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([209.51.188.17]) by blaine.gmane.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1hwPae-000cIq-F7 for ged-emacs-devel@m.gmane.org; Sat, 10 Aug 2019 13:31:16 +0200 Original-Received: from localhost ([::1]:35838 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hwPac-0004eT-Qx for ged-emacs-devel@m.gmane.org; Sat, 10 Aug 2019 07:31:14 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:48111) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hwPa1-0004eL-62 for emacs-devel@gnu.org; Sat, 10 Aug 2019 07:30:38 -0400 Original-Received: from fencepost.gnu.org ([2001:470:142:3::e]:52163) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hwPZz-0002c7-6Q; Sat, 10 Aug 2019 07:30:35 -0400 Original-Received: from [176.228.60.248] (port=4147 helo=home-c4e4a596f7) by fencepost.gnu.org with esmtpsa (TLS1.2:RSA_AES_256_CBC_SHA1:256) (Exim 4.82) (envelope-from ) id 1hwPZx-0001Ux-TX; Sat, 10 Aug 2019 07:30:34 -0400 In-reply-to: (message from martin rudalics on Fri, 9 Aug 2019 10:59:33 +0200) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.23 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" Xref: news.gmane.org gmane.emacs.devel:239305 Archived-At: > Cc: Eli Zaretskii , emacs-devel@gnu.org > From: martin rudalics > Date: Fri, 9 Aug 2019 10:59:33 +0200 > > > You are right, I ignored those use cases, but I still don't think that > > the faces are the right place to flag that. The line extension maybe > > needs to be decided based on another text property. Maybe there are > > already some conditions we can check dynamically. Because adding a flag > > is a bit error prone when there are already some conditions. > > > > There is also the case when the face to use comes from FACE_FOR_CHAR or > > another is merged over that. Or when there is a highlight inside the > > region at the end of the line text... That, in the display engine, I am > > not clear yet how are handled. > > OTOH, the display engine could simply delegate some design decisions > to the face specification apparatus and attribute any faults to the > latter. I don't think this is workable, because of face merging. The actual face used to display the last character on a screen line can (and frequently does) come from merging several faces, and there's no meaningful answer to the question: which face did this attribute come from? For a face merged from 2 or more faces defined via defface, how do you tell whether or not to extend it? Thus, such delegation can only yield inconsistent behavior and more bug reports.