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.devel Subject: Re: Major modes using `widen' is a good, even essential, programming practice. Date: Sun, 07 Aug 2022 20:23:21 +0300 Message-ID: <83pmhcvugm.fsf@gnu.org> References: <6ae35c9306ade07b4c45@heytings.org> <835yj4xhh7.fsf@gnu.org> <83y1w0w0gk.fsf@gnu.org> Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="3178"; mail-complaints-to="usenet@ciao.gmane.io" Cc: gregory@heytings.org, emacs-devel@gnu.org To: Alan Mackenzie Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Sun Aug 07 19:24:54 2022 Return-path: Envelope-to: ged-emacs-devel@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 1oKk1F-0000cW-JJ for ged-emacs-devel@m.gmane-mx.org; Sun, 07 Aug 2022 19:24:53 +0200 Original-Received: from localhost ([::1]:38306 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1oKk1E-0005Yc-J5 for ged-emacs-devel@m.gmane-mx.org; Sun, 07 Aug 2022 13:24:52 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:55782) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oKk04-0004UX-LL for emacs-devel@gnu.org; Sun, 07 Aug 2022 13:23:42 -0400 Original-Received: from fencepost.gnu.org ([2001:470:142:3::e]:58240) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oKk02-0000sa-R3; Sun, 07 Aug 2022 13:23:39 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=gnu.org; s=fencepost-gnu-org; h=References:Subject:In-Reply-To:To:From:Date: mime-version; bh=BovIUSGCiI4Sn3ToucLYMlqUNNZ1jwH/s8UhejLkE2I=; b=SfbgQuQd3RNT Oh+kJe1n2aHDpvJwhfp/wa9WlhkW0+fWiv+inJ4dpnedBFFVNNMUYV3+xisaz6AbbQNfS8SN7QykI e+xvf/qOclIs0zpawa6qEzYETW/nwauMKcbgsws9F8qE7PFSFP3WHyHUNcB37CHHQ325hHvmFH9Pd ZFR89HrWGGU0/bkgzQTBhAGcD2I5KpRJ0edHGfTSKzytUov+13VEoDS0ou7uHKM+7qLV/o1oe6Icp 6igyGRu47Cr83HhkPAI3SboWv+GRHpu8yAw/YBrPCbRmgNYMKMyGU7zzaD2T5Tk+FGVY4mfavoQhW SOXqDTQjn8LkiYHAPI3vZw==; Original-Received: from [87.69.77.57] (port=2386 helo=home-c4e4a596f7) by fencepost.gnu.org with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oKk02-0007FJ-AJ; Sun, 07 Aug 2022 13:23:38 -0400 In-Reply-To: (message from Alan Mackenzie on Sun, 7 Aug 2022 17:01:09 +0000) X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.29 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-mx.org@gnu.org Original-Sender: "Emacs-devel" Xref: news.gmane.io gmane.emacs.devel:293221 Archived-At: > Date: Sun, 7 Aug 2022 17:01:09 +0000 > Cc: gregory@heytings.org, emacs-devel@gnu.org > From: Alan Mackenzie > > > > Consider the second jit-lock chunk > > > at the beginning of xdisp.c. Fontifying that chunk involves looking > > > back 1500 characters before BEG to see that it needs > > > font-lock-comment-face. You might argue that that information will be > > > in a cache anyway, but that's not dependable. > > > Either in the cache or in the buffer: the previous chunk was > > fontified, so its end has the font-lock-comment-face. So you know. > > No, you don't. The buffer might be being opened by desktop in a large > comment in the middle of the file. You've changed the scenario, yes? > What jit-lock/font-lock actually do at the moment is to widen, then use > syntax-ppss, i.e. in effect scan from BOB. Yes, and that's SLOOOWWWW! > > > Also, the (BEG END) region will typically get rounded up to whole lines, > > > again "violating" that chunk. > > > That's a far cry from going to BOB. And if you ask nicely, we could > > arrange that jit-lock calls you only on line boundaries (unless lines > > are longer than some reasonable value). > > The search for line boundaries is done by font-lock.el. I don't trust it to DTRT when lines are very long. > > > In principle, font-lock needs to look outside of (BEG END). > > > No, it doesn't. A string cannot begin before a beginning of a > > function, for example. And if you need to go too far, just give up > > and blame the user who writes such code. It is much better than > > letting every use of CC Mode wait because once in a blue moon someone > > could have a very long string. > > That "needing to go too far" is an instantaneous jump, not a scanning. Please tell that to someone who doesn't edit C sources as frequently as I do. > The string start will be in a parse-partial-sexp result somewhere. > Sometimes people write long strings. They certainly write long comments. Why do I have top suffer every day just because someone, somewhere, might do that? I'd rather we "punish" those few people who do it (rarely).