From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Stefan Monnier Newsgroups: gmane.emacs.devel Subject: Re: Major modes using `widen' is a good, even essential, programming practice. Date: Mon, 08 Aug 2022 05:25:21 -0400 Message-ID: References: <6ae35c9306ade07b4c45@heytings.org> <83fsi7wjqe.fsf@gnu.org> Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="9782"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/29.0.50 (gnu/linux) Cc: acm@muc.de, gregory@heytings.org, emacs-devel@gnu.org To: Eli Zaretskii Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Mon Aug 08 11:29:35 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 1oKz4o-0002PD-Q9 for ged-emacs-devel@m.gmane-mx.org; Mon, 08 Aug 2022 11:29:34 +0200 Original-Received: from localhost ([::1]:56400 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1oKz4n-0005OJ-Qc for ged-emacs-devel@m.gmane-mx.org; Mon, 08 Aug 2022 05:29:33 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:38610) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oKz0s-0001OF-VL for emacs-devel@gnu.org; Mon, 08 Aug 2022 05:25:31 -0400 Original-Received: from mailscanner.iro.umontreal.ca ([132.204.25.50]:30266) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oKz0q-0007HP-4e; Mon, 08 Aug 2022 05:25:29 -0400 Original-Received: from pmg3.iro.umontreal.ca (localhost [127.0.0.1]) by pmg3.iro.umontreal.ca (Proxmox) with ESMTP id 1AFBA440C44; Mon, 8 Aug 2022 05:25:26 -0400 (EDT) Original-Received: from mail01.iro.umontreal.ca (unknown [172.31.2.1]) by pmg3.iro.umontreal.ca (Proxmox) with ESMTP id C0588440AF2; Mon, 8 Aug 2022 05:25:24 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=iro.umontreal.ca; s=mail; t=1659950724; bh=fE9uc+ImhXImYOgP70dmhVymqGZgGe9MDl0+RqRQObw=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=ihs0J4txyPFKsNc3uH3MqDcUW5h5v4fG1Grujo7+yxBugkOIcbtAgTlmPSwuhWU0M YEaMbvi9u/zXapm1MyLyYeiCe4rxGldIKIAcEeoynzaY3lB2VkO9AOBqk3txz4hBD3 BIeHT1NQSxlxC//zc42nzNsWtXuCicASvlTyFOd+Z9upoO3TcOBm5ciQt9GhcPglxA 8sYK6KbXtvDoYUoWoDvBCU2eQ/iYMDiOu2MKvh03aNCZGN6O1oqaC7Ms/ATxkUegYY reAXRMXymBVJLkAT58cnkn53OdjTWEghUCxiZGsI/KO+n2h7PNy4tCbTs9+PCOlHeY ny8WB3kDRg6HQ== Original-Received: from milanesa (dyn.144-85-181-226.dsl.vtx.ch [144.85.181.226]) by mail01.iro.umontreal.ca (Postfix) with ESMTPSA id E093B1203E5; Mon, 8 Aug 2022 05:25:23 -0400 (EDT) In-Reply-To: <83fsi7wjqe.fsf@gnu.org> (Eli Zaretskii's message of "Mon, 08 Aug 2022 05:29:45 +0300") Received-SPF: pass client-ip=132.204.25.50; envelope-from=monnier@iro.umontreal.ca; helo=mailscanner.iro.umontreal.ca X-Spam_score_int: -42 X-Spam_score: -4.3 X-Spam_bar: ---- X-Spam_report: (-4.3 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action 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:293245 Archived-At: >> Eli Zaretskii [2022-08-07 17:20:52] wrote: >> > jit-lock calls the functions with two arguments, BEG and END, and >> > expects them to work only on that chunk of text. >> >> That is not the case: it expects the function to "fontify" *at least* >> from BEG to END, but is quite happy to let it fontify more (and the >> function can return a value indicating which portion was actually >> returned in that case). Furthermore, it's clear that fontification of >> BEG..END may need to look at text before BEG (and occasionally beyond >> END as well). > > The intent is clearly that fontifications don't look far beyond these > two points, because otherwise the whole design of jit-lock and its > invocations during redisplay is basically thrown out the window. Usually, font-lock rules don't look before BOL or after EOL, indeed, *except* via `syntax-ppss` which does look at all the text from BOB to point. To make up for that, `syntax-ppss` relies heavily on caching, so that it *usually* doesn't need to look very far at all (and if there's no `syntax-propertize-function`, it's usually quite fast because it's fully coded in C). For GB-sized buffers, even the fast C code of `syntax-ppss` incurs a significant delay in the "unusual" case, so have various options: - suck it up (potentially wait several minutes when jumping to the end of the file). - give up providing more or less correct highlighting (either via some arbitrary narrowing like we do now, or turning off font-lock). - try and find some clever heuristic that can find a "nearby safe spot", i.e. a position for which we can guess the PPSS value (usually we look for a position that is "known" to be outside of any string, comment, or parenthesis). - display the buffer quickly without highlighting while the fontification is computed in the background. Stefan