From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Alan Mackenzie Newsgroups: gmane.emacs.devel Subject: Re: bug-reference-prog-mode slows down CC Mode's scrolling by ~7% Date: Fri, 3 Sep 2021 10:47:41 +0000 Message-ID: References: <83a6kuyysv.fsf@gnu.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="27715"; mail-complaints-to="usenet@ciao.gmane.io" Cc: monnier@iro.umontreal.ca, emacs-devel@gnu.org To: Eli Zaretskii Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Fri Sep 03 12:49:16 2021 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 1mM6l1-0006ym-Bx for ged-emacs-devel@m.gmane-mx.org; Fri, 03 Sep 2021 12:49:15 +0200 Original-Received: from localhost ([::1]:41474 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mM6l0-00041O-99 for ged-emacs-devel@m.gmane-mx.org; Fri, 03 Sep 2021 06:49:14 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:36666) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mM6jc-0002uG-3d for emacs-devel@gnu.org; Fri, 03 Sep 2021 06:47:48 -0400 Original-Received: from colin.muc.de ([193.149.48.1]:32015 helo=mail.muc.de) by eggs.gnu.org with smtp (Exim 4.90_1) (envelope-from ) id 1mM6jY-0000a5-T8 for emacs-devel@gnu.org; Fri, 03 Sep 2021 06:47:47 -0400 Original-Received: (qmail 75186 invoked by uid 3782); 3 Sep 2021 10:47:42 -0000 Original-Received: from acm.muc.de (p4fe1598b.dip0.t-ipconnect.de [79.225.89.139]) (using STARTTLS) by colin.muc.de (tmda-ofmipd) with ESMTP; Fri, 03 Sep 2021 12:47:41 +0200 Original-Received: (qmail 5107 invoked by uid 1000); 3 Sep 2021 10:47:41 -0000 Content-Disposition: inline In-Reply-To: <83a6kuyysv.fsf@gnu.org> X-Submission-Agent: TMDA/1.3.x (Ph3nix) X-Primary-Address: acm@muc.de Received-SPF: pass client-ip=193.149.48.1; envelope-from=acm@muc.de; helo=mail.muc.de X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action 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-mx.org@gnu.org Original-Sender: "Emacs-devel" Xref: news.gmane.io gmane.emacs.devel:273762 Archived-At: Hello, Eli. On Fri, Sep 03, 2021 at 09:10:24 +0300, Eli Zaretskii wrote: > > Date: Thu, 2 Sep 2021 19:24:51 +0000 > > From: Alan Mackenzie > > Cc: emacs-devel@gnu.org > > In words (;-), only the first function on jit-lock-functions should be > > able to expand the region which gets `fontified' text properties. This > > expanded region will then be supplied to the subsequent functions. > > Given how little used the `jit-lock-bounds' mechanism is (there is one > > function in Emacs, font-lock-default-fontify-region, which uses it, and > > a web search revealed only a single other instance, in lsp-mode on > > git-hub), this shouldn't cause problems. In fact, I'm not sure the > > lsp-mode use of it is even correct. > Bother: this is not future-proof, and certainly isn't scalable. If we > are changing the protocol, can we instead come up with a more scalable > change, so that functions won't "fight" in the future who gets to be > "the first"? I think we need to be clear about the current situation versus my proposal. If there is only one element (typically font-lock-fontify-region) on jit-lock-functions, nothing changes. With several elements: Current situation: The region marked with 'fontified text properties is the _smallest_ returned by the jit-lock-functions functions. If such a function returns nil (which is usual), that region becomes precisely (BEG END), and we lose all the benefit of jit-lock-bounds. Proposed mechanism: The region marked with 'fontified is that supplied by the first j-l-f function, typically font-lock-fontify-region. This is an enhancement. Note that it is difficult to use the jit-lock-bounds returned by a subsequent function, if they exceed the bounds returned by the first function. To do this safely, we would have to re-run all the previous jit-lock-functions on the newly enlarged region. This would be clumsy, and wouldn't fit in well with our current scheme. As for "fighting" to be the first function in j-l-f, I don't think that should be a problem. We can document the new &optional parameter to jit-lock-register (not yet implemented) to say "don't use this unless you really know what you're doing". What we have isn't scalable in the sense you mean, and I don't think it can be made scalable without massive changes in the jit-lock mechanism, which might well reverse the benefits of using jit-lock-bounds (the 7% saving in font locking time in CC Mode (and surely other modes, too)). -- Alan Mackenzie (Nuremberg, Germany).