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: Tick Reduction Date: Sat, 20 Nov 2021 08:34:23 +0200 Message-ID: <83tug7tjww.fsf@gnu.org> References: <87bl2hyzca.fsf@gnus.org> <835ysoursn.fsf@gnu.org> <831r3cugcp.fsf@gnu.org> <83y25judps.fsf@gnu.org> Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="9855"; mail-complaints-to="usenet@ciao.gmane.io" Cc: larsi@gnus.org, emacs-devel@gnu.org To: Stefan Monnier Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Sat Nov 20 07:35:26 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 1moJy9-0002N5-P1 for ged-emacs-devel@m.gmane-mx.org; Sat, 20 Nov 2021 07:35:25 +0100 Original-Received: from localhost ([::1]:38790 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1moJy8-0003ys-M2 for ged-emacs-devel@m.gmane-mx.org; Sat, 20 Nov 2021 01:35:24 -0500 Original-Received: from eggs.gnu.org ([209.51.188.92]:53536) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1moJx7-0003Hv-Pr for emacs-devel@gnu.org; Sat, 20 Nov 2021 01:34:21 -0500 Original-Received: from [2001:470:142:3::e] (port=57482 helo=fencepost.gnu.org) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1moJx7-0005uo-DD; Sat, 20 Nov 2021 01:34:21 -0500 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=7cA1uKljTCPLr7zXFWYMdKhwJ5G1Ey8jWsnzb/S/jao=; b=K+KG/fJbyssQ 3qcgKCgaTIBfcwYKOU4vHIakvwmdPVtI7Jl0qhn010R1x3Z6ukCeJrpP53vwumpS4nB5iYWUFM4XT NCQ3lMpDonCAm9H7lMAeMASkU84Fret/pW+vCv0wsktS2xpkEbZe42hbg3Ni7qLWgjBG8iWtiA27O a6M/SKYP1DC59V+lURkUFCA7V3H7EgGw5tglceCULrEmK/JNHNhqqbwFI9fGgIiGj5LnQ3aBS6dr1 YjtPaqvh6kjU57yyNSo8vW9ds6K5d9tIqRHHWdKr08SJ3PUZllOUzjWzW6VY2IxQn+oluC2CGw5oN tblVMiMwmAlIZaCL/GQn9A==; Original-Received: from [87.69.77.57] (port=3752 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 1moJx6-0001oO-VW; Sat, 20 Nov 2021 01:34:21 -0500 In-Reply-To: (message from Stefan Monnier on Fri, 19 Nov 2021 16:09:44 -0500) 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:279784 Archived-At: > From: Stefan Monnier > Cc: larsi@gnus.org, emacs-devel@gnu.org > Date: Fri, 19 Nov 2021 16:09:44 -0500 > > > The display code only assumes the current glyph matrix is up-to-date > > if a set of very conservative tests succeeds. In the other cases, it > > doesn't use the contents of the current glyph matrix. > > So far it indeed doesn't use the old glyph matrix, but that matrix is > still around and (for the lines that preceded the currently processed > text) should still be up-to-date. > So we could conceivably use that. IME, that road is full of pitfalls and mines. The current display code stays away of that for a good reason. > > And if this is not enough, let me remind you that the display engine > > also includes a set of functions that "emulate" redisplay, and those > > cannot use the glyph matrices at all, because they many times are used > > for text that is not displayed at all. > > Yes, we may have to declare that for functions that "emulate" the > redisplay internally, the resulting horizontal position info might not > always be quite right (might not reflect what you'll see on the glass) > for text tat uses the new alignment functionality :-( That will break quite a few features, I'm afraid. Including redisplay cycles themselves, which sometimes use this emulation to decide how to proceed or which buffer position to use as window-start. But also vertical-motion, for example, and stuff that depends on it, like line-move-visual.