From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Alan Mackenzie Newsgroups: gmane.emacs.bugs Subject: bug#32863: Unsatisfactory "definition" of "vertical scroll position" in Emacs lisp manual and doc string of window-vscroll Date: Mon, 15 Oct 2018 18:33:01 +0000 Message-ID: <20181015183301.GD5623@ACM> References: <20180928152832.GA5172@ACM> <837ej5710d.fsf@gnu.org> <20181015114803.GB5623@ACM> <83y3azrzt6.fsf@gnu.org> NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: blaine.gmane.org 1539628750 13827 195.159.176.226 (15 Oct 2018 18:39:10 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Mon, 15 Oct 2018 18:39:10 +0000 (UTC) User-Agent: Mutt/1.10.1 (2018-07-13) Cc: 32863@debbugs.gnu.org To: Eli Zaretskii Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane.org@gnu.org Mon Oct 15 20:39:06 2018 Return-path: Envelope-to: geb-bug-gnu-emacs@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1gC7lh-0003TO-3f for geb-bug-gnu-emacs@m.gmane.org; Mon, 15 Oct 2018 20:39:05 +0200 Original-Received: from localhost ([::1]:54076 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gC7nn-0007aa-QO for geb-bug-gnu-emacs@m.gmane.org; Mon, 15 Oct 2018 14:41:15 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:44865) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gC7nf-0007aQ-Gv for bug-gnu-emacs@gnu.org; Mon, 15 Oct 2018 14:41:08 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gC7nb-00056J-QJ for bug-gnu-emacs@gnu.org; Mon, 15 Oct 2018 14:41:07 -0400 Original-Received: from debbugs.gnu.org ([208.118.235.43]:47153) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1gC7nZ-00055k-VM for bug-gnu-emacs@gnu.org; Mon, 15 Oct 2018 14:41:02 -0400 Original-Received: from Debian-debbugs by debbugs.gnu.org with local (Exim 4.84_2) (envelope-from ) id 1gC7nZ-0000PH-Le for bug-gnu-emacs@gnu.org; Mon, 15 Oct 2018 14:41:01 -0400 X-Loop: help-debbugs@gnu.org Resent-From: Alan Mackenzie Original-Sender: "Debbugs-submit" Resent-CC: bug-gnu-emacs@gnu.org Resent-Date: Mon, 15 Oct 2018 18:41:01 +0000 Resent-Message-ID: Resent-Sender: help-debbugs@gnu.org X-GNU-PR-Message: followup 32863 X-GNU-PR-Package: emacs X-GNU-PR-Keywords: Original-Received: via spool by 32863-submit@debbugs.gnu.org id=B32863.15396288481537 (code B ref 32863); Mon, 15 Oct 2018 18:41:01 +0000 Original-Received: (at 32863) by debbugs.gnu.org; 15 Oct 2018 18:40:48 +0000 Original-Received: from localhost ([127.0.0.1]:51411 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1gC7nM-0000Oj-7W for submit@debbugs.gnu.org; Mon, 15 Oct 2018 14:40:48 -0400 Original-Received: from colin.muc.de ([193.149.48.1]:16303 helo=mail.muc.de) by debbugs.gnu.org with smtp (Exim 4.84_2) (envelope-from ) id 1gC7nK-0000Oa-KM for 32863@debbugs.gnu.org; Mon, 15 Oct 2018 14:40:47 -0400 Original-Received: (qmail 49514 invoked by uid 3782); 15 Oct 2018 18:40:44 -0000 Original-Received: from acm.muc.de (p5B14745F.dip0.t-ipconnect.de [91.20.116.95]) by colin.muc.de (tmda-ofmipd) with ESMTP; Mon, 15 Oct 2018 20:40:43 +0200 Original-Received: (qmail 28776 invoked by uid 1000); 15 Oct 2018 18:33:01 -0000 Content-Disposition: inline In-Reply-To: <83y3azrzt6.fsf@gnu.org> X-Delivery-Agent: TMDA/1.1.12 (Macallan) X-Primary-Address: acm@muc.de X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 208.118.235.43 X-BeenThere: bug-gnu-emacs@gnu.org List-Id: "Bug reports for GNU Emacs, the Swiss army knife of text editors" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane.org@gnu.org Original-Sender: "bug-gnu-emacs" Xref: news.gmane.org gmane.emacs.bugs:151281 Archived-At: Hello, Eli. Thanks for such a rapid review! On Mon, Oct 15, 2018 at 18:32:05 +0300, Eli Zaretskii wrote: > > Date: Mon, 15 Oct 2018 11:48:03 +0000 > > Cc: 32863@debbugs.gnu.org > > From: Alan Mackenzie > > I propose to amend windows.texi, and two doc strings in windows.c in the > > emacs-26 branch as follows. I think that these amendments would have > > prevented my initial puzzlement. Any comments? > The changes to doc strings are fine (but please use "display" instead > of "redisplay", as the latter is a technical term not necessarily > accurate in this context). Done. > As for the changes to windows.texi, I admit that I don't really > understand how such insignificant changes could prevent your > puzzlement. Are you sure it isn't the result of reading my > explanations, which caused the text to "talk" to you more clearly? I've thought of that, and been as careful as I can be to reconstruct my mental state at the time I raised the bug. I think my emphasis on "when displaying it" is sufficient to establish a context for understanding. > > @dfn{Vertical fractional scrolling} means shifting text in a window > > -up or down by a specified multiple or fraction of a line. Each window > > +up or down by a specified multiple or fraction of a line. Emacs uses it > > +on images and text rows which are taller than the window. Each window > Here you added a sentence that tells when is this feature used. (Btw, > nothing prevents Emacs from using it even with lines that are not > taller than the window, and it even does so sometimes. So this is > just an example, and I'd suggest to say that. Also, please don't use > "rows" in the manual: that is the terminology of xdisp.c, but Lisp > programmers are unfamiliar with it. I prefer to use "screen lines".) Done (both). > > has a @dfn{vertical scroll position}, which is a number, never less than > > -zero. It specifies how far to raise the contents of the window. > > -Raising the window contents generally makes all or part of some lines > > -disappear off the top, and all or part of some other lines appear at the > > -bottom. The usual value is zero. > > +zero. It specifies how far to raise the contents of the window when > > +redisplaying it. Raising the window contents generally makes all or > > +part of some lines disappear off the top, and all or part of some other > > +lines appear at the bottom. The usual value is zero. > Here you just added "when redisplaying it". If this is such a > crucially important detail, I'm all for it (but again, please say > "displaying"). However, I wonder whether it really is all that > stood between you and the eureka. I believe it is. > > The vertical scroll position is measured in units of the normal line > > height, which is the height of the default font. Thus, if the value is > > -.5, that means the window contents are scrolled up half the normal line > > -height. If it is 3.3, that means the window contents are scrolled up > > -somewhat over three times the normal line height. > > +.5, that means the window contents will be scrolled up half the normal > > +line height. If it is 3.3, that means the window contents are scrolled > > +up somewhat over three times the normal line height. > And here, you just replaced "are scrolled" with "will be scrolled" > (only once out of 2 instances). Again, one wonders whether this is > all that you missed to see the light. This attempts to fix a fundamental ambiguity in the use of the words "is" and "are" with a past participle. For example, compare these two sentences: 1. Emacs 26.1 is released. 2. Emacs is released every few months. In the first, "is released" refers to a one-time event in the past. In the second, it refers to a habitual action, still happening. That same ambiguity with "are" in "...means the window contents are scrolled up" confused me. The "will be" helps eliminate the interpretation "have ALREADY been scrolled up", the 1. above. > I'm not saying I object to these changes -- I don't -- but I'm a bit > surprised that such minor changes could have such a profound effect on > clarity. When I first read the page I was totally lacking in context. I think I've added enough context to have helped me, were I coming to it again for the first time. OK, amended (final?) version: diff --git a/doc/lispref/windows.texi b/doc/lispref/windows.texi index 265067146d..960573d865 100644 --- a/doc/lispref/windows.texi +++ b/doc/lispref/windows.texi @@ -4200,18 +4200,20 @@ Vertical Scrolling @cindex vertical scroll position @dfn{Vertical fractional scrolling} means shifting text in a window -up or down by a specified multiple or fraction of a line. Each window -has a @dfn{vertical scroll position}, which is a number, never less than -zero. It specifies how far to raise the contents of the window. -Raising the window contents generally makes all or part of some lines -disappear off the top, and all or part of some other lines appear at the -bottom. The usual value is zero. +up or down by a specified multiple or fraction of a line. Emacs uses +it, for example, on images and screen lines which are taller than the +window. Each window has a @dfn{vertical scroll position}, which is a +number, never less than zero. It specifies how far to raise the +contents of the window when displaying them. Raising the window +contents generally makes all or part of some lines disappear off the +top, and all or part of some other lines appear at the bottom. The +usual value is zero. The vertical scroll position is measured in units of the normal line height, which is the height of the default font. Thus, if the value is -.5, that means the window contents are scrolled up half the normal line -height. If it is 3.3, that means the window contents are scrolled up -somewhat over three times the normal line height. +.5, that means the window contents will be scrolled up half the normal +line height. If it is 3.3, that means the window contents are scrolled +up somewhat over three times the normal line height. What fraction of a line the vertical scrolling covers, or how many lines, depends on what the lines contain. A value of .5 could scroll a > Thanks. -- Alan Mackenzie (Nuremberg, Germany).