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From: Yuan Fu <casouri@gmail.com>
To: Eli Zaretskii <eliz@gnu.org>
Cc: help-gnu-emacs <help-gnu-emacs@gnu.org>
Subject: Re: Set-window-vscroll sometimes doesn't work
Date: Tue, 27 Oct 2020 14:10:58 -0400	[thread overview]
Message-ID: <E02DEA0D-9756-4DAB-A67A-E0FD4305CE32@gmail.com> (raw)
In-Reply-To: <838sbwhz3k.fsf@gnu.org>



> On Oct 24, 2020, at 3:17 AM, Eli Zaretskii <eliz@gnu.org> wrote:
> 
>> From: Yuan Fu <casouri@gmail.com>
>> Date: Fri, 23 Oct 2020 16:30:40 -0400
>> Cc: help-gnu-emacs@gnu.org
>> 
>> I really need to set them in the same time because when I scroll down, and stopped at a tall image (or tall line), I don’t want to scroll to the top of that image immediately. Instead, I want to scroll just enough to show the bottom of it. This requires setting window-start to that image and set vscroll = image height - line height.
> 
> This makes no sense to me, because you want to deliberately deny the
> user from showing the entire screen line or its important parts.  

Only when the line is a tall image, which will break smooth scrolling if I try to show it completely. Instead, I want to reveal the image a bit at a time, so there is no surprise when scrolling through them. If the user wants to see the entire line they can press C-l.

> The
> bottom of a large image will generally not show anything important,
> and most of the screen line with the surrounding text could remain
> undisplayed.  Why is that a good idea? just because some other editor
> behaves like that?
> 

This is not about other editors, really. The main motivation is that with the current behavior, if I have images and text in the same buffer and I scroll down/up, the display jumps up and down and I get lost: I kind of lost track of where I am in the buffer. The desired behavior is, of course, a stable, smooth, unsurprised scrolling.

Maybe you (and many) scroll by half-screen, but I bet a large chunk of people using Emacs scrolls by 1 line, and expects a smooth scrolling behavior.


>> So maybe setting both window-start and vscroll should be considered as a valid thing to do?
> 
> You can still do that as I've shown before, by inserting (sit-for 0)
> in the middle, right?  But I urge you not to do that because it makes
> no sense when text is mixed with images.
> 

Will that make sense if the image is on a line by itself (which is often the case)? Inserting (sit-for 0) gives me flickers, Emacs will show the full image for like 0.1 second and scroll to the desired vscroll.

> This is a misunderstanding: I have nothing against making image
> scrolling more smooth.  The disagreement between us is not about the
> user-facing feature, it is about low-level details of the
> implementation, and how the display engine interprets certain flags.
> (Actually, such a discussion should be held on emacs-devel or the
> issue tracker, not here, precisely because it might confuse people who
> dwell here.)

How should I move the discussion to emacs-devel? Should I post a new thread and explain the disagreement/confusion?

I think it does make sense for window-start and vscroll to work together, and the implementation of redisplay seems to suggest that. Could you explain how is inserting sit-for makes sense but setting both flags at the same time doesn’t?

Yuan




  parent reply	other threads:[~2020-10-27 18:10 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-18  0:35 Set-window-vscroll sometimes doesn't work Yuan Fu
2020-10-18 14:34 ` Eli Zaretskii
2020-10-18 17:24   ` Yuan Fu
2020-10-18 17:31     ` Eli Zaretskii
2020-10-18 17:51       ` Yuan Fu
2020-10-18 17:55         ` Eli Zaretskii
2020-10-18 18:02           ` Yuan Fu
2020-10-18 19:12           ` Yuan Fu
2020-10-18 19:19             ` Eli Zaretskii
2020-10-18 20:06               ` Yuan Fu
2020-10-19  2:23                 ` Eli Zaretskii
     [not found]                   ` <B1D235FE-49B8-4F0A-9C02-78B7E3244C47@gmail.com>
2020-10-19  6:00                     ` Yuan Fu
2020-10-19 16:24                     ` Eli Zaretskii
2020-10-19 16:56                       ` Yuan Fu
2020-10-19 17:23                         ` Eli Zaretskii
2020-10-19 20:39                           ` Yuan Fu
2020-10-20 16:04                             ` Eli Zaretskii
2020-10-20 18:00                               ` Yuan Fu
2020-10-20 18:19                               ` Yuan Fu
2020-10-21 16:25                                 ` Eli Zaretskii
2020-10-21 19:05                                   ` Yuan Fu
2020-10-22  4:16                                     ` Yuan Fu
2020-10-22 16:08                                       ` Eli Zaretskii
2020-10-22 16:50                                         ` Yuan Fu
2020-10-22 17:09                                           ` Eli Zaretskii
2020-10-22 19:33                                             ` Yuan Fu
2020-10-23  6:05                                               ` Eli Zaretskii
2020-10-23 16:48                                                 ` Yuan Fu
2020-10-23 18:11                                                   ` Eli Zaretskii
2020-10-23 20:30                                                     ` Yuan Fu
2020-10-24  7:17                                                       ` Eli Zaretskii
2020-10-26  8:38                                                         ` Jens C. Jensen
2020-10-26 15:18                                                           ` Eli Zaretskii
2020-10-27 18:10                                                         ` Yuan Fu [this message]
2020-10-27 18:32                                                           ` Eli Zaretskii
2020-10-22 16:05                                     ` Eli Zaretskii

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