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Re: Set-window-vscroll sometimes doesn't work
From: |
Yuan Fu |
Subject: |
Re: Set-window-vscroll sometimes doesn't work |
Date: |
Mon, 19 Oct 2020 12:56:38 -0400 |
> On Oct 19, 2020, at 12:24 PM, Eli Zaretskii <eliz@gnu.org> wrote:
>
>> From: Yuan Fu <casouri@gmail.com>
>> Date: Mon, 19 Oct 2020 00:59:33 -0400
>> Cc: help-gnu-emacs@gnu.org
>>
>>>> Cool. I’m thinking about wrapping move_it_by_lines in
>>>> window_scroll_pixel_based with a version that regards images (and tall
>>>> lines) as several lines. Do you see some potential problems with that?
>>>
>>> What is the problem with the existing code that you are trying to
>>> solve? Whatever it is, it is highly likely that the solution already
>>> exists, and no new code is needed.
>>
>> The problem I have is that when I scroll over images they jumps in and out
>> of the window: (bad-scrolling.mp4)
>
> AFAICT, you are trying to scroll an image that is smaller than the
> window? That's not supported by the current code, you will need to
> modify the criteria for entering the vscroll mode there.
>
> But in any case, I don't see how move_it_by_lines can have anything to
> do with this: whatever you do, an image must always remain a single
> "display element", and the only way we currently have to scroll
> partial images is via vscroll. Which works, so I don't understand why
> you need any changes in window_scroll_pixel_based.
>
What I came up with is this:
For (scroll-up 1):
1. If the first row is a normal line (i.e., with normal height), scroll up
normally by one display line.
2. If the first row is an image, adjust vscroll +=
frame-default-pixel-line-height
3. If the first row is an image and we have scrolled to the bottom of the
image, i.e., vscroll = image-height, scroll up one display line and set vscroll
to 0.
In other words, sometimes we are not really scrolling, but faking a scroll by
adjusting vscroll. IIUC window_scroll_pixel_based moves it by move_it_by_lines
and set window-start to it. That’s not what we want when we want to fake scroll
by adjusting vscroll: in that case we don’t want to change window-start.
Some questions:
1. Is there a way to get the line-height that an it is on?
2. Where is the code that ensures point is always fully visible? When I move
point around Emacs adjusts scrolling to keep the point fully visible, but I
don’t know who’s doing that work.
Yuan
- Re: Set-window-vscroll sometimes doesn't work, (continued)
- Re: Set-window-vscroll sometimes doesn't work, Yuan Fu, 2020/10/18
- Re: Set-window-vscroll sometimes doesn't work, Eli Zaretskii, 2020/10/18
- Re: Set-window-vscroll sometimes doesn't work, Yuan Fu, 2020/10/18
- Re: Set-window-vscroll sometimes doesn't work, Yuan Fu, 2020/10/18
- Re: Set-window-vscroll sometimes doesn't work, Eli Zaretskii, 2020/10/18
- Re: Set-window-vscroll sometimes doesn't work, Yuan Fu, 2020/10/18
- Re: Set-window-vscroll sometimes doesn't work, Eli Zaretskii, 2020/10/18
- Re: Set-window-vscroll sometimes doesn't work, Yuan Fu, 2020/10/19
- Re: Set-window-vscroll sometimes doesn't work, Yuan Fu, 2020/10/19
- Re: Set-window-vscroll sometimes doesn't work, Eli Zaretskii, 2020/10/19
- Re: Set-window-vscroll sometimes doesn't work,
Yuan Fu <=
- Re: Set-window-vscroll sometimes doesn't work, Eli Zaretskii, 2020/10/19
- Re: Set-window-vscroll sometimes doesn't work, Yuan Fu, 2020/10/19
- Re: Set-window-vscroll sometimes doesn't work, Eli Zaretskii, 2020/10/20
- Re: Set-window-vscroll sometimes doesn't work, Yuan Fu, 2020/10/20
- Re: Set-window-vscroll sometimes doesn't work, Yuan Fu, 2020/10/20
- Re: Set-window-vscroll sometimes doesn't work, Eli Zaretskii, 2020/10/21
- Re: Set-window-vscroll sometimes doesn't work, Yuan Fu, 2020/10/21
- Re: Set-window-vscroll sometimes doesn't work, Yuan Fu, 2020/10/22
- Re: Set-window-vscroll sometimes doesn't work, Eli Zaretskii, 2020/10/22
- Re: Set-window-vscroll sometimes doesn't work, Yuan Fu, 2020/10/22