From: Eli Zaretskii <eliz@gnu.org>
To: help-gnu-emacs@gnu.org
Subject: Re: Set-window-vscroll sometimes doesn't work
Date: Sun, 18 Oct 2020 17:34:21 +0300 [thread overview]
Message-ID: <83eelvsivm.fsf@gnu.org> (raw)
In-Reply-To: <72B62847-3F35-412A-9F74-88442A936B19@gmail.com> (message from Yuan Fu on Sat, 17 Oct 2020 20:35:00 -0400)
> From: Yuan Fu <casouri@gmail.com>
> Date: Sat, 17 Oct 2020 20:35:00 -0400
>
> Normally if you scroll back onto an image, the image appears completely. I want to instead only show part of the image, like what pixel scrolling would do. If everything works as expected I should only see the bottom of the image, instead I see the whole image.
>
> It seems to be because (set-window-vscroll nil (- img-height (frame-char-height)) t) didn’t take effect, if you call that again with M-: or wrap it in (run-with-timer), then it works as expected.
>
> Is this caused by some redisplay optimization or something?
No. The problem is in your code. First, you use set-window-start and
scroll-down, both of which tramp window-vscroll (as you probably
realize if you think about what those do). And after all that, you
need one "normal" redisplay cycle before you can set the vscroll, so,
for example, a single change below should make the code work as you
expect.
(progn
(switch-to-buffer (get-buffer-create "test"))
(erase-buffer)
(insert "\n\n")
(insert-image (create-image "abby road.jpeg" nil nil :scale 0.1)
"x")
(insert "\n")
(let ((after-img (point)))
(set-window-start nil (point))
(scroll-down 1)
(sit-for 0) ;; <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
(let* ((img (plist-get (text-properties-at (window-start)) 'display))
(img-height (cdr (image-size img t))))
(set-window-vscroll nil (- img-height (frame-char-height)) t))))
next prev parent reply other threads:[~2020-10-18 14:34 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 [this message]
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
2020-10-27 18:32 ` Eli Zaretskii
2020-10-22 16:05 ` Eli Zaretskii
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