[PATCH] ox: Prevent dispatcher from starting in scrolled window

[Kyle Meyer <kyle@kyleam.com>]

Gustavo Barros writes:

> On Tue, Jun 09 2020 at 01:48, Kyle Meyer <kyle@kyleam.com> wrote:
>
>> I've tried to trigger it with your minimal configuration and haven't
>> observed the displacement you describe, even when making my frame 
>> height
>> very small.
>
> I was afraid there might be things in the environment which could affect 
> this (DE? distro? monitor size? Emacs configure options? I don't know), 
> but it does reproduce every single time for me with the recipe I 
> provided.

I've managed to trigger it now.  Your picture gave me the hint that
maybe my "making my frame height very small" wasn't the thing to do.
Plus I should have realized that the default-frame-alist in your minimal
configuration probably isn't going to matter on my end because I use a
tiling window manager.  So here's what I could trigger it:

  (setq scroll-margin 1)  ; or anything > 0
  (setq display-buffer-base-action '(display-buffer-at-bottom))

For reasons I don't really understand, if I make my frame height small
(say half my computer screen) the issue goes away.

Anyway, I'm able to resolve the issues I see with this patch.  Can you
confirm that it fixes things on your end?

-- >8 --
Subject: [PATCH] ox: Prevent dispatcher from starting in scrolled window

* lisp/ox.el (org-export--dispatch-ui): Restore buffer position after
inserting text to avoid auto-scrolling at start.

When filling in the dispatch buffer, point ends up at the end of the
buffer, which can cause the buffer to be re-centered on point when
org-fit-window-to-buffer is called, in particular if scroll-margin is
above zero and there is a vertical split.  Avoid this by putting point
where it was before the buffer was refreshed.

Reported-by: Gustavo Barros <gusbrs.2016@gmail.com>
https://orgmode.org/list/87tv3a56vv.fsf@gmail.com
---
 lisp/ox.el | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/lisp/ox.el b/lisp/ox.el
index 869164737..456dd9bef 100644
--- a/lisp/ox.el
+++ b/lisp/ox.el
@@ -6878,10 +6878,12 @@ (defun org-export--dispatch-ui (options first-key expertp)
       (with-current-buffer "*Org Export Dispatcher*"
 	;; Refresh help.  Maintain display continuity by re-visiting
 	;; previous window position.
-	(let ((pos (window-start)))
+	(let ((pt (point))
+	      (wstart (window-start)))
 	  (erase-buffer)
 	  (insert help)
-	  (set-window-start nil pos)))
+	  (goto-char pt)
+	  (set-window-start nil wstart)))
       (org-fit-window-to-buffer)
       (org-export--dispatch-action
        standard-prompt allowed-keys entries options first-key expertp))))

base-commit: f471768a54d8921ff383516af6a605adc061af30
-- 
2.26.2