From: Noam Postavsky <npostavs@gmail.com>
To: Sean McAfee <eefacm@gmail.com>
Cc: 35334@debbugs.gnu.org
Subject: bug#35334: 26.2; Changes to position of point are undone during with-current-buffer if window is visible but not current
Date: Sun, 21 Apr 2019 22:38:41 -0400 [thread overview]
Message-ID: <87lg02sr0u.fsf@gmail.com> (raw)
In-Reply-To: <CANan03aBgC2n7P=NT+msBVGW=5YjUbiS0VMWL01rTG=Vs9yv-A@mail.gmail.com> (Sean McAfee's message of "Sun, 21 Apr 2019 16:32:48 -0700")
Sean McAfee <eefacm@gmail.com> writes:
> Starting with two windows visible, the scratch buffer and a window showing
> empty buffer "a", I evaluate this expression in the scratch buffer:
>
> (start-process "count" "a" "bash" "-c" "for i in {1..10}; echo $i; sleep 1; done")
[missing a "do" before the "echo $i", by the way]
> I see the numbers 1-10 inserted into buffer "a", one second apart, as
> expected. The position of point in buffer "a" follows the new lines as
> they're inserted.
>
> Now I define the function ordinary-insertion-filter, as found on this page:
>
> https://www.gnu.org/software/emacs/manual/html_node/elisp/Filter-Functions.html
>
> That function is described as "mimicking the actions of the default
> filter." However, if I erase buffer "a" and evaluate this expression in
> the scratch buffer:
>
> (let ((proc (start-process "count" "a" "bash" "-c" "for i in {1..10}; echo $i; sleep 1; done")))
> (set-process-filter proc #'ordinary-insertion-filter))
>
> ...then I see the numbers inserted as before, but now the position of point
> in buffer "a" doesn't move
Okay, interesting. The difference seems to be that
`internal-default-process-filter' actually uses `insert-before-markers'
rather than plain `insert'. I guess the window point is implemented as
a marker, so inserting this way happens to move it as well.
(defun ordinary-insertion-filter (proc string)
(when (buffer-live-p (process-buffer proc))
(with-current-buffer (process-buffer proc)
(let ((moving (= (point) (process-mark proc))))
(save-excursion
;; Insert the text, advancing the process marker.
(goto-char (process-mark proc))
(insert-before-markers string) ; <------------ change here
(set-marker (process-mark proc) (point)))
(if moving (goto-char (process-mark proc)))))))
next prev parent reply other threads:[~2019-04-22 2:38 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-20 4:00 bug#35334: 26.2; Changes to position of point are undone during with-current-buffer if window is visible but not current Sean McAfee
2019-04-20 4:10 ` Noam Postavsky
2019-04-21 23:32 ` Sean McAfee
2019-04-22 2:38 ` Noam Postavsky [this message]
2019-04-22 7:22 ` Eli Zaretskii
2019-04-27 21:05 ` Sean McAfee
2019-04-28 2:19 ` Noam Postavsky
2019-04-30 21:58 ` Sean McAfee
2019-05-01 0:55 ` Noam Postavsky
2019-04-27 21:07 ` Noam Postavsky
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