--- Begin Message ---
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Subject: |
23.1.50; before-string overlay and show-paren-mode |
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Date: |
Mon, 02 Nov 2009 15:49:55 +0100 |
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User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/23.1.50 (gnu/linux) |
Start Emacs with -Q, insert the following text into a buffer:
begin
(test)
end
then eval the following:
(defun my-test ()
""
(interactive)
(widen)
(goto-char (point-min))
(let ((begin (search-forward "begin")))
(search-forward "end")
(narrow-to-region (1+ begin) (line-beginning-position))
(goto-char (point-min)))
(unless (let ((ovlist (overlays-in (1- (point)) (1+ (point)))))
(when ovlist (overlay-get (car ovlist) 'before-string)))
(let ((ov (make-overlay (point) (point) nil t t)))
(overlay-put ov 'before-string "* "))))
(global-set-key "\C-cy" 'my-test)
and now type `C-c y' in the buffer with the inserted text. The buffer
nows displays this:
* (test)
As expected, now repeating `C-c y' does not alter the display, i.e. does
not add more overlays. Now enable show-paren-mode (e.g. by checking
"Paren Match Highlighting" in the Options menu). Now repeating `C-c y'
display one additional "* " for each repetition (provided point remains
on `('). Surprisingly, however, typing `M-x my-test' repeatedly does
not add any "* ". In addition, typing a self-inserting character and
then deleting it has the effect that typing `C-c y' no longer adds "* ";
except after widening and removing the overlays: then repeating `C-c y'
adds "* " once only, as when show-paren-mode is disabled.
If the described behavior after enabling show-paren-mode is not a bug,
can anyone explain it?
In GNU Emacs 23.1.50.1 (i686-pc-linux-gnu, GTK+ Version 2.14.4)
of 2009-10-27 on escher
Windowing system distributor `The X.Org Foundation', version 11.0.10502000
Important settings:
value of $LC_ALL: nil
value of $LC_COLLATE: nil
value of $LC_CTYPE: nil
value of $LC_MESSAGES: nil
value of $LC_MONETARY: nil
value of $LC_NUMERIC: nil
value of $LC_TIME: nil
value of $LANG: en_US.UTF-8
value of $XMODIFIERS: @im=local
locale-coding-system: utf-8-unix
default enable-multibyte-characters: t
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--- Begin Message ---
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Subject: |
Re: bug#4854: 23.1.50; before-string overlay and show-paren-mode |
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Date: |
Mon, 04 Jul 2016 00:23:18 +0200 |
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User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/25.1.50 (gnu/linux) |
On Sun, 03 Jul 2016 11:58:16 -0400 address@hidden wrote:
> Eli Zaretskii <address@hidden> writes:
>
>>> From: address@hidden
>>> Date: Sun, 03 Jul 2016 11:36:01 -0400
>>> Cc: address@hidden
>>>
>>> Well, it's possible to avoid moving overlays to minibuffer, but then
>>> show-paren-mode stops working in the minibuffer, which I don't think is
>>> so great.
>>
>> To say the least. Please don't, I edit expressions in the minibuffer
>> quite a lot, and find show-paren invaluable in general and there in
>> particular.
>
> Don't worry, I wasn't intending to. That patch was just for
> demonstration.
I completely agree that preventing show-paren-mode from working in the
minibuffer is out of the question.
> I suppose it might be possible to have paren overlay
> per-buffer, so that the overlay doesn't disappear and reappear all the
> time, but I don't think it's worth the complication. I'm pretty sure it
> would remain possible to write a command that's able to observe some
> inconsistencies regardless: since show-paren-mode relies on idle-timers,
> the behaviour is affected by the timing of the user's keystrokes.
It's probably not worth putting much effort into trying to change it,
though I still think it's surprising, and not unlikely an unintended
consequence of the implementation of show-paren-mode, that the effect of
invoking a command that interacts with it differs depending on how it's
invoked (self-insert-command is really a special case, I think).
> It's
> best to write commands that are oblivious to what show-paren-mode does
> (e.g., the (cl-some ...) condition I posted in that same message).
This is certainly sound advice, and indeed I applied it long ago in
dealing with the issue (in todo-mode.el) that prompted this bug report.
Again, thanks for the feedback and clarifying the issue. I'm closing
this bug now.
Steve Berman
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