From: <tomas@tuxteam.de>
To: help-gnu-emacs@gnu.org
Subject: Re: custom function getting initialized randomly
Date: Mon, 27 Mar 2023 17:20:22 +0200 [thread overview]
Message-ID: <ZCG0Nuyi6U5PcpAV@tuxteam.de> (raw)
In-Reply-To: <CAPM58ohQQbNgyPBRy1V6cqsAwqNaq0+LP=c9k1HumAfaoJbeqQ@mail.gmail.com>
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On Mon, Mar 27, 2023 at 02:56:01PM +0100, Richard Copley wrote:
> On Mon, 27 Mar 2023 at 10:21, Michael Maurer <maurer.michael@gmail.com> wrote:
> >
> > Hello,
> >
> > I wrote the following function to copy the kill-ring to the scratch
> > buffer, but it only gets initialized sometimes at the start of emacs,
> > sometimes not. Why?
> >
> > (defun copy-to-scratch-on-kill
> > ()
> > "Copy every kill (delete or yank) to *scratch* buffer."
> > (let
> > ((cur-kill-string
> > (current-kill 0 t)))
> > (when
> > (and
> > (not
> > (equal cur-kill-string ""))
> > (not
> > (equal cur-kill-string prev-kill-string))
> > (get-buffer "*scratch*"))
> > (with-current-buffer "*scratch*"
> > (goto-char
> > (point-max))
> > (insert cur-kill-string "\n")
> > (goto-char
> > (point-max))))
> > (setq prev-kill-string cur-kill-string)))
> >
> > (add-hook 'post-command-hook #'copy-to-scratch-on-kill)
> >
>
> If an error propagates from the hook function (most likely "Kill ring
> is empty", signalled by `current-kill`) then Emacs removes the
> function from the hook. See the docstring for variable
> `post-command-hook`.
There's more: where does the variable `prev-kill-string' come from?
- if nobody has set it previously, this will be the error
killing your hook (this is my hunch)
- if somebody has, you are lucky if that somebody was you
(otherwise you are into an entertaining debugging session
If you are using a global variable like that, it makes sense
to declare, document and perhaps initialize it with `defvar'
Another possibility would be to hide it away in a closure [1]
(you are using lexical binding, aren't you?). Just ask around
here if the concept is unfamiliar to you.
Cheers
--
t
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next prev parent reply other threads:[~2023-03-27 15:20 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-27 8:22 custom function getting initialized randomly Michael Maurer
2023-03-27 13:56 ` Richard Copley
2023-03-27 14:56 ` Michael Maurer
2023-03-27 15:06 ` Richard Copley
2023-03-27 15:20 ` tomas [this message]
2023-03-27 15:30 ` Michael Maurer
2023-03-27 15:52 ` tomas
-- strict thread matches above, loose matches on Subject: below --
2023-03-27 8:29 Michael Maurer
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