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From: Stephen Berman <stephen.berman@gmx.net>
To: uzibalqa <uzibalqa@proton.me>
Cc: uzibalqa via Users list for the GNU Emacs text editor
	<help-gnu-emacs@gnu.org>
Subject: Re: Using button-label in pcase
Date: Mon, 24 Jul 2023 22:07:11 +0200	[thread overview]
Message-ID: <87pm4hvztc.fsf@gmx.net> (raw)
In-Reply-To: <HpLE9qFeEkx9mnVyoJ60t6o5jYhs8A37d0mnqg-UkeryefTBuCZSxhE2Vm8ATdPAw9zAANGl7GBY1SN6F32ILzGscuHELwWiF6FDmn53EyY=@proton.me> (uzibalqa@proton.me's message of "Mon, 24 Jul 2023 19:14:27 +0000")

On Mon, 24 Jul 2023 19:14:27 +0000 uzibalqa <uzibalqa@proton.me> wrote:

> Want to print some text as a result of clicking a button.  With the code below
> I end up with
>
> (wrong-type-argument integer-or-marker-p nil)
>   buffer-substring-no-properties(nil nil)
>   button-label(#<overlay in no buffer>)
>   (let* ((val (button-label button))) (if (equal val '"[FA]") (let nil (insert qrh-c))))
>   (closure ((button . #<overlay in no buffer>)) nil (let* ((val (button-label button))) (if (equal val '"[FA]") (let nil (insert qrh-c)))))()
>   help--window-setup("*Help*" (closure ((button . #<overlay in no buffer>)) nil (let* ((val (button-label button))) (if (equal val '"[FA]") (let nil (insert qrh-c))))))
>   qrh-b(#<overlay in no buffer>)
>   button-activate(#<overlay in no buffer> t)
>   push-button(3 t)
>
> What is going on.  Is there a fix?
>
> (defconst qrh-c "[FA] Some Text")
>
> (defun qrh-b (button)
>   "Prints information about how to install emacs."
>   (with-help-window (help-buffer)
>     (pcase (button-label button)
>       ("[FA]" (insert qrh-c))) ))
>
> (defun qrh-a ()
>   "Prints information about how to install emacs."
>   (interactive)
>   (with-help-window (help-buffer)
>     (insert-button "[FC]"
>       'action 'qrh-b 'follow-link t) ))

The error is raised because qrh-b calls with-help-window with the *Help*
buffer current, but with-help-window erases the buffer, so when
`(button-label button)' is evaluated, there is no button and this
signals the error.

If you want to use the existing *Help* buffer, just remove the call to
with-help-window in qrh-b.  However, *Help* buffers are read-only, so
trying to insert text will raise another error.  To avoid this, you can
let-bind buffer-read-only in qrh-b.  However, since qrh-a inserts "[FC]"
but qrh-b tries to match "[FA]", the match will fail, so the insertion
in qrh-b will not happen.

Steve Berman



  reply	other threads:[~2023-07-24 20:07 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-07-24 19:14 Using button-label in pcase uzibalqa
2023-07-24 20:07 ` Stephen Berman [this message]
2023-07-24 21:35   ` uzibalqa
2023-07-24 21:51     ` Stephen Berman
2023-07-24 22:24       ` uzibalqa
2023-07-24 22:36         ` Stephen Berman
2023-07-24 22:40           ` uzibalqa
2023-07-24 22:53             ` Stephen Berman
2023-07-24 23:40               ` uzibalqa

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