Re: Using button-label in pcase

[Stephen Berman]

On Mon, 24 Jul 2023 21:35:44 +0000 uzibalqa <uzibalqa@proton.me> wrote:

> ------- Original Message -------
> On Tuesday, July 25th, 2023 at 8:07 AM, Stephen Berman
> <stephen.berman@gmx.net> wrote:
>
>
>> 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.
>
> That what was wrong then.

That there was no button.  When you execute your command qrh-a and then
in the resulting *Help* buffer press the button, it disappears.

>> 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.
>
> I do not experience the problem you mention.  What error are you referring to,
> and how can it be triggered ?

Did you remove the call the with-help-window in qrh-b and correct the
match condtion (or change the string in qrh-a to match the one in
qrh-b)?  If so, then when you press the button in the *Help* buffer, you
will get the error "Buffer is read-only: #<buffer *Help*>".

Steve Berman