Re: Using button-label in pcase

[Stephen Berman]

On Mon, 24 Jul 2023 22:24:33 +0000 uzibalqa <uzibalqa@proton.me> wrote:

> ------- Original Message -------
> On Tuesday, July 25th, 2023 at 9:51 AM, Stephen Berman
> <stephen.berman@gmx.net> wrote:
>
>
>> 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
>
> I did the changes and have the following
>
>   (pcase (button-label button)
>     ("[FA]"
>        (with-help-window (help-buffer)  ; Print in help buffer
>          (insert qrh-c)))

Sure, that's a fine way to avoid the problem with the read-only state of
the *Help* buffer.

Steve Berman