Re: Using button-label in pcase

[uzibalqa <uzibalqa@proton.me>]

------- 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.
 
> 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 ?

> 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

That was an error from my part.