Re: Using button-label in pcase

[uzibalqa <uzibalqa@proton.me>]

------- Original Message -------
On Tuesday, July 25th, 2023 at 10:36 AM, Stephen Berman <stephen.berman@gmx.net> wrote:


> 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

I replicated the error you mentioned though.  Why does it happen ?  Is that because
the insert would be within an (with-help-window (help-buffer) ?