editable-list widgets: how to create one child automatically

editable-list widgets: how to create one child automatically

[Michael Heerdegen]

Hello,

and sorry to Mauro, I CC'd you directly because I know you are a widget
expert, and there are only few of them.

I often want an editable-list widget to be created along with one child
instead of none.  Zero childs often has no useful meaning in the context
of the widget, and starting with one child already created when the
editable-list widget gets inserted is often is good choice and nicer to
the user.

Is there some tool designed for this purpose I have missed?  So far the
only way I know of is to specify a widget property

#+begin_src emacs-lisp
  :value-create
  (lambda (w)
    (unless (widget-get w :value)
      (widget-put w :value (list my-first-default)))
    (widget-editable-list-value-create w))
#+end_src

Is there a better way?

TIA,

Michael.

Re: editable-list widgets: how to create one child automatically

[Mauro Aranda]

On 13/3/24 04:23, Michael Heerdegen wrote:
 > Hello,
 >
 > and sorry to Mauro, I CC'd you directly because I know you are a widget
 > expert, and there are only few of them.

Hi Michael.  I appreciate you CCing me, so no need to feel sorry.

 > Is there some tool designed for this purpose I have missed?  So far the
 > only way I know of is to specify a widget property
 >
 > #+begin_src emacs-lisp
 >   :value-create
 >   (lambda (w)
 >     (unless (widget-get w :value)
 >       (widget-put w :value (list my-first-default)))
 >     (widget-editable-list-value-create w))
 > #+end_src
 >
 > Is there a better way?
 >

You should be able to specify the :value property directly, rather than
overriding :value-create.  Something like:

(widget-create 'editable-list
                :value (list my-first-default)
                ;; Change according to the child type.
                '(editable-field))

Does that not do what you want?

Re: editable-list widgets: how to create one child automatically

[Michael Heerdegen via Users list for the GNU Emacs text editor]

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Mauro Aranda <maurooaranda@gmail.com> writes:

> (widget-create 'editable-list
>                :value (list my-first-default)
>                ;; Change according to the child type.
>                '(editable-field))
>
> Does that not do what you want?

I think I can't use this: I don't create an ad-hoc widget, I need an
`define-widget' expression to define the widget to behave accordingly
when created.

And the widget this is about is a part of a group widget definition so
there will never be an explicit `widget-create' call by me, the widget
will always be created implicitly by the parent.

And in this definition a :value spec is more or less ignored - in my
tests that child widget will always be created with a nil widget value.

I am attaching the code in question so that you don't have to guess -
you can find the relevant part by searching for the comment

  ;; Is there a better approach, Mauro?

or simply just your name.


Thanks so far,

Michael.


[-- Attachment #2: find-cmd-widget.el.zip --]
[-- Type: application/zip, Size: 12562 bytes --]

Re: editable-list widgets: how to create one child automatically

[Mauro Aranda]

On 13/3/24 22:58, Michael Heerdegen via Users list for the GNU Emacs 
text editor wrote:
 > Mauro Aranda <maurooaranda@gmail.com> writes:
 >
 >> (widget-create 'editable-list
 >>                 :value (list my-first-default)
 >>                 ;; Change according to the child type.
 >>                 '(editable-field))
 >>
 >> Does that not do what you want?
 >
 > I think I can't use this: I don't create an ad-hoc widget, I need an
 > `define-widget' expression to define the widget to behave accordingly
 > when created.

OK, but still the :value should be respected when given inside a
define-widget.

 > And the widget this is about is a part of a group widget definition so
 > there will never be an explicit `widget-create' call by me, the widget
 > will always be created implicitly by the parent.
 >
 > And in this definition a :value spec is more or less ignored - in my
 > tests that child widget will always be created with a nil widget value.

This shouldn't happen.  But what I think is happening is that when
you're creating the find widget, I guess when funcalling this:

(defvar find-cmd-widget-default-start-fun
   (lambda ()
     (setq-local find-cmd-widget-main-widget (widget-create 'find))))

The find widget gets created with a nil value, which, when trying to
match against its children values, won't match when the editable-list
has a different value, like (list default-directory)

Because of that, the code understands that it should override the :value
property of the editable-list to a nil value, hence the empty
editable-list.

So I think a better way is to provide a matching value for the find
widget that will allow it to create its children with their default
values.

Re: editable-list widgets: how to create one child automatically

[Michael Heerdegen via Users list for the GNU Emacs text editor]

Mauro Aranda <maurooaranda@gmail.com> writes:

> So I think a better way is to provide a matching value for the find
> widget that will allow it to create its children with their default
> values.

Thank you very much.  I think your analysis is correct.

But this approach sounds inconvenient: I would have to maintain default
values of inner widgets in separate code locations (right?), and I would
also have to remember that I need to update the structure of the default
value of the "big" widget to be in sync with the structure of the widget
definition, should I once change it.

So, that the outer widget forces a value that I did not even specify
explicitly does not seem so useful to me.

Michael.