GNU bug report logs - #75171
30.0.50; Checklist widget inside a group does not initialize correctly

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Message #17 received at 75171 <at> debbugs.gnu.org (full text, mbox):

From: Mauro Aranda <maurooaranda <at> gmail.com>
To: Al Haji-Ali <abdo.haji.ali <at> gmail.com>, 75171 <at> debbugs.gnu.org
Subject: Re: bug#75171: 30.0.50; Checklist widget inside a group does not
 initialize correctly
Date: Fri, 3 Jan 2025 10:05:26 -0300

Al Haji-Ali <abdo.haji.ali <at> gmail.com> writes:

> On 02/01/2025, Mauro Aranda wrote:
>
>> Al Haji-Ali <abdo.haji.ali <at> gmail.com> writes:
>> There's no explicit :value for the group widget, so its value is nil,
>> and then the Widget library tries to create all four children with a nil
>> value.  The radio-button-choice widget differs from the checklist widget
>> in that the former tries to be created with a selected choice, and tries
>> harder than the checklist widget, which is fine with a value of nil.
>>
>> That way, you see that the specified value is obeyed in
>> radio-button-choice but not in the checklist widget.
>>
>> FTR, I'm not saying this is 100% correct.  I'm just trying to explain
>> how it works now.
>
> Thanks, this makes sense. Did I miss an explanation of this issue
> somewhere in the docs?

I don't think so.  The manual is still missing good explanations.

>> This is intended behavior, AFAIU.  The parent can override values for
>> the children, and that way we can recreate widgets with new values just
>> by changing the values of the parent.
>
> I was aware of this behaviour for the group, but I didn't twig the
> consequence on a checklist.
>
> I have to say that I find it a bit counter-intuitive. Also the fact
> that there is no way to set the value of a checklist without repeating
> it in the group is somewhat awkward (certainly it will complicate my
> implementation)

Note that you don't necessarily need to repeat it in the checklist
widget.  In my example, you only need to pass the :value in group:

(defun widget-test ()
  (let ((items '((item :format "%[One%] " :value 1)
                 (item :format "%[Two%] " :value 2)
                 (item :format "%[Three%] " :value 3))))
    (widget-create
     'group
     :value '(2 (1 2))
     (append '(radio-button-choice
               :format "Not inline radio:\n%v\n")
             items)
     (append '(checklist
               :format "Not inline checks:\n%v\n")
             items)))
  (widget-setup))

When created, radio-button-choice will get its :value set to 2 and
checklist will get it set to (1 2).

> and a bit inconsistent since setting the value of the
> checklist after the group creation would override the value of the
> group. A fix, or a some way, that would prevents the group from
> overriding the values of the children would be useful, IMO.

> With that being said, this issue should probably be closed as "not a 
bug".

I'd like to take some time to study this and see if there's a way to
improve the situation.

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