Re: Community improvements to the Emacs Widget Library manual?

[bovine]

On 2023-07-14 10:41, Mauro Aranda wrote:
> Bryce Carson <bovine@cyberscientist.ca> writes:
>
> > Further, I can't seem to get these functions to work as documented or
> > expected.
> >
> > Without these defined when I'm creating a widget with the following
> > code, I do get a button but the internal value is displayed in the 
> > clickable
> > button. I'd like the external value to be displayed in the button %v, 
> > just
> > as the menu-tag is is "externally facing".
> >
> > <<widget>>=
> > (define-widget 'project-widget 'list
> >   :tag (let ((s "\n\tProject"))
> >          (put-text-property 0 (length s) 'face 'bold s) s)
> >   :format "%t\n%v "
> >   :offset 0
> >   :indent 0
> >   :convert-widget 'widget-types-convert-widget
> >   :args '((menu-choice
> >            :tag "EmacSQL-supported backend"
> >            :format "%[%t%]: %[%v%]"
> >            :value "sqlite"
> >            :value-to-external <<menu-choice internal value to external 
> > lambda>>
> >            :value-to-internal <<menu-choice external value to internal 
> > lambda>>
> >            (choice-item :menu-tag "MySQL" :value "mysql")
> >            (choice-item :menu-tag "PostgreSQL" :value "postgresql")
> >            (choice-item :menu-tag "SQLite" :value "sqlite"))))
> > <<menu-choice internal value to external lambda>>=
> > (lambda (widget internal-value)
> >   "Converts lowercase, internal values to the casing of trademarks."
> >   (pcase internal-value
> >     ("mysql" "MySQL")
> >     ("sqlite" "SQLite")
> >     ("postgresql" "PostgreSQL")))
> > <<menu-choice external value to internal lambda>>=
> > (lambda (widget external-value)
> >   "Converts the casing of trademarked names to lowercase, internal 
> > values."
> >   (pcase external-value
> >     ("MySQL" "mysql")
> >     ("SQLite" "sqlite")
>
> When possible, please post code that can be evaled without making
> tweaks.
>
> Some things I noted:
>
> - Since the super is a list widget, then you don't need to specify
> :convert-widget.  The :convert-widget function is one of the few that
> gets called for all supers, so you end up converting twice the widget.
> In this case, it doesn't seem you want that.
>
> - You're specifying a value in the internal format for the menu-choice.
> The manual specifies that when creating a widget or defining a new
> one, the ‘:value’ should be in the external format.
>
> - I think you should give similar conversion functions to all
> choice-item, and also pass the :value in external format.
>
> Let me know if you still find problems after fixing these things.

I fixed those issues and I do not see the invalid or void state, but 
only nil is ever displayed in the buffer.
Below is the code I defined.

---

(define-widget 'project-widget 'list
  "A mimimal example to demonstrate 'styled' choice item buttons in a 
choice menu."
  :tag (let ((s "\n\tProject"))
         (put-text-property 0 (length s) 'face 'bold s) s)
  :format "%t\n%v "

  :args '((menu-choice
           :tag "EmacSQL-supported backend"
           :size 50
           :format "%[%t%]: %[%v%] \n"

           :value "SQLite"
           :choice (database-choice-item :menu-tag "SQLite" :value 
"SQLite")

           :value-to-external menu-choice-value-to-external
           :value-to-internal menu-choice-value-to-internal

           (database-choice-item :menu-tag "MySQL"      :value "MySQL")
           (database-choice-item :menu-tag "PostgreSQL" :value 
"PostgreSQL")
           (database-choice-item :menu-tag "SQLite"     :value 
"SQLite"))))

(defun menu-choice-value-to-internal (widget external-value)
  "Converts the casing of trademarked names to lowercase, internal 
values."
  (pcase external-value
    ("MySQL" "mysql")
    ("SQLite" "sqlite")
    ("PostgreSQL" "postgresql")))

(defun menu-choice-value-to-external (widget internal-value)
  "Converts lowercase, internal values to the casing of trademarks."
  (pcase internal-value
    ("mysql" "MySQL")
    ("sqlite" "SQLite")
    ("postgresql" "PostgreSQL")))

(define-widget 'database-choice-item 'choice-item
  nil
  :value-to-external #'menu-choice-value-to-external
  :value-to-internal #'menu-choice-value-to-internal)

(defun widget-value-conversion-example ()
       (interactive)
       (switch-to-buffer "*Widget Value Conversion Example*")
       (kill-all-local-variables)
       (let ((inhibit-read-only t))
         (erase-buffer))
       (remove-overlays)
       (widget-insert "Widget value conversion example.\n\n")
       (widget-create 'repeat 'project-widget)
       (use-local-map widget-keymap)
       (widget-setup))