Re: Community improvements to the Emacs Widget Library manual?

[Mauro Aranda]

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.