Re: Little help with defcustom

[Joost Kremers <joostkremers@fastmail.fm>]

On Mon, Nov 09 2020, Jean Louis wrote:
>   :type '(repeat
> 	  (list :tag "Dynamical User Sets"
> 		(string :tag "  Server")
> 		(string :tag "Set name")
> 		(string :tag " Node ID"))))
[...]
> I see that to achieve best formatting I have to pad with spaces those
> strings. Is there maybe better way?

Not that I know of, no. I never bother, but it would be nice to be able to align
the fields.

> Is there a way to make sure that field is not empty?

Honestly, I don't know. The Elisp manual says there's a `:validate' keyword that
can be used to provide a function for validating the input. I've never used it,
but here's an example from the Emacs sources (`lisp/calendar/todo.el`):

```
(defcustom todo-prefix ""
  "String prefixed to todo items for visual distinction."
  :type '(string :validate
                 (lambda (widget)
                   (when (string= (widget-value widget) todo-item-mark)
                     (widget-put
                      widget :error
                      (format-message
                       "Invalid value: must be distinct from `todo-item-mark'"))
                     widget)))
  :initialize 'custom-initialize-default
  :set 'todo-reset-prefix
  :group 'todo-display)
```

You could even test whether a field has the correct format.

HTH

-- 
Joost Kremers
Life has its moments