bug#71415: 30.0.50; vtable-current-object off by one

[Eli Zaretskii <eliz@gnu.org>]

> From: john muhl <jm@pub.pink>
> Date: Fri, 07 Jun 2024 09:15:07 -0500
> 
> After updating an object, ‘vtable-current-object’ in the displayer
> and formatter functions points to the object after the one that
> was updated. Running the following:
> 
>   (with-current-buffer (get-buffer-create "vtable-demo")
>     (require 'vtable)
>     (erase-buffer)
>     (make-vtable
>      :columns '("Index" "Number")
>      :objects `((1 ,(random)) (2 ,(random)) (3 ,(random)))
>      :displayer (lambda (value &rest _)
>                   ;; vtable-current-object is off by one; e.g.
>                   ;; update the first row and v-c-o will be the second row;
>                   ;; update the final row and v-c-o will be nil.
>                   (message "%s %s" value (vtable-current-object))
>                   (propertize (number-to-string value) 'face 'vtable)))
>     (let* ((table (vtable-current-table))
>            (first (nth 0 (vtable-objects table)))
>            (other (nth 1 (vtable-objects table)))
>            (final (nth 2 (vtable-objects table))))
>       (setf (nth 1 first) 1)
>       (setf (nth 1 other) 2)
>       (setf (nth 1 final) 3)
>       (vtable-update-object table first)
>       (vtable-update-object table other)
>       (vtable-update-object table final)))
> 
> I see in the messages buffer:
> 
>   1 (2 2) [2 times]
>   2 (3 3) [2 times]
>   3 nil [2 times]
> 
> when I expect to see:
> 
>   1 (1 1) [2 times]
>   2 (2 2) [2 times]
>   3 (3 3) [2 times]

Adam, any comments or suggestions?

Thanks.