[BUG] widget-field-overlay becomes wrong

[Lars Hansen]

One for the bug-list :-)

When a widget-field-overlay goes all the way to the next or previous 
widget, it becomes wrong when that next or previous widget is changed.
A test case is attached.

Richard has written a comment in widget-default-value-set which probably 
is about the same thing.

I don't know how to fix this bug, it seems quite tricky.
Of cause a work-around is to never have a widget field adjacent to 
another widget.

;-----------------------------------------------------------------------------------------------
;  widget-field-overlay-bug.el
;-----------------------------------------------------------------------------------------------

(require 'wid-edit)

(defvar w1 nil)
(defvar w2 nil)
(defvar w3 nil)

(defun widget-field-overlay-bug ()
  (interactive)
  (switch-to-buffer "*test*")
  (setq w1 (widget-create 'editable-field :format "%v" :size 3 :value "xxx"))
  (setq w2 (widget-create 'editable-field :format " %v " :size 3 :value "foo"))
  (setq w3 (widget-create 'editable-field :format "%v" :size 3 :value "yyy"))
  (widget-setup)
  (message "w1: %s\nw2: %s\nw3: %s"
           (widget-get w1 :field-overlay)
           (widget-get w2 :field-overlay)
           (widget-get w3 :field-overlay))
  (when (y-or-n-p "Continue ")
    (widget-value-set w2 "bar")
    (widget-setup)
    ;; Markers are OK, but overlay of w1 and w3 are wrong!
    (message "w1: %s\nw2: %s\nw3: %s"
             (widget-get w1 :field-overlay)
             (widget-get w2 :field-overlay)
             (widget-get w3 :field-overlay))
    (display-buffer "*Messages*")
    (goto-char (point-max))))