bug#56682: locked narrowing

[Juri Linkov]

>> There is another side-effect: after evaluating manually 'M-:
>> (pos-visible-in-window-p) RET' at the position 1000000, point moves to
>> the position 749873 afterwards.  It seems this is related to locked
>> narrowing, because point doesn't jump after customizing
>> long-line-locked-narrowing-region-size to 0.
>
> I cannot reproduce that.  With the following recipe:
>
> emacs -Q
> C-x C-f dictionary.json RET
> M-g c 1000000 RET
> M-: (pos-visible-in-window-p) RET
>
> point does not move.  Is there something missing in that recipe?

The prerequisite is this setting:

  (add-hook 'find-file-hook 'toggle-truncate-lines)