bug#52092: 28.0.60; hs-toggle-hiding does not toggle once folded

[Eli Zaretskii <eliz@gnu.org>]

> Date: Thu, 25 Nov 2021 13:10:51 +0530
> From: Mohammed Sadiq <sadiq@sadiqpk.org>
> 
> 
> With hs-minor-mode enabled, I could hide the visibility of a block with
> hs-toggle-hiding, but using it again doesn't unfold the region.
> 
> Tested with c-mode and css-mode.

It seems that unhiding works only if you are at the beginning of the
hidden block.  In C Mode, that means cursor is on the opening brace of
the block.

The problem seems to be inside hs-already-hidden-p:

  (defun hs-already-hidden-p ()
    "Return non-nil if point is in an already-hidden block, otherwise nil."
    (save-excursion
      (let ((c-reg (hs-inside-comment-p)))
	(if (and c-reg (nth 0 c-reg))
	    ;; point is inside a comment, and that comment is hideable
	    (goto-char (nth 0 c-reg))
	  (end-of-line)

That call to end-of-line moves point outside of the braces _unless_
point is on the left brace that starts the hidden block.  That
movement then makes it appear as if we are in the outer block, not in
the one that you've just hidden.

I don't know enough about hideshow.el and don't use it enough to
propose a robust enough solution for this which won't break some use
case out there.