Re: (pos-visible-in-window-p t nil t) returns wrong position/is suboptimally documented.

[Eli Zaretskii <eliz@gnu.org>]

> Date: Wed, 30 Sep 2015 10:22:31 +0000
> Cc: emacs-devel@gnu.org
> From: Alan Mackenzie <acm@muc.de>
> 
> > > However 2: I think there's a bug in the functionality, too.  If there is
> > >   o - a text buffer
> > >   o - with no terminating LF on its last line, and
> > >   o - that last line is above the window's last line
> > > then (pos-visible-in-window t nil t) returns the coordinates of the last
> > > lines's EOL.  This is the case in both a Linux virtual terminal and an X
> > > windows session.
> 
> > It's not a bug.  If you think it's important to mention this marginal
> > use case, I can add that, too.
> 
> OK, it's deliberate.  It's a touch puzzling, though.  I should grep the
> elisp sources to find out what it's for.  I do think it should be
> mentioned in the doc, even if only for preventing somebody like me
> raising a spurious bug report in the future.
> 
> How about expressing the piece of documentation as:
> 
>     "If POSITION is `t', that means to check the position the first
>     visible position of the last visible screen line with text in
>     WINDOW; but if the end of the window's buffer is on the window, this
>     position is used instead."

I already committed a change to describe that.  The doc string now
says

  If POS is t, it specifies either the first position displayed on the
  last visible screen line in WINDOW, or the end-of-buffer position,
  whichever comes first.

and similar text is in the ELisp manual.

OK?