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

[Alan Mackenzie <acm@muc.de>]

Hello Emacs.

In emacs -Q, with a buffer in a window such that there is text in the
window's last line, I run

    M-: (pos-visible-in-window-p t nil t)

.  (Those parameters are in order POS, WINDOW, and PARTIALLY)

The return value is, e.g., (0 64), the X and Y coordinates of the
_beginning_ of the last line.  (On an X window, the result is (0 920).)

With PARTIALLY non-nil, and POS set to t, the function should return the
coordinates of "the last visible position in WINDOW", according to elisp
page "Window Start and End".

I would expect the "last visible position" to mean the _end_ of the last
line, not the beginning.

Which is correct?  The function or the documentation?

-- 
Alan Mackenzie (Nuremberg, Germany).