Clarify documentation of pos-visible-in-window-p

* src/window.c (Fpos_visible_in_window_p): Clarify the meaning of
t for POS.  See
http://lists.gnu.org/archive/html/emacs-devel/2015-09/msg01040.html
for the original report.

* doc/lispref/windows.texi (Window Start and End): Clarify the
meaning of t for the POSITION argument of pos-visible-in-window-p.

1 files changed, 1 insertions, 1 deletions

diff --git a/doc/lispref/windows.texi b/doc/lispref/windows.texi
index 00161b28b66..881d364232a 100644
--- a/doc/lispref/windows.texi
+++ b/doc/lispref/windows.texi
@@ -3179,7 +3179,7 @@ Locations that are partially obscured are not considered visible unless
 @var{partially} is non-@code{nil}.  The argument @var{position} defaults
 to the current position of point in @var{window}; @var{window}, to the
 selected window.  If @var{position} is @code{t}, that means to check the
-last visible position in @var{window}.
+first visible position of the last visible screen line in @var{window}.
 
 This function considers only vertical scrolling.  If @var{position} is
 out of view only because @var{window} has been scrolled horizontally,