+The @code{pos-visible-in-window-p} function considers only vertical
+scrolling. If @var{position} is out of view only because @var{window}
+has been scrolled horizontally, @code{pos-visible-in-window-p} returns
+non-@code{nil} anyway. @xref{Horizontal Scrolling}.
+
+If @var{position} is visible, @code{pos-visible-in-window-p} returns
+@code{t} if @var{partially} is @code{nil}; if @var{partially} is
+non-@code{nil}, it returns a list of the form @code{(@var{x} @var{y}
+@var{fully})}, where @var{x} and @var{y} are the pixel coordinates
+relative to the top left corner of the window, and @var{fully} is
+@code{t} if the character after @var{position} is fully visible and
+@code{nil} otherwise.
+