Allow count-lines to ignore invisible lines

* doc/lispref/positions.texi (Text Lines): Document it (bug#23675).

* lisp/simple.el (count-lines): Add an optional parameter to
ignore invisible lines (bug#23675).

1 files changed, 4 insertions, 1 deletions

diff --git a/doc/lispref/positions.texi b/doc/lispref/positions.texi
index d7856ce73e3..91419702ca1 100644
--- a/doc/lispref/positions.texi
+++ b/doc/lispref/positions.texi
@@ -411,7 +411,7 @@ function counts that line as one line successfully moved.
 In an interactive call, @var{count} is the numeric prefix argument.
 @end deffn
 
-@defun count-lines start end
+@defun count-lines start end &optional ignore-invisible-lines
 @cindex lines in region
 @anchor{Definition of count-lines}
 This function returns the number of lines between the positions
@@ -420,6 +420,9 @@ This function returns the number of lines between the positions
 1, even if @var{start} and @var{end} are on the same line.  This is
 because the text between them, considered in isolation, must contain at
 least one line unless it is empty.
+
+If the optional @var{ignore-invisible-lines} is non-@code{nil},
+invisible lines will not be included in the count.
 @end defun
 
 @deffn Command count-words start end