Implement offsets for absolute line numbers

* src/xdisp.c (syms_of_xdisp) <display-line-numbers-offset>:
New variable to add an offset to absolute line numbers.
(syms_of_xdisp) <display-line-numbers>: Mention it in docstring.
(maybe_produce_line_number): Use it.

* doc/emacs/display.texi (Display Custom): Document it.

* etc/NEWS (value): Announce it.

* lisp/frame.el: Add `display-line-numbers-offset' to list of
variables which should trigger redisplay of the current buffer.

1 files changed, 1 insertions, 0 deletions

diff --git a/lisp/frame.el b/lisp/frame.el
index 51b3b621ff4..018c2f578e4 100644
--- a/lisp/frame.el
+++ b/lisp/frame.el
@@ -2726,6 +2726,7 @@ See also `toggle-frame-maximized'."
         display-line-numbers-widen
         display-line-numbers-major-tick
         display-line-numbers-minor-tick
+        display-line-numbers-offset
         display-fill-column-indicator
         display-fill-column-indicator-column
         display-fill-column-indicator-character