Add new minor mode `header-line-indent-mode'

This is mostly factored out from tabulated-list.el (with bugs fixed).

* doc/lispref/modes.texi (Header Lines): Document it.
* lisp/display-line-numbers.el (header-line-indent): New variable.
(header-line-indent--line-number-width)
(header-line-indent--watch-line-number-width)
(header-line-indent--window-scroll-function): New helper functions.
(header-line-indent-mode): New minor mode.

* lisp/display-line-numbers.el (header-line-indent-width): New
variable.

* lisp/emacs-lisp/tabulated-list.el (tabulated-list-line-number-width)
(tabulated-list-watch-line-number-width)
(tabulated-list-window-scroll-function): Make into obsolete aliases.
(tabulated-list-mode): Use 'header-line-indent-mode'.

* lisp/emacs-lisp/tabulated-list.el (tabulated-list-init-header):
Adjust the header line format and computation.

* src/buffer.c (syms_of_buffer): Mention header-line-indent-mode.

1 files changed, 5 insertions, 2 deletions

diff --git a/src/buffer.c b/src/buffer.c
index 57137b2a067..548d7b1c65c 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -5598,8 +5598,11 @@ the mode line appears at the bottom.  */);
                      &BVAR (current_buffer, header_line_format),
                      Qnil,
                      doc: /* Analogous to `mode-line-format', but controls the header line.
-The header line appears, optionally, at the top of a window;
-the mode line appears at the bottom.  */);
+The header line appears, optionally, at the top of a window; the mode
+line appears at the bottom.
+
+Also see `header-line-indent-mode' if `display-line-number-mode' is
+used.  */);
 
   DEFVAR_PER_BUFFER ("mode-line-format", &BVAR (current_buffer, mode_line_format),
                      Qnil,