Can header-line track a row in my file?

Can header-line track a row in my file?

[Lee]

I have a file in a large table that I have to scroll around in.  It
would be nice to hang the first row of the table, which tells me what
is in what column, at the top of the buffer and have it update as I
scroll horizontally through the table.

Seems like the header line (analogous to the mode line) would be
perfect, but I am at a loss as how to set header-line-format to
accomplish this.  Any suggestions?

Thanks,
Lee

Re: Can header-line track a row in my file?

[Stefan Monnier <foo@acm.com>]

>>>>> "Lee" == Lee  <mus5mk2ly001@sneakemail.com> writes:
> I have a file in a large table that I have to scroll around in.  It
> would be nice to hang the first row of the table, which tells me what
> is in what column, at the top of the buffer and have it update as I
> scroll horizontally through the table.

Try something like

  (set (make-local-variable 'header-line-format)
       '(:eval (save-excursion
                 (goto-char (point))
                 (move-to-column (window-hscroll))
                 (buffer-substring (point) (line-end-position)))))


-- Stefan

Re: Can header-line track a row in my file?

[Lee]

"Stefan Monnier <foo@acm.com>" <monnier+gnu.emacs.help/news/@flint.cs.yale.edu> wrote in message news:<5lpttyz0ux.fsf@rum.cs.yale.edu>...
> >>>>> "Lee" == Lee  <mus5mk2ly001@sneakemail.com> writes:
> > I have a file in a large table that I have to scroll around in.  It
> > would be nice to hang the first row of the table, which tells me what
> > is in what column, at the top of the buffer and have it update as I
> > scroll horizontally through the table.
> 
> Try something like
> 
>   (set (make-local-variable 'header-line-format)
>        '(:eval (save-excursion
>                  (goto-char (point))
>                  (move-to-column (window-hscroll))
>                  (buffer-substring (point) (line-end-position)))))

Awesome, thanks!  In my case I want to track a particular line, so it would be

   (set (make-local-variable 'header-line-format)
        '(:eval (save-excursion
                  (goto-line 18)
                  (move-to-column (window-hscroll))
                  (buffer-substring (point) (line-end-position)))))

Thanks again,
Lee

Re: Can header-line track a row in my file?

[Lee]

And at last, here is the final version (I hope).  I found that having
tabs would sometimes offset the header and I have also unhardcoded the
line number.  You can just put the cursor on the line you want
displayed in the header and then do M-x my-set-header-line-format:

(defun my-set-header-line-format ()
  (interactive)
  (set (make-local-variable 'my-line-number)
        (save-restriction
          (widen)
          (save-excursion
            (beginning-of-line)
            (1+ (count-lines 1 (point))))))
  (set (make-local-variable 'header-line-format)
       '(" " (:eval
              (save-excursion
                (goto-line my-line-number)
                (move-to-column (window-hscroll))
                (untabify (point) (line-end-position))
                (buffer-substring (point) (line-end-position)))))))

Lee