In the default Emacs configuration, C-l is bound to recenter-top-bottom.
This function has an interesting behaviour: when called once, it scrolls the
current window so that the current line appears at the middle of the screen.
When called several times in a row, it cycles through three scrolling
position: middle, top and bottom.
This has always bugged me because I only need one of the three behaviours, and none of these positions are useful to me. In pratice, I want to focus on the line I am working on, which means putting it at eye level. In my case at roughly 20% of the top of the window.
Fortunately Emacs is easy to customize. As it turns out, recenter-top-bottom
is based on recenter which is easy to use:
(defcustom g-recenter-window-eye-level 0.2
"The relative position of the line considered as eye level in the
current window, as a ratio between 0 and 1.")
(defun g-recenter-window ()
"Scroll the window so that the current line is at eye level."
(interactive)
(let ((line (round (* (window-height) g-recenter-window-eye-level))))
(recenter line)))
(global-set-key (kbd "C-l") 'g-recenter-window)