efaq: Scrolling only one line
5.45 How can I force Emacs to scroll only one line when I move past the bottom of the screen?
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Customize the ‘scroll-conservatively’ variable with ‘M-x
customize-variable <RET> scroll-conservatively <RET>’ and set it to a
large value like, say, 10000. For an explanation of what this means,
(emacs)Auto Scrolling.
Alternatively, use the following Lisp form in your ‘.emacs’:
(setq scroll-conservatively most-positive-fixnum)