Precision scrolling in Emacs 29 introduces several variables to control the momentum effect while scrolling.

Are these terms defined anywhere in more detail, possibly by using a formula or two to explain how they are related to each other if appropriate?

  • It is described clearly enough IMO
    – shynur
    Jan 7 at 10:39

1 Answer 1


You don't say what's unclear about any description you found for pixel-scroll-precision-use-momentum, and your question is only where to find such a description.

  1. pixel-scroll-precision-use-momentum is a user option, so it's described in its doc string: C-h v.

  2. pixel-scroll-precision-use-momentum is used in only one place: function pixel-scroll-start-momentum. The source code of that function shows you how it's used.

  3. To watch how it's used, try M-x debug-on-entry pixel-scroll-start-momentum. (That might be difficult to walk through, however.) Or copy the definition of that function, insert calls to message at various places in your copy, then evaluate your copy. Examine the message output in buffer *Messages*.

Similarly, for any of the other "several variables" you're interested in.

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