emacs smooth scrolling not effect after system upgrade to MacOS 10.12

Question

I have used Gnu Emacs 24.5.1 under MacBook/MacOS 10.11.6. And I have a good "smooth scrolling" (use trackpad) with a correct setting in .emacs:

(setq mouse-wheel-scroll-amount '(1 ((shift) . 1) ((control) . nil)))
(setq mouse-wheel-progressive-speed nil)

But, after I upgrade to MacOS Sierra (10.12), the smooth scrolling seems have no effect anymore. I notice that every scroll still has 1 line per step. But the "mouse-wheel-progressive-speed" seems not work correctly.

After upgrade to MacOS Sierra, the other applications still have "correct" scrolling style, e.g. iTerm2.

Please help and many thanks!

Answer 1

Clicking through here:

https://discussions.apple.com/thread/7679256?start=0&tstart=0

Led me to the solution. Which for me is 2 things. One, what the user on the apple support forum said:

This time I went into Accessibility. Then Click on Mouse and Trackpad. Now click on Trackpad Options. The scrolling box is most likely highlighted already. Toggle it off and then back on and see if that fixes it - it did for me. Now go back to the Trackpad in System Preferences and make sure you have everything selected as desired.

Go to Preferences > Accessibility > Mouse & Trackpad > Mouse Options

Then toggle off, then back on the scrolling check box, then click OK. This seems to clean things up. Possibly reset some things somewhere in the code.

Double check your mouse settings in Preferences to ensure they are as expected. Test your scrolling in chrome to make sure it works as desired.

It should work as expected in Java based apps now and terminal apps as well. For reference, i had this issue with emacs/spacemacs. For reference, this is what my settings are in my .spacemacs config settings.

(defun dotspacemacs/user-config ()
  [...]

  ;; Scrolling
  (setq mouse-wheel-scroll-amount '(3 ((shift) . 1) ((control) . nil)))
  (setq mouse-wheel-progressive-speed nil)
)

And with those, it scrolls smoothly.