turning off `mouse-wheel-progressive-speed' breaks scrolling

[Nathaniel Cunningham]

While cleaning up my Preferences.el, I discovered just now (in nightly build from July 25, on OS 10.12) that setting

(setq mouse-wheel-progressive-speed nil)

makes mouse wheel scrolling stop working altogether, with no errors. (By default, it is set to t.) I confirmed this bug in a new session without customizations.

Investigating with describe-key still shows `mwheel-scroll' properly bound to mousewheel scroll events; but mwheel-scroll no longer does anything!

Turning mouse-wheel-progressive-speed back on makes things work fine again.

Nathaniel

[Nathaniel Cunningham]

Same behavior in the lastest nightly (July 31).

-- Nathaniel

[David Reitter]

Interesting. Did you find out anything else … about where the bug might be?

> --
> You received this message because you are subscribed to the Google Groups "aquamacs-devel" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to aquamacs-deve...@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/aquamacs-devel/CAAGwS86%2BC6ak%3Dra2myGWbbTRJhqrMJPAE9ChamjyzOZob0Teyg%40mail.gmail.com.

[Nathaniel Cunningham]

I'll look into it tonight or tomorrow.

To view this discussion on the web visit https://groups.google.com/d/msgid/aquamacs-devel/772F5D0C-A087-412C-BEFA-F80A8E1D8471%40gmail.com.

[Nathaniel Cunningham]

I located the bug, in the recent introduction of `mouse-wheel-progressive-decelerator' into aquamacs.el.

There are two issues:

1) The requested scroll amount is divided by the `-progressive-decelerator' value, even when progressive scrolling is turned off.
2) Integer division results in zero scroll size requested,
  a) always, when progressive scrolling is off; and
  b) for the first few scrolls with progressive scrolling on.

The combination of (1) and (2a) is the reason that turning off progressive scrolling makes scrolling unresponsive.

I have submitted a patch and pull request that:
A) changes `mouse-wheel-progressive-decelerator' to a float value so division gives floating-point (untruncated!) result;
B) applies `ceiling' to the (float) result from division, because the `scroll-up' and `scroll-down' functions that are subsequently called will (apparently) only scroll a single line if given a float argument, regardless of value. And zero is never a reasonable amount to scroll, so we don't want to round down.

C) only divides scroll amount by `-progressive-decelerator' value when progressive scrolling is on.

Nathaniel

[David Reitter]

Awesome. Merged. Thank you.

> To view this discussion on the web visit https://groups.google.com/d/msgid/aquamacs-devel/CAAGwS84gycvXuHrE85EGnBcg_oSfNwZ-c_tXD9zUMfuSutu4og%40mail.gmail.com.