On Windows, a two finger scroll on a long window followed by control-swipe with one finger causes page zoom go do something extreme in some direction, whichever way you happened to swipe. I'm seeing this behavior in Win10 on a new Surface Book with the required gestures enabled. I can reproduce it in release and Nightly reliably. Previous scrolling-and-momentum bugs: https://bugzilla.mozilla.org/show_bug.cgi?id=574663 https://bugzilla.mozilla.org/show_bug.cgi?id=669979

Your STR aren't very clear to me (I also don't have my touch-enabled Windows device handy so I can't easily try it myself). By "control-swipe", you mean holding down the control key and doing a one-finger swipe gesture? What version of Firefox are you running, and if you go to about:support, what does it say under "Async Pan/Zoom"? And do you have e10s enabled?

STRS are: - Find a relatively long page. - Two-finger swipe down it. - While it's still scrolling, take your fingers off the trackpad and press the control key. On this Surface Book doing that reliably causes the page to zoom in and out to the limits of the zoom function.

I'm on current Nightly with E10S enabled, and have "wheel input enabled; touch input enabled" in Async Pan/Zoom.

Ah, thanks for the clarification. This sounds like a dupe of bug 1199737 then. Optimistically duping, please un-dupe if you feel it's a different bug.

Yup, that's the same bug. I didn't see it when I searched for this one. Thanks!