Maybe we already have data here? Ideally we would know the ratio of page-per-wheel users to not that.

("fixlater" here just means "sooner than backlog but not a fixnow")

I don't know what telemetry you're looking for exactly but we have https://mzl.la/29iE0eb

Thanks, kats! I was looking for info on DOMMouseScroll event. Specifically I'd like to know how many users have their scroll wheel set to scroll-by-page and how often that's used. Looking at https://dxr.mozilla.org/mozilla-central/source/gfx/layers/apz/util/ScrollInputMethods.h, do these values relate to DOMMouseScroll? ApzWheelPixel, // wheel events, pixel scrolling mode ApzWheelLine, // wheel events, line scrolling mode ApzWheelPage, // wheel events, page scrolling mode

The probe gives us some data about that, assuming users have APZ enabled. It looks like we don't have the data for the non-APZ wheel scrolling (perhaps we should add it). And yes, comparing the proportion of ApzWheelPage to the sum of ApzWheel* will give you the ratio of wheel scroll events that are scroll-by-page. Note that there is some bias here because (a) this is only data from where APZ is enabled and (b) page-scrolling scrolls a larger distance, so in general users will do it less frequently to scroll a given distance. This artificially depresses the page-scrolling numbers somewhat. But even so the data seems to indicate the number of scroll-by-page events is quite small. If you want it as proportion of users, I think we can get that by using some custom telemetry analysis and looking at the number of users who submitted those events compared to the total number of users submitting ApzWheel* events.

I guess we need to count this in Windows widget level code so that if during firefox session wheel event with deltaMode=page was ever dispatched is compared to those firefox sessions where such event wasn't ever dispatched.

And this needs someone with access to Windows dev environment to check that the patch actually works.

Jim, do you think you could do comment 5 (or do you know someone who could?)? See the blocker bug here for what we want this information for.

(In reply to Andrew Overholt [:overholt] from comment #7) > Jim, do you think you could do comment 5 (or do you know someone who > could?)? See the blocker bug here for what we want this information for. I can try to fit this in someplace. What's the time frame here?

(In reply to Jim Mathies [:jimm] from comment #8) > (In reply to Andrew Overholt [:overholt] from comment #7) > > Jim, do you think you could do comment 5 (or do you know someone who > > could?)? See the blocker bug here for what we want this information for. > > I can try to fit this in someplace. What's the time frame here? I'd like to figure out the situation with DOMMouseScroll sooner rather than later. I know you're super-busy so say ... 1-2 months?

Never found time to get to this.