Adjust timeline zoom sensitivity on Firefox

[fbarl]

Resolves #2768 by taking the defaultWheelDelta logic from https://github.com/d3/d3-zoom.

Zooming transitions were made also animated to make them smoother (especially on Firefox which sometimes does discrete jumps).

Edit: Tracking of zoom events was wrapped into a debounce method to prevent excessive Mixpanel reporting.

[davkal]

Really difficult to test this on FF. Both master and this branch have a baseline of 75% CPU use. The adjustment seems to help with zoom sensitivity but is overshadowed by general lag. Is it just my machine?

The zoom track still seems a bit excessive. What do you hope to learn? If it's binary use vs non-use, maybe use some once logic, or otherwise massively turn up the debounce interval (request handling eats into drawing performance).

FWIW Chrome works perfectly fine.

I recommend changing the tracking, then merge this, and then do profiling for FF in a separate PR.

[rade]

The FF performance is probably #2302.

[fbarl]

The zoom track still seems a bit excessive. What do you hope to learn? If it's binary use vs non-use, maybe use some once logic, or otherwise massively turn up the debounce interval (request handling eats into drawing performance).

I hope to see at which depth the users are using the timeline, i.e. whether they are more interested in moving through minutes/hours/days/etc... With that in mind, I will increase ZOOM_TRACK_DEBOUNCE_INTERVAL from 1s to 10s and also replace the durationPerPixelInMilliseconds float with a rounded humanized time unit (minutes, hours, etc..) to make it easier to interpret the Mixpanel data.

[fbarl]

@davkal I've updated the PR.

@rade Maybe you'd want to test the FF behaviour (modulo lagging) before I merge it.

[rade]

Maybe you'd want to test the FF behaviour (modulo lagging) before I merge it.

Nah, it can hardly have gotten worse ;)