add onWheel prop

[implausible]

This is a follow up to #541.

The PR simply exposes the onWheel prop for Grid.

[bvaughn]

I'm not sure I want to expose a "wheel" event handler on Grid. While scroll events are async, wheel and touch* events are sync (at least by default) and so can cause performance problem.s

[implausible]

Well, without the ability to force react-virtualized to run wheel events synchronously, react-virtualized has huge tearing issues in electron. We talked about this previously, what would you suggest we do now?

[implausible]

Perhaps you could modify this approach to enable your onWheel handler to be injected in? eg what if Grid exposed a new onWheel: PropTypes.func (optinoal) property that enabled you to inject your own throttled wheel handler? This way if it works well for your use-case you could continue to use it without potentially causing regressions for existing apps.

This is where we left off last time, we haven't had the need to update react-virtualized in awhile, but we're planning on updating react-virtualized, soon. Before we can update react-virtualized, we need to make sure that we can fix the tearing that occurs in multiple grid scrolling. Since this seemed to be the direction we wanted to go last time, if it's no longer the direction you intend, what do we do now?

[bvaughn]

Don't know. Need to think about it. Not immediately comfortable with encouraging usage of "wheel" events (with an explicit onWheel prop) since they have known perf impact. (Also there are no other top-level event handlers, excluding onScroll, which is a custom thing and not a pass-thru for the built-in "scroll" event.

Maybe some kind of rest prop that just lets you pass through unfiltered properties to the root <div> element created by Grid.

You're right that I mentioned onWheel as a possible solution a few months back. 😄

[implausible]

I'll revise for a rest prop.

[athomann]

Also was looking for an onWheel prop. We are attempting to prevent the parent container from scrolling when you reach the bottom of the virtual list. So far I can only implement that with onWheel, unless you know of another way?

[athomann]

Nevermind, I should be able to solve it when this is released.

[bvaughn]

This feature has been released in version 9.10.0. Thank you for contributing!