add prop for disabling the wheel handler

[httnn]

Description

adds a new boolean prop disableWheelHandler, that, when enabled, will disable handling wheel events.
adds a new boolean prop onVerticalScroll, that works like onHorizontalScroll.

Motivation and Context

we have a use-case in which we need to handle the wheel by ourselves since we are using window scrolling with the table. now we need to resort to a hack like this:

<Table
  ref={e => e && (e._wheelHandler = () => {})}
...

which is very ugly, so would be nice to be able to do this "officially" via a property!

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.

[KamranAsif]

I think a better solution is extending onVerticalScroll to stop propagation if it returns false.
We did a change for onHorizontalScoll here: https://github.com/schrodinger/fixed-data-table-2/blob/master/src/FixedDataTable.js#L1136

Thoughts?

[KamranAsif]

You also need to handle ReactWheelHandler being initalized here:
https://github.com/schrodinger/fixed-data-table-2/blob/master/src/FixedDataTable.js#L334

[httnn]

why? ReactWheelHandler takes both _shouldHandleWheel* functions as parameters, and since it is initialised in componentWillMount, changing disableWheelHandler during the lifecycle of the component wouldn't change any behaviour.

[KamranAsif]

Sorry meant this one https://github.com/schrodinger/fixed-data-table-2/blob/master/src/FixedDataTable.js#L411

[httnn]

oh! why doesn't this wheelHandler use the same _shouldHandleWheel* functions?

[KamranAsif]

I'm not really sure (we inherited this code from the original repo)
I'm guessing one reason is that it doesn't have access to this.props yet.

@wcjordan This seems like a big memory leak, creating unnecessary wheel handlers if the table switches from overflow on and off.

It seems unnecessary to create it in that function, since the handler is already initialized in componentWillMount.

[httnn]

wouldn't changing onVerticalScroll also disable scroll bars? this prop would only be concerned with blocking the wheel event from being listened to.

[KamranAsif]

No, overflowX/overflowY set to none disables the scrollbars.
Heres an example of how it works for horizontal scrolling:
https://jsfiddle.net/ffjxxkee/

[httnn]

hmm I see. maybe that might be sensible since horizontal scrolling is already working that way. then we also wouldn't have to worry about changing wheelHandler functionality in this PR.

[KamranAsif]

LGTM, sorry for the delay; I was on vacation.
Do you need a new version?