ScrollZoomHandler does not always apply options properly

[bartcorremans]

mapbox-gl-js version: v0.41.0

Steps to Trigger Behavior

1. Call map.scrollZoom.disable() (or set scrollZoom to false in options when creating map)
2. Call map.scrollZoom.enable()
3. Call map.scrollZoom.enable({ around: 'center' })

Expected Behavior

Calling enable() the second time should apply the options object and make the scroll zoom handler scroll around the centre of the map instead of the cursor.

Actual Behavior

The scroll zoom handler does not apply the options on the second call.

The opposite is true also; calling enable() with options and then calling enable() again without options will not properly reset the options.

https://jsbin.com/tupovojawu/1/edit?html,js,output

[mollymerp]

@bartcorremans thanks for using mapbox and for the detailed report!
As the function is written, if you call map.scrollZoom.enable() when the control is already enabled, it returns without doing anything, and this is consistent with the rest of our mouse/keyboard handlers. Your example works if you add a call to map.scrollZoom.disable() in the first timeout.

It might make sense to add a method that allows users to set the around option separately from enabling/disabling the handler.

https://jsbin.com/tupovojawu/1/edit?html,js,output

mapbox-gl-js/src/ui/handler/scroll_zoom.js

Lines 61 to 62 in c5554ff

	enable(options: any) {
	if (this.isEnabled()) return;

[mollymerp]

adding a setter for around falls under #4029

[bartcorremans]

Thanks for the reply!