ScrollZoomHandler: allow to set zoomRate

[sf31]

Hello there, first PR here, I hope I'm doing it right.

I noticed that scroll zoom on desktop browsers is really slow when using mouse since you need to 'wheel' so many times. I didn't find a way to set 'scroll/zoom sensibility' so I've edited ScrollZoomHandler class and added setZoomRate(number) and setWheelZoomRate(number) methods.
These basically allow to set/override default values of 'defaultZoomRate' and 'wheelZoomRate'.

It seems to work pretty well, I'm sending this PR to let you know about this possiblity in case you want to include that in the library.

Thanks for your work!

Launch Checklist

• briefly describe the changes in this PR
• write tests for all new functionality
• document any changes to public APIs
• post benchmark scores
• manually test the debug page
• tagged @mapbox/studio and/or @mapbox/maps-design if this PR includes style spec changes

[andrewharvey]

👍 here's the tickets this relates to

• likely closes Allow configuring zoom speed/step #4723: Allow configuring zoom speed/step
• related to Mousewheel zoom very slow - Chrome/Linux #7572: Mousewheel zoom very slow - Chrome/Linux, I think to close this ticket it would need to change the defaults to be faster, not just make it configurable.

[sf31]

I think to close this ticket it would need to change the defaults to be faster, not just make it configurable

In this case it could be enough change those constants to a higher value, but then you are just moving the problem to those people who want an high precision/small steps in scroll zoom. Why do you think it should not be configurable?

[pathmapper]

#7572 is about making the mousewheel zoom behavior consistent across different OS/browser/mouse combinations.

[ryanhamley]

Yeah it looks like to close #7572, we'd need to add something like https://github.com/facebookarchive/fixed-data-table/blob/master/src/vendor_upstream/dom/normalizeWheel.js but I think that's not necessarily in scope of this PR. If the author wants to tackle that, great, but this PR doesn't need to include scroll normalization to be considered "done".

[andrewharvey]

Why do you think it should not be configurable?

Oh, I think it should be configurable 💯%, so I'm happy to see your PR.

Yeah it looks like to close #7572, we'd need to add something like https://github.com/facebookarchive/fixed-data-table/blob/master/src/vendor_upstream/dom/normalizeWheel.js but I think that's not necessarily in scope of this PR. If the author wants to tackle that, great, but this PR doesn't need to include scroll normalization to be considered "done".

Absolutely, sorry I didn't mean to derail this into #7572.

[ryanhamley]

Hi @sf31 sorry for the delay in reviewing your PR. It looks good to me. I just requested some minor changes to the comments and documentation if you'd still like to contribute this.

[sf31]

Hi, I've added/updated missing comments, let me know if more is needed!

[ryanhamley]

Thanks!