Inconsistant mouse wheel zoom step on Firefox

[Nekzuris]

URL

https://ideditor.netlify.app/#background=fr.ign.bdortho&disable_features=boundaries&map=19.00/48.03756/7.01676

How to reproduce the issue?

Zoom out with the mouse wheel and observe the zoom value in URL (on https://ideditor.netlify.app or https://www.openstreetmap.org/id, because https://www.openstreetmap.org/edit doesn't show fractional zoom levels #10091).

Sometimes the step is 0.20 sometimes 0.21, on Chrome it's always 0.20.

Screenshot(s) or anything else?

No response

Which deployed environments do you see the issue in?

Development version at ideditor.netlify.app

What version numbers does this issue effect?

2.31.0-dev

Which browsers are you seeing this problem on?

Firefox

[Nekzuris]

Okay so this is because Firefox report a WheelEvent.deltaY of 102 for some reason, it's 100 on Chrome.
Chrome also scales it inversely proportional to page zoom, while Firefox just changes it to 108 🤷‍♂️.

I'm tempted to change this logic to hard code the zoom step but I'm not sure it will work great for all mice and trackpads.

iD/modules/util/zoom_pan.js

Lines 32 to 34 in 28183c7

	function defaultWheelDelta(d3_event) {
	return -d3_event.deltaY * (d3_event.deltaMode === 1 ? 0.05 : d3_event.deltaMode ? 1 : 0.002);
	}

deltaY is also used here with many specific conditions:

iD/modules/renderer/map.js

Line 480 in 28183c7

var dY = source.deltaY;