@tldraw/editor/src/lib/utils/normalizeWheel.ts

tldraw infinite canvas SDK (editor).

// Reasonable defaults
const MAX_ZOOM_STEP = 10
const IS_DARWIN = /Mac|iPod|iPhone|iPad/.test(
	// eslint-disable-next-line @typescript-eslint/no-deprecated
	typeof window === 'undefined' ? 'node' : window.navigator.platform
)

// Adapted from https://stackoverflow.com/a/13650579
/** @internal */
export function normalizeWheel(event: WheelEvent | React.WheelEvent<HTMLElement>) {
	let { deltaY, deltaX } = event
	let deltaZ = 0

	// wheeling
	if (event.ctrlKey || event.altKey || event.metaKey) {
		deltaZ = (Math.abs(deltaY) > MAX_ZOOM_STEP ? MAX_ZOOM_STEP * Math.sign(deltaY) : deltaY) / 100
	} else {
		if (event.shiftKey && !IS_DARWIN) {
			deltaX = deltaY
			deltaY = 0
		}
	}

	return { x: -deltaX, y: -deltaY, z: -deltaZ }
}