disable-scrolling-while-enabling-pinching.js

import Hammer from 'hammerjs'

const hammer = new Hammer(backdropEl, { touchAction: 'auto' })
hammer.get('pinch').set({ enable: true })

let isPinching = false

hammer.on('pinchstart', () => {
    isPinching = true
})

hammer.on('pinchend', () => {
    isPinching = false
})

backdropEl.addEventListener('touchmove', (ev) => {
    if (!isPinching) {
        ev.preventDefault()
    }
})