Allow zooming further with pinch gesture on mobile devices

[francoischalifour]

Allow zooming further with pinch gesture on mobile devices

[francoischalifour]

I haven't dug very much into the behavior but I think that the issue comes from somewhere else.

We dismiss the zoom when (simplified):

• The zoomed image is clicked
• The scroll position exceeds the original scroll position + the offset (40px by default)

My assumption is that when you pinch the image, the scroll position changes, causing the zoom to be dismissed.

We would therefore need to add a new condition in the scroll handling function to not close the zoom when the image is pinched:

medium-zoom/src/medium-zoom.js

Lines 36 to 39 in 78e0974

	const _handleScroll = () => {
	if (isAnimating || !active.original) {
	return
	}

From reading the documentation on ToucheEvent.touches, it seems like we can change the state on touchstart and touchend when touches.length >= 2 (as pointed out by @tuelsch) to return early in this function.

That's only my assumption based on what I tried blindly on my phone.

If you've got time, feel free to send a PR!

[gfellerph]

Can a pinch gesture be detected by inspecting the event.touches >= 2 property? This means that two or more fingers/pointers are involved. Say, if more than two "touches" are detected, don't close the image and let the browser do its thing.