ScrollTo Plugin: Jumping on ongoing touch gestures

[grommas 1 Likes (Newbie)]

Hi there, 

 

Based on TweenMax, the ScrollTo Plugin and ScrollMagic (this is probably not where the problem came from):

I wanna have a hero section on top of a page, only tweening downwards if the user is scrolling from the very beginning. Everything works as expected on my laptop (MBP). Following problem: If I use a touch-device (iPhone SE, iOS 12.4.1) and use a short touch gesture, the window is tweening to the destination withouth any issue. But if I keep my finger on the screen, the page starts to flicker and jumps back to the top after the tween finished.

 

Is there any way to fix this behaviour? Already tried to toggle preventDefault with eventListeners on Callbacks as well as setting the position again onComplete.

 

Since it's not working with Codepen on my mobile device (maybe because of the iframe issue since iOS11?):

http://grommas-dietz.com/reduced-test.html
 

See the Pen YzKEQME by grommas (@grommas) on CodePen

[mikel 2,138 Likes (Superhero)]

Hey @grommas,

 

Please look at this post on stackoverflow https://stackoverflow.com/questions/2863547/javascript-scroll-event-for-iphone-ipad

 

Best regards

Mikel

[grommas 1 Likes (Newbie)]

Hi @mikel,

 

Thank you for your response. Can’t get it work with the tips in your link. The stackoverflow post is a couple of years old, I think with turning off the passive state of the touch event listeners you don’t need to listen to the scroll itself, with document.scrollingElement.scrollTop I don’t have to to get the window.pageYOffset. But I tried it nevertheless. Could you explain your answer so that I get a clue what you exactly mean?

 

Here are my tries:

// assume the feature isn't supported
var supportsPassive = false;
// create options object with a getter to see if its passive property is accessed
var opts = Object.defineProperty && Object.defineProperty({}, 'passive', { get: function(){ supportsPassive = true }});
// create a throwaway element & event and (synchronously) test out our options
document.addEventListener('test', function() {}, opts);

// var allowScroll = true;

function preventDefault(e) {
	e = e || window.event;
	if (e.preventDefault) {
		e.preventDefault();
	}
	//	if (e.stopImmediatePropagation) {
	//		e.stopImmediatePropagation();
	//	}
	if (e.stopPropagation) {
		e.stopPropagation();
	}
	e.returnValue = false;
}
function getBodyScrollTop() {
	var el = document.scrollingElement || document.documentElement;
	return el.scrollTop;
	// return window.pageYOffset
}
function setBodyScrollTop(scrollTop) {
	var el = document.scrollingElement || document.documentElement;
	el.scrollTop = scrollTop;
	// window.pageYOffset = scrollTop;
}
function addMousewheelListener() {
	if (e.addEventListener)
	{
	    // IE9, Chrome, Safari, Opera
	    e.addEventListener("mousewheel", preventScroll, supportsPassive ? { passive: false } : false);
	    // Firefox
	    e.addEventListener("DOMMouseScroll", preventScroll, supportsPassive ? { passive: false } : false);
	}
	// IE 6/7/8
	else
	{
	    e.attachEvent("onmousewheel", preventScroll);
	}
}
function removeMousewheelListener() {
	if (e.removeEventListener)
	{
	    // IE9, Chrome, Safari, Opera
	    e.removeEventListener("mousewheel", preventScroll, supportsPassive ? { passive: false } : false);
	    // Firefox
	    e.removeEventListener("DOMMouseScroll", preventScroll, supportsPassive ? { passive: false } : false);
	}
	// IE 6/7/8
	else
	{
	    e.detachEvent("onmousewheel", preventScroll);
	}
}
function removeTouchListeners(e) {
	window.removeEventListener("scroll",     preventScroll);
	window.removeEventListener("touchmove",  preventScroll);
	window.removeEventListener("touchstart", removeTouchListeners);
	window.removeEventListener("touchend",   removeTouchListeners);
}
function preventScroll(e) {
	// if(TweenMax.isTweening(window) || !allowScroll) {
		// e.preventDefault();
		// e.stopImmediatePropagation();
		preventDefault(e)
	// }
}
function deactivateScroll() {
	// allowScroll = false;
	console.log('fired 1');
	// window.addEventListener("touchstart", preventScroll, { passive: false });
	window.addEventListener("touchmove", preventScroll, { passive: false });
	window.addEventListener("scroll", preventScroll, { passive: false });
	addMousewheelListener();
}
function activateScroll() {
	// allowScroll = true;
	removeMousewheelListener();
	// var scrollTop = y;
	// var scrollTop = getBodyScrollTop;
	// setBodyScrollTop(scrollTop);
	window.addEventListener("touchstart", removeTouchListeners, { passive: false });
	window.addEventListener("touchend", removeTouchListeners, { passive: false });
	// var event1 = new Event('touchstart');
	// var event2 = new Event('touchmove'); 
	// var event3 = new Event('touchend'); 
	// window.dispatchEvent(event1); 
	// window.dispatchEvent(event2); 
	// window.dispatchEvent(event3);
}

Of course with the callbacks in my tween:

var vh = window.innerHeight * 0.01;
document.documentElement.style.setProperty('--vh', `${vh}px`);

var ctrl = new ScrollMagic.Controller();
var sceneLeave = new ScrollMagic.Scene({
  triggerElement: "#content",
  triggerHook: "onEnter",
  offset: 1
})
  .addTo(ctrl)
  .on("enter", function(event) {
    TweenMax.to(window, 1, {
      scrollTo: {
        y: "#content",
        autoKill: false
      },
      onStart: deactivateScroll,
      onComplete: activateScroll
    });
  });

 

[mikel 2,138 Likes (Superhero)]

Hey @grommas,

 

There is a direct relationship between iOS scrolling and headaches.

 

Please do some searches in the net I´m not an expert ...

 

Good luck.

Mikel

[grommas 1 Likes (Newbie)]

I did without any luck. The plugin is supposed to scroll the window on all plattforms, that’s why I'm asking.. but thanks anyway, @mikel!

 

Are there any plans to get something like this fixed, or is it a rare case and only partially related? Could try to reproduce it without ScrollMagic, to see if the problem still exist.

[mikel 2,138 Likes (Superhero)]

Hey @grommas,

 

I built this web for a friend some time ago. Here's the problem with IOS, too - but it's limited:

 

http://www.cutandprint.de/ 

 

Maybe it helps ...

Mikel

[OSUblake 11,347 Likes (Superhero)]

6 hours ago, grommas said:

Are there any plans to get something like this fixed, or is it a rare case and only partially related? Could try to reproduce it without ScrollMagic, to see if the problem still exist.

 

What makes you think the problem is related to GSAP? You're using a 3rd party scroll library. You should probably check that first.

https://github.com/janpaepke/ScrollMagic

 

 

[OSUblake 11,347 Likes (Superhero)]

I think this is just an iOS issue. Even trying to prevent the body from scrolling during the animation (overflow: hidden) results in the jumpy behavior.

[grommas 1 Likes (Newbie)]

39 minutes ago, OSUblake said:

 

What makes you think the problem is related to GSAP? You're using a 3rd party scroll library. You should probably check that first.

https://github.com/janpaepke/ScrollMagic

 

 

Other animations (moving header and content) are not affected, only when the ScrollTo plugin is triggered. That’s why I thought it could be related to the plugin. Sorry if I got it wrong!

[OSUblake 11,347 Likes (Superhero)]

No need to be sorry. You're good. I checked and the plugin seems to be the problem, but I don't know of if it's an issue we can fix. That's what I was trying to say in my last post. It's a deeper problem related to iOS.

 

 

[mikel 2,138 Likes (Superhero)]

 

This solution is a bit unusual and maybe overdone.

based on uturn.js

But seems to get the IOS stress under control ...

 

See the Pen zYOPabe by mikeK (@mikeK) on CodePen

 

And here the live version for the iPhone test.

 

All the best ...

Mikel

[grommas 1 Likes (Newbie)]

Thank you all for your input, I will stick to my solution and disable it on touch devices. Not sure yet. Annoying, when it’s almost working.