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Broken auto-play, draggable & inertia, marquee animation

Krause test
Moderator Tag

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Hi there beloved community.


Note: The codepen url is a test-project to show code previews.


I'm in the process of launching a new portfolio but there's a bug with my GSAP-based marquee which showcases my projects in a gallery. From what I can see it looks like my code doesn't calculate the proper width & height of all of the media's inside of the marquee. And sometimes on load it only loads some of the actual content inside.


Another thing: the marquee height is clamped, and inside of my runMarquee function it looks like the height doesn't adapt when resizing.


I use:

SvelteKit (framework)

Hygraph (GraphQL)


Another issue I'm facing is that most of my content inside of the marquee's has different aspect-ratios, especially the videos doesn't load in the proper format. So please also look for a solution to this.


Maybe: I would also like for the "dragging" to have less strength if possible, and then on mobile have stronger


Preview link of website:


sometimes it works and sometimes it doesn't. I need it to be bullet-proof.


If you have a stronger code for the same results, please let me know!


HTML structure:

<div class="marquee">
  <div class="track">
    <!-- Media will go here -->
    <video autoplay loop muted src={url} type="video/mp4" />
    <img src={url} alt="" />



.marquee {
  height: clamp(18.75rem, 12.5rem + 16.6667vw, 25rem);
  position: relative;
  overflow: hidden;
  display: block;
  margin-left: calc(var(--space) * -1);
  width: 100vw;

.marquee .track {
  height: 100%;
  transform-origin: 0 0;
  display: block;
  position: relative;

.marquee .track > * {
  height: 100%;
  width: auto;
  padding-left: 4px;
  position: absolute;
  object-fit: cover;



onMount(() => {
  function runMarquee() {
    const allMarquees = document.querySelectorAll('.marquee');
    allMarquees.forEach((marquee, index) => {
      const allItems = marquee.querySelectorAll('.marquee>.track>*'),
            proxy = document.createElement('div');
      let totalX = 0,
          marqueeH = 0;
      allItems.forEach((item, i) => {
        const itemW = item.offsetWidth,
              itemH = item.offsetHeight;
        (totalX += itemW),
          gsap.set(item, {
          x: totalX,
          width: itemW,
          height: itemH
          itemH > marqueeH && (marqueeH = itemH);
      const marqueeVal = gsap.utils.wrap(0, totalX),
            marqueeProgress = gsap.utils.wrap(0, 1);
      gsap.set([marquee], {
        height: marqueeH
      const stringX = `-=${totalX}`,
            animation = gsap.to(allItems, {
              repeat: -1,
              duration: 300,
              x: stringX,
              ease: 'none',
              paused: !0,
              modifiers: {
                x: function (x, target) {
                  return `${(x =
                             ((parseInt(x) - totalX) % totalX) + (totalX - target.offsetWidth))}px`;

      function updateProgress() {
        const dragValue = marqueeVal((this.deltaX / 2) * -1) / totalX,
              currentProgressAnim = animation.progress(),
              endProgress = marqueeProgress(currentProgressAnim + dragValue);
      Draggable.create(proxy, {
        type: 'x',
        trigger: marquee,
        inertia: !0,
        onDrag: updateProgress,
        onThrowUpdate: updateProgress
        window.addEventListener('resize', function resize() {
        animation.render(animation.time(), !1, !0);


Thanks :-)

CleanShot 2023-08-16 at 1.41.42.gif

See the Pen zYMyMyK by asgerkrause (@asgerkrause) on CodePen

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We can't debug live sites and your example is doing some weird style update to the images as they have a 6 pixels width 🤷‍♂️


I strongly suggest you to use the Horizontal Endless Loop helper function that works great and even has Draggable and Inertia baked into it (since you have access to the plugin it should work the way you intend):

See the Pen gOvvJee by GreenSock (@GreenSock) on CodePen


Hopefully this helps.

Happy Tweening!

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