2012743 - dxp.salam.sa - Page scrolling is slow

Status: RESOLVED FIXED

(Web Compatibility :: Site Reports, defect, P3)

Description

[Bernadett Farkas]

Environment:
Operating system: Windows 10
Firefox version: Firefox 147.0 / Firefox Nightly 149.0a1 (2026-01-26)

Steps to reproduce:

1. Access: https://dxp.salam.sa/ar/consumer/home/salam-fiber/fiber-postpaid/#%D8%A7%D9%84%D8%AA%D8%AD%D9%82%D9%82-%D9%85%D9%86-%D8%A7%D9%84%D8%A3%D9%87%D9%84%D9%8A%D8%A9
2. Scroll up and down on the page
3. Observe

Expected Behavior:
The scroll is working accordingly

Actual Behavior:
Page scrolling is slow

Notes:

• Reproduces regardless of the status of ETP
• Reproduces in firefox-nightly, and firefox-release
• Does not reproduce in chrome

Created from https://github.com/webcompat/web-bugs/issues/204095

Comment 1

[Bernadett Farkas]

Attachment: slow scroll issue Nightly vs Chrome

Comment 2

[BugBot [:suhaib / :marco]]

Since nightly and release are affected, beta will likely be affected too.
For more information, please visit BugBot documentation.

Comment 3

[Alice0775 White]

disable https://dxp.salam.sa/assets/vanilla_scripts-C4LCum1r.js

Comment 4

[Kagami Rosylight 🏳️‍🌈🏳️‍⚧️ [:saschanaz] (they/them)]

Site has: https://dxp.salam.sa/assets/vanilla_scripts-C4LCum1r.js (as Alice0075 mentioned, but that was vague...)

  function c() {
    if (!o) return;
    const a = o.getBoundingClientRect().top + l();
    let u = null,
    m = 1 / 0;
    r.forEach(
      (s, y) => {
        const f = s.getBoundingClientRect().top - a;
        f <= 0 &&
        Math.abs(f) < m &&
        (m = Math.abs(f), u = y)
      }
    ),
    Math.abs(
      window.innerHeight + window.scrollY - document.documentElement.scrollHeight
    ) < 5 &&
    (u = Array.from(r.keys()).pop() || null),
    e.forEach(
      s => {
        const y = s.closest('.anchor-link');
        s.getAttribute('href') === `#${ u }` ? (
          y == null ||
          y.classList.add('anchor-link--is-active'),
          y == null ||
          y.scrollIntoView({
            behavior: 'smooth',
            inline: 'center',
            block: 'nearest'
          })
        ) : y == null ||
        y.classList.remove('anchor-link--is-active')
      }
    )
  }

  window.addEventListener('scroll', c, {
    passive: !0
  }),

This event listener is problematic, disabling this one fixes the scroll issue. Here, y is the tab in the top of the screen, and that's already in the screen. Somehow calling scrollIntoView in an non-passive scroll event listener causes the scroll to stop?

Comment 5

[Kagami Rosylight 🏳️‍🌈🏳️‍⚧️ [:saschanaz] (they/them)]

Site works as expected now with the fix on nightly. Bernadett, can you confirm?

Comment 6

[Bernadett Farkas]

I can confirm that the scroll functionality is working correctly in Firefox Nightly 151.0a1 (2026-03-31).

Comment 7

[Kagami Rosylight 🏳️‍🌈🏳️‍⚧️ [:saschanaz] (they/them)]

Thank you!