Delayed Momentum Scrolling in Safari Extension Popover on macOS

[MineGene]

Prerequisites

• I verified that this is not a filter list issue. Report any issues with filter lists or broken website functionality by using the chat icon in the popup panel.
• This is NOT a YouTube, Facebook or Twitch report. These sites MUST be reported by clicking their respective links.
• This is not a support issue or a question. For support, questions, or help, visit /r/uBlockOrigin.
• I performed a cursory search of the issue tracker to avoid opening a duplicate issue.
• The issue is not present after disabling uBO Lite in the browser.

I tried to reproduce the issue when...

• uBO Lite is the only extension.
• using a new, unmodified browser profile.

Description

In the Safari extension popover on macOS, scrollable content initially lacks momentum (inertial) scrolling. After several minutes (~5 minutes), momentum scrolling begins to work as expected.

Possibly coincides with the filter conversion.

A specific URL where the issue occurs.

uBOL popover.

Steps to Reproduce

1. Install uBlock Origin Lite in Safari on macOS.
2. Click the uBOL icon in the Safari toolbar to open the popover.
3. Attempt to scroll using a trackpad. Observe: Scroll stops abruptly; no momentum/inertial scrolling.
4. Wait approximately 5 minutes without changing settings.
5. Open the popover again and try scrolling. Observe: Momentum scrolling now works as expected.
6. Change a setting, such as switching from “Complete” to “Optimal”.
7. Try scrolling again. Observe: Momentum scrolling is immediately lost again.

Expected behavior

Momentum scrolling always present, not just intermittently.

Actual behavior

Momentum scrolling seems to be occurring for the first few minutes after a change to uBOL Lite.

uBO Lite version

2025.515.1528

Browser name and version

Version 18.5 (20621.2.5.11.8)

Operating system and version

macOS 15.5 (24F74)

[MineGene]

Visual Comparison

Momentum scrolling

Screen.Recording.2025-05-16.at.15.55.11.mov

Non-Momentum scrolling

Screen.Recording.2025-05-16.at.15.55.36.mov

[gorhill]

uBOL is using standard HTML/CSS/JS, and I don't know what is "momentum" scrolling, and in any case I wouldn't want to overcomplicate the vanilla HTML/CSS/JS being used for optimal compatibility across all supported platforms.

---

The Chromium version of uBOL is the reference one since it supports all the filtering abilities, and doesn't exhibit undue delays when toggling filter lists or filtering modes. If a platform behaves differently than the reference version, the issue is probably something specific to that platform which should be reported as a platform issue to the developers of that platform.

[MineGene]

Understood.

Since this report I have noticed something else.
I used a MacBook Pro so use the trackpad for most things, but occasionally I have a use for a physical mouse.

When using the scroll wheel with a physical USB connected mouse inside the uBOL popover, the window does not scroll at all during the slow period I mentioned above. The only way to be able to scroll again using the physical mouse is to begin scrolling with the trackpad first (which is janky) which then allow the scroll wheel on the mouse to work again or quit Safari and reopen it.

To reproduce the loss of ability to scroll with the mouse wheel perform the following:

1. Select uBOL extension in Safari Toolbar. Observe scrolling working fine with both the trackpad and mouse
2. Select Open the Dashboard
3. Make a change, such as switching filtering mode from Complete to Optimal
4. Select the uBOL extension in Safari Toolbar. Observe scrolling does not work with the mouse at all, and scrolling is extremely janky with the trackpad.

Digging into this a little first, when using the below snippet in Console, the wheel events are being seen by Safari, yet the uBOL popover does not move when using the scroll wheel. It's only when I use the trackpad that the scroll wheel movements take effect inside the uBOL popover:

document.addEventListener('wheel', (e) => {
  console.log('Wheel event:', {
    deltaY: e.deltaY,
    deltaMode: e.deltaMode,
    ctrlKey: e.ctrlKey,
    sourceCapabilities: e.sourceCapabilities,
    isTrusted: e.isTrusted
  });
});

In the below screen recording, what you're seeing is:

1. The scroll wheel registrations in Console and the uBOL popover not scrolling, then
2. The trackpad scrolling, then
3. The scroll wheel registrations with the registrations actually taking effect in the uBOL popover

Screen record.mov.zip