CodeMirror overlay scrollbars are not activated on hover

[anewuser]

Prerequisites

• I verified that this is not a filter list issue. Report any issues with filter lists or broken website functionality in the uAssets issue tracker.
• 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 in the browser.
• I checked the documentation to understand that the issue I am reporting is not normal behavior.

I tried to reproduce the issue when...

• uBO is the only extension.
• uBO uses default lists and settings.
• using a new, unmodified browser profile.

Description

Bug 1967663 - CodeMirror overlay scrollbars are not activated on hover:

The scrollbar is hidden when you start typing, and then never reappears on hover.

---

So this is really just a bug in CodeMirror, with this element failing to perfectly pretend to be a regular scrollbar in this case. Maybe it's fixed upstream, though? At least, I don't see the same issue in https://codemirror.net/try/ .

[...] If this is fixed upstream, we'd need to update the imported copy of the library there in order to fix this; and uBlock Origin would need to do the same.

A specific URL where the issue occurs.

Dashboard tabs: My filters, My rules.

Steps to Reproduce

1. Open the My filters tab on a system that uses overlay scrollbars by default, e.g. Windows 11 or Ubuntu 24.04
2. Paste some dummy text to make the vertical scrollbar appear
3. Keep typing for the scrollbar to be hidden automatically
4. Move your mouse cursor towards the scrollbar

Expected behavior

The scrollbar to reappear.

Actual behavior

The scrollbar doesn't reappear on hover.

uBO version

1.64.1b0

Browser name and version

Firefox Nightly

Operating System and version

Windows 11

[gorhill]

I see that CodeMirror is forcing an inline pointer-events: none on the element containing the scrollbar.

Removing that style fixes the issue, but since I do not know why it's added by CodeMirror, I don't know if there will be negative side effect.

I will add a .CodeMirror-vscrollbar { pointer-events: initial !important; } to override the inline style.

[anewuser]

Overlay scrollbars are actually supposed to be re-enabled as soon as we move our cursors anywhere over the scrollable area (Bug 1967663#c4), and this is the behavior on this CodeMirror test page:

Try.CodeMirror.mp4

Your fix does re-enable them when I move the cursor towards their locations, though, and this is good enough for me:

uBlock.Origin.1.64.1b1.mp4

[gorhill]

That's CodeMirror 6, uBO uses CodeMirror 5 and I can see the same issues in 5's demos: https://codemirror.net/5/.

[gorhill]

Ok I looked further and there is nothing more I can do with CodeMirror 5. The scrollbar is a standalone widget, not part of the text area, and the browser will only reveal the scrollbar when hovering over the area associated with it, but there is none for that scrollbar, it's just a scrollbar with nothing to hover except itself.

There are many CodeMirror 5-related issues in uBO, and the only way to solve them would be to move to CodeMirror 6, but seems to be a whole lot of work given all the CM customizations done in uBO.