1876269 - [X11/KDE] CSS `cursor:none` not working, fixed in KDE 5.27

Status: RESOLVED WORKSFORME

(Core :: Widget: Gtk, defect, P3)

Description

[Christian Lampe [:lampe2020]]

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:123.0) Gecko/20100101 Firefox/123.0

Steps to reproduce:

I played a YouTube video in fullscreen in Firefox Developer Edition 123.0b1.
Then I played a video on my own website (Lampe2020.de).

Actual results:

The cursor jumped a few pixels to the right when YouTube hid its video UI and back to the left when YouTube unhid its UI.
Same behaviour on my own website, except that the cursor jumped diagonally instead of horizontally.

Expected results:

The cursor should have disappeared in both cases.

Comment 1

[BugBot [:suhaib / :marco/ :calixte]]

The Bugbug bot thinks this bug should belong to the 'Core::Audio/Video: Playback' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.

Comment 2

[Christian Lampe [:lampe2020]]

This seems to be an issue with hiding the cursor in general, as it just gets stuck on whatever it was before hiding when mousing over any element with CSS cursor:none;.

Comment 3

[Christian Lampe [:lampe2020]]

(In reply to BugBot [:suhaib / :marco/ :calixte] from comment #1)

The Bugbug bot thinks this bug should belong to the 'Core::Audio/Video: Playback' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.

This seems to be a problem with applying the CSS cursor:none; rule, as mousing over any element that has cursor:none; set shows the cursor that was set on the element the mouse came from. So when going from a link to said element the hand cursor is shown, going from a <div> for example to the same element with cursor:none; shows the normal arrow pointer.

Comment 4

[Christian Lampe [:lampe2020]]

On my own website I have now implemented a workaround, which is setting the cursor to a single transparent pixel if possible, using none only as a fallback. That works except for when the cursor isn't updated in fullscreen inside a diamond-shaped area whose corners are at each screen edge's mid-point, just like the previous solution (cursor:none) for Firefox Developer Edition <=122.0b9.

Comment 5

[Christian Lampe [:lampe2020]]

I just discovered that totem has the exact same bug but not Ungoogled Chromium, so it can't really be a KDE problem, I think. And because Ungoogled Chromium is (as far as I know) also built on Gtk it can't really be a Gtk bug either, except if it's on a version that newer Firefox and totem use but not Ungoogled Chromium.

Comment 6

[Christian Lampe [:lampe2020]]

Attachment: Screen recording of bug 1876269 happening in Firefox Developer Edition 123.0b3

Don't worry about the random string in the bottom right corner of the attached recording, it's an element in OBS for my YouTube videos which I forgot to hide before starting the recording.

Comment 7

[Christian Lampe [:lampe2020]]

This isn't only a problem in YouTube, this affects all websites, that's why I changed the title.

Comment 8

[Jonathan Kew [:jfkthame]]

I'm not seeing this on macOS. It sounds more like a platform-integration issue than a CSS bug, I think; moving to Widget for investigation.

Comment 9

[Christian Lampe [:lampe2020]]

I just tested it on Fluxbox (X11) and the cursor hides just fine as it seems.
And I updated KDE Plasma from the official Ubuntu 22.04's 5.24 to the ubuntu backports' 5.27 (because I wanted to have the floating panel) and now the cursor hides fine again. So maybe it's a KWin-and-GTK-not-cooperating-properly problem.

Should I close this because using newer KDE (from a backports PPA) doesn't seem to cause the problem, or should I keep this open because normal Ubuntu 22.04 users will still experience this bug?

Comment 10

[Martin Stránský [:stransky] (ni? me)]

Les't close it if it's fixed in 5.27.