:hover CSS pseudo-class sometimes keeps matching ever after mouse has left the element

[Chris Rebert]

Created attachment 280426 [details]
Video of the bug in action

Steps to reproduce:
1. Open https://jsfiddle.net/cvrebert/rgq9zwc2/ in WebKit Nightly or Safari 9.
2. Move the mouse pointer to the star in the lower-right corner.
3. Observe that a tooltip appears.
4. Move the mouse pointer vertically upward along the column of stars.

Actual result:
Several of the gray boxes turn blue and stay blue,
indicating that the :hover pseudo-class is applying to several of them simultaneously.
See attached video, courtesy of https://github.com/RopoMen

Expected result:
Only the box currently being hovered over should be blue.
Each box should turn gray again immediately after the pointer moves outside of the box's respective bounds.

Original Bootstrap bug:
https://github.com/twbs/bootstrap/issues/20012

[Benjamin Poulain]

I know what is up.
Not looking forward to writing more tests though :(

[Radar WebKit Bug Importer]

<rdar://problem/26905293>

[Benjamin Poulain]

Created attachment 281709 [details]
Patch

[WebKit Commit Bot]

Attachment 281709 [details] did not pass style-queue:


ERROR: Source/WebCore/ChangeLog:35:  Need whitespace between colon and description  [changelog/filechangedescriptionwhitespace] [5]
Total errors found: 1 in 7 files


If any of these errors are false positives, please file a bug against check-webkit-style.

[Benjamin Poulain]

Created attachment 281710 [details]
Patch

[Build Bot]

Comment on attachment 281710 [details]
Patch

Attachment 281710 [details] did not pass ios-sim-ews (ios-simulator-wk2):
Output: http://webkit-queues.webkit.org/results/1539894

New failing tests:
fast/css/ancestor-of-hovered-element-detached.html
fast/css/ancestor-of-hovered-element-removed.html

[Build Bot]

Created attachment 281713 [details]
Archive of layout-test-results from ews121 for ios-simulator-wk2

The attached test failures were seen while running run-webkit-tests on the ios-sim-ews.
Bot: ews121  Port: ios-simulator-wk2  Platform: Mac OS X 10.11.4

[Benjamin Poulain]

I'll have to skip those tests on iOS before landing.

[Simon Fraser (smfr)]

Comment on attachment 281710 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=281710&action=review

Please fix or skip the test for iOS.

> Source/WebCore/ChangeLog:14
> +        -"a" starts being removed from the tree, its renderer are destroyed.

its render is

> Source/WebCore/ChangeLog:16
> +         and call hoveredElementDidDetach().

calls

> Source/WebCore/ChangeLog:20
> +         and call hoveredElementDidDetach().

calls

[Benjamin Poulain]

Created attachment 281812 [details]
Patch

[WebKit Commit Bot]

Comment on attachment 281812 [details]
Patch

Clearing flags on attachment: 281812

Committed r202324: <http://trac.webkit.org/changeset/202324>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.