Bug 224483 – text-decoration-thickness property doesn't always trigger repaint when changed

• Component: Text
• Status: RESOLVED FIXED

[Vanita Barrett-Smith]

Created attachment 425866 [details]
HTML example (alternative to CodePen)

## Steps to reproduce
1. Open https://codepen.io/36degrees/pen/LYxQBbm or the attached example.html
2. Hover over both links of the links on the line “17px link / with colour change” - text decoration thickness property expands to 3px
3. Hover over both of the links on the line “19px link / with colour change” - text decoration thickness property only expands to 3px on the link with colour change.

## Expected Behaviour 
The text underline thickness should increase to 3px on all links when hovered.

## Actual Behaviour
In this example, the text-decoration-thickness only increases to 3px on hover on links up to a font-size of 19px, unless the link also has a colour change on hover.

The font-size at which the text-decoration-thickness property stops working changes depending on the thickness being set on hover. In the CodePen / attached example, text-decoration-thickness is set to 3px on hover and stops working at links of font-size: 19px. Other examples:

text-decoration-thickness on hover: 2px 
font-size value at which it stops working: 15px

text-decoration-thickness on hover: 5px 
font-size value at which it stops working: 27px

[Alexey Proskuryakov]

In Safari 14.1, the underlines for 19px+ links are not painted at all (but the color ones are). Not sure if we'd want to track this aspect as a separate bug.

[Radar WebKit Bug Importer]

<rdar://problem/76895249>

[Tim Nguyen (:ntim)]

I have a fix for this.

[Tim Nguyen (:ntim)]

Pull request: https://github.com/WebKit/WebKit/pull/8372

[Tim Nguyen (:ntim)]

Submitted web-platform-tests pull request: https://github.com/web-platform-tests/wpt/pull/37799

[EWS]

Committed 258641@main (6be98ae1629f): <https://commits.webkit.org/258641@main>

Reviewed commits have been landed. Closing PR #8372 and removing active labels.