1902974 - Spurious lines generated at auto-hyphenation breakpoint when clearing a float

Status: RESOLVED FIXED

(Core :: Layout: Text and Fonts, defect)

Description

[Jonathan Kew [:jfkthame]]

Testcase: https://codepen.io/jfkthame/pen/BaeJOmE?editors=1100

Observe how as the blue float grows, in the left-hand example (using hyphens: manual) the text is pushed down smoothly to just clear the bottom of the float box. This is the expected behavior.

The right-hand example, which uses hyphens: auto, should behave exactly the same, but it doesn't: observe how the text below the float jumps down by line-height increments, because spurious empty lines are being generated, each of which then displays a hyphen.

This is the underlying cause of the hang in bug 1901624.

Comment 1

[Jonathan Kew [:jfkthame]]

Attachment: Bug 1902974 - Don't allow a hyphenation break to be used at start-of-line.

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/e15156aa45be
Don't allow a hyphenation break to be used at start-of-line. r=layout-reviewers,emilio

Comment 3

[Web Platform Test Sync Bot [:wpt-sync] (Matrix: #interop:mozilla.org)]

Created web-platform-tests PR https://github.com/web-platform-tests/wpt/pull/46784 for changes under testing/web-platform/tests

Comment 4

[Jonathan Kew [:jfkthame]]

Attachment: Bug 1902974 - Don't allow a hyphenation break to be used at start-of-line.

Original Revision: https://phabricator.services.mozilla.com/D213926

Comment 5

[Jonathan Kew [:jfkthame]]

Although this isn't a recent regression, the fact that it has resulted in a browser hang on a real-world site (see bug 1901624 and the original report in bug 1901377), together with the minimal nature of the fix, makes it worth uplifting to beta IMO, so that it gets out to users sooner.

Comment 6

[Serban Stanca [:SerbanS]]

https://hg.mozilla.org/mozilla-central/rev/e15156aa45be

Comment 7

[Phabricator Automation]

beta Uplift Approval Request

• User impact if declined: possible hang/crash depending on web-page content
• Code covered by automated testing: yes
• Fix verified in Nightly: no
• Needs manual QE test: no
• Steps to reproduce for manual QE testing: n/a
• Risk associated with taking this patch: minimal
• Explanation of risk level: simple condition to prevent spurious line-breaks when hyphenation is used
• String changes made/needed: none
• Is Android affected?: yes

Comment 8

[Web Platform Test Sync Bot [:wpt-sync] (Matrix: #interop:mozilla.org)]

Upstream PR merged by moz-wptsync-bot

Comment 9

[Pulsebot]

https://hg.mozilla.org/releases/mozilla-beta/rev/6ed5b1775bff