1426827 - An emoji sequence (e.g. base emoji + fitzpatrick modifier) may be split into 2 halves in separate lines

Status: VERIFIED FIXED

(Core :: Layout: Text and Fonts, defect, P3)

Description

[Fanolian]

Attachment: Reduced testcase showing emoji was split into 2 lines

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:59.0) Gecko/20100101 Firefox/59.0
Build ID: 20171221220104

Steps to reproduce:

1. Open the attached reduced testcase. (Or visit the original page: https://ol.mingpao.com/php/showbiz3.php?nodeid=1513917011660&subcate=latest&issue=20171222)
2. Observe the emoji at the end of the paragraph.


Actual results:

The emoji is split into halves and displayed on separate lines.

Note:
If I delete Emoji Modifier Fitzpatrick Type-1-2 from the emoji, it will display as a whole on a new line.

Comment 1

[Fanolian]

Attachment: Screenshot of the issue

Comment 2

[Jonathan Kew [:jfkthame]]

Yes, I can reproduce this on macOS as well, by slightly adjusting the line width in the testcase.

I guess the problem arises because in general, the line-break code allows a break between emoji characters; but it doesn't recognize that the fitzpatrick modifiers should always remain attached to the preceding character. This, combined with the fact that a line-break is _not_ allowed before the following punctuation character, results in breaking the line before the modifier. :(

A somewhat related issue is that text selection and caret movement doesn't treat the emoji+modifier combination as a single unit: it can be selected in two separate parts. Presumably for some of the complex family emoji sequences, etc., the issue would be even worse.

Comment 3

[İsmail Dönmez]

Also the same issue on Linux (tested with "Apple Color Emoji"), interestingly if you check the source code it's rendered properly.

Comment 4

[Terence Eden]

This is also an issue on Android v61.0

See https://twitter.com/edent/status/1016960926178840577

Comment 5

[Fanolian]

FYI, the testcase is currently affected by bug 1463161.

Comment 6

[Jonathan Kew [:jfkthame]]

Attachment: Treat Fitzpatrick skin-tone modifiers as cluster extenders when building textrun

Similar to the tag characters in bug 1477010, I think we should treat these as cluster-extenders to force them to stay attached to their base glyph.

Comment 7

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/a1ef0307687c
Treat Fitzpatrick skin-tone modifiers as cluster extenders when building textruns. r=m_kato

Comment 8

[Sebastian Hengst [:aryx] (needinfo me if it's about an intermittent or backout)]

https://hg.mozilla.org/mozilla-central/rev/a1ef0307687c

Comment 9

[Fanolian]

I can verify the bug is fixed in 2018-07-26 Nightly. Thanks.

Comment 10

[Cristian Comorasu, QA [:ccomorasu], Releae Desktop QA - Please contact [e-mail]]

Updating the tracking flag as per comment 9.