Bug 198543

Summary:

[css-text] line-break: anywhere takes chars of zero-width related classes as forced breaks

Product:

WebKit

Reporter:

Javier Fernandez <jfernandez>

Component:

Text

Assignee:

Nobody <webkit-unassigned>

Status:

RESOLVED CONFIGURATION CHANGED

Severity:

Normal

CC:

ahmad.saleem792, jfernandez, karlcow, mmaxfield

Priority:

Version:

WebKit Nightly Build

Hardware:

Unspecified

OS:

Unspecified

See Also:

https://bugs.webkit.org/show_bug.cgi?id=196169

Attachments:

Description	Flags
Test case to reproduce the issue	none
Actual result	none
Expected result	none
Test case to reproduce the issue	none
Actual result	none

Javier Fernandez

Reported 2019-06-04 14:16:01 PDT

Created attachment 371331 [details] Test case to reproduce the issue What steps will reproduce the problem? (1) Load the attached test case What is the expected result? No char is sick out from the green box; all the zero-width chars are ignored and should not affect the height of the line (expected.png) What happens instead? The 3 zero-width class chars are used as forced break points, affecting the height of the line, which sicks out below the green box (actual.png)

Attachments
Test case to reproduce the issue (372 bytes, text/html) 2019-06-04 14:16 PDT, Javier Fernandez	no flags	Details
Actual result (893 bytes, image/png) 2019-06-04 14:23 PDT, Javier Fernandez	no flags	Details
Expected result (228 bytes, image/png) 2019-06-04 14:24 PDT, Javier Fernandez	no flags	Details
Test case to reproduce the issue (371 bytes, text/html) 2019-06-06 02:43 PDT, Javier Fernandez	no flags	Details
Actual result (510 bytes, image/png) 2019-06-06 02:44 PDT, Javier Fernandez	no flags	Details
Show Obsolete (2) View All Add attachment proposed patch, testcase, etc.

Javier Fernandez

Comment 1 2019-06-04 14:23:48 PDT

Created attachment 371333 [details] Actual result

Javier Fernandez

Comment 2 2019-06-04 14:24:07 PDT

Created attachment 371334 [details] Expected result

Javier Fernandez

Comment 3 2019-06-04 14:24:56 PDT

This issue is only reproducible in Mac and iOs platforms, so that means that the bug is in the SimpleLineLayout codepath.

Javier Fernandez

Comment 4 2019-06-06 02:43:42 PDT

Created attachment 371482 [details] Test case to reproduce the issue

Javier Fernandez

Comment 5 2019-06-06 02:44:07 PDT

Created attachment 371483 [details] Actual result

Javier Fernandez

Comment 6 2019-06-06 04:59:39 PDT

After debugging the test case, I've got new information regarding this issue. First of all, this is not affecting the SimpleLineLayout codepath at all, which is not executed if the value of the line-break property is different than 'auto'. Hence, the bug is affecting the BreakingContext path. Additionally, since other ports also use the BreakingContext path, why this bug is not reproducible in WebKitGtk+ ? The reason seems to be that the root cause of this issue is the #196169 bug (maybe duplicated ?) Debugging the attached test case, I've got the following data: * Mac platform - availableWidth (1ch) = 7.796875 - charWidth = 7.80126953 * Gtk platform - availableWidth (1ch) = 8 - charWidth = 8 The consequence of having a charWidth bigger than the availableWidth is that the line breaking logic may have to break just after the char, even that theoretically the single char should fit. Hence, the problem is not related to the line-break: anywhere feature, but more with how WebKit deals with the monospace font and the 'ch' sizing unit.

Ahmad Saleem

Comment 7 2025-12-11 23:10:12 PST

I am not able to reproduce this on Safari 26.1. Marking this as `Configuration Changed`, please reopen if it is still reproducing. Thanks1

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