253143 - Letter spacing is applied to zero width characters (zwsp, zwj, zwnj)

Status: RESOLVED FIXED

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

Description

[Grey Nicholson (they/them)]

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.1; en-GB; rv:1.7) Gecko/20040724 Firefox/0.9.1+
Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-GB; rv:1.7) Gecko/20040724 Firefox/0.9.1+

Where a zero width space exists but there is no line-break, CSS letter-spacing
is applied to the zero width space.

Testcase follows.

Reproducible: Always
Steps to Reproduce:
1.
2.
3.

Comment 1

[Grey Nicholson (they/them)]

Attachment: Zero width spaces letter- and word-spacing test case

Comment 2

[Mike Cowperthwaite]

Opera 7.5 behaves the same.
IE6 behaves as expected.

Comment 3

[Grey Nicholson (they/them)]

Attachment: Test case v2

Added another line (to the top) - a "control group" with no zero-width spaces.

The second line should look like the first line. Failing that, the third line
should look like the first line - it has negative word-spacing applied. The
fourth line demonstrates that positive word-spacing also isn't applied to
zero-width spaces.

Comment 4

[Grey Nicholson (they/them)]

(In reply to comment #3)
> Failing that, the third line
> should look like the first line - it has negative word-spacing applied. The
> fourth line demonstrates that positive word-spacing also isn't applied to
> zero-width spaces.

By the way, these bits are bug 253144.

Comment 6

[Simon Montagu :smontagu]

Editing summary per duplicate bug.

Comment 7

[j. 'mach' wust]

This used to work just fine in Firefox 3.6, but Firefox 4 beta 6 suffers from this bug again.

Comment 8

[j. 'mach' wust]

Attachment: New testcase with actual example from German

New testcase with actual sample words from German that were displayed fine in Firefox 3.6 on Mac OS but incorrectly on Firefox 4 Beta 7 (and 6).

Comment 9

[Patrick Dark]

Attachment: This is a testcase which tests the zero‐width space, non‐joiner, and joiner characters in conjunction with the letter‐spacing property.

I’m adding an updated testcase. It unifies the two existing testcases by testing all of the three characters mentioned in the title of this bug, removes extraneous tests of the word-spacing property, and uses modern HTML.

In this testcase, only the test involving the zero‐width space character fails to display correctly in Firefox 34. The tests for the other two characters, zero‐width non‐joiner and zero‐width joiner, are displayed correctly. (So, apparently, this bug is 2⁄3s of the way fixed.)

As for other browsers, Chrome 39 displays the entire testcase correctly, and Internet Explorer 11 fails the same test as Firefox.

I’m on Windows 8.1, so the platform listed (x86 Windows XP) must be incorrect.

Comment 10

[Duan Yao]

(In reply to Patrick Garies from comment #9)
> In this testcase, only the test involving the zero‐width space character
> fails to display correctly in Firefox 34. The tests for the other two
> characters, zero‐width non‐joiner and zero‐width joiner, are displayed
> correctly. (So, apparently, this bug is 2⁄3s of the way fixed.)
> 

Not exactly, I think. Although zero‐width non‐joiner and zero‐width joiner don't contribute to letter-spacing they can still affect font selection (tested on FF36 Linux 64). As a result, texts contains zero‐width non‐joiner or zero‐width joiner may looks different from those contains none.

On my computer, "Control"(without special chars) is displayed with font "Source Han Sans SC Normal", while "Test 2" is displayed with fonts "DejaVu Sans" + "Source Han Sans SC Normal", and "Test 3" is displayed with font "DejaVu Sans".

Comment 13

[Jonathan Kew [:jfkthame]]

Attachment: Do not add letter-spacing after zero-width format controls such as ZWSP

This fixes the problem for the examples here, AFAICS, as well as for similar format characters (zero-width no-break space, word joiner).

Comment 14

[Jonathan Kew [:jfkthame]]

Attachment: Add a web-platform reftest for letter-spacing in the presence of zero-width format controls

Comment 15

[Tobi Reif]

Thanks Jonathan et al for fixing this!

Comment 17

[Jonathan Watt [:jwatt]]

https://treeherder.mozilla.org/#/jobs?repo=try&revision=bcfcac55d611ac6292e8f9b174d6531a5d1c708e

Comment 18

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/9162eefca30f
Do not add letter-spacing after zero-width format controls such as ZWSP. r=jwatt
https://hg.mozilla.org/integration/mozilla-inbound/rev/b81999f30c15
Add a web-platform reftest for letter-spacing in the presence of zero-width format controls. r=jwatt

Comment 19

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

Created web-platform-tests PR https://github.com/w3c/web-platform-tests/pull/9864 for changes under testing/web-platform/tests

Comment 20

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

Upstream PR merged

Comment 21

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

https://hg.mozilla.org/mozilla-central/rev/9162eefca30f
https://hg.mozilla.org/mozilla-central/rev/b81999f30c15

Comment 22

[Grey Nicholson (they/them)]

Thanks everyone for all your work on this over the years, particularly for expanding the scope to other affected characters.

I'm especially impressed by how robust our standard process seems to be now for automated regression testing of web platform features.

Great work everyone!

Comment 23

[Jonathan Watt [:jwatt]]

Thanks, Tobi and Greg. It's nice to seem some positive comments in bugzilla once in a while. :)

Comment 24

[Tobi Reif]

Checked letter-spacing in combination with ​ in Nightly - works :)

Comment 25

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

Upstream PR merged