543353 - Characters in cyrillic text overlap with font:.8em Arial

Status: RESOLVED FIXED

(Core :: Layout: Text and Fonts, defect, P2)

Description

[Nickolay_Ponomarev]

Attachment: testcase

When opening the attached testcase in a clean Firefox profile on (at least) Mac OS X 10.5 with default fonts (the culprit is /Library/Fonts/Arial.ttf - version 5.01.2x - part of the default install per http://support.apple.com/kb/HT1642 ), some words are unreadable because some characters are drawn at incorrect positions.

This happens on Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-US; rv:1.9.3a1pre) Gecko/20100129 Minefield/3.7a1pre
but not on Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-US; rv:1.9.2) Gecko/20100115 Firefox/3.6

This is similar to bug 288047, which is said to be fixed in Gecko 1.9. Didn't find other reports of this with newer Geckos.

whimboo confirmed this on his 10.5 install. Help with getting a regression range would be appreciated.

Comment 1

[Nickolay_Ponomarev]

Attachment: screenshot

Comment 2

[Nickolay_Ponomarev]

Works in 2009-09-26-03-mozilla-central
http://hg.mozilla.org/mozilla-central/rev/149c3820e8a8

Fails in f-2009-09-27-16-mozilla-central
http://hg.mozilla.org/mozilla-central/rev/61620a8558c4

Checkin range: http://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=149c3820e8a8&tochange=61620a8558c4

From the description, I guess bug 517877?

Comment 3

[Jonathan Kew [:jfkthame]]

I'm not seeing this problem on 10.6.2 with a nightly from 2009-09-28 or with a current trunk build.

The version number of Arial.ttf here appears to be the same as your 10.5 version, so I suspect this may be a bug in Core Text on Leopard.

Comment 4

[Nickolay_Ponomarev]

Asking for blocking1.9.3, since this (possibly combined with other issues with similar symptoms) makes many web sites hard to read on a supported system (10.5).

Comment 5

[Robert O'Callahan (:roc) (email my personal email if necessary)]

Jonathan, do you have 10.5 available?

Comment 6

[Jonathan Kew [:jfkthame]]

(In reply to comment #5)
> Jonathan, do you have 10.5 available?

Not currently. Presumably I could try installing it to an external drive for testing.

Comment 7

[Jonathan Kew [:jfkthame]]

Ok, I've been testing this on 10.5, and confirmed that it is definitely a Core Text bug on Leopard, and appears to be fixed on Snow Leopard. I'll be filing a report with Apple after cleaning up my testcase a bit further.

I believe we can work around the problem by breaking the text into separate script runs before passing it to Core Text for shaping. This appears to resolve the spacing problems in my testing, at least. The harfbuzz work (bug 449292) already includes a patch to do this ("part 4" there), so if we can get that landed then I expect it to resolve this bug even when using the Core Text backend.

Comment 8

[Jonathan Kew [:jfkthame]]

Attachment: test program showing incorrect results from Core Text

This standalone tool demonstrates the bug. It calls Core Text to do layout of the sample text, and reports the resulting glyph positions. Comparing results for the full sample string and results for the last pure-Cyrillic run when processed alone, the errors are clearly visible in the reported glyph advances.

Filed with Apple as rdar://7840668.

Comment 9

[Jonathan Kew [:jfkthame]]

I would appreciate people testing trunk nightlies to confirm whether this is still a problem. I believe it should have been fixed as a side-effect of the restructuring of text-run creation that was done in bug 449292.

Comment 10

[Nickolay_Ponomarev]

The testcase works fine with Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-US; rv:1.9.3a6pre) Gecko/20100614 Minefield/3.7a6pre

Henrik, can you confirm that?

Comment 11

[Henrik Skupin [:whimboo][⌚️UTC+1]]

I don't have 10.5 anymore. All my systems are running on 10.5 now. So if it works for you we should be fine.