308208 - Diacritics applied to wrong characters when using Trebuchet MS

Status: NEW

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

Description

[Marek Stępień [:marcoos, inactive]]

When some texts in Polish are rendered in certain sizes of the bold version of
Trebuchet MS (and occasionally some other fonts), diacritics is sometimes
positioned above the preceding letter, not the one it should.

In the following testcase (UTF-8, requires Trebuchet MS from the ms-core-fonts
package) the text in each line should be rendered with the acute symbol over the
letters "c" and "n", more-less like this:

  ,      ,
byc zielen

Instead, the "'" is sometimes rendered above the letter "y" in the first word
and above the letter "e" in the second word:

 ,      ,
byc zielen

which is obviously wrong. 

It usually happens when the font-size is between 12 and 15 px (or corresponding
em/ex/pt values).

This may have something in common with other bugs with diacritics, but all the
bugs I found where about non-Latin alphabets, so I'm no sure if it's a duplicate
of any of those.

I reproduced this bug in the following builds:
- latest Firefox nightly build, 1.5 trunk
- Firefox 1.0.6 
- Mozilla suite 1.7.8

all under Linux.

A testcase and a screenshot follow.

Comment 1

[Marek Stępień [:marcoos, inactive]]

Attachment: testcase

Comment 2

[Marek Stępień [:marcoos, inactive]]

Attachment: Screenshot

This screenshot shows the rendering of the testcase. Parts of the image that
have been colored green are correct, parts colored yellow and red are wrong.

Comment 3

[Jo Hermans]

For comparison purposes: works for me in Mac OS X 10.2.8
Mozilla/5.0 (Macintosh; U; PPC Mac OS X Mach-O; en-US; rv:1.8b4) Gecko/20050908
Firefox/1.4

Comment 4

[Marek Stępień [:marcoos, inactive]]

People seem to be still seeing this bug on Linux, even with 3.0rc2, as reported in this blog:

http://zibik.jogger.pl/2008/06/09/ot-to-tylko-kolejny-problem-z-ff/

Comment 5

[u294409]

yep, it's true on minefield@linux.