619061 - OpenType Sanitizer default settings break GPOS kerning for downloadable fonts

Status: RESOLVED WONTFIX

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

Description

[Jens]

User-Agent:       Mozilla/5.0 (Macintosh; U; PPC Mac OS X 10.5; de; rv:1.9.2.13) Gecko/20101203 Firefox/3.6.13
Build Identifier: Mozilla/5.0 (Macintosh; U; PPC Mac OS X 10.5; de; rv:1.9.2.13) Gecko/20101203 Firefox/3.6.13

The Mac OS X layout engine doesn't apply GPOS kerning if no GSUB OpenType table is present.

The OpenType sanitizer introduced in Firefox release 3.6.13 doesn't preserve OpenType Layout tables by default (other than on Windows, gfx.downloadable_fonts.sanitize.preserve_otl_tables is set to false on Mac by default), so kerning is not applied to @font-face fonts anymore. It used to work in 3.6.12.

Is there any reason why OpenType layout tables are not preserved on Mac?

Reproducible: Always

Comment 1

[Jonathan Kew [:jfkthame]]

This is expected; it is to improve security and stability. We strip the OpenType layout tables before passing the font to Apple's text-layout APIs because errors or inconsistencies (whether accidental or deliberate/malicious) in such font tables can cause crashes.

In Firefox 4 beta, you should find that GPOS kerning (and other OpenType features) work properly with downloadable fonts, as we use different layout code that is more robust. For 3.6, this was disabled by default to protect users.