465395 - Honor TEXT_DISABLE_OPTIONAL_LIGATURES in the Windows font backend

Status: RESOLVED FIXED

(Core :: Graphics, defect, P3)

Description

[Zack Weinberg (:zwol)]

Fragment of bug 464168 (q.v. for discussion) -- the Windows
implementation of gfxFontGroup needs to honor the
TEXT_DISABLE_OPTIONAL_LIGATURES flag in the return value of
nsLayoutUtils::GetTextRunFlagsForStyle.

Comment 1

[Jonathan Kew [:jfkthame]]

The preferred way to do this would be to disable the ligature features (except "required" ligatures, e.g., for Arabic) when doing glyph shaping. AFAIK, this is not supported via Uniscribe's ScriptShape API, which is what we're currently using; it would require moving to the newer ScriptShapeOpenType. However, this is only available on Vista, or on XP if we can ensure the availability of usp10.dll version 1.600 or later. Are we licensed to redistribute Uniscribe?

Comment 2

[Jonathan Kew [:jfkthame]]

As we're now using the harfbuzz backend as our primary shaping path, and it supports the TEXT_DISABLE_OPTIONAL_LIGATURES flag, I think this bug is essentially obsolete. Should we resolve it as FIXED (indirectly, by using a different path), or as WONTFIX (because it's no longer important), or what?

Comment 3

[Jonathan Kew [:jfkthame]]

Just FTR, changed bug summary as gfxWindowsFontGroup no longer exists.
Resolving as FIXED, as the issue is fixed since we enabled the harfbuzz path.