上下文替换似乎不适用于 LuaLateX，但它可以很好地与 XeLateX 配合使用。是我做错了什么，还是这是一个错误？
\documentclass{article}
\usepackage{fontspec}
\setmainfont{Linux Libertine O}
\begin{document}
\textvbaraccent{i} fä f?
\end{document}
西拉特克斯
LuaLaTeX
（注意“f”上部与“ä”第一个点之间的间距以及“f”与“？”之间的间距）
答案1
TeX Live 2013 的新版本（目前为测试版）似乎已经解决了这个问题。以下是使用
> lualatex --version
This is LuaTeX, Version beta-0.76.0-2013052718 (TeX Live 2013) (rev 4627)
Execute 'luatex --credits' for credits and version details.
There is NO warranty. Redistribution of this software is covered by
the terms of the GNU General Public License, version 2 or (at your option)
any later version. For more information about these matters, see the file
named COPYING and the LuaTeX source.
Copyright 2013 Taco Hoekwater, the LuaTeX Team.
这是文件列表
*File List*
article.cls 2007/10/19 v1.4h Standard LaTeX document class
size10.clo 2007/10/19 v1.4h Standard LaTeX file (size option)
fontspec.sty 2013/05/20 v2.3c Font selection for XeLaTeX and LuaLaTeX
expl3.sty 2013/03/14 v4469 L3 Experimental code bundle wrapper
l3names.sty 2012/12/07 v4346 L3 Namespace for primitives
l3bootstrap.sty 2013/01/08 v4420 L3 Experimental bootstrap code
luatex.sty 2010/03/09 v0.4 LuaTeX basic definition package (HO)
infwarerr.sty 2010/04/08 v1.3 Providing info/warning/error messages (HO)
ifluatex.sty 2010/03/01 v1.3 Provides the ifluatex switch (HO)
etex.sty 1998/03/26 v2.0 eTeX basic definition package (PEB)
luatex-loader.sty 2010/03/09 v0.4 Lua module loader (HO)
pdftexcmds.sty 2011/11/29 v0.20 Utility functions of pdfTeX for LuaTeX (HO)
ltxcmds.sty 2011/11/09 v1.22 LaTeX kernel commands for general use (HO)
ifpdf.sty 2011/01/30 v2.3 Provides the ifpdf switch (HO)
l3basics.sty 2013/01/10 v4428 L3 Basic definitions
l3expan.sty 2013/02/03 v4458 L3 Argument expansion
l3tl.sty 2013/01/08 v4415 L3 Token lists
l3seq.sty 2013/01/12 v4434 L3 Sequences and stacks
l3int.sty 2013/01/13 v4444 L3 Integers
l3quark.sty 2012/11/04 v4268 L3 Quarks
l3prg.sty 2013/02/13 v4459 L3 Control structures
l3clist.sty 2013/01/08 v4414 L3 Comma separated lists
l3token.sty 2013/01/10 v4428 L3 Experimental token manipulation
l3prop.sty 2013/01/09 v4423 L3 Property lists
l3msg.sty 2013/01/08 v4412 L3 Messages
l3file.sty 2013/01/14 v4446 L3 File and I/O operations
l3skip.sty 2013/01/13 v4444 L3 Dimensions and skips
l3keys.sty 2013/02/24 v4461 L3 Experimental key-value interfaces
l3fp.sty 2013/01/19 v4449 L3 Floating points
l3box.sty 2013/01/08 v4411 L3 Experimental boxes
l3coffins.sty 2012/09/09 v4212 L3 Coffin code layer
l3color.sty 2012/08/29 v4156 L3 Experimental color support
l3luatex.sty 2012/08/03 v4049 L3 Experimental LuaTeX-specific functions
l3candidates.sty 2013/03/14 v4468 L3 Experimental additions to l3kernel
xparse.sty 2013/03/12 v4467 L3 Experimental document command parser
luaotfload.sty 2013/05/23 v2.2d OpenType layout system
luatexbase.sty 2013/05/11 v0.6 Resource management for the LuaTeX macro progr
ammer
luatexbase-compat.sty 2011/05/24 v0.4 Compatibility tools for LuaTeX
luatexbase-modutils.sty 2013/05/11 v0.6 Module utilities for LuaTeX
luatexbase-loader.sty 2013/05/11 v0.6 Lua module loader for LuaTeX
luatexbase-regs.sty 2011/05/24 v0.4 Registers allocation for LuaTeX
luatexbase-attr.sty 2013/05/11 v0.6 Attributes allocation for LuaTeX
luatexbase-cctb.sty 2013/05/11 v0.6 Catcodetable allocation for LuaTeX
luatexbase-mcb.sty 2013/05/11 v0.6 Callback management for LuaTeX
fontspec-patches.sty 2013/05/20 v2.3c Font selection for XeLaTeX and LuaLaTeX
fixltx2e.sty 2006/09/13 v1.1m fixes to LaTeX
fontspec-luatex.sty 2013/05/20 v2.3c Font selection for XeLaTeX and LuaLaTeX
fontenc.sty
eu2enc.def 2010/05/27 v0.1h Experimental Unicode font encodings
eu2lmr.fd 2009/10/30 v1.6 Font defs for Latin Modern
xunicode.sty 2011/09/09 v0.981 provides access to latin accents and many othe
r characters in Unicode lower plane
eu2lmss.fd 2009/10/30 v1.6 Font defs for Latin Modern
graphicx.sty 1999/02/16 v1.0f Enhanced LaTeX Graphics (DPC,SPQR)
keyval.sty 1999/03/16 v1.13 key=value parser (DPC)
graphics.sty 2009/02/05 v1.0o Standard LaTeX Graphics (DPC,SPQR)
trig.sty 1999/03/16 v1.09 sin cos tan (DPC)
graphics.cfg 2010/04/23 v1.9 graphics configuration of TeX Live
pdftex.def 2011/05/27 v0.06d Graphics/color for pdfTeX
fontspec.cfg
t3cmr.fd 2001/12/31 TIPA font definitions
supp-pdf.mkii
epstopdf-base.sty 2010/02/09 v2.5 Base part for package epstopdf
grfext.sty 2010/08/19 v1.1 Manage graphics extensions (HO)
kvdefinekeys.sty 2011/04/07 v1.3 Define keys (HO)
kvoptions.sty 2011/06/30 v3.11 Key value format for package options (HO)
kvsetkeys.sty 2012/04/25 v1.16 Key value parser (HO)
etexcmds.sty 2011/02/16 v1.5 Avoid name clashes with e-TeX commands (HO)
epstopdf-sys.cfg 2010/07/13 v1.3 Configuration of (r)epstopdf for TeX Live
***********