[XeTeX] ICU and vertical layout support

[Jjgod Jiang]

Hi,

I wondering what's the best way to handle a font with 'vert' feature
of a specific script, say FangSong_GB2312 distributed with
Windows:

$ otfinfo --script=hani -f /Users/jjgod/Library/Fonts/simfang.ttf
vert    Vertical Writing

$ otfinfo -t /Users/jjgod/Library/Fonts/simfang.ttf
1609927 EBDT
    736 EBLC
    252 GSUB
     86 OS/2
  38968 cmap
     22 cvt
     82 fpgm
2299650 glyf
     54 head
     36 hhea
  15358 hmtx
  30324 loca
     32 maxp
   1021 name
     32 post
      8 prep

But ATSFontGetTable(.., gsubTableTag, ..) failed. So in
LayoutEngineFactory() of XeTeXOTLayoutEngine.cpp,
XeTeXHanLayoutEngine is not used for vertical layout,
whichi results very bad output for:

\font\zhfont="FangSong_GB2312/ICU:vertical:script=hani"

Is there any solution to workaround this?

- jjgod.