[Freetype] How to obtain the information in Vhea table(TTF)?

[yandongyao]

Hi:
   I want to get the Vhea(TTF) talbe's information,such as ascent,
descent. But I can't find which freetype's API can do this job.
And I look at the Freetype's source code, I found the metrics(such as
ascender, descender, height,max_advance) information in FT_Face,
FT_Size_Metrics come from TTF's head, hhea table, and freetype does not
consider vhea table at all. If this is true, I think we will meet with
problems when display text vertically. 
   Is this true? Thank you very much!