We have to implement "TATEGAKI" for Asian font support. This word "tategaki" means vertically writing in Japanese.
The tategaki font name begins by "@". For example, The font name "@MS Gothic" indicates a rotated font of "MS Gothic". Usually tategaki are used with font rotation.
However arbitary font rotation will be later work.
Keywords are: FT_HAS_VERTICAL and FT_LOAD_VERTICAL_LAYOUT.
If FT_HAS_VERTICAL(face) is true, the face has vertical text layout. Then, you can use "@" plus font name. If you loads a glyph with FT_LOAD_VERTICAL_LAYOUT, the loaded glyph might have special layout (especially Asian-specific characters of class Tu or class Tr). In tategaki font (with @), the characters of class U and class Tr should spin 90 degrees counterclockwise. The character of class R has no difference in rendering. See freetype documents for details. See VerticalOrientation-17.txt for character classification.
The tategaki font names should be enumerated with "@", by EnumFontFamiliesEx function.