The GetFontUnicodeRanges function returns information about which Unicode
characters are supported by a font. The information is returned as a
GLYPHSET structure.

WINGDIAPI DWORD WINAPI GetFontUnicodeRanges(
HDC hdc, // handle to the device context
LPGLYPHSET lpgs // pointer to the glyph set structure
);
參見MSDN ：
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/gdi/fontext_2alv.asp