I need to get ranges of the available glyphs in a given font file/face.
The brute force of iterating cp in 0..65535, calling FT_Get_Char_Index(cp), and checking for 0 result seems wrong, both because Unicode code point could be more than u16, and because it seems wasteful.
Is there any "iteration" API?
The functions FT_Get_First_Char and FT_Get_Next_Char can be used to parse all character codes available in a given charmap.
There is an example at FT_Get_First_Char.