UTF-8 Font Support

[tomky]

Although it is stated on Preware that wTerm supports UTF-8, it cannot display Asia characters in UTF-8 properly. I guess this is a font-related issue?

[stbuehler]

Not only a font related issue; all supported glyphs are rendered (on demand) in one big texture; supporting all glyphs would make the texture very big (never tried it...). Also we only use 2*7 bits (2 color channels in a texture) to describe a character, including 2 bits for font type selection (bold,underline,both,none). We group the unicode characters in slots with 128 elements; so we have 2^9 slots but can only support 2^5.

In https://github.com/RyanHope/wTerm/blob/master/src/plugin/sdl/sdlfontgl.cpp#L27 we have the list which slots are available.

(Unicode codepoints > 0xffff are not supported at all)