Correct UTF8 decoding for drawString

[d4rkmen]

There is a problem: the UTF8 stream decoder does not handle full 4 bytes encoded characters, like EMOJI, so, instead of drawing a missing character it draws 2-3 random garbage instead of
Even if the font does not support the code-points after 0xFFFF it should not ruin the entire text

[d4rkmen]

https://github.com/d4rkmen/plai/blob/main/components/LovyanGFX/src/lgfx/v1/LGFXBase.cpp#L2056-L2099

my workaround. could be helpful for someone

[tobozo]

Hi,

thanks for sharing your research 👍

Is it just a fix for the random garbage after the missing character symbol, or does it also unlock four bytes emoji support?

It doesn't seem to break any of the existing unicode examples so it'll be added to the code base.

If you want credit for your work please submit a pull request against the develop branch, otherwise I can take care of it.

[d4rkmen]

@tobozo its just removes the garbage. It returns valid codepoint value for 4bytes characters but current u8g2 fonts cant render it, because the font format designed for 16bit codepoints. take care plz