Fullwidth characters are mapped wrong

[emilk]

Starting at https://unicode-table.com/en/FF33/ the characters are off by one.

Using emoji-icon-font.ttf, this is how the text ＰＱＲＳＴＵＶＷＸＹＺ is rendered like this in Font Book in Mac:

This can also be seen in the Font Book demo at www.egui.rs:

Ｓ is rendered as a window icon, and every letter after that is off-by-one. Ｙ is missing, and then Ｚ is correct again.

[emilk]

You can also see the problem at http://jslegers.github.io/emoji-icon-font/:

[xTibor]

The fullwidth backslash character is also mismapped as an "@" symbol (U+FF3C).