* All code points <= 0xFFFF should work as before
* Start the same tmux session in two Konsoles
* Change background to fully transparent in one of them and put it in
front of the other one, so that all text will overlap
* Generate characters with:
```
perl -XCSDL -e 'print map{chr($_), " "} 1..0xffff'
```
(you can pipe it to `fold -s | less -r`)
* Compare output visually.
* Code points > 0xFFFF should not be truncated to 16 bits
* "𝐀" and "퐀" should be different characters
* Some code points > 0xFFFF should have single width
* Vertical lines below should align:
```
𝐀 |
🐈|
```