Unicode-based frames are misaligned

[chubin]

Very interesting project. I thought about writing something like this myself,
but as you already wrote it, I can save some time :) Thank you very much for it.

One minor issue that I immediately found (hopefully will find and report more in fuiture):

Maybe this issue is already reported, but I didn't find anything at the first glance.

Unicode-based frames look like:

Ncurses-based frames are displayed correctly:

What is even more interesting,
the same output may be displayed differently (once well, once broken):

(please ignore the emoji line above; it is a known issue; we are talking only about the frames)