Is your feature request related to a problem? Please describe.
When working with a big piece of text, I sometimes scroll down and copy some text into another tab. When switching back to the first tab, both the input and the output pane is back on top. So I don't know where I was working just now.

Describe the solution you'd like
After tab switching, scroll position should be remembere

python 3.9.0 is soon to be released.

check if borg works on py39, try manually and also run our tests.

add it to tox.ini, travis-ci, vagrant boxes, setup.py (metadata).

everything in the title :)

I've been treating tuShorten/tuWiden as a string-ish conversion between UTF16 and UTF 8, so I recommend this.

Here's the code; add it to the end of every tuShorten/tuWiden function.
if (out < (original_out + out_len)) out = 0;