Holy fucking shit, who cares? If this was done by LETTER WIDTH, we wouldn't see the problem-
EXACTLY! That is why you do not want "N characters". I don't understand what your problem is here.
It is true that for this example most programmers would scan from the start, finding the longest string that fits with an ellipsis at the end.
What I was trying to point out is that if you want to be clever, you can guess as to an insertion point. But 11 bytes is just as good of a guess as 11 "characters" and since 11 characters requires scanning you are not saving any time.
You are perfectly correct that after you stick the ellipsis in there you need to test to see if the rendering fits and perhaps try another guess. The idea is that you will do fewer measurements, but that such insertion can be done using byte offsets, and "N characters" is a useless concept that never enters into it.