Set width of TextView in terms of characters

Answering my own question...

And the winner is: set the minEms attribute (android:minEms) !!!

So "ems" it turns out refers to the size of the widest character, typically an "M", get it? So setting minEms to an integer value say 3, on an EditText or TextView should ensure it's at least 3 characters wide. You can set the maxEms as well.

So Kyle's answer on this thread, although wrong, caused me to find the answer, so thanks Kyle.

ems, contrary to popular beliefs (or at least from most thread about ems here), is not based from the width of a single 'M'.

It was originally like that in typography, but in digital medium, including Android, its meaning was shifted to the size of the typeface used, or in other word, its height (excluding any padding for accents/diacritics).

So that means when you specify the ems for a TextView, it will used its textSize as a base and multiply it by the ems specified.

As a sample, if you set a 16sp TextView's ems to 4, its width will be 64sp wide. You can easily test it by using two TextView (with includeFontPadding set to false) side-by-side inside a ConstraintLayout (to leverage its layout_constraintDimensionRatio).