> >  I'm trying to increase/decrease the font size in the selected region.
> So I need a base value to work with.
>
> And relative values like 1.2 or 0.8 don't fit the bill in your case?
> Using relative sizes frees you from the need to compute absolute size
> values.
>
I'm exploring a scenario where the text is inside a fixed shape. So
absolute size is important.