Is it just me, or is

**
** Return the styled segments for the given zero based line index.
** The result is a list of Int/RichTextStyle pairs where the Int
** specifies a zero based char offset of the line.
**
List lineStyling(Int lineIndex)

a really awkward API? I kept trying to think of a way to put pairs into a list, until finally I looked at some example code and realize that no, it wants a list that goes [int, style, int, style...]. And then I had to read the docs several times, and try an experiment, to be sure whether it meant the Int was, an index from the beginning of this particular line, or, an index of the line in the full text.

That just seems really awkward and error-prone, to me. On the other hand, I don't really have any suggestions for how to fix it. :-)

An ordered map from region to style is a good solution.

I agree it is a litle awkward, but at the same time that is one of the most performance critical APIs in the text editor. So I want to avoid created complicated deep structures. Since styles are often immutable, I can't really think of anything better then just a list.