Not clear how to map some String position to the Characters position, and vice-versa.

[marcglasberg]

If you have some text in a TextField you can get the caret's (also called cursor) position. If you want to delete the character at the caret's position, you must be able to say that, say, the 7th position in the String maps to the 5th position in the Characters, so that you can delete this char.

The same problem arises if you want to add some character in the caret's position.

But is there a way to do this? Doesn't seem so, or at least it's not obvious to me.

This is important, since the TextField will report positions in the String, not in the Characters. I suggest the following to methods:

int convertFromStringIndex(int stringIndex)
int convertFromCharactersIndex(int charactersIndex)

If you want to be really complete, you can also have these methods:

List<int> getAllStringIndexes()
List<int> getAllCharactersIndexes()

[lrhn]

I'd prefer to not expose indices in the Characters class API.

A more indirect approach would be constructors for the CharacterRange class which take a position, or a range, in the input code units, and then produces a CharacterRange covering that position or range.

To go the other way, the CharacterRange has stringBefore and stringAfter, which can give you the code unit count before and after the range. We could easily add stringBeforeLength and stringAfterLength as well, to avoid unnecessary allocation when finding that length.

It's not an "index'. But it is, really.

[lrhn]

Some functionality added.