I don't think that answers my question - let me provide some more info.
I'm using InsertText and DeleteText to synchronize my syntaxeditor's content with some textboxes (and we're not at a time in development for altering this approach). I like comparing my UI text changes with SyntaxEditor.Document.Text since the offsets match until I find my first char difference (my source text also has line terminators).
However, I've found that using the offset from Document.Text doesn't work in InsertText and DeleteText - they seem to want offsets that exlcude the line terminators. I tried calculating the line terminators manually and subtracting from my offset but that didn't work. Thus, I was wondering if there's an appropriate function that will do that conversion or if I'm stuck with the manual calculation approach.