Disable only certain parts of text from being edited

[JaggerJo]

Text in the green rectangle should be editable. Text in the red box not. Let's assume it's as simple as checking if the line contains => and if it does the text after it is read only (and styled differently). How would I prevent users from editing
certain parts of the text?

I've been implementing a custom VisualLineElementGenerator like explained here, so styling the text differently works.

[Gillibald]

AvaloniaEdit/src/AvaloniaEdit/Editing/TextArea.cs

Line 722 in cfaddb7

public IReadOnlySectionProvider ReadOnlySectionProvider

[JaggerJo]

Thanks!