Request for 'invisible text'

Not directly but you might be able to use a combination of collapsed outlining nodes, read-only regions, and indicators to support something like that.

I have a similar approach I have to use. There's a file format I must support that adds a bunch of data at the end of each line of code to provide additional information about that line. I don't, however, want that code to appear in the editor.

As a result, my process of loading/saving documents is a two-step process. To load the document, I load the full source file into a temporary document. I then parse that document and remove all the extra data at the end of the lines and store that information in a collection that notes the original line where the data was stored. Once all data has been parsed and removed from the temporary document, I get the Text property of the temporary document (since data has been removed) and use it to set the Text property of the document that will officially hold the document. I then go through my collection of line data and add zero-width non-expanding SpanIndicators to the document at the beginning of each line where the data was originally stored. Using SpanIndicators allows the data to "move" with the document as edits are made and also ensures the line data is deleted if the entire line is deleted from the document. Saving the document is a similar process where I copy the text to a temporary document and then re-add the extra line data in that document. I then save the temporary document to a file.

The main reason I used a temporary document for this process is so that the UndoRedo stack wouldn't contain the edits I used to add/remove the extra line data. This also helped ensure that document modification tracking didn't show those lines as being edited.

For your purposes, you could use a similar approach. You could use special delimiter characters to mark the beginning and end of your hidden data. Load the file into a temporary document and parse for those delimiters. Remove the text of the hidden data from the document and mark the offset where the data came from. Once all data has been removed and offsets recorded, copy the text to a new document and create zero-width non-expanding SpanIndicators at every offset where data was removed. You'll need to create a custom SpanIndicator class to do this, and your class can store the details about the hidden text. When saving, copy your text to a temporary document and then re-insert the hidden text based on the current offsets of the SpanIndicators.

Thanks. Parsing the data ahead of time was something I had thought about doing. The details provided will really make this something that should be pretty straightforward. Thanks much for all the info!