notes about why not fixing syntax package

app/src/processing/app/syntax/README.md

@@ -1,3 +1,28 @@
+🐉 Fixing this code: here be dragons. 🐉
+
+Every few years, we've looked at replacing this package with [RSyntaxArea](https://github.com/bobbylight/RSyntaxTextArea), most recently with two attempts during the course of developing [Processing 4](https://github.com/processing/processing4/wiki/Processing-4).
+
+So that I don't repeat this attempt again, some reminders as to why it's not worth the effort. As noted in the link above, the time is better spent with starting from scratch with a different approach—a Language Server implementation and probably a lightweight (HTML/JS) GUI on top of it.
+
+* At a minimum, replacing this text component would break all Modes, because of how they're invoked.
+* The token coloring uses a completely different system, which would also need to be expanded across Modes. 
+* Everything that lives in `PdeTextAreaPainter`,  the error squiggles, popups, etc would need to be rewritten. 
+* Similarly, line numbering is supported by default in `RSyntaxArea` so we'd need to carefully remove all our “left gutter” hacking.
+* Most methods throw `BadLocationException`, which we'd either need to include, and break more existing code, or hide, and have undefined behavior. Not a good investment.
+* The current `Editor` object evolved from a time when we didn't even support individual tabs. As a result, there's a lot of “current tab” state that still lives inside `Editor`, and other state that lives in `SketchCode`. 
+* Most of those `Editor` methods should instead be talking to `SketchCode` objects, however that kind of change is likely to introduce small regressions with *major* effects. Again, just not worth it.
+* More ways to introduce regressions when fixing: `SketchCode` currently syncs between `program`, `savedProgram`, and `Document` objects. 
+* The text area needs to be moved into individual tabs. More breaking changes, but necessary to cleanly separate all Undo behavior.
+* So many small quirks, hard-learned lessons from over the years that may no longer be necessary, but the amount of testing necessary is too significant. For instance, inside File → Print, all the Document objects for the tabs are synched up. This might no longer be necessary if we do this properly—it's a gross hack—but we don't have time to find out. There are dozens of situations like this.
+
+I don't enjoy having the code in this state, but it's there and working, and a larger-scale replacement is a better use of time.
+
+— Ben Fry, 20 January 2022
+
+
+The old license for this code follows:
+
+```
 OLDSYNTAX PACKAGE README
 
 I am placing the jEdit 2.2.1 syntax highlighting package in the public
@@ -44,3 +69,4 @@ remains intact in all source distributions of this package.
 -- Slava Pestov
 25 September 2000
 <sp@gjt.org>
+```