[DaiPlusPlus]

> My impression is that Google Docs never used contentEditable and instead wrote their own layout and editing engine that manually rendered out DOM, and they're now changing that to render out to canvas.

Back before Google owned Google Docs, it was a non-Google company and website called Writely, and their website was basically a document-hosting system tied to a fairly stock `contentEditable` editor.

This was around 2005 - back when every web-application development client would insist that users have WYSIWYG/rich-text editors - of course they had no idea how WYSIANLWYG (What you see is absolutely nothing like what you'll get) those WYSIWYG editors are like.