So, I have been using the gedit text editor for years, often with multiple files open at a time in tabs.
Today, I find that my two gedit sessions and all the files open in them are suddenly all in "[read only]" mode and won't let me edit the files I was editing earlier with that same loading of the program (but a couple of days ago, and the computer has been put to sleep and awakened a few times since).
I'm still logged in as my usual account, the files are owned by that account and the owner (me) has permissions to edit them.
Opening new files in a new gedit window also results in them being loaded read-only.
I have looked through the various menus I could find and see nothing that seems relevant.
None of what I have done is new to my experience, and I have used gedit for years in this sort of way without ever having seen this happen to me. What's it caused by and how could I get the files back to editable short of closing and reloading them?