After an hour or two of experimentation, I’ve finally figured out where the problem with text field inputs is. For most of the editing stuff, I’ve been capturing mouse input and handing it off to special mouse-input processing functions from the top down. Apparently, these functions are stopping the text field editing event… sort of? One of the reasons this has taken me so long to find is that the text fields are receiving click events just fine, they’re just not actually processing them in the expected “select and edit” manner of input text fields. It also doesn’t explain why this is a problem with specifically the entity editor and the text fields in the map and tile editors work just fine. So, well, some mysteries remain to be solved.
So… I guess I know APPROXIMATELY where the problem with text field inputs is. Or, at least, I know several places where it ISN’T. I’m still not sure how to approach solving the problem, but I’m tired, so this will have to do for now.