In BaseX 7.2 just now, I pressed Command-Q to quit the program. My query had changed, so the program put up a dialog box to ask "Save changes to file?" with buttons for Yes, No, and Cancel.
As I looked at the dialog box, I noticed that the query in question was not the one I had thought it was (for a project I was closing down) but a different one (the project I was intending to focus on next). So I didn't want to quit the program after all. I clicked on Cancel, expecting that my request to shut BaseX down would be canceled and BaseX would continue running with my query file still in place. But in fact BaseX exited anyway. As far as I can tell, it didn't save the query (no great loss, in this case, I think), so that Cancel effectively had the same effect as No.
It's been a long time since I read anything about standard user interface idioms, so I don't want to go so far as to say that this is a bug. But it did surprise me, and so I suggest that it might be helpful to make the Cancel button in this dialog box cancel the quit action. Consider it a request for enhancement.
Thanks!
Michael