When you have unsaved changes the close button on a standard Mac window shows a dark circle instead of a cross. But it does not in Qt Creator. See 'unsaved data.png' to see how it should look. Weirder yet when you do click close or try and quit when there is unsaved data you get a combination of the dark circle and the cross icon which no Cocoa apps ever show. This happens while the Save Files dialog is shown. See 'weird.png'.