The FileDialog spec says the following about the
the modal behavior of FileDialog:
  Since it is a modal dialog, when the application calls its show
  method to display the dialog, it blocks the rest of the application
  until the user has chosen a file.

The Dialog (the parent of FileDialog) says the following
about modal dialogs:
  A modal dialog blocks input to the parent window when shown.


The 2 specs contradict each other on this subject; the first one
asserts that a modal dialog blocks input to all the windows in the
application, while the second one asserts that a modal dialog blocks
input to only the parent window of the modal dialog.