base interface for all event listeners interfaces.
Description
Interface to be implemented by a FilePicker listener.
The XFilePickerListener interface must be implemented by
the clients of the FilePicker service which need to be informed about
events while the FilePicker service is displayed.
A client receives this event if the size of the FilePicker dialog
has changed. If the FilePicker dialog contains a preview the client
may ask for the new dimension of the preview area.
A help string which the FilePicker dialog should use to display
a help for a specific control. If the returned string is empty it is
undefined how the FilePicker implementation will behave.
It may show a message 'no help available' or may show no
help at all.
A client receives this event if the size of the FilePicker dialog
has changed. If the FilePicker dialog contains a preview the client
may ask for the new dimension of the preview area.