Currently the implementors can only use PS.getSelection() which returns the FeatureDescriptor selected in the PS JTable.
This is fine so far one click to the area outside of the inner JTable (no FD at that place). In this case the getSelection() still returns the last selected FD.
PS.getSelection(FeatureDescriptor) would be better. The given FD will correspond to the FD where the popup is being opened or null if there's no FD at that place.