if (fSelections.isEmpty()) {
fSelectionCategory= _SELECTION_POSITION_CATEGORY + hashCode();
fSelectionUpdater= new NonDeletingPositionUpdater(fSelectionCategory);
document.addPositionCategory(fSelectionCategory);
document.addPositionUpdater(fSelectionUpdater);
}
try {
final Position position= new Position(selection.x, selection.y);