Bug 267242 [JFace] Add API to configure table and tree columns in a keyboard-accessible way
bundles/org.eclipse.ui.views/src/org/eclipse/ui/views/properties/PropertySheetPage.java
/**
     * Adds drag and drop support.
     */
    protected void initDragAndDrop() {
        int operations = DND.DROP_COPY;
        Transfer[] transferTypes = new Transfer[] { TextTransfer.getInstance() };
        DragSourceListener listener = new DragSourceAdapter() {
            public void dragSetData(DragSourceEvent event) {
                performDragSetData(event);
            }
            public void dragFinished(DragSourceEvent event) {
                
            }
        };
        DragSource dragSource = new DragSource(
                viewer.getControl(), operations);
        dragSource.setTransfer(transferTypes);
        dragSource.addDragListener(listener);
    }
    /**
     * The user is attempting to drag.  Add the appropriate
     * data to the event.
     * @param event The event sent from the drag and drop support.
     */
    void performDragSetData(DragSourceEvent event) {
        
        IStructuredSelection selection = (IStructuredSelection) viewer
                .getSelection();
        if (selection.isEmpty()) {
			return;