private void createDropTypes(Composite parent) {
	parent.setLayout(new RowLayout(SWT.VERTICAL));
	Button textButton = new Button(parent, SWT.CHECK);
	textButton.setText("Text Transfer");
	textButton.addSelectionListener(new SelectionAdapter() {
		public void widgetSelected(SelectionEvent e) {
			Button b = (Button)e.widget;
			if (b.getSelection()) {
				addDropTransfer(TextTransfer.getInstance());			
			} else {
				removeDropTransfer(TextTransfer.getInstance());
			}
		}
	});
	
	Button b = new Button(parent, SWT.CHECK);
	b.setText("RTF Transfer");
	b.addSelectionListener(new SelectionAdapter() {
		public void widgetSelected(SelectionEvent e) {
			Button b = (Button)e.widget;
			if (b.getSelection()) {
				addDropTransfer(RTFTransfer.getInstance());			
			} else {
				removeDropTransfer(RTFTransfer.getInstance());
			}
		}
	});
	
	
	b = new Button(parent, SWT.CHECK);
	b.setText("HTML Transfer");
	b.addSelectionListener(new SelectionAdapter() {
		public void widgetSelected(SelectionEvent e) {
			Button b = (Button)e.widget;
			if (b.getSelection()) {
				addDropTransfer(HTMLTransfer.getInstance());			
			} else {
				removeDropTransfer(HTMLTransfer.getInstance());
			}
		}
	});
	
	b = new Button(parent, SWT.CHECK);
	b.setText("URL Transfer");
	b.addSelectionListener(new SelectionAdapter() {
		public void widgetSelected(SelectionEvent e) {
			Button b = (Button)e.widget;
			if (b.getSelection()) {
				addDropTransfer(URLTransfer.getInstance());			
			} else {
				removeDropTransfer(URLTransfer.getInstance());
			}
		}
	});
	
	b = new Button(parent, SWT.CHECK);
	b.setText("File Transfer");
	b.addSelectionListener(new SelectionAdapter() {
		public void widgetSelected(SelectionEvent e) {
			Button b = (Button)e.widget;
			if (b.getSelection()) {
				addDropTransfer(FileTransfer.getInstance());			
			} else {
				removeDropTransfer(FileTransfer.getInstance());
			}
		}
	});
	
	// initialize state
	textButton.setSelection(true);
	addDropTransfer(TextTransfer.getInstance());
}