Bug 255229 [Viewers] [3.5] NPE in ColumnViewerToolTipSupport
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/ColumnViewerToolTipSupport.java
private ColumnViewer viewer;
	private static final String VIEWER_CELL_KEY = Policy.JFACE
			+ "_VIEWER_CELL_KEY"; 
	private static final int DEFAULT_SHIFT_X = 10;
	private static final int DEFAULT_SHIFT_Y = 0;
	/**
	 * Enable ToolTip support for the viewer by creating an instance from this
	 * class. To get all necessary informations this support class consults the
	 * {@link CellLabelProvider}.
	 *
	 * @param viewer
	 *            the viewer the support is attached to
	 * @param style
	 *            style passed to control tool tip behavior
	 *
	 * @param manualActivation
	 *            <code>true</code> if the activation is done manually using
	 *            {@link #show(Point)}
	 */
	protected ColumnViewerToolTipSupport(ColumnViewer viewer, int style,
			boolean manualActivation) {
		super(viewer.getControl(), style, manualActivation);
		this.viewer = viewer;
	}
	/**
	 * Enable ToolTip support for the viewer by creating an instance from this
	 * class. To get all necessary informations this support class consults the