Bug 265856 [Viewers] TreeViewer Widget Dispose Error
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/SWTFocusCellManager.java
*/
	public SWTFocusCellManager(ColumnViewer viewer,
			FocusCellHighlighter focusDrawingDelegate,
			CellNavigationStrategy navigationDelegate) {
		this.viewer = viewer;
		this.cellHighlighter = focusDrawingDelegate;
		this.navigationStrategy = navigationDelegate;
		hookListener(viewer);
	}
	/**
	 * This method is called by the framework to initialize this cell manager.
	 */
	void init() {
		this.cellHighlighter.init();
		this.navigationStrategy.init();
	}
	private void handleMouseDown(Event event) {
		ViewerCell cell = viewer.getCell(new Point(event.x, event.y));
		if (cell != null) {
			if (!cell.equals(focusCell)) {
				setFocusCell(cell);
			}
		}
	}
	private void handleKeyDown(Event event) {
		ViewerCell tmp = null;
		if (navigationStrategy.isCollapseEvent(viewer, focusCell, event)) {
			navigationStrategy.collapse(viewer, focusCell, event);
		} else if (navigationStrategy.isExpandEvent(viewer, focusCell, event)) {
			navigationStrategy.expand(viewer, focusCell, event);