Bug 32254 [Viewers] AbstractTreeViewer uses HashSet to remember expansion state
I20030216 The custom hash table should be used instead. Otherwise expansion state may be lost due to a different equals implementation of the element and the IElementComparer.
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/StructuredViewer.java
import org.eclipse.jface.util.ListenerList;
import org.eclipse.jface.util.OpenStrategy;
import org.eclipse.jface.util.SafeRunnable;
/**
 * Abstract base implementation for structure-oriented viewers (trees, lists,
 * tables). Supports custom sorting, filtering, and rendering.
 * <p>
 * Any number of viewer filters can be added to this viewer (using
 * <code>addFilter</code>). When the viewer receives an update, it asks each
 * of its filters if it is out of date, and refilters elements as required.
 * </p>
 * 
 * @see ViewerFilter
 * @see ViewerSorter
 */
public abstract class StructuredViewer extends ContentViewer
		implements
			IPostSelectionProvider {
	/**
	 * A map from the viewer's model elements to SWT widgets. (key type:
	 * <code>Object</code>, value type: <code>Widget</code>).
	 * <code>null</code> means that the element map is disabled.
	 */
	private CustomHashtable elementMap;
	/**
	 * The comparer to use for comparing elements, or <code>null</code> to use
	 * the default <code>equals</code> and <code>hashCode</code> methods on
	 * the element itself.
	 */
	private IElementComparer comparer;