Bug 5774 Unpredicatable behaviour on double click in packages view
from EC: If you double click a file in the packages view, it opens the file (technically, compilation unit I believe) -- if not already open. However, if the file is already open, a single click selects it as the active editor tag; a double click expands its structure in the packages view. This is unpredictable behavior ;
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/packageview/PackageExplorerPart.java
if (decorator == null) {
			fViewer.setLabelProvider(javaProvider);
		} else {
			fViewer.setLabelProvider(new DecoratingLabelProvider(javaProvider, decorator));
		}
	}
	
	/**
	 * Gets the standard label flags
	 */
	private int getLabelProviderFlags() {
		return JavaElementLabelProvider.SHOW_BASICS | JavaElementLabelProvider.SHOW_OVERLAY_ICONS |
					JavaElementLabelProvider.SHOW_SMALL_ICONS | JavaElementLabelProvider.SHOW_VARIABLE | JavaElementLabelProvider.SHOW_PARAMETERS;
	}		
	/*
	 * @see IPropertyChangeListener#propertyChange(PropertyChangeEvent)
	 */
	public void propertyChange(PropertyChangeEvent event) {
		if (event.getProperty() != IPreferencesConstants.SHOW_CU_CHILDREN) 
			return;
					
		if (fViewer != null) {
			IPreferenceStore store= JavaPlugin.getDefault().getPreferenceStore();
			boolean b= store.getBoolean(IPreferencesConstants.SHOW_CU_CHILDREN);
			((JavaElementContentProvider)fViewer.getContentProvider()).setProvideMembers(b);
			fViewer.refresh();
		}
	}
}