public String check(JComponent component) { UndoManager undoManager = ((LayerManagerProxy) JUMPWorkbench.getInstance().getFrame().getActiveInternalFrame()) .getLayerManager() .getUndoableEditReceiver() .getUndoManager(); if (component != null) component.setToolTipText(undoManager.getUndoPresentationName()); return (!undoManager.canUndo()) ? I18N.get( "com.vividsolutions.jump.workbench.ui.plugin.UndoPlugIn.nothing-to-undo") : null; }