Bug 93400 LTK UI should provide official API for structural content in the preview page
org.eclipse.ltk.ui.refactoring/src/org/eclipse/ltk/internal/ui/refactoring/PreviewWizardPage.java
if (fValidationStatus != null && fValidationStatus.hasFatalError()) {
			RefactoringWizard wizard= getRefactoringWizard();
			MessageDialog.openError(wizard.getShell(), wizard.getWindowTitle(), 
				Messages.format(
					RefactoringUIMessages.RefactoringUI_cannot_execute, 
					fValidationStatus.getMessageMatchingSeverity(RefactoringStatus.FATAL)));
			return true;
		}
		return true;
	} 
	
	/* (non-JavaDoc)
	 * Method defined in IWizardPage
	 */
	public boolean canFlipToNextPage() {
		return false;
	}
	
	/* (Non-JavaDoc)
	 * Method defined in IWizardPage
	 */
	public void createControl(Composite parent) {
		initializeDialogUnits(parent);
		fPageContainer= new PageBook(parent, SWT.NONE);
		fStandardPage= createStandardPreviewPage(fPageContainer);
		fNullPage= createNullPage(fPageContainer);
		setControl(fPageContainer);
		PlatformUI.getWorkbench().getHelpSystem().setHelp(getControl(), IRefactoringHelpContextIds.REFACTORING_PREVIEW_WIZARD_PAGE);
	}
	private Composite createStandardPreviewPage(Composite parent) {