@Override
  public void closeOperation(boolean operationOK, boolean addToHistory, int mode) {
    ICompositeOperation endedComposite = null;

    synchronized (openCompositeLock) {
      if (DEBUG_OPERATION_HISTORY_UNEXPECTED) {
        if (openComposite == null) {
          Tracing.printTrace(
              "OPERATIONHISTORY",
              "Attempted to close operation when none was open"); //$NON-NLS-1$//$NON-NLS-2$
          return;
        }
      }
      // notifications will occur outside the synchonized block
      if (openComposite != null) {
        if (DEBUG_OPERATION_HISTORY_OPENOPERATION) {
          Tracing.printTrace(
              "OPERATIONHISTORY",
              "Closing operation " + openComposite); // $NON-NLS-1$ //$NON-NLS-2$
        }
        endedComposite = openComposite;
        openComposite = null;
      }
    }
    // any mode other than EXECUTE was triggered by a request to undo or
    // redo something already in the history, so undo and redo
    // notification will occur at the end of that sequence.
    if (endedComposite != null) {
      if (operationOK) {
        if (mode == EXECUTE) {
          notifyDone(endedComposite);
        }
        if (addToHistory) {
          add(endedComposite);
        }
      } else {
        if (mode == EXECUTE) {
          notifyNotOK(endedComposite);
        }
      }
    }
  }
  @Override
  public IStatus execute(IUndoableOperation operation, IProgressMonitor monitor, IAdaptable info)
      throws ExecutionException {
    Assert.isNotNull(operation);

    // error if operation is invalid
    if (!operation.canExecute()) {
      return IOperationHistory.OPERATION_INVALID_STATUS;
    }

    // check with the operation approvers
    IStatus status = getExecuteApproval(operation, info);
    if (!status.isOK()) {
      // not approved. No notifications are sent, just return the status.
      return status;
    }

    /*
     * If we are in the middle of an open composite, then we will add this
     * operation to the open operation rather than add the operation to the
     * history. We will still execute it.
     */
    boolean merging = false;
    synchronized (openCompositeLock) {
      if (openComposite != null) {
        // the composite shouldn't be executed explicitly while it is
        // still
        // open
        if (openComposite == operation) {
          return IOperationHistory.OPERATION_INVALID_STATUS;
        }
        openComposite.add(operation);
        merging = true;
      }
    }

    /*
     * Execute the operation
     */
    if (!merging) {
      notifyAboutToExecute(operation);
    }
    try {
      status = operation.execute(monitor, info);
    } catch (OperationCanceledException e) {
      status = Status.CANCEL_STATUS;
    } catch (ExecutionException e) {
      notifyNotOK(operation);
      throw e;
    } catch (Exception e) {
      notifyNotOK(operation);
      throw new ExecutionException(
          "While executing the operation, an exception occurred", e); // $NON-NLS-1$
    }

    // if successful, the notify listeners are notified and the operation is
    // added to the history
    if (!merging) {
      if (status.isOK()) {
        notifyDone(operation);
        add(operation);
      } else {
        notifyNotOK(operation, status);
        // dispose the operation since we did not add it to the stack
        // and will no longer have a reference to it.
        operation.dispose();
      }
    }
    // all other severities are not interpreted. Simply return the status.
    return status;
  }