text: 
  // Copyright NVIDIA Corporation 2009-2010
  // Redistribution and use in source and binary forms, with or without
  // modification, are permitted provided that the following conditions
  // are met:
  //  * Redistributions of source code must retain the above copyright
  //    notice, this list of conditions and the following disclaimer.
  //  * Redistributions in binary form must reproduce the above copyright
  //    notice, this list of conditions and the following disclaimer in the
  //    documentation and/or other materials provided with the distribution.
  //  * Neither the name of NVIDIA CORPORATION nor the names of its
  //    contributors may be used to endorse or promote products derived
  //    from this software without specific prior written permission.
  //
  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ``AS IS'' AND ANY
  // EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  // PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
  // CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  // EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  // PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  // PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  // OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  
  #include <QEvent>
  #include <QUndoView>
  #include <QContextMenuEvent>
  #include "Viewer.h"
  #include "UndoWidget.h"
  
  UndoWidget::UndoWidget(QWidget *parent)
    : QDockWidget( "Undo Stack", parent )
  {
    setObjectName( "UndoWidget" );
    m_undoView = new QUndoView( &GetSceneStateUndoStack(), this );
  
    setWidget( m_undoView );
  }
  
  UndoWidget::~UndoWidget()
  {
  }
  
  bool UndoWidget::empty() const
  {
    return( m_undoView->stack()->count() == 0 );
  }
  
  void UndoWidget::clear()
  {
    m_undoView->stack()->clear();
  }
  
  void UndoWidget::contextMenuEvent( QContextMenuEvent * event )
  {
    QDockWidget::contextMenuEvent( event );
  
    if ( m_undoView->stack()->count() )
    {
      QMenu menu( "Undo Context Menu", this );
      QAction * action = menu.addAction( QApplication::translate( VIEWER_APPLICATION_NAME, "&Clear Undo Stack" ) );
      connect( action, SIGNAL(triggered()), this, SLOT(clear()) );
  
      menu.exec( event->globalPos() );
    }
  }
  