WCPositionEH.h

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//# WCPositionEH.h: WorldCanvas position event handler
//# Copyright (C) 1993,1994,1995,1996,1998,1999,2000
//# Associated Universities, Inc. Washington DC, USA.
//# 
//# This library is free software; you can redistribute it and/or modify it
//# under the terms of the GNU Library General Public License as published by
//# the Free Software Foundation; either version 2 of the License, or (at your
//# option) any later version.
//# 
//# This library is distributed in the hope that it will be useful, but WITHOUT
//# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
//# FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
//# License for more details.
//# 
//# You should have received a copy of the GNU Library General Public License
//# along with this library; if not, write to the Free Software Foundation,
//# Inc., 675 Massachusetts Ave, Cambridge, MA 02139, USA.
//# 
//# Correspondence concerning AIPS++ should be addressed as follows:
//#        Internet email: aips2-request@nrao.edu.
//#        Postal address: AIPS++ Project Office
//#                        National Radio Astronomy Observatory
//#                        520 Edgemont Road
//#                        Charlottesville, VA 22903-2475 USA
//# 
//# $Id$

#ifndef TRIALDISPLAY_WCPOSITIONEH_H
#define TRIALDISPLAY_WCPOSITIONEH_H

#include <casa/aips.h>
#include <display/DisplayEvents/WCPositionEvent.h>

namespace casa { //# NAMESPACE CASA - BEGIN

//
// <summary>
// Base class for handling WorldCanvas position events.
// </summary>
//
//  
// <prerequisite>
// <li> <linkto class="WCPositionEvent">WCPositionEvent</linkto>
// <li> Understanding of Display library event-handling methodology
// </prerequisite>
//
// <etymology>
// WCPositionEH : WorldCanvas Position Event-Handler
// </etymology>
//
// <synopsis>
// WCPositionEH is a base class.  Its operator() function is called by mechanisms within
// the Display Library when a keyboard key or mouse button is pressed while within the
// area of the world canvas.
//
// Users must derive from this class and override the op () function to catch key
// and button presses.  Positions in world, linear, and pixel coordinates are
// returned.
//
// This base class does have a concrete implementation, namely to report
// to stdout events it receives.  To effect this behaviour, create an instance
// this class and register it as an event-handler on a WorldCanvas.
// </synopsis>
//
// <motivation>
// Provide the user with an object-oriented approach to event handling and
// include world-coordinate position information.
// </motivation>
//
// <example>
// see the test programs in Display/test.
// </example>
//

class WCPositionEH {

 public:

  // Default Constructor Required
  WCPositionEH();

  // Default just prints the event to cout
  virtual void operator()(const WCPositionEvent & ev) = 0;

  // Destructor
  virtual ~WCPositionEH();

};


} //# NAMESPACE CASA - END

#endif