/*=========================================================================

  Program:   Visualization Toolkit
  Module:    vtkObjectFactory.h
  Language:  C++
  Date:      $Date$
  Version:   $Revision$
  Thanks:    Thanks to William A. Hoffman who developed this class

Copyright (c) 1993-2000 Ken Martin, Will Schroeder, Bill Lorensen 
All rights reserved.

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 name of Ken Martin, Will Schroeder, or Bill Lorensen nor the names
   of any contributors may be used to endorse or promote products derived
   from this software without specific prior written permission.

 * Modified source versions must be plainly marked as such, and must not be
   misrepresented as being the original software.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``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 REGENTS 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.

=========================================================================*/
// .NAME vtkObjectFactory - abstract base class for vtkObjectFactories
// .SECTION Description
// vtkObjectFactory is used to create vtk objects.   The base class
// vtkObjectFactory contains a static method CreateInstance which is used
// to create vtk objects from the list of registerd vtkObjectFactory 
// sub-classes.   The first time CreateInstance is called, all dll's or shared
// libraries in the environment variable VTK_AUTOLOAD_PATH are loaded into
// the current process.   The C function vtkLoad is called on each dll.  
// vtkLoad should return an instance of the factory sub-class implemented
// in the shared library. VTK_AUTOLOAD_PATH is an environment variable 
// containing a colon separated (semi-colon on win32) list of paths.
//
// This can be use to overide the creation of any object in VTK.  
//



#ifndef __vtkObjectFactory_h
#define __vtkObjectFactory_h




#include "vtkObject.h"

class vtkObjectFactoryCollection;

class VTK_EXPORT vtkObjectFactory : public vtkObject
{
public:  
  // Methods from vtkObject
  vtkTypeMacro(vtkObjectFactory,vtkObject);
  // Description:
  // Print ObjectFactor to stream.
  virtual void PrintSelf(ostream& os, vtkIndent indent);

  // Class Methods used to interface with the registered factories
  
  // Description:
  // Create and return an instance of the named vtk object.
  // Each loaded vtkObjectFactory will be asked in the order
  // the factory was in the VTK_AUTOLOAD_PATH.  After the
  // first factory returns the object no other factories are asked.
  static vtkObject* CreateInstance(const char* vtkclassname);
  // Description:
  // Re-check the VTK_AUTOLOAD_PATH for new factory libraries.
  // This calls UnRegisterAll before re-loading
  static void ReHash(); 
  // Description:
  // Register a factory so it can be used to create vtk objects
  static void RegisterFactory(vtkObjectFactory* );
  // Description:
  // Remove a factory from the list of registered factories
  static void UnRegisterFactory(vtkObjectFactory*);
  // Description:
  // Unregister all factories
  static void UnRegisterAllFactories();
  
  // Description:
  // All sub-classes of vtkObjectFactory should must return the version of 
  // VTK they were built with.  This should be implemented with the macro
  // VTK_SOURCE_VERSION and NOT a call to vtkVersion::GetVTKSourceVersion.
  // As the version needs to be compiled into the file as a string constant.
  // This is critical to determine possible incompatible dynamic factory loads.
  virtual const char* GetVTKSourceVersion() = 0;
protected:
  // Description:
  // This method is provioded by sub-classes of vtkObjectFactory.
  // It should create the named vtk object or return 0 if that object
  // is not supported by the factory implementation.
  virtual vtkObject* CreateObject(const char* vtkclassname ) = 0;
  
  
  vtkObjectFactory();
  ~vtkObjectFactory();
  vtkObjectFactory(const vtkObjectFactory&) {};
  void operator=(const vtkObjectFactory&) {};
private:
  // Description:
  // Initialize the static members of vtkObjectFactory.   RegisterDefaults
  // is called here.
  static void Init();
  // Description:
  // Register default factories which are not loaded at run time.
  static void RegisterDefaults();
  // Description:
  // Load dynamic factories from the VTK_AUTOLOAD_PATH
  static void LoadDynamicFactories();
  // Description:
  // Load all dynamic libraries in the given path
  static void LoadLibrariesInPath( const char*);
  
  // list of registered factories
  static vtkObjectFactoryCollection* RegisterdFactories; 
  
  // member variables for a factory set by the base class
  // at load or register time
  void* LibraryHandle;
  unsigned long LibraryDate;
  char* LibraryPath;
};

#endif
