TGeoGlobalMagField.cxx

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// @(#)root/geom:$Id$

/*************************************************************************
 * Copyright (C) 1995-2000, Rene Brun and Fons Rademakers.               *
 * All rights reserved.                                                  *
 *                                                                       *
 * For the licensing terms see $ROOTSYS/LICENSE.                         *
 * For the list of contributors see $ROOTSYS/README/CREDITS.             *
 *************************************************************************/

#include "TROOT.h"
#include "TGeoGlobalMagField.h"

/** \class TGeoGlobalMagField
\ingroup Geometry_classes

Global magnetic field manager. Provides access to
and owns the actual magnetic field set via `SetField()`. The field is deleted
upon destruction of the field manager at the end of ROOT session or
by calling:

~~~ {.cpp}
TGeoGlobalMagField::Instance()->SetField(0).
~~~

The previous global field is deleted upon replacement with notification.

The global field manager provides access to the global field via:

~~~ {.cpp}
  TGeoGlobalMagField::Instance()->GetField()
~~~

One can directly call the Field() method of a field via the global field manager:

~~~ {.cpp}
  TGeoGlobalMagField::Instance()->Field(x,B)
~~~
*/

ClassImp(TGeoGlobalMagField)

TGeoGlobalMagField *TGeoGlobalMagField::fgInstance = NULL;

////////////////////////////////////////////////////////////////////////////////
/// Global field default constructor.

TGeoGlobalMagField::TGeoGlobalMagField()
{
   fField = NULL;
   fLock = kFALSE;
   if (fgInstance) {
      TVirtualMagField *field = fgInstance->GetField();
      if (field)
         Fatal("TGeoGlobalMagField", "A global field manager already existing and containing a field. \
         \n If you want a new global field please set it via: \
         \n   TGeoGlobalMagField::Instance()->SetField(myField).");
      else
         Warning("TGeoGlobalMagField", "A global field manager already existing. Please access via: \
         \n   TGeoGlobalMagField::Instance().");
      delete fgInstance;
   }
   gROOT->GetListOfGeometries()->Add(this); // list of cleanups not deleted
   fgInstance = this;
}

////////////////////////////////////////////////////////////////////////////////
/// Global field destructor.

TGeoGlobalMagField::~TGeoGlobalMagField()
{
   gROOT->GetListOfGeometries()->Remove(this);
   if (fField) {
      TVirtualMagField *field = fField;
      fField = NULL;
      delete field;
   }
   fgInstance = NULL;
}

////////////////////////////////////////////////////////////////////////////////
/// Field setter. Deletes previous field if any. Acts only if fLock=kFALSE.

void TGeoGlobalMagField::SetField(TVirtualMagField *field)
{
   if (field==fField) return;
   // Check if we are allowed to change the old field.
   if (fField) {
      if (fLock) {
         Error("SetField", "Global field is already set to <%s> and locked", fField->GetName());
         return;
      }
      // We delete the old global field and notify user.
      Info("SetField", "Previous magnetic field <%s> will be deleted", fField->GetName());
      TVirtualMagField *oldfield = fField;
      fField = NULL;
      delete oldfield;
   }
   fField = field;
   if (fField) Info("SetField", "Global magnetic field set to <%s>", fField->GetName());
}

////////////////////////////////////////////////////////////////////////////////
/// Static getter that does not create the object.

TGeoGlobalMagField *TGeoGlobalMagField::GetInstance()
{
   return fgInstance;
}

////////////////////////////////////////////////////////////////////////////////
/// Returns always a valid static pointer to the field manager.

TGeoGlobalMagField *TGeoGlobalMagField::Instance()
{
   if (fgInstance) return fgInstance;
   return new TGeoGlobalMagField();
}

////////////////////////////////////////////////////////////////////////////////
/// Locks the global magnetic field if this is set. Cannot be unlocked.

void TGeoGlobalMagField::Lock()
{
   if (!fField) {
      Warning("Lock", "Cannot lock global magnetic field since this was not set yet");
      return;
   }
   fLock = kTRUE;
   Info("Lock", "Global magnetic field <%s> is now locked", fField->GetName());
}