DisplayOptions.h

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//# DisplayOptions.h: option parsing for display classes
//# Copyright (C) 1999,2000,2002
//# 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 DISPLAY_DISPLAYOPTIONS_H
#define DISPLAY_DISPLAYOPTIONS_H

#include <casa/aips.h>
#include <casa/Containers/Record.h>
#include <casa/Arrays/Array.h>
#include <casa/Arrays/ArrayLogical.h>

namespace casa { //# NAMESPACE CASA - BEGIN

// <summary>
// Class to provide option parsing routines for display classes.
// </summary>

// <use visibility=local>

// <reviewed reviewer="Peter Barnes" date="1999/10/27" tests="tDisplayOptions" demos="">
// </reviewed>

// <prerequisite>
// <li> <linkto class=Record>Record</linkto>
// </prerequisite>

// <etymology>
// DisplayOptions contains methods for parsing "Options" for
// various "Display" classes.
// </etymology>

// <synopsis>
// DisplayOptions is a simple class which provides methods for parsing
// Records containing fields which conform to "options" as used in the
// Display Library classes.  Consider a record having the following
// structure:
// <srcblock>
// rec.minimum.value = 4.0
// rec.minimum.otherfield = "some text"
// rec.maximum = 8.0
// </srcblock>
// The DisplayOptions methods can be used to extract the values of the
// <src>minimum</src> and <src>maximum</src> fields of the Record
// <src>rec</src>, regardless of whether the value itself is stored in
// a <src>value</src> sub-field, or at the next higher level.  The
// DisplayOptions methods also offer the capability to detect "unset"
// Record values.
//
// This class can be used as-is, or inherited from by higher-level
// classes.
// </synopsis>

// <example>
// The following example shows the use of DisplayOptions as a 
// stand-alone class.
// <srcblock>
// /* assume some Record "rec" is to be parsed */
// DisplayOptions dopt;
// Bool error;
//
// Float min = 0.0;
// if (dopt.readOptionRecord(min, error, rec, "minimum") && !error) {
//   cerr << "minimum found and changed, new value is " << min << endl;
// }
// 
// String color;
// Bool colorIsUnset = False;
// if (dopt.readOptionRecord(color, colorIsUnset, error,
//                           rec, "color") && !error) {
//   if (colorIsUnset) {
//     cerr << "color found and unset" << endl;
//   } else {
//     cerr << "color found and changed, new value is " << color << endl;
//   }
// }
// </srcblock>
// </example>

// <motivation>
// Options are used prolifically throughout the display classes,
// so some unified processing of options is desirable.
// </motivation>

// <thrown>
// None.
// </thrown>

// <todo asof="1999/08/26">
// <li> add unset support for Bool, Float and Int types
// </todo>

class DisplayOptions {

 public:

  // Constructor.
  DisplayOptions();
  
  // Destructor.
  virtual ~DisplayOptions() { };

  // Find the field <src>fieldname</src> in Record <src>rec</src>,
  // containing the requested type (Bool, String, Float, Int) in
  // itself or its "value" sub-field, and return the value in
  // <src>target</src>.  If the field doesn't exist, or does not
  // contain the requested type, or a "value" sub-field containing the
  // requested type, then <src>error</src> is set True.  When
  // <src>error</src> is False, the return value indicates whether
  // <src>target</src> was modified.  The Float version will also read
  // records containing Ints or Doubles, and cast their value to
  // Float.  
  // <group>

  template <class T> Bool readOptionRecord(Vector<T> &target, Bool &error, 
                                           const Record &rec,
                                           const String &fieldname) const;

  template <class T> Bool readOptionRecord(T &target, Bool &error, const Record &rec,
                                           const String &fieldname) const;
  // </group>

  // Find the field <src>fieldname</src> in Record <src>rec</src>,
  // containing the requested type (String) in itself or its "value"
  // sub-field, and return the value in <src>target</src>.  If the
  // field (or "value" sub-field) instead contains an "unset" Record,
  // then <src>unsetTarget</src> is set True.  If the field doesn't
  // exist, or does not contain the requested type (String) or an
  // "unset" Record, or a "value" sub-field containing either of
  // these, then <src>error</src> is set True.  When <src>error</src>
  // is False, the return value indicates whether <src>target</src>
  // (or <src>unsetTarget</src>) was modified.
  virtual Bool readOptionRecord(String &target, Bool &unsetTarget,
                                Bool &error, const Record &rec,
                                const String &fieldname) const;

  // Return a Record which is an "unset" Record, ie. has a field with
  // name <src>String("i_am_unset")</src> whose value is
  // <src>String("i_am_unset")</src>.
  Record unset() const
    { return itsUnsetRecord; }

  // Return True or False indicating if the provided Record is equal
  // to an "unset" Record.
   Bool isUnset(const Record &rec) const;

 protected:

  // (Required) copy constructor.
  DisplayOptions(const DisplayOptions &other);

  // (Required) copy assignment.
  void operator=(const DisplayOptions &other);

private:
  // A utility to check if two types are compatible. (I.e. double is 
  // "compatible" with int. Used by readOptionRecord.
  Bool compatible(const DataType &compareme, const DataType &tome) const;

  // An unset record to return with protected <src>unset()</src>
  // function.
  Record itsUnsetRecord;

};


} //# NAMESPACE CASA - END
#ifndef AIPS_NO_TEMPLATE_SRC
#include <display/Utilities/DisplayOptionsTemplate.tcc>
#endif
#endif