glib/glibmm/variant.h

// Generated by gmmproc 2.64.2 -- DO NOT MODIFY!
#ifndef _GLIBMM_VARIANT_H
#define _GLIBMM_VARIANT_H


/* Copyright 2010 The glibmm Development Team
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library.  If not, see <http://www.gnu.org/licenses/>.
 */


#include <glibmmconfig.h>
#include <glibmm/varianttype.h>
#include <glibmm/variantiter.h>
#include <glibmm/variantdbusstring.h>
#include <glibmm/refptr.h>
#include <glibmm/ustring.h>
#include <glibmm/error.h>
#include <utility>
#include <vector>
#include <map>
#include <memory>
#include <tuple>
#include <stdexcept>
#include <typeinfo>
#include <cstddef>

namespace Glib
{
class Bytes;

/** @defgroup Variant Variant Data Types
 *
 * The Variant classes deal with strongly typed
 * variant data. A Variant stores a value along with
 * information about the type of that value. The range of possible
 * values is determined by the type. The type system used is VariantType.
 *
 * See the VariantBase class and its derived types, such as VariantContainerBase,
 * and the Variant<> template type.
 *
 * Variant instances always have a type and a value (which are given
 * at construction time). The type and value of a Variant
 * can never change other than by the Variant itself being
 * destroyed.  A Variant cannot contain a pointer.
 *
 * Variant is heavily optimised for dealing with data in serialised
 * form. It works particularly well with data located in memory-mapped
 * files. It can perform nearly all deserialisation operations in a
 * small constant time, usually touching only a single memory page.
 * Serialised Variant data can also be sent over the network.
 *
 * Variant is largely compatible with D-Bus.  Almost all types of
 * Variant instances can be sent over D-Bus.  See VariantType for
 * exceptions.
 *
 * There is a Python-inspired text language for describing Variant
 * values. Variant includes a printer for this language and a parser
 * with type inferencing.
 */

//Note: We wrap this because it is thrown by GtkBuilder's functions.
// See https://bugzilla.gnome.org/show_bug.cgi?id=708206
// It would also be thrown by parse() if we wrap g_variant_parse().
// Now (2014-01-30) it's also thrown by Gio::Action::parse_detailed_name().
/**  %Exception class for Variant parse errors.
 */
class GLIBMM_API VariantParseError : public Glib::Error
{
public:
  /**  @var Code FAILED
   * Generic error (unused).
   *
   *  @var Code BASIC_TYPE_EXPECTED
   * A non-basic VariantType was given where a basic type was expected.
   *
   *  @var Code CANNOT_INFER_TYPE
   * Cannot infer the VariantType.
   *
   *  @var Code DEFINITE_TYPE_EXPECTED
   * An indefinite VariantType was given where a definite type was expected.
   *
   *  @var Code INPUT_NOT_AT_END
   * Extra data after parsing finished.
   *
   *  @var Code INVALID_CHARACTER
   * Invalid character in number or unicode escape.
   *
   *  @var Code INVALID_FORMAT_STRING
   * Not a valid Variant format string.
   *
   *  @var Code INVALID_OBJECT_PATH
   * Not a valid object path.
   *
   *  @var Code INVALID_SIGNATURE
   * Not a valid type signature.
   *
   *  @var Code INVALID_TYPE_STRING
   * Not a valid Variant type string.
   *
   *  @var Code NO_COMMON_TYPE
   * Could not find a common type for array entries.
   *
   *  @var Code NUMBER_OUT_OF_RANGE
   * The numerical value is out of range of the given type.
   *
   *  @var Code NUMBER_TOO_BIG
   * The numerical value is out of range for any type.
   *
   *  @var Code TYPE_ERROR
   * Cannot parse as variant of the specified type.
   *
   *  @var Code UNEXPECTED_TOKEN
   * An unexpected token was encountered.
   *
   *  @var Code UNKNOWN_KEYWORD
   * An unknown keyword was encountered.
   *
   *  @var Code UNTERMINATED_STRING_CONSTANT
   * Unterminated string constant.
   *
   *  @var Code VALUE_EXPECTED
   * No value given.
   *
   *  @var Code RECURSION
   * Variant was too deeply nested; Variant is only guaranteed to handle nesting up to 64 levels (Since: 2.64).
   *
   *  @enum Code
   *
   * %Error codes returned by parsing text-format GVariants.
   */
  enum Code
  {
    FAILED,
    BASIC_TYPE_EXPECTED,
    CANNOT_INFER_TYPE,
    DEFINITE_TYPE_EXPECTED,
    INPUT_NOT_AT_END,
    INVALID_CHARACTER,
    INVALID_FORMAT_STRING,
    INVALID_OBJECT_PATH,
    INVALID_SIGNATURE,
    INVALID_TYPE_STRING,
    NO_COMMON_TYPE,
    NUMBER_OUT_OF_RANGE,
    NUMBER_TOO_BIG,
    TYPE_ERROR,
    UNEXPECTED_TOKEN,
    UNKNOWN_KEYWORD,
    UNTERMINATED_STRING_CONSTANT,
    VALUE_EXPECTED,
    RECURSION
  };

  VariantParseError(Code error_code, const Glib::ustring& error_message);
  explicit VariantParseError(GError* gobject);
  Code code() const;

#ifndef DOXYGEN_SHOULD_SKIP_THIS
private:

  static void throw_func(GError* gobject);

  friend GLIBMM_API void wrap_init(); // uses throw_func()

  #endif //DOXYGEN_SHOULD_SKIP_THIS
};


//TODO: Add this documentation from the API if we are confident of it for the C++ wrapper:
// #GVariant is completely threadsafe.  A #GVariant instance can be
// concurrently accessed in any way from any number of threads without
// problems.
// Note that we don't copy GVariant's documentation about Memory Use because
// it seems easy to get out of sync and people can look at that C documentation if necessary.

/** This is the base class for all Variant types.
 *
 * If the actual type is known at compile-time then you should use a specific
 * Variant<>, such as Variant<int>. Otherwise, you may use get_type(),
 * is_of_type(), or cast_dynamic().
 *
 * @newin{2,28}
 * @ingroup Variant
 */
class GLIBMM_API VariantBase
{
  public:
#ifndef DOXYGEN_SHOULD_SKIP_THIS
  using CppObjectType = VariantBase;
  using BaseObjectType = GVariant;
#endif /* DOXYGEN_SHOULD_SKIP_THIS */

  /** Constructs an invalid object.
   * E.g. for output arguments to methods. There is not much you can do with
   * the object before it has been assigned a valid value.
   */
  VariantBase();

  // Use make_a_copy=true when getting it directly from a struct.
  explicit VariantBase(GVariant* castitem, bool make_a_copy = false);

  VariantBase(const VariantBase& src);
  VariantBase& operator=(const VariantBase& src);

  VariantBase(VariantBase&& other) noexcept;
  VariantBase& operator=(VariantBase&& other) noexcept;

  ~VariantBase() noexcept;

  void swap(VariantBase& other) noexcept;

  GVariant*       gobj()       { return gobject_; }
  const GVariant* gobj() const { return gobject_; }

  ///Provides access to the underlying C instance. The caller is responsible for freeing it. Use when directly setting fields in structs.
  GVariant* gobj_copy() const;

protected:
  GVariant* gobject_;

private:


public:

#ifndef GLIBMM_DISABLE_DEPRECATED

  /** This typedef is just to make it more obvious that
   * our operator const void* should be used like operator bool().
   *
   * @deprecated Use the explicit operator bool() instead.
   */
  using BoolExpr = const void*;

  /** Test whether the Variant has an underlying instance.
   *
   * Mimics usage of pointers:
   * @code
   *   if (variant)
   *     do_something();
   * @endcode
   *
   * @deprecated Use the explicit operator bool() instead.
   *
   * @newin{2,36}
   */
   operator BoolExpr() const;
#endif // GLIBMM_DISABLE_DEPRECATED


   /** Test whether the Variant has an underlying instance.
    *
    * @newin{2,50}
    */
   explicit operator bool() const;

  /** Replace the underlying GVariant.
   * This is for use by methods that take a VariantBase& as an output
   * parameter.
   *
   * @param cobject The GVariant* obtained from a C function.
   * @param take_a_reference Whether this method should take a reference, for
   * instance if the C function has not given one.
   */
  void init(const GVariant* cobject, bool take_a_reference = false);

// It's necessary to take an extra reference of the 'const GVariantType*'
// returned by g_variant_get_type() because it doesn't do that already.


  /** Determines the type of @a value.
   *
   * The return value is valid for the lifetime of @a value and must not
   * be freed.
   *
   * @newin{2,24}
   *
   * @return A VariantType.
   */
  VariantType get_type() const;


  /** Returns the type string of @a value.  Unlike the result of calling
   * g_variant_type_peek_string(), this string is nul-terminated.  This
   * string belongs to Variant and must not be freed.
   *
   * @newin{2,24}
   *
   * @return The type string for the type of @a value.
   */
  std::string get_type_string() const;

  /** Checks whether @a value has a floating reference count.
   *
   * This function should only ever be used to assert that a given variant
   * is or is not floating, or for debug purposes. To acquire a reference
   * to a variant that might be floating, always use g_variant_ref_sink()
   * or g_variant_take_ref().
   *
   * See g_variant_ref_sink() for more information about floating reference
   * counts.
   *
   * @newin{2,26}
   *
   * @return Whether @a value is floating.
   */
  bool is_floating() const;

  /** Checks if a value has a type matching the provided type.
   *
   * @newin{2,24}
   *
   * @param type A VariantType.
   * @return <tt>true</tt> if the type of @a value matches @a type.
   */
  bool is_of_type(const VariantType& type) const;

  /** Checks if @a value is a container.
   *
   * @newin{2,24}
   *
   * @return <tt>true</tt> if @a value is a container.
   */
  bool is_container() const;

  /** Classifies @a value according to its top-level type.
   *
   * @newin{2,24}
   *
   * @return The VariantClass of @a value.
   */
  GVariantClass classify() const;


  /** Determines the number of bytes that would be required to store @a value
   * with g_variant_store().
   *
   * If @a value has a fixed-sized type then this function always returned
   * that fixed size.
   *
   * In the case that @a value is already in serialised form or the size has
   * already been calculated (ie: this function has been called before)
   * then this function is O(1).  Otherwise, the size is calculated, an
   * operation which is approximately O(n) in the number of values
   * involved.
   *
   * @newin{2,24}
   *
   * @return The serialised size of @a value.
   */
  gsize get_size() const;

#ifndef GLIBMM_DISABLE_DEPRECATED

  /** Returns a pointer to the serialised form of a Variant instance.
   * The returned data may not be in fully-normalised form if read from an
   * untrusted source.  The returned data must not be freed; it remains
   * valid for as long as @a value exists.
   *
   * If @a value is a fixed-sized value that was deserialised from a
   * corrupted serialised container then <tt>nullptr</tt> may be returned.  In this
   * case, the proper thing to do is typically to use the appropriate
   * number of nul bytes in place of @a value.  If @a value is not fixed-sized
   * then <tt>nullptr</tt> is never returned.
   *
   * In the case that @a value is already in serialised form, this function
   * is O(1).  If the value is not already in serialised form,
   * serialisation occurs implicitly and is approximately O(n) in the size
   * of the result.
   *
   * To deserialise the data returned by this function, in addition to the
   * serialised data, you must know the type of the Variant, and (if the
   * machine might be different) the endianness of the machine that stored
   * it. As a result, file formats or network messages that incorporate
   * serialised Variants must include this information either
   * implicitly (for instance "the file always contains a
   * G_VARIANT_TYPE_VARIANT and it is always in little-endian order") or
   * explicitly (by storing the type and/or endianness in addition to the
   * serialised data).
   *
   * @newin{2,24}
   *
   * @deprecated Use the const version instead.
   *
   * @return The serialised form of @a value, or <tt>nullptr</tt>.
   */
  gconstpointer get_data();
#endif // GLIBMM_DISABLE_DEPRECATED


  /** Returns a pointer to the serialised form of a Variant instance.
   * The returned data may not be in fully-normalised form if read from an
   * untrusted source.  The returned data must not be freed; it remains
   * valid for as long as @a value exists.
   *
   * If @a value is a fixed-sized value that was deserialised from a
   * corrupted serialised container then <tt>nullptr</tt> may be returned.  In this
   * case, the proper thing to do is typically to use the appropriate
   * number of nul bytes in place of @a value.  If @a value is not fixed-sized
   * then <tt>nullptr</tt> is never returned.
   *
   * In the case that @a value is already in serialised form, this function
   * is O(1).  If the value is not already in serialised form,
   * serialisation occurs implicitly and is approximately O(n) in the size
   * of the result.
   *
   * To deserialise the data returned by this function, in addition to the
   * serialised data, you must know the type of the Variant, and (if the
   * machine might be different) the endianness of the machine that stored
   * it. As a result, file formats or network messages that incorporate
   * serialised Variants must include this information either
   * implicitly (for instance "the file always contains a
   * G_VARIANT_TYPE_VARIANT and it is always in little-endian order") or
   * explicitly (by storing the type and/or endianness in addition to the
   * serialised data).
   *
   * @newin{2,46}
   *
   * @return The serialised form of @a value, or <tt>nullptr</tt>.
   */
  gconstpointer get_data() const;

  /** Returns a pointer to the serialised form of a Variant instance.
   * The semantics of this function are exactly the same as
   * g_variant_get_data(), except that the returned Bytes holds
   * a reference to the variant data.
   *
   * @newin{2,46}
   *
   * @return A new Bytes representing the variant data.
   */
  Glib::RefPtr<const Glib::Bytes> get_data_as_bytes() const;

  /** Stores the serialised form of @a value at @a data.  @a data should be
   * large enough.  See g_variant_get_size().
   *
   * The stored data is in machine native byte order but may not be in
   * fully-normalised form if read from an untrusted source.  See
   * g_variant_get_normal_form() for a solution.
   *
   * As with g_variant_get_data(), to be able to deserialise the
   * serialised variant successfully, its type and (if the destination
   * machine might be different) its endianness must also be available.
   *
   * This function is approximately O(n) in the size of @a data.
   *
   * @newin{2,24}
   *
   * @param data The location to store the serialised data at.
   */
  void store(gpointer data) const;


  /** Pretty-prints @a value in the format understood by g_variant_parse().
   *
   * The format is described [here][gvariant-text].
   *
   * If @a type_annotate is <tt>true</tt>, then type information is included in
   * the output.
   *
   * @newin{2,24}
   *
   * @param type_annotate <tt>true</tt> if type information should be included in
   * the output.
   * @return A newly-allocated string holding the result.
   */
  Glib::ustring print(bool type_annotate =  false) const;


  /** Generates a hash value for a Variant instance.
   *
   * The output of this function is guaranteed to be the same for a given
   * value only per-process.  It may change between different processor
   * architectures or even different versions of GLib.  Do not use this
   * function as a basis for building protocols or file formats.
   *
   * The type of @a value is #gconstpointer only to allow use of this
   * function with HashTable.  @a value must be a Variant.
   *
   * @newin{2,24}
   *
   * @return A hash value corresponding to @a value.
   */
  guint hash() const;


  /** Checks if @a *this and @a other have the same type and value.
   *
   * @newin{2,24}
   *
   * @param other The Variant to compare with.
   * @return <tt>true</tt> if @a *this and @a other are equal.
   */
  bool equal(const VariantBase& other) const;

  /** Gets a VariantBase instance that has the same value as this variant and
   * is trusted to be in normal form.
   *
   * If this variant is already trusted to be in normal form then a new
   * reference to the variant is returned.
   *
   * If this variant is not already trusted, then it is scanned to check if it
   * is in normal form. If it is found to be in normal form then it is marked
   * as trusted and a new reference to it is returned.
   *
   * If this variant is found not to be in normal form then a new trusted
   * VariantBase is created with the same value as this variant.
   *
   * It makes sense to call this function if you've received variant data from
   * untrusted sources and you want to ensure your serialised output is
   * definitely in normal form.
   *
   * @param result A location in which to store the trusted VariantBase.
   * @newin{2,24}
   */
  void get_normal_form(VariantBase& result) const;


  /** Checks if @a value is in normal form.
   *
   * The main reason to do this is to detect if a given chunk of
   * serialised data is in normal form: load the data into a Variant
   * using g_variant_new_from_data() and then use this function to
   * check.
   *
   * If @a value is found to be in normal form then it will be marked as
   * being trusted.  If the value was already marked as being trusted then
   * this function will immediately return <tt>true</tt>.
   *
   * There may be implementation specific restrictions on deeply nested values.
   * GVariant is guaranteed to handle nesting up to at least 64 levels.
   *
   * @newin{2,24}
   *
   * @return <tt>true</tt> if @a value is in normal form.
   */
  bool is_normal_form() const;

  /** Performs a byteswapping operation on the contents of this variant. The
   * result is that all multi-byte numeric data contained in the variant is
   * byteswapped. That includes 16, 32, and 64bit signed and unsigned integers
   * as well as file handles and double precision floating point values.
   *
   * This function is an identity mapping on any value that does not contain
   * multi-byte numeric data. That include strings, booleans, bytes and
   * containers containing only these things (recursively).
   *
   * The returned value is always in normal form and is marked as trusted.
   *
   * @param result A location in which to store the byteswapped form of this
   * variant.
   * @newin{2,24}
   */
   void byteswap(VariantBase& result) const;


  /** Checks if calling g_variant_get() with @a format_string on @a value would
   * be valid from a type-compatibility standpoint.  @a format_string is
   * assumed to be a valid format string (from a syntactic standpoint).
   *
   * If @a copy_only is <tt>true</tt> then this function additionally checks that it
   * would be safe to call g_variant_unref() on @a value immediately after
   * the call to g_variant_get() without invalidating the result.  This is
   * only possible if deep copies are made (ie: there are no pointers to
   * the data inside of the soon-to-be-freed Variant instance).  If this
   * check fails then a g_critical() is printed and <tt>false</tt> is returned.
   *
   * This function is meant to be used by functions that wish to provide
   * varargs accessors to Variant values of uncertain values (eg:
   * g_variant_lookup() or Glib::menu_model_get_item_attribute()).
   *
   * @newin{2,34}
   *
   * @param format_string A valid Variant format string.
   * @param copy_only <tt>true</tt> to ensure the format string makes deep copies.
   * @return <tt>true</tt> if @a format_string is safe to use.
   */
  bool check_format_string(const std::string& format_string, bool copy_only =  false) const;

   //Ignore private API from gvariant-core.h:


   /** Cast to a specific variant type.
    * For instance:
    * @code
    * Variant<std::string> derived = VariantBase::cast_dynamic< Variant<std::string> >(base);
    * @endcode
    *
    * @param v The variant to cast to a specific type.
    * @result The variant as a specific type.
    * @throws std::bad_cast if the Variant was not of the expected type.
    */
   template<class V_CastTo>
   static V_CastTo cast_dynamic(const VariantBase& v);


protected:
#ifndef DOXYGEN_SHOULD_SKIP_THIS
  /** Used by cast_dynamic().
   * In addition to an exact match, the following casts are possible:
   * - VARIANT_TYPE_OBJECT_PATH and VARIANT_TYPE_SIGNATURE can be cast to
   *   VARIANT_TYPE_STRING (Glib::ustring).
   * - VARIANT_TYPE_STRING, VARIANT_TYPE_OBJECT_PATH and VARIANT_TYPE_SIGNATURE
   *   can be cast to VARIANT_TYPE_BYTESTRING (std::string).
   * - VARIANT_TYPE_HANDLE can be cast to VARIANT_TYPE_INT32.
   *
   * These casts are possible also when they are parts of a more complicated type.
   * E.g. in Variant<std::map<Glib::ustring, std::vector<std::string> > > the map's keys
   * can be VARIANT_TYPE_OBJECT_PATH and the vector's elements can be VARIANT_TYPE_SIGNATURE.
   * @newin{2,46}
   */
  bool is_castable_to(const VariantType& supertype) const;
#endif //DOXYGEN_SHOULD_SKIP_THIS

private:
  /** Relational operators are deleted to prevent invalid conversion
   * to const void*.
   */
  bool operator<(const VariantBase& src) const;

  /// See operator<().
  bool operator<=(const VariantBase& src) const;

  /// See operator<().
  bool operator>(const VariantBase& src) const;

  /// See operator<().
  bool operator>=(const VariantBase& src) const;

  /// See operator<().
  bool operator==(const VariantBase& src) const;

  /// See operator<().
  bool operator!=(const VariantBase& src) const;


};

template<class V_CastTo>
V_CastTo VariantBase::cast_dynamic(const VariantBase& v)
{
  if(!(v.gobj()))
  {
    return V_CastTo();
  }
  if(v.is_castable_to(V_CastTo::variant_type()))
  {
    return V_CastTo(const_cast<GVariant*>(v.gobj()), true);
  }
  else
  {
   throw std::bad_cast();
  }
}

/** Base class from which string variant classes derive.
 * @newin{2,28}
 * @ingroup Variant
 */
class GLIBMM_API VariantStringBase : public VariantBase
{
  // Trick gmmproc into thinking this is derived from GVariant to wrap some methods.
  public:
#ifndef DOXYGEN_SHOULD_SKIP_THIS
  using CppObjectType = VariantStringBase;
  using BaseObjectType = GVariant;
#endif /* DOXYGEN_SHOULD_SKIP_THIS */

private:


public:
  using CType = GVariant*;
  using CppType = VariantStringBase;

  /// Default constructor.
  VariantStringBase();

  /** GVariant constructor.
   * @param castitem The GVariant to wrap.
   * @param take_a_reference Whether to take an extra reference of the
   * GVariant or not (not taking one could destroy the GVariant with the
   * wrapper).
   */
  explicit VariantStringBase(GVariant* castitem,  bool take_a_reference = false);

  /** Creates a D-Bus object path variant with the contents of @a object_path.
   * @a object_path must be a valid D-Bus object path. Use is_object_path() if unsure.
   *
   * @param[out] output A location in which to store the new object path variant
   * instance.
   * @param object_path An object path string.
   * @newin{2,28}
   */
  static void create_object_path(VariantStringBase& output,
    const std::string& object_path);


  /** Determines if a given string is a valid D-Bus object path.  You
   * should ensure that a string is a valid D-Bus object path before
   * passing it to g_variant_new_object_path().
   *
   * A valid object path starts with `/` followed by zero or more
   * sequences of characters separated by `/` characters.  Each sequence
   * must contain only the characters `[A-Z][a-z][0-9]_`.  No sequence
   * (including the one following the final `/` character) may be empty.
   *
   * @newin{2,24}
   *
   * @param string A normal C nul-terminated string.
   * @return <tt>true</tt> if @a string is a D-Bus object path.
   */
  static bool is_object_path(const std::string& string);

  /** Creates a D-Bus type signature variant with the contents of @a signature.
   * @a signature must be a valid D-Bus type signature. Use is_signature() if unsure.
   *
   * @param[out] output A location in which to store the new signature variant
   * instance.
   * @param signature A signature string.
   * @newin{2,28}
   */
  static void create_signature(VariantStringBase& output,
    const std::string& signature);


  /** Determines if a given string is a valid D-Bus type signature.  You
   * should ensure that a string is a valid D-Bus type signature before
   * passing it to g_variant_new_signature().
   *
   * D-Bus type signatures consist of zero or more definite VariantType
   * strings in sequence.
   *
   * @newin{2,24}
   *
   * @param string A normal C nul-terminated string.
   * @return <tt>true</tt> if @a string is a D-Bus type signature.
   */
  static bool is_signature(const std::string& string);


};

/** The base class for multiple-item Variants, such as Variants containing
 * tuples or arrays, and also for maybe-typed (that is, nullable) Variant types.
 *
 * @newin{2,28}
 * @ingroup Variant
 */
class GLIBMM_API VariantContainerBase : public VariantBase
{
  // Trick gmmproc into thinking this is derived from GVariant to wrap some methods.
  public:
#ifndef DOXYGEN_SHOULD_SKIP_THIS
  using CppObjectType = VariantContainerBase;
  using BaseObjectType = GVariant;
#endif /* DOXYGEN_SHOULD_SKIP_THIS */

private:


public:
  using CType = GVariant*;
  using CppType = VariantContainerBase;

  /// Default constructor.
  VariantContainerBase();

  /** GVariant constructor.
   * @param castitem The GVariant to wrap.
   * @param take_a_reference Whether to take an extra reference of the
   * GVariant or not (not taking one could destroy the GVariant with the
   * wrapper).
   */
  explicit VariantContainerBase(GVariant* castitem, bool take_a_reference = false);

  /** Create a tuple variant from a vector of its variant children.
   * @param children The vector containing the children of the container.
   * @return The newly created tuple variant (as a VariantContainerBase).
   */
  static VariantContainerBase create_tuple(const std::vector<VariantBase>& children);

  /** Create a tuple variant with a single variant child.
   * @param child The child variant.
   * @return The newly created tuple variant (as a VariantContainerBase).
   */
  static VariantContainerBase create_tuple(const VariantBase& child);


  /** Depending on if @a child is <tt>nullptr</tt>, either wraps @a child inside of a
   * maybe container or creates a Nothing instance for the given @a type.
   *
   * At least one of @a child_type and @a child must be non-<tt>nullptr</tt>.
   * If @a child_type is non-<tt>nullptr</tt> then it must be a definite type.
   * If they are both non-<tt>nullptr</tt> then @a child_type must be the type
   * of @a child.
   *
   * If @a child is a floating reference (see g_variant_ref_sink()), the new
   * instance takes ownership of @a child.
   *
   * @newin{2,24}
   *
   * @param child_type The VariantType of the child, or <tt>nullptr</tt>.
   * @param child The child value, or <tt>nullptr</tt>.
   * @return A floating reference to a new Variant maybe instance.
   */

  static VariantContainerBase create_maybe(const VariantType& child_type,
    const VariantBase& child = VariantBase());


  /** Determines the number of children in a container Variant instance.
   * This includes variants, maybes, arrays, tuples and dictionary
   * entries.  It is an error to call this function on any other type of
   * Variant.
   *
   * For variants, the return value is always 1.  For values with maybe
   * types, it is always zero or one.  For arrays, it is the length of the
   * array.  For tuples it is the number of tuple items (which depends
   * only on the type).  For dictionary entries, it is always 2
   *
   * This function is O(1).
   *
   * @newin{2,24}
   *
   * @return The number of children in the container.
   */
  gsize get_n_children() const;

  /** Reads a child item out of this instance. This method is valid for
   * variants, maybes, arrays, tuples and dictionary entries.
   *
   * It is an error if @a index is greater than the number of child items in
   * the container. See get_n_children().
   *
   * This function is O(1).
   *
   * @param index The index of the child to fetch.
   * @param child A location in which to store the child at the specified
   * index.
   * @throw std::out_of_range
   * @newin{2,28}
   */
  void get_child(VariantBase& child, gsize index = 0) const;


  /** Reads a child item out of a container Variant instance.  This
   * includes variants, maybes, arrays, tuples and dictionary
   * entries.  It is an error to call this function on any other type of
   * Variant.
   *
   * It is an error if @a index is greater than the number of child items
   * in the container.  See g_variant_n_children().
   *
   * The returned value is never floating.  You should free it with
   * g_variant_unref() when you're done with it.
   *
   * There may be implementation specific restrictions on deeply nested values,
   * which would result in the unit tuple being returned as the child value,
   * instead of further nested children. Variant is guaranteed to handle
   * nesting up to at least 64 levels.
   *
   * This function is O(1).
   *
   * @newin{2,24}
   *
   * @param index The index of the child to fetch.
   * @return The child at the specified index.
   */
  VariantBase get_child(gsize index =  0);

  /* TODO?:
  /// A get() method to return the contents of the variant in the container.
  template <class DataType>
  DataType get_child(gsize index = 0) const;
  */

  /** If this is a maybe-typed instance, try to extract its value. If there is
   * no value (the value is <tt>nothing</tt>), return <tt>false</tt>. Otherwise,
   * the value is copied to the supplied Variant and <tt>true</tt> is returned.
   *
   * @param maybe A place in which to return the value, if it isn’t
   * <tt>nothing</tt>.
   * @newin{2,28}
   */
  bool get_maybe(VariantBase& maybe) const;


protected:
#ifndef DOXYGEN_SHOULD_SKIP_THIS
  /** Used by get_iter() in the subclasses.
   * @newin{2,46}
   */
  VariantIter get_iter(const VariantType& container_variant_type) const;
#endif //DOXYGEN_SHOULD_SKIP_THIS


};

template<>
GLIBMM_API VariantContainerBase VariantBase::cast_dynamic<VariantContainerBase>(const VariantBase& v);

/** Template class used for the specialization of the Variant<> classes.
 * @newin{2,28}
 * @ingroup Variant
 */
template<class T>
class Variant : public VariantBase
{
public:
  using CppType = T;
};

/****************** Specializations ***********************************/

/** Specialization of Variant containing a VariantBase.
 * Perhaps the main use of this is as a maybe-typed (i.e. nullable) Variant, as
 * it inherits the methods create_maybe() and get_maybe() from
 * VariantContainerBase, plus get_n_children() to allow checking whether there
 * is a contained value, i.e. the inner Variant is not <tt>nothing</tt>.
 *
 * @newin{2,28}
 * @ingroup Variant
 */
template<>
class GLIBMM_API Variant<VariantBase> : public VariantContainerBase
{
  // Trick gmmproc into thinking this is derived from GVariant to wrap some methods.
  public:
#ifndef DOXYGEN_SHOULD_SKIP_THIS
  using CppObjectType = Variant<VariantBase>;
  using BaseObjectType = GVariant;
#endif /* DOXYGEN_SHOULD_SKIP_THIS */

private:


public:
  using CType = GVariant*;
  using CppType = VariantBase;
  using CppContainerType = Variant<VariantBase>;

  /// Default constructor.
  Variant<VariantBase>();

  /** GVariant constructor.
   * @param castitem The GVariant to wrap.
   * @param take_a_reference Whether to take an extra reference of the
   * GVariant or not (not taking one could destroy the GVariant with the
   * wrapper).
   */
  explicit Variant<VariantBase>(GVariant* castitem, bool take_a_reference = false);

  /** Gets the VariantType.
   * @return The VariantType.
   * @newin{2,28}
   */
  static const VariantType& variant_type() G_GNUC_CONST;

  //This must have a create() method because otherwise it would be a copy
  //constructor.
  /** Creates a new Variant<VariantBase>.
   * @param data The value of the new Variant.
   * @return The new Variant.
   * @newin{2,28}
   */
  static Variant<VariantBase> create(const VariantBase& data);


  //TODO: Documentation
  void get(VariantBase& variant) const;

  //TODO: Deprecate this in favour of get(VariantBase&)?

  /** Unboxes @a value.  The result is the Variant instance that was
   * contained in @a value.
   *
   * @newin{2,24}
   *
   * @return The item contained in the variant.
   */
  VariantBase get() const;


};

/** Specialization of Variant containing a Variant<T>.
 * Perhaps the main use of this is as a maybe-typed (i.e. nullable) Variant, as
 * it inherits the methods create_maybe() and get_maybe() from
 * VariantContainerBase, plus get_n_children() to allow checking whether there
 * is a contained value, i.e. the inner Variant is not <tt>nothing</tt>.
 *
 * @newin{2,36}
 * @ingroup Variant
 */
template<class T>
class Variant< Variant<T> > : public VariantContainerBase
{
public:
  using CType = GVariant*;
  using CppType = Variant<T>;
  using CppContainerType = Variant<CppType>;

  /// Default constructor.
  Variant< Variant<T> >();

  /** GVariant constructor.
   * @param castitem The GVariant to wrap.
   * @param take_a_reference Whether to take an extra reference of the
   * GVariant or not (not taking one could destroy the GVariant with the
   * wrapper).
   * @newin{2,36}
   */
  explicit Variant< Variant<T> >(GVariant* castitem, bool take_a_reference = false);

  /** Gets the VariantType.
   * @return The VariantType.
   * @newin{2,36}
   */
  static const VariantType& variant_type() G_GNUC_CONST;

  /** Creates a new Variant< Variant<T> >.
   * @param data The value of the new Variant.
   * @return The new Variant.
   * @newin{2,36}
   */
  static Variant< Variant<T> > create(const Variant<T>& data);

  /** Gets the contents of the Variant.
   * @return The contents of the Variant.
   * @newin{2,36}
   */
  Variant<T> get() const;
};

/** Specialization of Variant containing a Glib::ustring, for variants of type
 * string, object path, or signature.
 * @newin{2,28}
 * @ingroup Variant
 */
template<>
class GLIBMM_API Variant<Glib::ustring> : public VariantStringBase
{
  // Trick gmmproc into thinking this is derived from GVariant to wrap some methods.
  public:
#ifndef DOXYGEN_SHOULD_SKIP_THIS
  using CppObjectType = Variant<Glib::ustring>;
  using BaseObjectType = GVariant;
#endif /* DOXYGEN_SHOULD_SKIP_THIS */

private:

public:
  using CType = char*;
  using CppType = Glib::ustring;

  /// Default constructor.
  Variant<Glib::ustring>();

  /** GVariant constructor.
   * @param castitem The GVariant to wrap.
   * @param take_a_reference Whether to take an extra reference of the
   * GVariant or not (not taking one could destroy the GVariant with the
   * wrapper).
   */
  explicit Variant<Glib::ustring>(GVariant* castitem,  bool take_a_reference = false);

  /** Gets the VariantType.
   * @return The VariantType.
   * @newin{2,28}
   */
  static const VariantType& variant_type() G_GNUC_CONST;

  /** Creates a new Variant<Glib::ustring>.
   * @param data The value of the new Variant.
   * @return The new Variant.
   * @newin{2,28}
   */
  static Variant<Glib::ustring> create(const Glib::ustring& data);

  //We can't use WRAP_METHOD() here because g_variant_get_string() takes an extra length parameter.
  /** Gets the contents of the Variant.
   * @return The contents of the Variant.
   * @newin{2,28}
   */
  Glib::ustring get() const;


};

//TODO: When we can break ABI, remove this template specialization.
template<>
GLIBMM_API Variant<Glib::ustring> VariantBase::cast_dynamic< Variant<Glib::ustring> >(const VariantBase& v);

/** Specialization of Variant containing a Glib::DBusObjectPathString,
 * for variants of type object path.
 * @newin{2,54}
 * @ingroup Variant
 */
template<>
class GLIBMM_API Variant<Glib::DBusObjectPathString> : public VariantStringBase
{
  // Trick gmmproc into thinking this is derived from GVariant to wrap some methods.
  public:
#ifndef DOXYGEN_SHOULD_SKIP_THIS
  using CppObjectType = Variant<Glib::DBusObjectPathString>;
  using BaseObjectType = GVariant;
#endif /* DOXYGEN_SHOULD_SKIP_THIS */

private:

public:
  using CType = char*;
  using CppType = Glib::DBusObjectPathString;

  /// Default constructor.
  Variant();

  /** GVariant constructor.
   * @param castitem The GVariant to wrap.
   * @param take_a_reference Whether to take an extra reference of the
   * GVariant or not (not taking one could destroy the GVariant with the
   * wrapper).
   */
  explicit Variant(GVariant* castitem,  bool take_a_reference = false);

  /** Gets the VariantType.
   * @return The VariantType.
   * @newin{2,54}
   */
  static const VariantType& variant_type() G_GNUC_CONST;

  /** Creates a new Variant<Glib::DBusObjectPathString>.
   * @param data The value of the new Variant.
   * @return The new Variant.
   * @newin{2,54}
   */
  static Variant<CppType> create(const CppType& data);

  //We can't use WRAP_METHOD() here because g_variant_get_string() takes an extra length parameter.
  /** Gets the contents of the Variant.
   * @return The contents of the Variant.
   * @newin{2,54}
   */
  CppType get() const;


};

/** Specialization of Variant containing a Glib::DBusSignatureString,
 * for variants of type signature.
 * @newin{2,54}
 * @ingroup Variant
 */
template<>
class GLIBMM_API Variant<Glib::DBusSignatureString> : public VariantStringBase
{
  // Trick gmmproc into thinking this is derived from GVariant to wrap some methods.
  public:
#ifndef DOXYGEN_SHOULD_SKIP_THIS
  using CppObjectType = Variant<Glib::DBusSignatureString>;
  using BaseObjectType = GVariant;
#endif /* DOXYGEN_SHOULD_SKIP_THIS */

private:

public:
  using CType = char*;
  using CppType = Glib::DBusSignatureString;

  /// Default constructor.
  Variant();

  /** GVariant constructor.
   * @param castitem The GVariant to wrap.
   * @param take_a_reference Whether to take an extra reference of the
   * GVariant or not (not taking one could destroy the GVariant with the
   * wrapper).
   */
  explicit Variant(GVariant* castitem,  bool take_a_reference = false);

  /** Gets the VariantType.
   * @return The VariantType.
   * @newin{2,54}
   */
  static const VariantType& variant_type() G_GNUC_CONST;

  /** Creates a new Variant<Glib::DBusSignatureString>.
   * @param data The value of the new Variant.
   * @return The new Variant.
   * @newin{2,54}
   */
  static Variant<CppType> create(const CppType& data);

  //We can't use WRAP_METHOD() here because g_variant_get_string() takes an extra length parameter.
  /** Gets the contents of the Variant.
   * @return The contents of the Variant.
   * @newin{2,54}
   */
  CppType get() const;


};

/** Specialization of Variant containing a std::string, for variants of type
 * bytestring, string, object path, or signature.
 * See also Variant<Glib::ustring> for UTF-8 strings.
 * @newin{2,28}
 * @ingroup Variant
 */
template<>
class GLIBMM_API Variant<std::string> : public VariantStringBase
{
  // Trick gmmproc into thinking this is derived from GVariant to wrap some methods.
  public:
#ifndef DOXYGEN_SHOULD_SKIP_THIS
  using CppObjectType = Variant<std::string>;
  using BaseObjectType = GVariant;
#endif /* DOXYGEN_SHOULD_SKIP_THIS */

private:

public:
  using CType = char*                ;
  using CppType = std::string;

  /// Default constructor.
  Variant<std::string>();

  /** GVariant constructor.
   * @param castitem The GVariant to wrap.
   * @param take_a_reference Whether to take an extra reference of the
   * GVariant or not (not taking one could destroy the GVariant with the
   * wrapper).
   */
  explicit Variant<std::string>(GVariant* castitem, bool take_a_reference = false);

  /** Gets the VariantType.
   * @return The VariantType.
   * @newin{2,28}
   */
  static const VariantType& variant_type() G_GNUC_CONST;

  /** Creates a new Variant<std::string>.
   * @param data The value of the new Variant.
   * @return The new Variant.
   * @newin{2,28}
   */
  static Variant<std::string> create(const std::string& data);

  //TODO: Documentation.
  std::string get() const;


};

//TODO: When we can break ABI, remove this template specialization.
template<>
GLIBMM_API Variant<std::string> VariantBase::cast_dynamic< Variant<std::string> >(const VariantBase& v);

/** Specialization of Variant containing a dictionary entry.  See also
 * Variant< std::map<K, V> >.
 * @newin{2,28}
 * @ingroup Variant
 */
template<class K, class V>
class Variant< std::pair<K, V> > : public VariantContainerBase
{
public:
  using CppType = std::pair<K, V>;
  using CppContainerType = Variant<CppType>;

  /// Default constructor.
  Variant< std::pair<K, V> >()
  : VariantContainerBase()
  {}

  /** GVariant constructor.
   * @param castitem The GVariant to wrap.
   * @param take_a_reference Whether to take an extra reference of the
   * GVariant or not (not taking one could destroy the GVariant with the
   * wrapper).
   */
  explicit Variant< std::pair<K, V> >(GVariant* castitem,
    bool take_a_reference = false)
  : VariantContainerBase(castitem, take_a_reference)
  {}

  /** Gets the VariantType.
   * @return The VariantType.
   * @newin{2,28}
   */
  static const VariantType& variant_type() G_GNUC_CONST;

  /** Creates a new Variant< std::pair<K, V> >.
   * @param data The value of the new Variant.
   * @return The new Variant.
   * @newin{2,28}
   */
  static Variant< std::pair<K, V> > create(const std::pair<K, V>& data);


  /** Gets the contents of the Variant.
   * @return The contents of the Variant.
   * @throw std::out_of_range
   * @newin{2,28}
   */
  std::pair<K, V> get() const;
};

/** Specialization of Variant containing an array of items.
 * @newin{2,28}
 * @ingroup Variant
 */
template<class T>
class Variant< std::vector<T> > : public VariantContainerBase
{
public:
  using CppType = T                    ;
  using CppContainerType = std::vector<T>;

  /// Default constructor.
  Variant< std::vector<T> >()
  : VariantContainerBase()
  {}

  /** GVariant constructor.
   * @param castitem The GVariant to wrap.
   * @param take_a_reference Whether to take an extra reference of the
   * GVariant or not (not taking one could destroy the GVariant with the
   * wrapper).
   */
  explicit Variant< std::vector<T> >(GVariant* castitem,
    bool take_a_reference = false)
  : VariantContainerBase(castitem, take_a_reference)
  {}

  /** Gets the VariantType.
   * @return The VariantType.
   * @newin{2,28}
   */
  static const VariantType& variant_type() G_GNUC_CONST;

  /** Creates a new Variant from an array of numeric types.
   * @param data The array to use for creation.
   * @return The new Variant.
   * @newin{2,28}
   */
  static Variant< std::vector<T> > create(const std::vector<T>& data);


  /** Gets a specific element of the array.  It is an error if @a index is
   * greater than the number of child items in the container.  See
   * VariantContainerBase::get_n_children().
   *
   * This function is O(1).
   *
   * @param index The index of the element.
   * @return The element at index @a index.
   * @throw std::out_of_range
   * @newin{2,28}
   */
  T get_child(gsize index) const;

  /** Gets the vector of the Variant.
   * @return The vector.
   * @newin{2,28}
   */
  std::vector<T> get() const;


  /** Gets a VariantIter of the Variant.
   * @return the VariantIter.
   * @newin{2,28}
   */
  VariantIter get_iter() const;
};

/** Specialization of Variant containing an array of UTF-8 capable
 * strings.
 * @newin{2,28}
 * @ingroup Variant
 */
template<>
class GLIBMM_API Variant< std::vector<Glib::ustring> > : public VariantContainerBase
{
public:
  using CppType = Glib::ustring                ;
  using CppContainerType = std::vector<Glib::ustring>;

  /// Default constructor.
  Variant< std::vector<Glib::ustring> >();

  /** GVariant constructor.
   * @param castitem The GVariant to wrap.
   * @param take_a_reference Whether to take an extra reference of the
   * GVariant or not (not taking one could destroy the GVariant with the
   * wrapper).
   */
  explicit Variant< std::vector<Glib::ustring> >(GVariant* castitem, bool take_a_reference = false);

  /** Gets the VariantType.
   * @return The VariantType.
   * @newin{2,28}
   */
  static const VariantType& variant_type() G_GNUC_CONST;

  /** Creates a new Variant from an array of strings.
   * @param data The array to use for creation.
   * @return The new Variant.
   * @newin{2,28}
   */
  static Variant< std::vector<Glib::ustring> >
    create(const std::vector<Glib::ustring>& data);

  /** Gets a specific element of the string array.  It is an error if @a index
   * is greater than the number of child items in the container.  See
   * VariantContainerBase::get_n_children().
   *
   * This function is O(1).
   *
   * @param index The index of the element.
   * @return The element at index @a index.
   * @throw std::out_of_range
   * @newin{2,28}
   */
  Glib::ustring get_child(gsize index) const;

  /** Gets the string vector of the Variant.
   * @return The vector.
   * @newin{2,28}
   */
  std::vector<Glib::ustring> get() const;


  /** Gets a VariantIter of the Variant.
   * @return the VariantIter.
   * @newin{2,28}
   */
  VariantIter get_iter() const;
};

/** Specialization of Variant containing an array of D-Bus object paths.
 *
 * @newin{2,54}
 * @ingroup Variant
 */
template<>
class GLIBMM_API Variant<std::vector<Glib::DBusObjectPathString>> : public VariantContainerBase
{
public:
  using CppType = Glib::DBusObjectPathString;
  using CppContainerType = std::vector<Glib::DBusObjectPathString>;

  /// Default constructor.
  Variant();

  /** GVariant constructor.
   * @param castitem The GVariant to wrap.
   * @param take_a_reference Whether to take an extra reference of the
   * GVariant or not (not taking one could destroy the GVariant with the
   * wrapper).
   */
  explicit Variant(GVariant* castitem, bool take_a_reference = false);

  /** Gets the VariantType.
   * @return The VariantType.
   * @newin{2,54}
   */
  static const VariantType& variant_type() G_GNUC_CONST;

  /** Creates a new Variant from an array of strings.
   * @param data The array to use for creation.
   * @return The new Variant.
   * @newin{2,54}
   */
  static Variant<CppContainerType> create(const CppContainerType& data);

  /** Gets a specific element of the string array.  It is an error if @a index
   * is greater than the number of child items in the container.  See
   * VariantContainerBase::get_n_children().
   *
   * This function is O(1).
   *
   * @param index The index of the element.
   * @return The element at index @a index.
   * @throw std::out_of_range
   * @newin{2,54}
   */
  CppType get_child(gsize index) const;

  /** Gets the string vector of the Variant.
   * @return The vector.
   * @newin{2,54}
   */
  CppContainerType get() const;

  /** Gets a VariantIter of the Variant.
   * @return the VariantIter.
   * @newin{2,54}
   */
  VariantIter get_iter() const;
};

/** Specialization of Variant containing an array of non-UTF-8 strings
 * (byte string arrays).
 * @newin{2,28}
 * @ingroup Variant
 */
template<>
class GLIBMM_API Variant< std::vector<std::string> > : public VariantContainerBase
{
public:
  using CppType = std::string                  ;
  using CppContainerType = std::vector<std::string>;

  /// Default constructor.
  Variant< std::vector<std::string> >();

  /** GVariant constructor.
   * @param castitem The GVariant to wrap.
   * @param take_a_reference Whether to take an extra reference of the
   * GVariant or not (not taking one could destroy the GVariant with the
   * wrapper).
   */
  explicit Variant< std::vector<std::string> >(GVariant* castitem, bool take_a_reference = false);

  /** Gets the VariantType.
   * @return The VariantType.
   * @newin{2,28}
   */
  static const VariantType& variant_type() G_GNUC_CONST;

  /** Creates a new Variant from an array of strings.
   * @param data The array to use for creation.
   * @return The new Variant.
   * @newin{2,28}
   */
  static Variant< std::vector<std::string> >
    create(const std::vector<std::string>& data);

  /** Creates a new Variant from an array of D-Bus object paths.
   * @param paths The array to use for creation.
   * @return The new Variant.
   * @newin{2,36}
   */
  static Variant< std::vector<std::string> >
    create_from_object_paths(const std::vector<std::string>& paths);

  /** Gets a specific element of the string array.  It is an error if @a index
   * is greater than the number of child items in the container.  See
   * VariantContainerBase::get_n_children().
   *
   * This function is O(1).
   *
   * @param index The index of the element.
   * @return The element at index @a index.
   * @throw std::out_of_range
   * @newin{2,28}
   */
  std::string get_child(gsize index) const;

  /** Gets the string vector of the Variant.
   * @return The vector.
   * @newin{2,28}
   */
  std::vector<std::string> get() const;


  // Object paths are merely strings so it is possible to get them already with
  // the existing get() methods in this class.


  /** Gets a VariantIter of the Variant.
   * @return the VariantIter.
   * @newin{2,28}
   */
  VariantIter get_iter() const;
};

/** Specialization of Variant containing a dictionary (a map of (key,
 * value) elements).
 * @newin{2,28}
 * @ingroup Variant
 */
template<class K, class V>
class Variant< std::map<K, V> >: public VariantContainerBase
{
public:
  using CppType = std::pair<K, V>;
  using CppContainerType = std::map<K, V>;

  /// Default constructor.
  Variant< std::map<K, V> >()
  : VariantContainerBase()
  {}

  /** GVariant constructor.
   * @param castitem The GVariant to wrap.
   * @param take_a_reference Whether to take an extra reference of the
   * GVariant or not (not taking one could destroy the GVariant with the
   * wrapper).
   */
  explicit Variant< std::map<K, V> >(GVariant* castitem,
    bool take_a_reference = false)
  : VariantContainerBase(castitem, take_a_reference)
  {}

  /** Gets the VariantType.
   * @return The VariantType.
   * @newin{2,28}
   */
  static const VariantType& variant_type() G_GNUC_CONST;

  /** Creates a new Variant containing a dictionary from a map.
   * @param data The map to use for creation.
   * @return The new Variant holding a dictionary.
   * @newin{2,28}
   */
  static Variant< std::map<K, V> > create(const std::map<K, V>& data);

  /** Gets a specific dictionary entry from the string array.  It is an error
   * if @a index is greater than the number of child items in the container.
   * See VariantContainerBase::get_n_children().
   *
   * This function is O(1).
   *
   * @param index The index of the element.
   * @return The dictionary entry at index @a index.
   * @throw std::out_of_range
   * @newin{2,28}
   */
  std::pair<K, V> get_child(gsize index) const;

  /** Looks up a value in a dictionary Variant.
   * @param key The key to look up.
   * @param value A location in which to store the value if found.
   * @return <tt>true</tt> if the key is found, <tt>false</tt> otherwise.
   */
  bool lookup(const K& key, V& value) const;


  /** Gets the map (the dictionary) of the Variant.
   * @return The vector.
   * @newin{2,28}
   */
  std::map<K, V> get() const;

  /** Gets a VariantIter of the Variant.
   * @return the VariantIter.
   * @newin{2,28}
   */
  VariantIter get_iter() const;
};

/** Specialization of Variant containing a tuple.
 * @newin{2,54}
 * @ingroup Variant
 */
template <class... Types>
class Variant<std::tuple<Types...>> : public VariantContainerBase
{
public:
  using CppContainerType = std::tuple<Types...>;

  /// Default constructor
  Variant<std::tuple<Types...>>()
  : VariantContainerBase()
  {}

  /** GVariant constructor.
   * @param castitem The GVariant to wrap.
   * @param take_a_reference Whether to take an extra reference of the GVariant
   *        or not (not taking one could destroy the GVariant with the wrapper).
   */
  explicit Variant<std::tuple<Types...>>(GVariant* castitem, bool take_a_reference = false)
  : VariantContainerBase(castitem, take_a_reference)
  {}

  /** Creates a new Variant containing a tuple.
   * @param data The tuple to use for creation.
   * @return The new Variant holding a tuple.
   * @newin{2,54}
   */
  static Variant<std::tuple<Types...>> create(const std::tuple<Types...>& data);

  /** Gets the VariantType.
   * @return The VariantType.
   * @newin{2,54}
   */
  static const VariantType& variant_type() G_GNUC_CONST;

  /** Gets a specific element from the tuple.
   * It is an error if @a index is greater than or equal to the number of
   * elements in the tuple. See VariantContainerBase::get_n_children().
   *
   * @param index The index of the element.
   * @return The tuple element at index @a index.
   * @throw std::out_of_range
   * @newin{2,54}
   */
  template<class T>
  T get_child(gsize index) const;

  template<class T>
  Variant<T> get_child_variant(gsize index) const;

  /** Gets the tuple of the Variant.
   * @return The tuple.
   * @newin{2,54}
   */
  std::tuple<Types...> get() const;

  /** Gets a VariantIter of the Variant.
   * @return The VariantIter.
   * @newin{2,54}
   */
  VariantIter get_iter() const;
};

} // namespace Glib


//We ignore g_variant_get_*() methods that are wrapped by Variant<> specializations, such as in variant_basictypes.h.m4.


/* Include generated specializations of Variant<> for fundamental types:
 */
#define _GLIBMM_VARIANT_H_INCLUDE_VARIANT_BASICTYPES_H
#include <glibmm/variant_basictypes.h>
#undef _GLIBMM_VARIANT_H_INCLUDE_VARIANT_BASICTYPES_H

namespace Glib
{

/*--------------------Variant< Variant<T> >---------------------*/

template<class T>
Variant< Variant<T> >::Variant()
: VariantContainerBase()
{
}

template<class T>
Variant< Variant<T> >::Variant(GVariant* castitem, bool take_a_reference)
: VariantContainerBase(castitem, take_a_reference)
{
}

// static
template<class T>
const VariantType& Variant< Variant<T> >::variant_type()
{
  return VARIANT_TYPE_VARIANT;
}

template<class T>
Variant< Variant<T> > Variant< Variant<T> >::create(const Variant<T>& data)
{
  Variant< Variant<T> > result = Variant< Variant<T> >(
    g_variant_new_variant(const_cast<GVariant*>(data.gobj())));
  return result;
}

template<class T>
Variant<T> Variant< Variant<T> >::get() const
{
  GVariant* const gvariant = g_variant_get_variant(gobject_);
  return Variant<T>(gvariant);
}

/*--------------------Variant< std::pair<K, V> >---------------------*/

// static
template<class K, class V>
const VariantType& Variant< std::pair<K, V> >::variant_type()
{
  static VariantType type(
    g_variant_type_new_dict_entry(Variant<K>::variant_type().gobj(),
    Variant<V>::variant_type().gobj()));

  return type;
}

template<class K, class V>
Variant< std::pair<K, V> >
Variant< std::pair<K, V> >::create(const std::pair<K, V>& data)
{
  Variant<K> key = Variant<K>::create(data.first);
  Variant<V> value = Variant<V>::create(data.second);

  Variant< std::pair<K, V> > result = Variant< std::pair<K, V> >(
    g_variant_new_dict_entry(key.gobj(), value.gobj()));

  return result;
}

template<class K, class V>
std::pair<K, V> Variant< std::pair<K, V> >::get() const
{
  // Get the key (the first element of this VariantContainerBase).
  Variant<K> key;
  VariantContainerBase::get_child(key, 0);

  // Get the value (the second element of this VariantContainerBase).
  Variant<V> value;
  VariantContainerBase::get_child(value, 1);

  std::pair<K, V> result(key.get(), value.get());

  return result;
}

/*---------------------Variant< std::vector<T> >---------------------*/

// static
template<class T>
const VariantType& Variant< std::vector<T> >::variant_type()
{
  static VariantType type =
    VariantType::create_array(Variant<T>::variant_type());

  return type;
}

template<class T>
Variant< std::vector<T> >
Variant< std::vector<T> >::create(const std::vector<T>& data)
{
  // Get the variant type of the array.
  VariantType array_variant_type = Variant< std::vector<T> >::variant_type();

  // Create a GVariantBuilder to build the array.
  GVariantBuilder* builder = g_variant_builder_new(array_variant_type.gobj());

  // Add the elements of the vector into the builder.
  for(const auto& element : data)
  {
    Glib::Variant<T> variant = Glib::Variant<T>::create(element);
    g_variant_builder_add_value(builder, variant.gobj());
  }

  // Create the variant using the builder.
  Variant< std::vector<T> > result =
    Variant< std::vector<T> >(g_variant_new(
      reinterpret_cast<const gchar*>(array_variant_type.gobj()), builder));

  g_variant_builder_unref(builder);

  return result;
}

template<class T>
T Variant< std::vector<T> >::get_child(gsize index) const
{
  if (index >= get_n_children())
    throw std::out_of_range(
      "Variant< std::vector<T> >::get_child(): Index out of bounds.");

  Glib::Variant<T> variant;

  GVariant* gvariant =
    g_variant_get_child_value(const_cast<GVariant*>(gobj()), index);

  variant.init(gvariant);
  return variant.get();
}

template<class T>
std::vector<T> Variant< std::vector<T> >::get() const
{
  std::vector<T> result;

  for (gsize i = 0, n_children = get_n_children(); i < n_children; ++i)
  {
    Glib::Variant<T> variant;

    GVariant* gvariant =
      g_variant_get_child_value(const_cast<GVariant*>(gobj()), i);

    variant.init(gvariant);
    result.emplace_back(variant.get());
  }

  return result;
}

template<class T>
VariantIter Variant< std::vector<T> >::get_iter() const
{
  return VariantContainerBase::get_iter(variant_type());
}

/*---------------------Variant< std::map<K, V> > --------------------*/

// static
template<class K, class V>
const VariantType& Variant< std::map<K, V> >::variant_type()
{
  static VariantType type =
    VariantType::create_array(Variant< std::pair<K, V> >::variant_type());

  return type;
}

template<class K, class V>
Variant< std::map<K, V> >
Variant< std::map<K, V> >::create(const std::map<K, V>& data)
{
  // Get the variant type of the elements.
  VariantType element_variant_type =
    Variant< std::pair<K, V> >::variant_type();

  // Get the variant type of the array.
  VariantType array_variant_type = Variant< std::map<K, V> >::variant_type();

  // Create a GVariantBuilder to build the array.
  GVariantBuilder* builder = g_variant_builder_new(array_variant_type.gobj());

  // Add the elements of the map into the builder.
  for(const auto& element : data)
  {
    auto dict_entry =
      Variant< std::pair<K, V> >::create(element);

    g_variant_builder_add_value(builder, dict_entry.gobj());
  }

  // Create the variant using the builder.
  Variant< std::map<K, V> > result = Variant< std::map<K, V> >(g_variant_new(
    reinterpret_cast<const gchar*>(array_variant_type.gobj()), builder));

  g_variant_builder_unref(builder);

  return result;
}

template<class K, class V>
std::pair<K, V>
Variant< std::map<K, V> >::get_child(gsize index) const
{
  Variant< std::pair<K, V> > dict_entry;
  VariantContainerBase::get_child(dict_entry, index);
  return dict_entry.get();
}

template<class K, class V>
bool Variant< std::map<K, V> >::lookup(const K& key, V& value) const
{
  // The code in this method pretty much reflects the g_variant_lookup_value()
  // function except that it's more general to deal with keys that are not
  // just strings.
  VariantIter iter = get_iter();

  Variant< std::pair<K, V> > entry;

  while(iter.next_value(entry))
  {
    std::pair<K, V> element = entry.get();

    if(element.first == key)
    {
      value = element.second;
      return true;
    }
  }

  return false;
}

template<class K, class V>
std::map<K, V> Variant< std::map<K, V> >::get() const
{
  std::map<K, V> result;
  VariantIter iter = get_iter();
  Variant< std::pair<K, V> > entry;

  while(iter.next_value(entry))
  {
    result.insert(entry.get());
  }

  return result;
}

template<class K, class V>
VariantIter Variant< std::map<K, V> >::get_iter() const
{
  return VariantContainerBase::get_iter(variant_type());
}

/*---------------------Variant<std::tuple<class... Types>> --------------------*/

// static
template <class... Types>
const VariantType& Variant<std::tuple<Types...>>::variant_type()
{
  std::vector<VariantType> types;
  auto expander = [&types](const VariantType &type) mutable -> int
  {
    types.push_back(type);
    return 0;
  };

  // expands the variadic template parameters
  using swallow = int[]; // ensures left to right order
  (void)swallow{(expander(Variant<Types>::variant_type()))...};
  static auto type = VariantType::create_tuple(types);

  return type;
}

#ifndef DOXYGEN_SHOULD_SKIP_THIS
namespace detail
{
// std::index_sequence and std::index_sequence_for are new in C++14,
// but this version of glibmm requires only C++11.
// The following code replaces std::index_sequence and std::index_sequence_for
// until we can require C++14 support.
// See https://bugzilla.gnome.org/show_bug.cgi?id=787648

  /// Class template integer_sequence
  template<typename T, T... Idx>
    struct integer_sequence
    {
      typedef T value_type;
      static constexpr std::size_t size() { return sizeof...(Idx); }
    };

  // Concatenates two integer_sequences.
  template<typename Iseq1, typename Iseq2> struct iseq_cat;

  template<typename T, std::size_t... Ind1, std::size_t... Ind2>
    struct iseq_cat<integer_sequence<T, Ind1...>, integer_sequence<T, Ind2...>>
    {
      using type = integer_sequence<T, Ind1..., (Ind2 + sizeof...(Ind1))...>;
    };

  // Builds an integer_sequence<T, 0, 1, 2, ..., Num-1>.
  template<typename T, std::size_t Num>
    struct make_intseq
    : iseq_cat<typename make_intseq<T, Num / 2>::type,
		typename make_intseq<T, Num - Num / 2>::type>
    { };

  template<typename T>
    struct make_intseq<T, 1>
    {
      typedef integer_sequence<T, 0> type;
    };

  template<typename T>
    struct make_intseq<T, 0>
    {
      typedef integer_sequence<T> type;
    };

  /// Alias template make_integer_sequence
  template<typename T, T Num>
    using make_integer_sequence = typename make_intseq<T, Num>::type;

  /// Alias template index_sequence
  template<std::size_t... Idx>
    using index_sequence = integer_sequence<std::size_t, Idx...>;

  /// Alias template make_index_sequence
  template<std::size_t Num>
    using make_index_sequence = make_integer_sequence<std::size_t, Num>;

  /// Alias template index_sequence_for
  template<typename... Types>
    using index_sequence_for = make_index_sequence<sizeof...(Types)>;

// End of code that replaces std::index_sequence and std::index_sequence_for

template <class Tuple, std::size_t... Is>
void expand_tuple(std::vector<VariantBase> &variants, const Tuple & t,
                  detail::index_sequence<Is...>)
{
  using swallow = int[]; // ensures left to right order
  auto expander = [&variants](const VariantBase &variant) -> int
  {
    variants.push_back(variant);
    return 0;
  };
  (void)swallow {(expander(Variant<typename std::tuple_element<Is, Tuple>::type>::create(std::get<Is>(t))))...};
}
} // namespace detail
#endif // DOXYGEN_SHOULD_SKIP_THIS

template <class... Types>
Variant<std::tuple<Types...>>
Variant<std::tuple<Types...>>::create(const std::tuple<Types...>& data)
{
  // create a vector containing all tuple values as variants
  std::vector<Glib::VariantBase> variants;
  detail::expand_tuple(variants, data, detail::index_sequence_for<Types...>{});

  using var_ptr = GVariant*;
  std::unique_ptr<var_ptr[]> var_array(new var_ptr[sizeof... (Types)]);

  for (std::vector<VariantBase>::size_type i = 0; i < variants.size(); i++)
    var_array[i] = const_cast<GVariant*>(variants[i].gobj());

  Variant<std::tuple<Types...>> result = Variant<std::tuple<Types...>>(
          g_variant_new_tuple(var_array.get(), variants.size()));

  return result;
}

template <class... Types>
template <class T>
T Variant<std::tuple<Types...>>::get_child(gsize index) const
{
  Variant<T> entry;
  VariantContainerBase::get_child(entry, index);
  return entry.get();
}

template <class... Types>
template <class T>
Variant<T> Variant<std::tuple<Types...>>::get_child_variant(gsize index) const
{
  Variant<T> entry;
  VariantContainerBase::get_child(entry, index);
  return entry;
}

#ifndef DOXYGEN_SHOULD_SKIP_THIS
namespace detail
{
// swallows any argument
template <class T>
constexpr int any_arg(T&& /* arg */)
{
  return 0;
}

template <class Tuple, std::size_t... Is>
void assign_tuple(std::vector<VariantBase> &variants, Tuple & t, detail::index_sequence<Is...>)
{
  int i = 0;
  using swallow = int[]; // ensures left to right order
  (void)swallow {(any_arg(std::get<Is>(t) = VariantBase::cast_dynamic<Variant<typename std::tuple_element<Is, Tuple>::type > >(variants[i++]).get()))...};
}
} // namespace detail
#endif // DOXYGEN_SHOULD_SKIP_THIS

template <class... Types>
std::tuple<Types...> Variant<std::tuple<Types...>>::get() const
{
  std::tuple<Types...> data;
  int i = 0;

  std::vector<VariantBase> variants;
  using swallow = int[]; // ensures left to right order
  auto expander = [&variants, &i](const VariantBase &variant) -> int
  {
    variants.push_back(variant);
    return i++;
  };
  (void)swallow{(expander(get_child_variant<Types>(i)))...};
  detail::assign_tuple(variants, data, detail::index_sequence_for<Types...>{});

  return data;
}

template< class... Types>
VariantIter Variant<std::tuple<Types...>>::get_iter() const
{
  const auto type = variant_type();
  return VariantContainerBase::get_iter(type);
}

#ifndef DOXYGEN_SHOULD_SKIP_THIS
// This is needed so Glib::VariantBase can be used with
// Glib::Value and _WRAP_PROPERTY in Gio::Action and elsewhere.
template <>
class GLIBMM_API Value<Glib::VariantBase> : public ValueBase_Variant
{
public:
  using CppType = Glib::VariantBase;

  void set(CppType data);
  CppType get() const;
};
#endif /* DOXYGEN_SHOULD_SKIP_THIS */

} // namespace Glib


namespace Glib
{

/** @relates Glib::VariantBase
 * @param lhs The left-hand side
 * @param rhs The right-hand side
 */
inline void swap(VariantBase& lhs, VariantBase& rhs) noexcept
  { lhs.swap(rhs); }

} // namespace Glib

namespace Glib
{

  /** A Glib::wrap() method for this object.
   *
   * @param object The C instance.
   * @param take_copy False if the result should take ownership of the C instance. True if it should take a new copy or ref.
   * @result A C++ instance that wraps this C instance.
   *
   * @relates Glib::VariantBase
   */
  GLIBMM_API
  Glib::VariantBase wrap(GVariant* object, bool take_copy = false);

} // namespace Glib


#endif /* _GLIBMM_VARIANT_H */