Here are the classes, structs, unions and interfaces with brief descriptions:

NGridFormat
NCompression
CBlocks	Stores the block sizes used for compressing the given amount of bytes
CCompressedBlocks	Stores the uncompressed/compressed block sizes after completion of a compression
CLZ4	Compressor using the lz4 compression library
CLZ4Options	Options for the lz4 compressor
CLZMA	Compressor using the lzma library
CLZMAOptions	Options for the lzma compressor
CZLIB	Compressor using the zlib library
CZLIBOptions	Options for the zlib compressor
NDolfinX
CCell
CPoint
CLagrangePolynomialGrid	Wrapper around a nodal dolfinx::FunctionSpace, exposing it as a mesh composed of lagrange elements with the order of the given function space
NDune
NTraits
CGridView
CGridView< LagrangePolynomialGrid< GV > >
CLagrangePolynomialGrid	Exposes a Dune::GridView as a grid composed of lagrange cells with the given order. Can be used to conveniently write Dune::Functions into grid files
CFunctionField	Implements the field interface for a Dune::Function defined on a (wrapped) Dune::GridView
CGridFactoryAdapter	Adapter around a Dune::GridFactory to be compatible with GridFormat::Concepts::GridFactory. Can be used to export a grid from a reader directly into a Dune::GridFactory. For instance:
NEncoding
CAscii	Ascii encoder
CBase64	Base64 encoder
CRawBinary	Raw binary encoder
NFileFormat
CFormatWithOptions	Base class for formats taking options
CVTKXMLFormatBase	Base class for VTK-XML formats
CAny	Selector for an unspecified file format. When using this format, GridFormat will automatically select a format or deduce from a file being read, for instance
CAnyTimeSeries	Time series variant of the Any format selector
CVTI	Selector for the .vti/.pvti image grid file format to be passed to the Writer
CVTR	Selector for the .vtr/.pvtr rectilinear grid file format to be passed to the Writer
CVTS	Selector for the .vts/.pvts structured grid file format to be passed to the Writer
CVTP	Selector for the .vtp/.pvtp file format for two-dimensional unstructured grids
CVTU	Selector for the .vtu/.pvtu file format for general unstructured grids
CVTKXMLTimeSeries	Selector for a time series of any VTK-XML format
CVTKHDFImage	Selector for the vtk-hdf file format for image grids. For more information, see here
CVTKHDFImageTransient	Transient variant of the vtk-hdf image data format
CVTKHDFUnstructured	Selector for the vtk-hdf file format for unstructured grids. For more information, see here
CVTKHDFUnstructuredTransient	Transient variant of the vtk-hdf unstructured grid format
CVTKHDFTransient	Selector for the transient vtk-hdf file format with automatic deduction of the flavour. If the grid for which a writer is constructed is an image grid, it selects the image-grid flavour, otherwise it selects the flavour for unstructured grids (which requires the respective traits to be specialized)
CVTKHDF	Selector for the vtk-hdf file format with automatic deduction of the flavour. If the grid for which a writer is constructed is an image grid, it selects the image-grid flavour, otherwise it selects the flavour for unstructured grids (which requires the respective traits to be specialized)
CPVD	Selector for the .pvd file format for a time series. For more information, see here
CPVDClosure	Closure for selecting the .pvd file format. Takes a VTK-XML format and returns an instance of PVD
CTimeSeriesClosure	Closure for time series format selection. Takes a sequential format and returns a time series variant
NPVTK
CPDataArrayHelper	Helper to add a PDataArray child to an xml element
CStructuredGridMapper
CStructuredGridMapperHelper
CStructuredParallelGridHelper
NTraits
CBasis< ConverterDetail::ConverterGrid >
CCellPoints< ConverterDetail::ConverterGrid, std::int64_t >
CCellPoints< DolfinX::LagrangePolynomialGrid< T >, DolfinX::Cell >
CCellPoints< dolfinx::mesh::Mesh< T >, DolfinX::Cell >
CCellPoints< Dune::GridView< Traits >, DuneDetail::Element< Dune::GridView< Traits > > >
CCellPoints< Dune::LagrangePolynomialGrid< GridView >, typename Dune::LagrangePolynomialGrid< GridView >::Cell >
CCellPoints< Grid, GridFormat::CGAL::Cell< Grid > >
CCellPoints< mfem::Mesh, GridFormat::MFEM::Cell >
CCellPoints< T, DealII::Cell< T > >
CCells< ConverterDetail::ConverterGrid >
CCells< DolfinX::LagrangePolynomialGrid< T > >
CCells< dolfinx::mesh::Mesh< T > >
CCells< Dune::GridView< Traits > >
CCells< Dune::LagrangePolynomialGrid< GridView > >
CCells< Grid >
CCells< mfem::Mesh >
CCells< T >
CCellType< ConverterDetail::ConverterGrid, std::int64_t >
CCellType< DolfinX::LagrangePolynomialGrid< T >, DolfinX::Cell >
CCellType< dolfinx::mesh::Mesh< T >, DolfinX::Cell >
CCellType< Dune::GridView< Traits >, DuneDetail::Element< Dune::GridView< Traits > > >
CCellType< Dune::LagrangePolynomialGrid< GridView >, typename Dune::LagrangePolynomialGrid< GridView >::Cell >
CCellType< Grid, GridFormat::CGAL::Cell< Grid > >
CCellType< mfem::Mesh, GridFormat::MFEM::Cell >
CCellType< T, DealII::Cell< T > >
CCommunicatorAccess	Can be specialized by parallel writers to expose their underlying communicator
CCommunicatorAccess< Writer >	Default specialization for writers that have a communicator() function
CExtents< ConverterDetail::ConverterGrid >
CExtents< Dune::GridView< Traits > >
CLocation< ConverterDetail::ConverterGrid, Entity >
CLocation< Dune::GridView< Traits >, Entity >
CNumberOfCellPoints< ConverterDetail::ConverterGrid, std::int64_t >
CNumberOfCellPoints< DolfinX::LagrangePolynomialGrid< T >, DolfinX::Cell >
CNumberOfCellPoints< dolfinx::mesh::Mesh< T >, DolfinX::Cell >
CNumberOfCellPoints< Dune::GridView< Traits >, DuneDetail::Element< Dune::GridView< Traits > > >
CNumberOfCellPoints< Dune::LagrangePolynomialGrid< GridView >, typename Dune::LagrangePolynomialGrid< GridView >::Cell >
CNumberOfCellPoints< Grid, GridFormat::CGAL::Cell< Grid > >
CNumberOfCellPoints< mfem::Mesh, GridFormat::MFEM::Cell >
CNumberOfCellPoints< T, DealII::Cell< T > >
CNumberOfCells< ConverterDetail::ConverterGrid >
CNumberOfCells< DolfinX::LagrangePolynomialGrid< T > >
CNumberOfCells< dolfinx::mesh::Mesh< T > >
CNumberOfCells< Dune::GridView< Traits > >
CNumberOfCells< Dune::LagrangePolynomialGrid< GridView > >
CNumberOfCells< Grid >
CNumberOfCells< mfem::Mesh >
CNumberOfCells< T >
CNumberOfPoints< ConverterDetail::ConverterGrid >
CNumberOfPoints< DolfinX::LagrangePolynomialGrid< T > >
CNumberOfPoints< dolfinx::mesh::Mesh< T > >
CNumberOfPoints< Dune::GridView< Traits > >
CNumberOfPoints< Dune::LagrangePolynomialGrid< GridView > >
CNumberOfPoints< Grid >
CNumberOfPoints< mfem::Mesh >
CNumberOfPoints< T >
COrdinates< ConverterDetail::ConverterGrid >
COrdinates< Dune::GridView< Traits > >
COrigin< ConverterDetail::ConverterGrid >
COrigin< Dune::GridView< Traits > >
CPointCoordinates< ConverterDetail::ConverterGrid, std::size_t >
CPointCoordinates< DolfinX::LagrangePolynomialGrid< T >, DolfinX::Point >
CPointCoordinates< dolfinx::mesh::Mesh< T >, DolfinX::Point >
CPointCoordinates< Dune::GridView< Traits >, DuneDetail::Vertex< Dune::GridView< Traits > > >
CPointCoordinates< Dune::LagrangePolynomialGrid< GridView >, typename Dune::LagrangePolynomialGrid< GridView >::Point >
CPointCoordinates< Grid, typename Grid::Vertex_handle >
CPointCoordinates< mfem::Mesh, GridFormat::MFEM::Point >
CPointCoordinates< T, DealII::Point< T > >
CPointId< ConverterDetail::ConverterGrid, std::size_t >
CPointId< DolfinX::LagrangePolynomialGrid< T >, DolfinX::Point >
CPointId< dolfinx::mesh::Mesh< T >, DolfinX::Point >
CPointId< Dune::GridView< Traits >, DuneDetail::Vertex< Dune::GridView< Traits > > >
CPointId< Dune::LagrangePolynomialGrid< GridView >, typename Dune::LagrangePolynomialGrid< GridView >::Point >
CPointId< Grid, typename Grid::Vertex_handle >
CPointId< mfem::Mesh, GridFormat::MFEM::Point >
CPointId< T, DealII::Point< T > >
CPoints< ConverterDetail::ConverterGrid >
CPoints< DolfinX::LagrangePolynomialGrid< T > >
CPoints< dolfinx::mesh::Mesh< T > >
CPoints< Dune::GridView< Traits > >
CPoints< Dune::LagrangePolynomialGrid< GridView > >
CPoints< Grid >
CPoints< mfem::Mesh >
CPoints< T >
CSpacing< ConverterDetail::ConverterGrid >
CSpacing< Dune::GridView< Traits > >
CStaticSize< Dune::FieldMatrix< T, R, C > >
CWritesConnectivity	Can be specialized by writers in case the file format does not contain connectivity information
CWritesConnectivity< APIDetail::SequentialOrParallelReader< S, P > >
CWritesConnectivity< PVDWriter< VTKWriter > >
CWritesConnectivity< PVTIWriter< Args... > >
CWritesConnectivity< PVTRWriter< Args... > >
CWritesConnectivity< VTIWriter< Args... > >
CWritesConnectivity< VTKHDFImageGridTimeSeriesWriter< Args... > >
CWritesConnectivity< VTKHDFImageGridWriter< Args... > >
CWritesConnectivity< VTKHDFTimeSeriesWriter< Grid, Args... > >
CWritesConnectivity< VTKHDFWriter< Grid, Args... > >
CWritesConnectivity< VTRWriter< Args... > >
NVTK
NDataFormat
CInlined	Inline data format (inside xml elements)
CAppended	Appended data format (all data is appended at the end of the xml file)
CAppendix	Stores vtk data arrays to be exported as vtk-xml appendix
CAppendixStreamObserver	Observer for appendices. Allows registering the offsets when streaming all fields that are part of the appendix
CDataArray	Wraps a field and exposes it as VTK data array. Essentially, this implements the operator<< to stream the field data in the way that VTK file formats require it
CHDFTransientOptions	Options for transient vtk-hdf file formats
CPXMLReaderBase	Base class for readers of parallel vtk-xml file formats
CPXMLStructuredGridReader	Base class for readers of parallel vtk-xml file formats for structured grids
CStructuredGridSpecs
CPXMLUnstructuredGridReader	Base class for readers of parallel vtk-xml file formats for unstructured grids
CXMLOptions	Options for VTK-XML files for setting the desired encoding, data format and compression
CXMLReaderHelper	Helper class for VTK-XML readers to use
CXMLWriterBase	Base class for VTK-XML Writer implementations
CWriteContext
NVTKHDF
CIOContext	Helper class to store processor offsets in parallel writes
CDataSetField	Field implementation that draws values from an open HDF5 file upon request
CAnyReaderFactory
CAsciiFormatOptions	Options for fomatted output of ranges with ascii encoding
CAsciiOutputStream	Wrapper around a given stream to write formatted ascii output
CBase64Decoder
CBase64EncoderOptions	Options for formatted output of ranges with base64 encoding
CBase64Stream	Wrapper around a given stream to write output encoded with base64
CConversionOptions	Options for format conversions
CEncodedField	Wraps a field and makes it streamable using encoding
CField	Abstract interface for fields of values that is used by writers/readers to store fields
CGridReader	Abstract base class for all readers, defines the common interface
CPieceLocation	Describes the location of a piece within a distributed structured grid
CFieldNames
CGridWriter	Abstract base class for grid file writers
CGridWriterBase	Base class for all writer implementations
CImageGrid	Predefined grid implementation that represents a structured, equispaced grid
CPVDReader	Reader for .pvd time series file format
CPVDWriter	Writer for .pvd time-series file format
CPVTIReader	Reader for .pvtp file format
CPVTIWriter	Writer for parallel .pvti files
CPVTPReader	Reader for .pvtp file format
CPVTPWriter	Writer for parallel .pvtu files
CPVTRReader	Reader for .pvtr file format
CPVTRWriter	Writer for parallel .pvtr files
CPVTSReader	Reader for .pvts file format
CPVTSWriter	Writer for parallel .pvts files
CPVTUReader	Reader for .pvtu file format
CPVTUWriter	Writer for parallel .pvtu files
CRawBinaryStream	Wrapper around a given stream to write raw binary data
CRawDecoder	For compatibility with Base64
CReader	Interface to the readers for all supported file formats
CReaderFactory	Factory class to create a reader for the given file format
CReaderFactory< FileFormat::PVD< PieceFormat > >	Specialization of the ReaderFactory for the .pvd time series file format
CReaderFactory< FileFormat::PVDClosure >	Specialization of the ReaderFactory for the .pvd time series closure type
CReaderFactory< FileFormat::VTI >	Specialization of the ReaderFactory for the .vti format
CReaderFactory< FileFormat::VTKHDF >	Specialization of the ReaderFactory for the vtk-hdf file format with automatic flavour selection
CReaderFactory< FileFormat::VTKHDFImage >	Specialization of the ReaderFactory for the vtk-hdf image grid format
CReaderFactory< FileFormat::VTKHDFImageTransient >	Specialization of the ReaderFactory for the transient vtk-hdf image grid format
CReaderFactory< FileFormat::VTKHDFTransient >	Specialization of the ReaderFactory for the transient vtk-hdf file format with automatic flavour selection
CReaderFactory< FileFormat::VTKHDFUnstructured >	Specialization of the ReaderFactory for the vtk-hdf unstructured grid format
CReaderFactory< FileFormat::VTKHDFUnstructuredTransient >	Specialization of the ReaderFactory for the vtk-hdf unstructured grid format
CReaderFactory< FileFormat::VTP >	Specialization of the ReaderFactory for the .vtp format
CReaderFactory< FileFormat::VTR >	Specialization of the ReaderFactory for the .vtr format
CReaderFactory< FileFormat::VTS >	Specialization of the ReaderFactory for the .vts format
CReaderFactory< FileFormat::VTU >	Specialization of the ReaderFactory for the .vtu format
CTimeSeriesGridWriter	Abstract base class for time series file writers
CVTIReader	Reader for .vti file format
CVTIWriter	Writer for .vti file format
CDomain
CVTKHDFImageGridReader	Reader for the VTK-HDF file format for image grids
CVTKHDFImageGridTimeSeriesWriter	Writer for the transient VTK HDF file format for image grids
CVTKHDFImageGridWriter	Writer for the VTK HDF file format for image grids
CVTKHDFImageGridWriterImpl
CVTKHDFReader	Convenience reader for the vtk-hdf file format that supports both the image & unstructured grid file formats
CVTKHDFTimeSeriesWriter	Convenience writer for the vtk-hdf file format, automatically selecting the image or unstructured grid format depending on the given grid type
CVTKHDFUnstructuredGridReader	Reader for the VTK-HDF file format for unstructured grids
CVTKHDFUnstructuredGridWriter	Writer for the VTK HDF file format for unstructured grids
CVTKHDFUnstructuredGridWriterImpl
CVTKHDFUnstructuredTimeSeriesWriter	Writer for the transient VTK HDF file format for unstructured grids
CVTKHDFWriter	Convenience writer for the vtk-hdf file format, automatically selecting the image or unstructured grid format depending on the given grid type
CVTKXMLTimeSeriesWriter	Writer for time series of a VTK-XML file format. Populates the "TimeValue" metadata field supported by VTK
CVTPReader	Reader for .vtp file format
CVTPWriter	Writer for .vtu file format
CVTRReader	Reader for .vtr file format
CVTRWriter	Writer for .vtr file format
CDomain
CVTSReader	Reader for .vts file format
CVTSWriter	Writer for .vts file format
CDomain
CVTUReader	Reader for .vtu file format
CVTUWriter	Writer for .vtu file format
CWriter	Interface to the writers for all supported file formats. Depending on the chosen format, this exposes the interface of grid file or time series writers
CWriterFactory	Factory class to create a writer for the given file format
CWriterFactory< FileFormat::Any >	Specialization of the WriterFactory for the any format selector
CWriterFactory< FileFormat::AnyTimeSeries >	Specialization of the WriterFactory for the time series variant of the any format selector
CWriterFactory< FileFormat::PVD< F > >	Specialization of the WriterFactory for the .pvd time series format
CWriterFactory< FileFormat::VTI >	Specialization of the WriterFactory for the .vti format
CWriterFactory< FileFormat::VTKHDF >	Specialization of the WriterFactory for the vtk-hdf file format with automatic flavour selection
CWriterFactory< FileFormat::VTKHDFImage >	Specialization of the WriterFactory for the vtk-hdf image grid format
CWriterFactory< FileFormat::VTKHDFImageTransient >	Specialization of the WriterFactory for the transient vtk-hdf image grid format
CWriterFactory< FileFormat::VTKHDFTransient >	Specialization of the WriterFactory for the transient vtk-hdf file format with automatic flavour selection
CWriterFactory< FileFormat::VTKHDFUnstructured >	Specialization of the WriterFactory for the vtk-hdf unstructured grid format
CWriterFactory< FileFormat::VTKHDFUnstructuredTransient >	Specialization of the WriterFactory for the transient vtk-hdf unstructured grid format
CWriterFactory< FileFormat::VTKXMLTimeSeries< F > >	Specialization of the WriterFactory for vtk-xml time series
CWriterFactory< FileFormat::VTP >	Specialization of the WriterFactory for the .vtp format
CWriterFactory< FileFormat::VTR >	Specialization of the WriterFactory for the .vtr format
CWriterFactory< FileFormat::VTS >	Specialization of the WriterFactory for the .vts format
CWriterFactory< FileFormat::VTU >	Specialization of the WriterFactory for the .vtu format
CWriterOptions	Options that writer implementations can pass to the base class