NAME

NewClass - adding a new class to wxPerl

CHECKLIST

• Are there constants or events that need to be wrapped?

  see "CONSTANTS" and "EVENTS".

• Is the class is derived from wxObject, from wxEvtHandler or from another class?

  see "CHOOSING A TYPEMAP".

• Are class instances destroyed by wxWidgets or should they be garbage collected like normal Perl objects?

  see "DESTRUCTORS AND THREADS".

• Does the class have overloaded methods?

  see "OVERLOADING".

• Does the class have virtual methods that should be overridable from Perl?

  see "VIRTUAL METHODS".

SKELETON

Add a new file XS/NewClass.xsp and update the MANIFEST. Choose a relevant .xs file in the top level directory (eg. Controls.xs) and add this line:

    INCLUDE_COMMAND: $^X -MExtUtils::XSpp::Cmd -e xspp -- -t typemap.xsp XS/NewClass.xsp

A skeleton for NewClass.xsp:

    %module{Wx};

    #include <wx/newclass.h> // use the relevant wxWidgets header(s)

    %name{Wx::NewClass} class wxNewClass : public wxSomeBaseClass
    {
        # constructors see the CONSTRUCTORS section
        wxNewClass( wxWindow* some_window, const wxString& str );

        # destructors
        ~wxNewClass();

        # methods
        wxString GetString() const;
        void SetString( const wxString& str );
    };

Add the typemap definition to typemap.tmpl. See "CHOOSING A TYPEMAP".

If adding a class related to one of the wxPerl submodules (Wx::RichText, Wx::Html, ...) add the .xsp file to the relevant subdirectory and modify the .xs and typemap files in that subdirectory.

CHOOSING A TYPEMAP

There are five typemaps that should work for most wxWidgets objects:

• O_NON_WXOBJECT

  for all classes that do not derive from wxObject AND do not need to be garbage collected.

• O_NON_WXOBJECT_THR

  for all classes that do not derive from wxObject AND need to be garbage collected (see "DESTRUCTORS AND THREADS").

• O_WXOBJECT

  for all classes that derive from wxObject AND do not need to be garbage collected.

• O_WXOBJECT_THR

  for all classes derived from wxObject AND need to be garbage collected (see "DESTRUCTORS AND THREADS").

• O_WXEVTHANDLER

  for all classes that derive from wxEvtHandler. See also "CONSTRUCTORS".

CONSTRUCTORS

For O_WXEVTHANDLER typemaps, there is some additional code that needs to be added to the constructor:

    wxNewClass( wxWindow* some_window, const wxString& str )
        %code{% RETVAL = new wxNewClass( some_window, str );
                wxPli_create_evthandler( aTHX_ RETVAL, CLASS );
                %};

DESTRUCTORS AND THREADS

For many classes not derived from wxEvtHandler you need to add a destructor to free the C++ object when the Perl object is garbage collected. At the XS++ level this means adding

    ~wxNewClass();

to the class definition, but there is a catch: the Perl threading model.

Without going into details, this is needed for Perl threads compatibility:

• Use the correct typemap

  choose either O_NON_WXOBJECT_THR or O_WXOBJECT_THR.

• Implement a CLONE method

  add this code inside the class declaration:

      %{
      static void
      wxNewClass::CLONE()
        CODE:
          wxPli_thread_sv_clone( aTHX_ CLASS, (wxPliCloneSV)wxPli_detach_object );
      %}

• Fix the destructor.

  modify the destructor like this:

      ~wxNewClass()
          %code%{  wxPli_thread_sv_unregister( aTHX_ "Wx::NewClass", THIS, ST(0) );
                   delete THIS;
                   %};

VIRTUAL METHODS

The wrapping of virtual functions whose arguments are simple C++ types (integrals, bool, floating point) and common wxWidgets types (wxString) should be automatic: at the top of the file, load the plugin that handles virtual methods

    %loadplugin{build::Wx::XSP::Virtual};

and decorate virtual/pure virtual methods using the %Virtual directive

    // pure virtual
    virtual wxString GetTitle() const = 0 %Virtual{pure};

    // virtual, not pure
    virtual int GetBestFittingWidth(unsigned int idx) const %Virtual;

If the class contains pure virtual methods, it will be marked as abstract, and it will have no constructors.

For abstract classes, XS++ will create an additional Perl-level class, called Wx::Pl<classname>; in order to override the virtual methods, you must derive from this class, and not from Wx::<classname>.

TODO allow changing the default behaviour for abstract/concrete classes

TODO allow overriding the class name

TODO allow specifying custom code

TODO handle multiple return values

TODO customized type mapping