Guide for the development of a SALOME module in C++

The purpose of this document is to describe the different steps in the development of a SALOME module in C++. It follows on from the Guide for the development of a SALOME module in Python document, that documents the PYHELLO module, and it uses the same approach: step by step construction of a HELLO module. Since many points are not repeated, it is recommended that this document should be read first.

Steps in the construction of the example module

The component chosen to illustrate the C++ construction process is the same as the process chosen to illustrate construction of the Python module: therefore, it will implement the same Corba idl interface. It will be completed by a graphic GUI written in Qt.

The various steps of the development will be as follows:
  • create a module structure
  • create a SALOME component that can be loaded by a C++ container
  • configure the module so that the component is known to SALOME
  • add a graphic GUI
  • make the component usable in the YACS module.

Creating the module tree structure

We will start by simply putting a SALOME component written in C++ and that can be loaded by a C++ container, into the example module. Therefore, all that is necessary is an idl interface and a C++ implantation of the component. We need to reproduce the following standard file tree structure, to use it in a SALOME module:

  + CMakeLists.txt
  + adm_local
    + CMakeLists.txt
    + cmake_files
      + CMakeLists.txt
      + FindSalomeHELLO.cmake
  + bin
    + CMakeLists.txt
  + idl
    + CMakeLists.txt
    + HELLO_Gen.idl
  + src
    + CMakeLists.txt
    + HELLO
      + CMakeLists.txt
      + HELLO.cxx
      + HELLO.hxx
  + doc

This is done by copying the PYHELLO tree structure, and modifying PYHELLO to HELLO if necessary:

mv idl/PYHELLO_Gen.idl idl/HELLO_Gen.idl
mv src/PYHELLO src/HELLO

IDL interface

We modify the HELLO_Gen.idl file in the idl directory: the defined module is named HELLO_ORB, and the interface is named HELLO_Gen. The service provided remains the same: starting from a character string supplied as the single argument, a character string derived from the concatenation of “Hello” and the input string is returned. This service is specified by the hello function.

A documentation utility based on doxygen has been implemented to compile a documentation of corba services starting from comments located in idl files. Therefore, we will add few comments to our idl, respecting the doxygen formalism. A doxygen comment begins with “/*” and ends with “*/”. They are grouped by module or subject, to provide a minimum structure for generated pages. We will use the following directive in our example:

\ingroup EXAMPLES

specifying that the generated documentation forms part of the EXAMPLES group (please refer to the site for further information about doxygen).

Finally, we will update the Makefile with the new component name:


C++ implementation


The C++ implementation of our CORBA HELLO module (HELLO_Gen idl interface) is made in the src/HELLO directory:


The following inclusions are necessary at the beginning of the header of our module (HELLO.hxx):

#include <SALOMEconfig.h>
#include "SALOME_Component_i.hxx"

The SALOMEconfig.h file contains a number of definitions useful for making the code independent from the version of CORBA used. SALOME_Component_i.hxx contains the interface of the C++ implementation class of the SALOME basic component (idl Engines::EngineComponent). Finally, the CORBA_SERVER_HEADER macro makes inclusion file names independent of the implementation of the CORBA ORB.

The next step is to define an implementation class called HELLO, derived from POA_HELLO_ORB::HELLO_Gen (abstract class generated automatically by CORBA during the compilation of the idl) and Engines_Component_i (because the HELLO_Gen idl interface is derived from Engines::EngineComponent like every SALOME component). This class contains a constructor whose arguments are imposed by SALOME, a virtual destructor, hello, goodbye and copyOrMove methods providing the required service:

class HELLO:
  public POA_HELLO_ORB::HELLO_Gen,
  public Engines_Component_i
  PortableServer::POA_ptr poa,
  PortableServer::ObjectId * contId,
  const char *instanceName,
  const char *interfaceName);
virtual ~HELLO();
HELLO_ORB::status hello  ( const char* name );
HELLO_ORB::status goodbye( const char* name );
void              copyOrMove( const HELLO_ORB::object_list& what,
                              SALOMEDS::SObject_ptr where,
                              CORBA::Long row, CORBA::Boolean isCopy );


The hello and goodbye functions use a char* as an argument and return status of the operation. The list of the statuses is defined in the HELLO_Gen.idl, see status enumeration for details.

Finally, we supply the standard interface of the HELLOEngine_factory function that will be called by the “FactoryServer C++” to load the HELLO component:

extern "C"
PortableServer::ObjectId * HELLOEngine_factory(CORBA::ORB_ptr orb,
                                               PortableServer::POA_ptr poa,
                                               PortableServer::ObjectId * contId,
                                               const char *instanceName,
                                               const char *interfaceName);

The definitions of the constructor and the HELLOEngine_factory instantiation function (both normalized!), hello, goodbye and copyOrMove are given in the source file (HELLO.cxx):

HELLO_ORB::status HELLO::hello( const char* name )

HELLO_ORB::status HELLO::goodbye( const char* name )

void HELLO::copyOrMove( const HELLO_ORB::object_list& what,
                        SALOMEDS::SObject_ptr where,
                        CORBA::Long row, CORBA::Boolean isCopy )


Create and add library to the project:

# --- options ---
# additional include directories
# libraries to link to
# --- headers ---
# header files / no moc processing
# --- sources ---
# sources / static
# --- rules ---

Review some of components:

  • HELLO_HEADERS contains the header files.
  • HELLO_SOURCES defines the name of source files
  • HELLOEngine - library name.
  • SALOME_INSTALL_LIBS path defines the directories in which library will be install.
  • Command INCLUDE_DIRECTORIES used to add /bin directories of some modules and packages.
  • Variable _link_LIBRARIES contains path to libraries of dependent modules and packages.

Controlling the component from Python (TUI mode)

When the module is compiled, the lib target of the Makefile in /idl provoked generation of a Python stub (stub at the customer end generated from the idl and providing an interface in the client language – in this case Python). Specifically, a HELLO_ORB python module containing a classe_objref_HELLO_Gen is created and used to call services of our C++ module from Python. To put this into application, we run SALOME in TUI mode:

runSalome --modules=HELLO -t --pinter --logger --killall

We import the LifeCycle module from the Python window, and use its services to load our component into the FactoryServer C++ container:

>>> import LifeCycleCORBA
>>> lcc = LifeCycleCORBA.LifeCycleCORBA()
>>> import salome
>>> salome.salome_init()
extStudy_1 1
>>> import HELLO_ORB
>>> hello = lcc.FindOrLoadComponent("FactoryServer", "HELLO")

HELLO_ORB has to be imported before FindOrLoadComponent is called, so that a typed object can be returned (“narrowing” operation). Otherwise, the returned object is generic of the Engines::EngineComponent type. Let us check that hello object is correctly typed, and we will call the hello service:

>>> print hello
<HELLO_ORB._objref_HELLO_Gen instance at 0x8274e94>
>>> status=hello.hello("Nicolas")
>>> print status

The previous commands were grouped in the test function of the /bin/ script.

Graphic interface


To go further with the integration of our module, we will add a graphic interface (developed in Qt) that is integrated into the SALOME application interface (IAPP). We will not describe operation of the SALOME IAPP herein, but in summary, the IAPP manages an event loop (mouse click, keyboard, etc.) and after processing these events redirects them towards the active module (the principle is that a single module is active at a given moment. When a module is activated, its Graphic User Interface is dynamically loaded). Therefore the programmer of a module GUI defines methods to process transmitted events correctly. The most important of these events are OnGUIEvent(), OnMousePress(), OnMouseMove(), OnKeyPress(), DefinePopup(), CustomPopup().

Strictly speaking, the GUI library is optional for each SALOME module. In some cases it’s enough to implement CORBA engine only. Then, the services of the module will be avaiable in a CORBA environment. The module can be loaded to the SALOME container and its services can be used in the SALOME supervision computation schemas, in Python scripts or/and in C++ implementation of other modules.

A GUI library is necessary only if it is planned to access the module functionality from the SALOME GUI session via menu actions, dialog boxes and so on.


These files provide the implementation of a GUI library of the HELLO module. In particular, these files specify menus, toolbars, dialog boxes and other such staff.

  • src/HELLOGUI/HELLO_msg_en.ts
  • src/HELLOGUI/HELLO_msg_fr.ts
  • src/HELLOGUI/HELLO_icons.ts

These files provide a description (internationalization) of GUI resources of the HELLO module. HELLO_msg_en.ts provides an English translation of the string resources used in a module (there can be also translation files for other languages, for instance French; these files are distinguished by the language suffix). HELLO_icons.ts defines images and icons resources used within the GUI library of HELLO module. Please refer to Qt linguist documentation for more details.

  • resources

This optional directory usually contains different resources files required for the correct operation of SALOME module.

  • resources/HELLO.png
  • resources/handshake.png
  • resources/goodbye.png
  • resources/testme.png

These are different module icon files. HELLO.png file provides main icon of HELLO module to be shown in the SALOME GUI desktop. Other files are the icons for the functions implemented by the module; they are used in the menus and toolbars.

  • resources/

The XML description of the CORBA services provided by the HELLO module. This file is parsed by SALOME supervision module (YACS) to generate the list of service nodes to be used in the calculation schemas. The simplest way to create this file is to use Catalog Generator utility provided by the SALOME KERNEL module, that can automatically generate XML description file from the IDL file. In GUI, this utility is available via the Tools main menu.

Syntax naming rules

A number of naming rules were used in the above description. This chapter gives more details about these rules. They are not all compulsory, but they make it easy to understand the program if they are respected!

Rules Formalism HELLO example Comment
Module name <Module> HELLO This is the name that appears in the modules catalog
CVS base <Module> EXAMPLES If the cvs base contains several modules, another name will be used.
Source directory <Module>_SRC HELLO1_SRC Index 1 is used because several versions of the module are provided.
Idl file <Module>_Gen.idl HELLO_Gen.idl  
CORBA module name <Module>_ORB HELLO_ORB Avoid the use of the module name (conflicts)
CORBA interface name <Module>_Gen HELLO_Gen The idl compilation generates an abstract class POA_<Module>_ORB::<Module>_Gen
Source file <Module>.cxx HELLO.cxx In the /src/<Module> directory
Implementation class <Module> HELLO This class inherits from POA_HELLO_ORB::HELLO_Gen
Instantiation function <Module>_Engine_factory HELLO_Engine_factory This function is called by the SALOME Container
Modules catalog <Module>Catalog.xml HELLOCatalog.xml In /resources
C++ library name lib<Module>Engine HELLO-Engine In the /src/<Module> directory
GUI C++ name lib<Module>GUI libHELLOGUI In the /src/<Module>GUI directory
Environment variable <Module>_ROOT_DIR… HELLO_ROOT_DIR