xIntegrateFormCommand (in xCommandOnGeomElem.h/cc) has an ambiguous usage. If you use it with a form that use an geo_appro xGeomElem object it do not work. The xCommandOnGeomElem base class provides openApproxElem method. But this methode do not change form instance according to the given geo_appro argument. So xIntegrateFormCommand::execute that run accumulate form method bugg because form geo_appro is not set. For over form kind this have presumelly no impact.
In xFied.h/cc xFillFieldFromZeroForm derive form xIntegrateFormCommand and overload openApproxElem to call form init with geo_appro.
Something have to be done to make xIntegrateFormCommand more secure (i.e. prohibite its direct usage with form needing a call to init to set geo_appro): make it abstract ? Add doc to expose limitation ? make it template on form and do template specialization ? ... ?