Defining interfaces in C++

Think of a name for the component. We'll use "Position" in this example; replace it with your chosen name in all the filenames and code samples below.

Create the file simulation2/components/ICmpPosition.h:

/* Copyright (C) 2010 Wildfire Games.
 * ...the usual copyright header...
 */

#ifndef INCLUDED_ICMPPOSITION
#define INCLUDED_ICMPPOSITION

#include "simulation2/Interface.h"

...any other forward declarations and includes you might need...

/**
 * Documentation to describe what this interface and its associated component types are
 * for, and roughly how they should be used.
 */
class ICmpPosition : public IComponent
{
public:
    /**
     * Documentation for each method.
     */
    virtual int DoWhatever(int x, int y) = 0;

    ...

    DECLARE_INTERFACE_TYPE(Position)
};

#endif // INCLUDED_ICMPPOSITION

This defines the interface that C++ code will use to access components.

Create the file simulation2/components/ICmpPosition.cpp:

/* Copyright (C) 2010 Wildfire Games.
 * ...the usual copyright header...
 */

#include "precompiled.h"

#include "ICmpPosition.h"

#include "simulation2/InterfaceScripted.h"

BEGIN_INTERFACE_WRAPPER(Position)
DEFINE_INTERFACE_METHOD_2("DoWhatever", int, ICmpPosition, DoWhatever, int, int)
...
END_INTERFACE_WRAPPER(Position)

This defines a JavaScript wrapper, so that scripts can access methods of components implementing that interface.

This wrapper should only contain methods that are safe to access from simulation scripts: they must not crash, they must return deterministic results, etc. Methods that are intended for use solely by C++ should not be listed here.

Interface method script wrappers

Interface methods are defined with the macro:

DEFINE_INTERFACE_METHOD_NumberOfArguments("MethodName", ReturnType, ICmpPosition, MethodName, !ArgType0, !ArgType1, ...)

corresponding to the C++ method ReturnType ICmpPosition::MethodName(!ArgType0, !ArgType1, ...)

There's a small limit to the number of arguments that are currently supported - if you need more, first try to save yourself some pain by using fewer arguments, otherwise you'll need to add a new macro into simulation2/InterfaceScripted.h and increase MAX_ARGS in scriptinterface/NativeWrapperDecls.h. (Not sure if anything else needs changing.)

To convert types between C++ and JS, ToJSVal<ReturnType> and FromJSVal<ArgTypeN> must be defined, as below.

Script type conversions

...