Make C++ plugin function with complex arguments scriptable

[andrew]

From a QCAD developer:

How can I make a class member function of a C++ plugin scriptable, with complex parameters or return values (such as a lists of vectors or a list of doubles)?

[andrew]

Let's have a look at such function from RVector:

static QList<double> RVector::getXList(const QList<RVector>& vectors);

This function expects a list of vectors as argument and returns a list of doubles.
In ECMAScript, the function might be called like this:

var res = RVector.getXList([new RVector(1,2), new RVector(3,4), new RVector(5,6)]);
// res==[1,3,5]

The script wrapper looks like this:

QScriptValue REcmaVector::getXList(QScriptContext* context, QScriptEngine* engine) {
    // check if one argument of type array is given:
    if (context->argumentCount()==1 && context->argument(0).isArray()) {
        // convert ECMAScript array to QList<RVector>:
        QList<RVector> a0;
        REcmaHelper::fromScriptValue(engine, context->argument(0), a0);

        // call C++ function:
        QList<double> cppResult = RVector::getXList(a0);
        return REcmaHelper::listToScriptValue(engine, cppResult);
    }
    else {
        return REcmaHelper::throwError("Wrong number/types of arguments for RVector.getXList().", context);
    }
}

REcmaHelper has many convenience functions to make script wrappers easier to implement. If your custom argument or return type is not supported by REcmaHelper, you might want to model your own helper function, similar like those provided in REcmaHelper.