The Invoke function of NPAIP is defined as :

typedef bool (*NPInvokeFunctionPtr)(NPObject *npobj, NPIdentifier name,
const NPVariant *args, uint32_t argCount,
NPVariant *result);

When javascript invokes the a method of the NPAPI, it will return a result to the Javascript. But now I just return only one output parameter. Could it return multiple outputs? And how? Should I define a NPObject myself?