////  BaseScriptEngine.h//  libraries/script-engine/src////  Created by Timothy Dedischew on 02/01/17.//  Copyright 2017 High Fidelity, Inc.////  Distributed under the Apache License, Version 2.0.//  See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html// #ifndef hifi_BaseScriptEngine_h#define hifi_BaseScriptEngine_h #include <functional>#include <QtCore/QDebug>#include <QtScript/QScriptEngine> // common base class for extending QScriptEngine itselfclass BaseScriptEngine : public QScriptEngine, public QEnableSharedFromThis<BaseScriptEngine> {    Q_OBJECTpublic:    static const QString SCRIPT_EXCEPTION_FORMAT;    static const QString SCRIPT_BACKTRACE_SEP;     // threadsafe "unbound" version of QScriptEngine::nullValue()    static const QScriptValue unboundNullValue() { return QScriptValue(0, QScriptValue::NullValue); }     BaseScriptEngine() {}     Q_INVOKABLE QScriptValue lintScript(const QString& sourceCode, const QString& fileName, const int lineNumber = 1);    Q_INVOKABLE QScriptValue makeError(const QScriptValue& other = QScriptValue(), const QString& type = "Error");    Q_INVOKABLE QString formatException(const QScriptValue& exception, bool includeExtendedDetails);     QScriptValue cloneUncaughtException(const QString& detail = QString());    QScriptValue evaluateInClosure(const QScriptValue& locals, const QScriptProgram& program);     // if there is a pending exception and we are at the top level (non-recursive) stack frame, this emits and resets it    bool maybeEmitUncaughtException(const QString& debugHint = QString());     // if the currentContext() is valid then throw the passed exception; otherwise, immediately emit it.    // note: this is used in cases where C++ code might call into JS API methods directly    bool raiseException(const QScriptValue& exception);     // helper to detect and log warnings when other code invokes QScriptEngine/BaseScriptEngine in thread-unsafe ways    static bool IS_THREADSAFE_INVOCATION(const QThread *thread, const QString& method);signals:    void unhandledException(const QScriptValue& exception); protected:    // like `newFunction`, but allows mapping inline C++ lambdas with captures as callable QScriptValues    // even though the context/engine parameters are redundant in most cases, the function signature matches `newFunction`    // anyway so that newLambdaFunction can be used to rapidly prototype / test utility APIs and then if becoming    // permanent more easily promoted into regular static newFunction scenarios.    QScriptValue newLambdaFunction(std::function<QScriptValue(QScriptContext *context, QScriptEngine* engine)> operation, const QScriptValue& data = QScriptValue(), const QScriptEngine::ValueOwnership& ownership = QScriptEngine::AutoOwnership); #ifdef DEBUG_JS    static void _debugDump(const QString& header, const QScriptValue& object, const QString& footer = QString());#endif}; // Standardized CPS callback helpers (see: http://fredkschott.com/post/2014/03/understanding-error-first-callbacks-in-node-js/)// These two helpers allow async JS APIs that use a callback parameter to be more friendly to scripters by accepting thisObject// context and adopting a consistent and intuitable callback signature://   function callback(err, result) { if (err) { ... } else { /* do stuff with result */ } }//// To use, first pass the user-specified callback args in the same order used with optionally-scoped  Qt signal connections://   auto handler = makeScopedHandlerObject(scopeOrCallback, optionalMethodOrName);// And then invoke the scoped handler later per CPS conventions://   auto result = callScopedHandlerObject(handler, err, result);QScriptValue makeScopedHandlerObject(QScriptValue scopeOrCallback, QScriptValue methodOrName);QScriptValue callScopedHandlerObject(QScriptValue handler, QScriptValue err, QScriptValue result); // Lambda helps create callable QScriptValues out of std::functions:// (just meant for use from within the script engine itself)class Lambda : public QObject {    Q_OBJECTpublic:    Lambda(QScriptEngine *engine, std::function<QScriptValue(QScriptContext *context, QScriptEngine* engine)> operation, QScriptValue data);    ~Lambda();    public slots:        QScriptValue call();    QString toString() const;private:    QScriptEngine* engine;    std::function<QScriptValue(QScriptContext *context, QScriptEngine* engine)> operation;    QScriptValue data;}; #endif // hifi_BaseScriptEngine_h