c++ - Creating QT Application as GUI for existing console-based application on windows

Question

i'm trying to set up a GUI with Qt for an existing application which is meant to be run in the windows commandline. It's not just running the app with the system() command, but i need to interact with the existing application via command line.

The system() command blocks the GUI when i start the existing executable. How can i run this executable in the background and trigger some inputs via my own GUI-Elements such as a button?

I want to simplify the usage of this command line tool for some of my colleagues.

It would be mainly used on windows.

Thanks for your help.

Answer 1

I found a solution for my needs and can do what i want to do.. Actually i'm a bit disappointed. I thought it would be something more complex.

First i have to say it's an QtQuick Application .. Maybe i should have said that earlier.

I simply outsourced the process functions to another class. This class is passed to QML via the qmlRegisterType<>() function. I connected some signals from the process ( QProcess ) to slots in my own class and wrote my own functions to handle reading/writing data from and to the console application. With the QML-onClicked events i can pass my parameters and strings to the console app. And with some application logic i can handle the in/out requests and timings.

WrapperClass.h

class WrapperClass: public QObject
{
    Q_OBJECT

public:
    explicit WrapperClass(QObject *parent = nullptr);

    QProcess *process;
    QString str_proc_output;

    Q_INVOKABLE void startProcess();
    Q_INVOKABLE void stopProcess();

    Q_INVOKABLE QString getOutput();
    Q_INVOKABLE void writeByte(QString str);


    Q_INVOKABLE QString getAllOutput();
private:

signals:

public slots:
    void mReadyRead();
    void mReadyReadStandardOutput();
    void mFinished(int code);
    void mBytesWritten(qint64 written);

};

WrapperClass.cpp

WrapperClass::WrapperClass(QObject *parent) : QObject(parent)
{
    process = new QProcess();
    process->setProgram("untitled.exe");
    process->setProcessChannelMode(QProcess::MergedChannels);

    str_proc_output = "";

    connect(process, SIGNAL(readyRead()), this, SLOT(mReadyRead()));
    connect(process, SIGNAL(readyReadStandardOutput()), this, SLOT(mReadyReadStandardOutput()));
    connect(process, SIGNAL(finished(int)), this, SLOT(mFinished(int)));
    connect(process, SIGNAL(bytesWritten(qint64)), this, SLOT(mBytesWritten(qint64)));

}

void WrapperClass::startProcess() {
    if(process->state() == QProcess::Running) {
        stopProcess();
    } else {
        process->open(QProcess::ReadWrite);
    }
}

void WrapperClass::stopProcess() {
    process->close();
}



QString WrapperClass::getOutput() {
    return str_proc_output;
}


QString WrapperClass::getAllOutput() {
    QString str = process->readAll();

    std::cout << str.toStdString() << std::endl;
    return str;
}


void WrapperClass::writeByte(QString str) {

    char cArr[str.length()] = {};

    memcpy(cArr, str.toStdString().c_str(), str.length());

    QByteArray arr = QByteArray(cArr, -1);
    process->write(arr);
}




void WrapperClass::mReadyRead() {
    QString s = QString(process->readAll());

    std::cout << "ReadyRead: " << s.toStdString() << std::endl;
    str_proc_output = s;
}

void WrapperClass::mReadyReadStandardOutput() {
    QString s = QString(process->readAllStandardOutput());

    std::cout << "ReadyReadStandardOutput: " << s.toStdString() << std::endl;

}

void WrapperClass::mFinished(int code) {
    std::cout << "Process finished! (" << code << ')' << std::endl;
}


void WrapperClass::mBytesWritten(qint64 written) {

    std::cout << "Bytes written: " << written << std::endl;

}

Main.cpp

int main(int argc, char *argv[])
{
    QGuiApplication app(argc, argv);

    qmlRegisterType<WrapperClass>("com.example.WrapperClass", 0, 1, "WrapperClass");

    QQmlApplicationEngine engine;
    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
    if (engine.rootObjects().isEmpty())
        return -1;

    return app.exec();
}

With registering the Cpp-Class to QML i'm able to trigger the read/write functions via Click-Events from QML-MouseArea or Button.