Dynamic update of QTextBrowser in a Qdialog from a file(that gets updated by another job)

Question

I have a log file that gets updated while the job is running. I want the text content displayed in the text browser, and that should be updated dynamically.

.h file

public:

    void fillloginfo();

    void initializeQTimer();

    void closeEvent(QCloseEvent *event);

    void fillLogInfoChronically(const QString& logFilePath);

private:

    QTimer* m_Timer;

    QString m_logFilePath;

    std::ifstream m_logFileStream;

public slots:

    void fillLogInfoChronicallySlot();

.cpp file

void logdialog::initializeQTimer(){

    m_Timer = NULL;

    //create the timer object
    m_Timer = new QTimer(this);

    QObject::connect(m_Timer,SIGNAL(timeout()), this,SLOT(fillLogInfoChronicallySlot()));

 }

void logdialog::closeEvent(QCloseEvent *event)
{
    m_Timer->stop();

    if ( m_logFileStream.is_open()){
         m_logFileStream.close();
    }
}



void logdialog::fillLogInfoChronically(const QString &logFilePath)
{
    uilog->textBrowser->clear();

    m_LastLinePos = 0;

    m_logFilePath = logFilePath;

    std::string m_logFilePathStr= m_logFilePath.toStdString();
    m_logFileStream.open(m_logFilePathStr.c_str());

    if (m_logFileStream.is_open()){

        fillloginfo();

        m_Timer->start(1000);
    }
}

void logdialog::fillloginfo()
{
    std::string line;
    while (getline(m_logFileStream,line)){
        uilog->textBrowser->append(QString::fromStdString(line));
    }  
}

void logdialog::fillLogInfoChronicallySlot()
{
    fillloginfo();
}

So, I am able to read the file only on the first call, rest of the calls to get an update from the file are not working.

Thanks in advance

I don't have a control over the log generated. I launch a job from my tool, and that updates the log file. — Karthik Chinta, Sep 06 '17 at 08:24
Then, are you sure the log is updated ? Because `getline` is blocking and you could wait indefinitely. — perencia, Sep 06 '17 at 08:28
Yes, I am sure log is getting updated, the block of the code I have written in the first iter is reading the file, but in the consecutive calls by the signal slot mechanism is doing nothing. — Karthik Chinta, Sep 06 '17 at 08:55

eyllanesc · Accepted Answer · 2018-11-09T18:43:25.013

You need to call std::ios::clear() in the input stream after the initial reading. When you read the whole file, it sets the failbit in the stream and refuses to continue reading, even though the file has changed in the meantime.

In your case you must do before reading again:

void logdialog::fillloginfo()
{
    std::string line;
    m_logFileStream.clear();
    while (getline(m_logFileStream,line)){
        uilog->textBrowser->append(QString::fromStdString(line));
    }
}

The complete code is in the following link

Dynamic update of QTextBrowser in a Qdialog from a file(that gets updated by another job)

1 Answers1