problem in QProcess

[wagmare]

hi friends,
please help
i create a code to embed gtk window to my Qt app ..
mainwindow.cpp

procc2 = new QProcess();
      procc2->setProcessChannelMode(QProcess::MergedChannels);
      connect(procc2, SIGNAL(readyReadStandardOutput()), this, SLOT(readFromStdout2()));

procc2 = new QProcess();
      procc2->setProcessChannelMode(QProcess::MergedChannels);
      connect(procc2, SIGNAL(readyReadStandardOutput()), this, SLOT(readFromStdout2()));

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this is a timer function calling every 400 milli sec

MainWindow::timeout{
     if(...)
    {
     QString program4 = "./gtk_demo2";
     QStringList arguments2;
                if(procc2->state() != QProcess::Running)
                {
                        procc2->start(program4, arguments2);
                }
        }

MainWindow::timeout{
     if(...)
    {
     QString program4 = "./gtk_demo2";
     QStringList arguments2;
                if(procc2->state() != QProcess::Running)
                {
                        procc2->start(program4, arguments2);
                }
        }

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readfromstdout() function will call the function to embed the process

MainWindow::readFromStdout2()
{
        int j = 0;
        bool ok;
        QString out;
        printf("in singal fin\n");
        out = procc2->readAllStandardOutput();
        j = out.toInt(&ok, 16);
        printf("j =%d\n",j);
        if(j == 1)
                printf("device not connected\n");
        else{
                printf("the device connected\n");
               embed();
           }
 
  }

MainWindow::readFromStdout2()
{
        int j = 0;
        bool ok;
        QString out;
        printf("in singal fin\n");
        out = procc2->readAllStandardOutput();
        j = out.toInt(&ok, 16);
        printf("j =%d\n",j);
        if(j == 1)
                printf("device not connected\n");
        else{
                printf("the device connected\n");
               embed();
           }

  }

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this is my code and the function embed() will embed the "gtk_demo" window if it returns 0 or anything ...
the problem is on first time if i spawn the signal "readyReadStandardOutput()"
is not emitted and readFromStdout2() slot is not called .
i closed the spawned gtk application "gtk_demo" and as i put the procc in loop again it spawn "gtk_demo" its emitting "readyReadStandardOutput()" and embedding perfectly ... why??
i changed gtk application to a Qt application and try the same thing its worked in the first attempt ...

please help me ...

[wysota]

Did you check the value of "ok" variable?

[wagmare]

no but even "in singal fin\n" is not printing ... its not entering the slot readFromStdout2()
.. only after closing the gtk window then only i get the output ....

[wysota]

Maybe the other process doesn't write anything on its standard output? Or it doesn't flush the descriptor...

[wagmare]

thanks for reply .. but i use merged channels and i am getting standard output but only after the process ie.. the gtk window closed ..

[wysota]

That's why I'm saying the other process is not flushing its stdout descriptor. Your data gets stuck in a pipe buffer between the two processes. If you are the author of "the other app", simply write a newline after the data or call (f)flush() on stdout.

[wagmare]

That's why I'm saying the other process is not flushing its stdout descriptor. Your data gets stuck in a pipe buffer between the two processes. If you are the author of "the other app", simply write a after the data or call (f)flush() on stdout.

thanks for reply ..
i try the both ((f)flush() ,newline )but still its giving the same ... when the process gets finished and closed only its giving the stdout.
i cant get any thing .........

[wysota]

What if you run that application separately from the terminal? Do you see its output immediately?

[wagmare]

yes its running quickly ... after i execute gtk_demo separately it shows the output before showing the window ... its quick ..

[wysota]

Could we see some more code of yours?

[wagmare]

my code or that Gtk code ..?

my Qt code:

timer2 = new QTimer(this);
                timer2->setSingleShot(TRUE);
 
        timer_FS = new QTimer(this);
        timer_FS->start(300);
 
        container2 = new QX11EmbedContainer(this);
        container2->setPalette(QPalette(Qt::red));
        container2->setAutoFillBackground(true);
 
 
        procc2 = new QProcess();
        procc2->setProcessChannelMode(QProcess::MergedChannels);
        connect(procc2, SIGNAL(readyReadStandardOutput()), this, SLOT(readFromStdout2()));

timer2 = new QTimer(this);
                timer2->setSingleShot(TRUE);

        timer_FS = new QTimer(this);
        timer_FS->start(300);

        container2 = new QX11EmbedContainer(this);
        container2->setPalette(QPalette(Qt::red));
        container2->setAutoFillBackground(true);


        procc2 = new QProcess();
        procc2->setProcessChannelMode(QProcess::MergedChannels);
        connect(procc2, SIGNAL(readyReadStandardOutput()), this, SLOT(readFromStdout2()));

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QHBoxLayout *layoout4 = new QHBoxLayout();
        layoout4->addWidget(container2);
 
        mainFrame5->setLayout(layoout4);
 
        connect(timer2, SIGNAL(timeout()), this, SLOT(embed2()));
        connect(FPSBackButton, SIGNAL(clicked()), this, SLOT(timeout_bg2()));
        connect(timer_FS, SIGNAL(timeout()), this, SLOT(timeout_FS()));

QHBoxLayout *layoout4 = new QHBoxLayout();
        layoout4->addWidget(container2);

        mainFrame5->setLayout(layoout4);

        connect(timer2, SIGNAL(timeout()), this, SLOT(embed2()));
        connect(FPSBackButton, SIGNAL(clicked()), this, SLOT(timeout_bg2()));
        connect(timer_FS, SIGNAL(timeout()), this, SLOT(timeout_FS()));

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/*setFPScanner =1 will be set when a embed Button is clicked in my Qt app*/

void
MainWindow::timeout_FS(){
 
        if(setFPScanner == 1)
                mainstackedWidget->setCurrentIndex(4);
        else if(embedFPScanner == 1)
        {
        QString program4 = "./gtk_demo2";
        //QString program4 = "./animate";
        QStringList arguments2;
                if(procc2->state() != QProcess::Running)
                {
                        procc2->start(program4, arguments2);
                }
        }
 
}

void
MainWindow::timeout_FS(){

        if(setFPScanner == 1)
                mainstackedWidget->setCurrentIndex(4);
        else if(embedFPScanner == 1)
        {
        QString program4 = "./gtk_demo2";
        //QString program4 = "./animate";
        QStringList arguments2;
                if(procc2->state() != QProcess::Running)
                {
                        procc2->start(program4, arguments2);
                }
        }

}

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void MainWindow::readFromStdout2()
{
        int j = 4;
        bool ok;
        QString out;
        out = procc2->readAllStandardOutput();
        j = out.toInt(&ok, 16);
        printf("j =%d\n",j);
        if(j == 1)
                printf("device not connected\n");
        else{
                printf("the device connected\n");
                timer2->start(2000);
           }
 
}

void MainWindow::readFromStdout2()
{
        int j = 4;
        bool ok;
        QString out;
        out = procc2->readAllStandardOutput();
        j = out.toInt(&ok, 16);
        printf("j =%d\n",j);
        if(j == 1)
                printf("device not connected\n");
        else{
                printf("the device connected\n");
                timer2->start(2000);
           }

}

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void MainWindow::embed2()
{
 
           container2->embedClient(widedit->text().toInt(&ok, 16));
}

void MainWindow::embed2()
{

           container2->embedClient(widedit->text().toInt(&ok, 16));
}

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/*this will be set setFpscanner when a back button in my Qt app is clicked*/

void MainWindow::timeout_bg2()
{
        timer_FS->stop();
        setFPScanner = 0;
        mainstackedWidget->setCurrentIndex(1);
        timer_FS->start();
}

void MainWindow::timeout_bg2()
{
        timer_FS->stop();
        setFPScanner = 0;
        mainstackedWidget->setCurrentIndex(1);
        timer_FS->start();
}

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this is my whole code in that part i written .... if u find any error please help me ...

[wysota]

And how do you output the data from the slave app?

[wagmare]

And how do you output the data from the slave app?

the gtk window will print 1 using printf if the device is not connected else it print 0 .. externly running
gtk_demo.c

if(retval != FTR_RETCODE_OK){
                if(retryCountLevel1 <= MAX_RETRY_COUNT){
                        FreeResource();
                        usleep(MAX_RETRY_SLEEP);
                        retryCountLevel1++;
                        goto retry_level1;
                }else{
                        dump_line(stdin);
                        printf("1");
 FreeResource();
                        return -1;
                }
        }
        printf("0\n");

if(retval != FTR_RETCODE_OK){
                if(retryCountLevel1 <= MAX_RETRY_COUNT){
                        FreeResource();
                        usleep(MAX_RETRY_SLEEP);
                        retryCountLevel1++;
                        goto retry_level1;
                }else{
                        dump_line(stdin);
                        printf("1");
 FreeResource();
                        return -1;
                }
        }
        printf("0\n");

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this is the gtk code ..
so i use
my Qt app
readyReadStandardOutput() for the process and i try to get that as

int j = 4;
        bool ok;
         const char *str;
         QByteArray ba;
        QString out;
        out = procc2->readAllStandardOutput();
         ba = out.toLatin1();
        str = ba.data();
        //j = out.toInt(&ok, 16);
        printf("the string on returning:%s\n",str);
        if(strcmp(str,"1") == 0){
                printf("device not connected\n");
        }
        else{
                printf("the device connected\n");
                timer2->start(2000);
        }
 
}

int j = 4;
        bool ok;
         const char *str;
         QByteArray ba;
        QString out;
        out = procc2->readAllStandardOutput();
         ba = out.toLatin1();
        str = ba.data();
        //j = out.toInt(&ok, 16);
        printf("the string on returning:%s\n",str);
        if(strcmp(str,"1") == 0){
                printf("device not connected\n");
        }
        else{
                printf("the device connected\n");
                timer2->start(2000);
        }

}

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did u find any thing i done foolishly ...
if so please help ..