problem in QProcess

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

Code:

---

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

---

this is a timer function calling every 400 milli sec

Code:

---

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

---

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

Code:

---

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();
           }
 
  }

---

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??:confused:
i changed gtk application to a Qt application and try the same thing its worked in the first attempt ... :confused:

please help me ...

Did you check the value of "ok" variable?

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 ....

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

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

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.

Quote:

---

Originally Posted by 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 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 .........

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

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

Could we see some more code of yours?

my code or that Gtk code ..?

my Qt code:

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()));

---

Code:

---

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()));

---

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

Code:

---

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);
                }
        }
 
}

---

Code:

---

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);
           }
 
}

---

Code:

---

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

---

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

Code:

---

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

---

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

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

Quote:

---

Originally Posted by wysota

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

Code:

---

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");

---

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

Code:

---

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);
        }
 
}

---

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