update a counter in PlainTextEdit on the same line

[qt_gotcha]

I have a PlainTextEdit called commandWindow in which I want to display a counter. The counter comes from a thread process. The counter is always on the last line of the PlainTextEdit. I made some test code, the sqrt is to delay the counter:

QString out;
QStringList list;
for (int i = 0; i < 100; i++)
{
	double x;
	out = commandWindow->toPlainText();
	list = out.split("\n");  
	list.removeLast();
	for (int j = 0; j < 10000; j++) 
            x = sqrt(847239);
	list << QString("%1 %2").arg(i).arg(x);
	out = list.join("\n");
	commandWindow->setPlainText(out);
}
commandWindow->appendPlainText("done\n");

QString out;
QStringList list;
for (int i = 0; i < 100; i++)
{
	double x;
	out = commandWindow->toPlainText();
	list = out.split("\n");  
	list.removeLast();
	for (int j = 0; j < 10000; j++) 
            x = sqrt(847239);
	list << QString("%1 %2").arg(i).arg(x);
	out = list.join("\n");
	commandWindow->setPlainText(out);
}
commandWindow->appendPlainText("done\n");

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this doesn't display the counter but only updates the commandWIndow whenit is done, it display 99. Also if I comment out the list.removeLast();, it only shows the hunderd lines after it is finished. Suggestions are welcome.

[Lesiok]

Because for loop is disabling event dispatcher. Just write Yours code like this :

....
    commandWindow->setPlainText(out);
    QCoreApplication::processEvents();
....

....
    commandWindow->setPlainText(out);
    QCoreApplication::processEvents();
....

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[qt_gotcha]

actually
QCoreApplication::sendPostedEvents(this, 0);
works better

I have a QProcess (calcProcess) that is linked to a unix programme that gives of blocks of bytes (no readlines, '\n'). It outputs only on the error channel. It outputs first its name, then an umpty line, then a counter that looks like "Execute timstep xxx". That output should be processed in a PlainTextEdit called commandWindow

my code now looks like this for those who are interested:

calcProcess->setReadChannel ( QProcess::StandardError );
connect(calcProcess, SIGNAL(readyReadStandardError()),this, SLOT(readFromStderr()) );
connect(calcProcess, SIGNAL(finished(int)),this, SLOT(finishedModel(int)) );

calcProcess->setReadChannel ( QProcess::StandardError );
connect(calcProcess, SIGNAL(readyReadStandardError()),this, SLOT(readFromStderr()) );
connect(calcProcess, SIGNAL(finished(int)),this, SLOT(finishedModel(int)) );

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In the starter function of the process:

{
[...] //get relevant proces info
 
	commandWindow->appendPlainText(" ");
	commandWindow->appendPlainText(" ");
	commandWindow->appendPlainText(" ");
	xlast = commandWindow->document()->lineCount();
	// append extra empty lines that will be replaced with the process output
 
	calcProcess->start(prog, args);
}

{
[...] //get relevant proces info

	commandWindow->appendPlainText(" ");
	commandWindow->appendPlainText(" ");
	commandWindow->appendPlainText(" ");
	xlast = commandWindow->document()->lineCount();
	// append extra empty lines that will be replaced with the process output

	calcProcess->start(prog, args);
}

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The function to proces the output on screen is as follows:

void nutshellqt::readFromStderr()
{
	QByteArray buf;
	buf.clear();
	buf = calcProcess->readAllStandardError();
	onScreen(QString(buf));
}
 
void nutshellqt::onScreen(QString buffer)
{
	QString output;
	QStringList list, listb;
	QTimer tT;
	tT.setSingleShot(true);
 
	buffer.replace('\r','\n');
	// replace unix CR with \n
        listb.clear();
	listb = buffer.split("\n");
	// split process output all out in seperate lines
 
	output = commandWindow->toPlainText();
	list = output.split("\n");
	// get the lines in the commandWindow, might get slow?
 
	foreach (QString str, listb)
	{
		if(str.contains("version") )
			list.replace(xlast-3,str);
		if (str.contains("Exec") )
			list.replace(xlast-1,str);
 
		QCoreApplication::sendPostedEvents(this, 0);
		// update the plaintextedit with these two actions
 
		tT.start(100);
                //delay slightly for readability
 
		output=list.join("\n");
		commandWindow->setPlainText(output);
		// join new lines and replace the commandWindow
 
		QTextCursor cur = commandWindow->textCursor();
		cur.setPosition(output.size());
		commandWindow->setTextCursor(cur);
		//put the cursor at the end
 
		QCoreApplication::sendPostedEvents(this, 0);
		// update plaintextedit with last actions
	}
}

void nutshellqt::readFromStderr()
{
	QByteArray buf;
	buf.clear();
	buf = calcProcess->readAllStandardError();
	onScreen(QString(buf));
}

void nutshellqt::onScreen(QString buffer)
{
	QString output;
	QStringList list, listb;
	QTimer tT;
	tT.setSingleShot(true);

	buffer.replace('\r','\n');
	// replace unix CR with \n
        listb.clear();
	listb = buffer.split("\n");
	// split process output all out in seperate lines

	output = commandWindow->toPlainText();
	list = output.split("\n");
	// get the lines in the commandWindow, might get slow?

	foreach (QString str, listb)
	{
		if(str.contains("version") )
			list.replace(xlast-3,str);
		if (str.contains("Exec") )
			list.replace(xlast-1,str);

		QCoreApplication::sendPostedEvents(this, 0);
		// update the plaintextedit with these two actions

		tT.start(100);
                //delay slightly for readability

		output=list.join("\n");
		commandWindow->setPlainText(output);
		// join new lines and replace the commandWindow

		QTextCursor cur = commandWindow->textCursor();
		cur.setPosition(output.size());
		commandWindow->setTextCursor(cur);
		//put the cursor at the end

		QCoreApplication::sendPostedEvents(this, 0);
		// update plaintextedit with last actions
	}
}

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