Issue updating curves in QwtPlot 6.1.3 - c++

Question

I am currently working on Ubuntu 14.04, using gcc 4.9.2 and Qwt 6.1.3; I have installed both Qt 4.8.6 and Qt 5.2.1 (and I wonder whether this could be connected to the issues I am experiencing).
I have a simple GUI with a QwtPlot and a QwtPlotCurve attached, which I am trying to update and redraw. In the setupUi() function, I create a few random data points and then plot them:
void ExampleMainWindow::setupUi(QMainWindow* mainWindow)
{
// run the inherited setupUi
Ui_MainWindow::setupUi(mainWindow);
// associate internal pointer to main window
this->mainWindow = mainWindow;
// create some data points
for(unsigned int i = 0; i < 10; i++)
{
this->createDataPoint();
}
for(unsigned int i = 0; i < this->xPlot.size(); i++)
{
cout << "Point #" << i << ": x=" << xPlot[i] << "; y=" << yPlot[i] << endl;
}
this->updateGraph();
// also, connect stuff
connect( this->pushButton, SIGNAL(clicked()), this, SLOT(synchronous()) );
return;
}
Now, this part works as it should. The result is something like this:
Later, I connected the pushButton to a method that should add 10 points to the curve and replot it. The relevant methods are:
void ExampleMainWindow::synchronous()
{
cout << "Creating 10 new data points..." << endl;
for(unsigned int i = 0; i < 10; i++) this->createDataPoint();
cout << "xPlot.size() = " << xPlot.size() << " ; yPlot.size() = " << yPlot.size() << endl;
this->updateGraph();
return;
}
void ExampleMainWindow::updateGraph()
{
// detach everything?
this->qwtPlot->detachItems();
// create a new curve
QwtPlotCurve* curve = new QwtPlotCurve("curve 1");
curve->setSamples( QVector<double>::fromStdVector( xPlot ), QVector<double>::fromStdVector( yPlot ) );
curve->attach( this->qwtPlot );
this->qwtPlot->replot();
//this->qwtPlot->show();
return;
}
Now, the issue is that pressing the pushButton on the GUI does not visually change anything in the QwtPlot. I am sure the program enters synchronous when the pushButton is clicked. So, there is probably something wrong with the function updateGraph, but I am missing something, as I cannot find the issue.
When I compile the project, I use Qt 4.8.6, with
qmake-qt4
make
and I get no compiling errors. My Qt project file is:
TEMPLATE = app
TARGET = example
QT += widgets
CONFIG += qwt
QMAKE_CXXFLAGS += -std=c++11
DEPENDPATH += ../. \
# for Qwt
/usr/local/qwt-6.1.3-svn/lib \
/usr/local/qwt-6.1.3-svn/include
# end for Qwt
INCLUDEPATH += ../. \
# for Qwt
/usr/local/qwt-6.1.3-svn/include
# end for Qwt
LIBS += -lqwt \
-L/usr/local/qwt-6.1.3-svn/lib
# Input
FORMS += example.ui
HEADERS = ExampleMainWindow.h
SOURCES = ExampleMainWindow.cpp \
main.cpp
Even looking at the examples I found online, I am unable to find the problem. Can you help me?
Thanks in advance for your support :-)
EDIT: The phrase pointing out the issue was cut out by mistake.

Answer 1

Ok, after several trials and errors, I found a solution: I installed Qwt (I guess 6.0) through Ubuntu's Software Center, and removed all the other Qwt versions (6.1.2 and 6.1.3) that I had manually installed. Now, the small GUI is working properly.
I guess the error was due to some issue in the paths I provided in the .pro file, but I could not pinpoint the exact mistake. Not really a satisfying answer, but at least it works.