[qwt] Plot is not displayed when using QwtPlot

[silviutp]

I want to use qwt to draw plots and I'm starting with some easy examples like the one bellow.

@ QwtPlot plot = new QwtPlot();
QwtPlotCurve f = new QwtPlotCurve("Line");
double xdata[10], ydata[10] ;
for (int i = 0; i< 10; i++) {
xdata[i] = i+1;
ydata[i] = (i+1)*10;
}
f->setRawSamples(xdata,ydata,10);
f->attach(plot);
plot->replot();@

The problem is that nothing happens, no window displayed.....

I use Qt 5.1.0 with mingw 4.8 and qwt 6.1 compiled also with mingw 4.8 on Windows 7 x86.

[SGaist]

Hi,

Do you call show on your plot somewhere ?
Do you put it in a layout in another widget ?

[silviutp]

Hi,

I use that code inside a function used in a QApplication;
I have also tried to use it main function, like this:
@
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;
w.show();
QwtPlot plot = new QwtPlot();
QwtPlotCurve f = new QwtPlotCurve("Line");
double xdata[10], ydata[10] ;
for (int i = 0; i< 10; i++) {
xdata[i] = i+1;
ydata[i] = (i+1)*10;
}
f->setRawSamples(xdata,ydata,10);
f->attach(plot);
plot->replot();

return a.exec();

}@

[SGaist]

You still don't call

@plot->show();@

You're also introducing a memory leak not deleting your plot after a.exec();

[silviutp]

Thank you, that was the problem..
Do I have to manually destroy the plot, doesn't this happen when I click the Close button (in the plot widget) ?

[SGaist]

It only happens if you have Qt::WA_DeleteOnClose set on your widget