[Solved] Adding a qwtPlot to a layout

[cl90]

Hi!

What i'm trying to do should be pretty easy. But somehow it doesn't work.
All i'm trying to do is to add a qwtPlot to an qt application, without launching the plot in its own application.
Every time i try, i end up with 2 application windows (one for the application and one for the plot) or with no application (because it crashes).
I tired this for quiet some time without any progress, so maybe you can help me out.

If i run this somewhere in my code i end up with 2 application windows. (not what i want)

QwtPlot* plot = new QwtPlot();
    plot->setTitle( "Plot Demo" );
    plot->setCanvasBackground( Qt::white );
    plot->setAxisScale( QwtPlot::yLeft, 0.0, 10.0 );
    plot->insertLegend( new QwtLegend() );
    [...]
    plot->show();

QwtPlot* plot = new QwtPlot();
    plot->setTitle( "Plot Demo" );
    plot->setCanvasBackground( Qt::white );
    plot->setAxisScale( QwtPlot::yLeft, 0.0, 10.0 );
    plot->insertLegend( new QwtLegend() );
    [...]
    plot->show();

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What i want is to add a plot to a specified layout inside my application.
every time i try to add a qwtPlot as a widget, my application crashes.

QwtPlot* plot = new QwtPlot();
    [...]
    ui->horizontalLayout->addWidget(plot);

QwtPlot* plot = new QwtPlot();
    [...]
    ui->horizontalLayout->addWidget(plot);

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Is this even Possible? i cant even find anything about this.

[Uwe]

Everything fine with your code snippet - putting QwtPlot inside a layout is probably what almost all applications do.

The bug is somewehere else in your code ( unrelated to Qwt ) - the debugger is your friend.

Uwe

[Santosh Reddy]

I will take a guess, clean build the application (just your application not Qwt).

[cl90]

Thanks for the quick replys.

I thought it must be something else, because qwt would be some kind of useless.

here is the whole code of a new app. which should work (but doesn't)

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    qwtplot w;
    w.show();
 
    return a.exec();
}

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    qwtplot w;
    w.show();

    return a.exec();
}

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qwtplot::qwtplot(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::qwtplot)
{
 
    QwtPlot* plot = new QwtPlot();
 
    plot->setTitle( "Plot Demo" );
    plot->setCanvasBackground( Qt::white );
    plot->setAxisScale( QwtPlot::yLeft, 0.0, 10.0 );
    plot->insertLegend( new QwtLegend() );
 
    ui->hlayout->addWidget(plot); // the app crashes here.
 
     [...]
 
    plot->show();
 
 
 
    ui->setupUi(this);
}

qwtplot::qwtplot(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::qwtplot)
{

    QwtPlot* plot = new QwtPlot();

    plot->setTitle( "Plot Demo" );
    plot->setCanvasBackground( Qt::white );
    plot->setAxisScale( QwtPlot::yLeft, 0.0, 10.0 );
    plot->insertLegend( new QwtLegend() );

    ui->hlayout->addWidget(plot); // the app crashes here.

     [...]

    plot->show();



    ui->setupUi(this);
}

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Could this mean that my qwt is not compiled right? or do i something wrong with linking?
I use Qt 5.2.1 with MSVC addin 5.2.1 with qwt 6.1.2.
I can run plots and they work as expected.

[Santosh Reddy]

Call ui->setupUI(this) before using anything in ui, better call it as first statement in constructor.

[cl90]

...
that was it -.-

Thanks. hard to believe that i didn't tryed that.