Custom QWidget doesn't show up in QGridLayout, only in a new window

[InverseTransform]

I have a custom QWidget-based class, MyChart , that internally creates a QChart. I would like to add instances of this widget to a QGridLayout of another custom QWidget, MyContainer. However, doing so results in MyChart not being displayed within the grid layout: an empty MyContainer pops up.

I can get MyChart to show in a new window if I call QChartView->setVisible(true) after adding MyChart to the QGridLayout, but that's not what I want. I would like it to show up in the grid layout.

Code:

// MyChart - works fine by itself, I just can't get it to show inside QGridLayout
class MyChart : public QWidget
{
    Q_OBJECT

public:
    explicit MyChart(QWidget *parent = 0);
    ~MyChart();

    void showChart() { _chartView->setVisible(true); } // For testing.

private:
    Ui::MyChart *ui;
    QtCharts::QChartView *_chartView;
    QtCharts::QChart *_chart;
};

MyChart::MyChart(QWidget *parent) : QWidget(parent), ui(new Ui::MyChart)
{
    ui->setupUi(this);

     // Sample chart.
    QtCharts::QChart *chart = new QtCharts::QChart();
    ... // Fills the chart with some sample data etc. _chart and _chartView are assigned at the end.
}

class MyContainer : public QWidget
{
    Q_OBJECT

public:
    explicit MyContainer(QWidget *parent = 0);
    ~MyContainer();

private:
    Ui::MyContainer *ui;	// Contains a QGridLayout.
};


MyContainer::MyContainer(QWidget *parent) : QWidget(parent), ui(new Ui::MyContainer)
{
    ui->setupUi(this);

    // Add sample stuff to MyContainer's QGridLayout.
    ui->gridLayout->addWidget(new QLabel("Sample label 1"), 0, 0, Qt::AlignCenter); // Works ok.

    MyChart *chart1 = new MyChart(this);
    ui->gridLayout->addWidget(chart1, 1, 0, Qt::AlignCenter);    // Nothing shows up.
	
    // chart1->showChart(); // Opens chart1 in a new window, but it should be inside the gridLayout.
}

// Application window.
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    MyContainer w;
    w.setWindowTitle("Test");
    w.show();    

    return app.exec();
}

What am I doing wrong? Am I supposed to create a QMainWindow to host MyContainer widget, or something similar?

[mrjj]

Hi
Can you try with
MyChart::MyChart(QWidget *parent) ...
QtCharts::QChart *chart = new QtCharts::QChart(this); // assign parent

also you are not initializing the chart member but a new local variable.
QtCharts::QChart *chart = new QtCharts::QChart();
should be
_chart = new QtCharts::QChart();

[InverseTransform]

Thanks, but this doesn't seem to work. Note: I'm initializing members at the end of that ctor, it's just not shown in the pasted code.
I can't assign parent like you specify, because QChart's ctor expects a QGraphicsItem type rather than QWidget, thus resulting in compiler error ...

Though you've given me an idea: it could be that I should be using QGraphicsGridLayout instead, and deriving MyChart from QGraphicsWidget instead of QWidget.

[mrjj]

@InverseTransform
Ah sorry, i forgot you need to use chartView to use charts with widgets.
Im not sure what could be wrong.
If it opens a window with
chart1->showChart()
did you set parent for _chartview ?

[InverseTransform]

@mrjj Yes, QChartView's parent is set to chart object and works normally: the chart itself is displayed as expected, but in a new window ...

[mrjj]

@InverseTransform
hmm thats very odd as normally it becomes a window if no parent is set. ( all widgets do)

I assume "chart object" is MyChart

There should be nothing wrong with QChartView in layout.

I wonder if it can be a size thing ?
I mean the widget get really compressed when added to layout ?

[InverseTransform]

I found the solution: you need to add QChartView object to the layout, not the widget itself:
ui->gridLayout->addWidget(chart->getQChartView(), 1, 0, Qt::AlignCenter);
where getQChartView() simply returns the QChartView* of the underlying QChart.