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c++qtqtcharts

QtChart - C++ - Saving a chart which wasn't displayed

I'm trying to save a chart to a file, in a QTextDocument in this example :

QTextDocument doc("Frame rate test\n");
QTextCursor cursor(&doc);
cursor.movePosition(QTextCursor::End);

if (getTestFinishedStatus())
{
    QPixmap pix = _pFrameRateChart->grab(); //_pFrameRateChart is QChartView
    cursor.insertImage(pix.toImage());
}

QTextDocumentWriter docWriter;
docWriter.setFileName("framerate.odf");
docWriter.setFormat("ODF");
docWriter.write(&doc);

The problem is the result isn't same if I'm displaying the chart in an ui. Here is the result when not displayed :

enter image description here

Here is the result when displayed :

enter image description here

Obviously I would like to have the second result even when I don't add the ChartView to a widget to display it on an ui. I've tried resizing the QChartView, resizing the QChart, adding the Chart to a temporarly widget and QVBoxLayout then saving it, showing temporarly the QChartView before saving it etc... but didn't managed to get a good result.

Solution

  • I didn't find any easy way to this, so here's my solution, which is more like a workaround though :

    QPixmap ChartView::getChartPixmap()
{
    QWidget* w = new QWidget; //creating a temporary widget, which will enable to display the chart

    w->resize(REPORT_IMAGE_WIDTH, REPORT_IMAGE_HEIGHT);
    QVBoxLayout *vl;
    vl = new QVBoxLayout(w);
    vl->addWidget(this); //'this' being the QChartView

    w->show(); //showing the widget so it is resized and can be grabbed with the correct dimensions

    QTest::qWait(500); //we need to wait for a little for the graph to be drawn otherwise you'll still have the same size problem

    QPixmap pixmap = w->grab(); //retrieve the pixmap

    w->hide(); //hiding the widget

    return pixmap;
}

    It's working but you'll have a small window opened with the graph for 500 ms.