Qt chart error: ASSERT: “width > 0.0” in file painting\qrasterizer.cpp, line 761

Question

I got an error when using QValueAxis in QtCharts :

ASSERT: "width > 0.0" in file painting\\qrasterizer.cpp, line 761

This happens when the QBarSet values are all 0 .

I have this example with the minimal necessary code below:

#include <QtWidgets/QApplication>
#include <QtWidgets/QMainWindow>
#include <QtCharts>

QT_CHARTS_USE_NAMESPACE

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    QChart *chart = new QChart;
    QBarSeries *series = new QBarSeries(chart);
    QBarSet *set = new QBarSet("BarSet", series);
    series->append(set);

    QValueAxis *valueAxisX = new QValueAxis(chart);

    QChartView *chartView = new QChartView(chart);

    for(int i = 0; i < 24; ++i) {
        set->append(0); //error
        //if I set like set->append(1) or anything just to make sure the values are not all 0, there will be no error.

    }
    chart->addSeries(series);
    chart->setAxisX(valueAxisX, series);

    QMainWindow window;
    window.setCentralWidget(chartView);
    window.resize(420, 300);
    window.show();

    return a.exec();
}

My program will initiate the QBarSet dynamically from a QMap . Like this:

for(auto it = map.cbegin(); it != map.cend(); ++it) {
    set->append(it.value());
}

And the QMap is initiated to something like this when the program starts:

QMap(("First", 0)("Second", 0)...)

Sometimes the QMap will not add values due to the use of the program, then all the QBarSet values will be initiated to 0 . Then the program will crash because of that error.

So how can I avoid this error when the QBarSet values are all initiated to 0 ?

Answer 1

As the error speaks:

ASSERT: "width > 0.0"

You need a value greater than zero.

Also QBarSet::append ,

void QBarSet::append(const qreal value)

expects a qreal or double value.

Perhaps you want to set it to 0.1 initially:

set->append(0.1);