QLineSeries ordering on UI

[Joe von Habsburg]

Hello I draw data with QLineSeries. I have 4 - 5 different datas, and they have own series.

QLineSeries *series1 = new QLineSeries;
QLineSeries *series2 = new QLineSeries;
QLineSeries *series3 = new QLineSeries;
QLineSeries *series4 = new QLineSeries;

They use opengl active

series1->setUseOpenGL(true);
series2->setUseOpenGL(true);
series3->setUseOpenGL(true);
series4->setUseOpenGL(true);

I always use same order,

chart->addSeries(series1);
chart->addSeries(series2);
chart->addSeries(series3);
chart->addSeries(series4);

When I draw data, they are different order on chart each run.
For example :
1st run : 2 3 1 4
2nd run : 1 2 4 3
3rd run : 1 2 3 4

they always come in a different order. I want to see them in the order in which I added them ( 1 2 3 4)