qt chart remove space for title/legend/

I want to display a QPolarChart in a QChartView.

I won't add a title or a legend anything else than the QPolarChart. Unfortunately, when I add my chart I have bit empty white space around the QPolarChart.I guess this is the space for the title and or the legend...

Is there a way to reduce this space?

I already used

chart->layout()->setContentsMargins(0, 0, 0, 0);
chart->setBackgroundRoundness(0);

which helped a bit.

I want to reduce the red margins:

image