title: How to remove margin from QChartView or QChart
body: <p>All <a href="https://doc.qt.io/qt-5/qtcharts-index.html" rel="noreferrer">Qt Charts</a> seem to have a margin and rounded corners.</p>
  
  <p><a href="https://i.stack.imgur.com/884Q7.png" rel="noreferrer"><img src="https://i.stack.imgur.com/884Q7.png" alt="Example image with red marked border"></a></p>
  
  <p><strong>How to remove both?</strong></p>
  
  <p>I want the white area to fill the entire dialog. I cannot find any informations in the Qt documentations. I found a screenshot of <a href="https://doc.qt.io/qt-5/qtcharts-callout-example.html" rel="noreferrer">one Example</a> that does not have this spacing. But I cannot find the code that disables it.</p>
  
  <p>My initialization code looks like this:</p>
  
  <pre><code>QPieSeries *series = new QPieSeries();
  series-&gt;append("Jane", 1);
  series-&gt;append("Joe", 2);
  series-&gt;append("Andy", 3);
  series-&gt;append("Barbara", 4);
  series-&gt;append("Axel", 5);
  
  QChart *chart = new QChart();
  chart-&gt;addSeries(series);
  
  QChartView *chartView = new QChartView(chart);
  chartView-&gt;setBackgroundBrush(Qt::red);
  chartView-&gt;setRenderHint(QPainter::Antialiasing);
  
  QMainWindow window;
  window.setCentralWidget(chartView);
  window.resize(400, 300);
  window.show();
  </code></pre>