Customizing BarSet in QML Charts - qt

Question

I am trying to change the look of a BarChart using QtCharts 2.1. At the moment I apply the desired color and styling to the single QBarSets like this:
import QtQuick 2.8
import QtQuick.Controls 2.0
import QtQuick.Layouts 1.0
import QtCharts 2.1
import QtQuick.Window 2.2
ChartView {
id: root
width: 600
height: 400
antialiasing: true
backgroundColor: "transparent"
legend.visible: false
property var histogramProvider
Connections {
target: histogramProvider
onHistogramChanged: {
console.log("histogram changed")
histogramProvider.updateSeries(histogramSeries)
console.log(histogramSeries)
console.log(histogramSeries.at(0))
histogramSeries.at(0).color = Qt.rgba(0.9, 0.2, 0.1, 0.5)
}
onAxesChanged: {
xAxis.min = xMin
xAxis.max = xMax
yAxis.min = yMin
yAxis.max = yMax
}
}
ValueAxis {
id: yAxis
min: 0
max: 100
tickCount: 3
gridVisible: false
labelsColor: Style.fontColorLight
labelsFont: Qt.font({pointSize: 8})
titleText: qsTr("Count")
labelFormat: "%.1f"
}
ValueAxis {
id: xAxis
tickCount: 3
gridVisible: false
labelsColor: "white"
labelFormat: "%i"
min: 0
max: 100
titleText: qsTr("Elongation")
}
StackedBarSeries {
id: histogramSeries
axisX: xAxis
axisY: yAxis
}
}
I can see the BarSets with the default colors in the chart, hwever I can not change the colors. The code produces the following console output from onHistogramChanged:
qml: QtCharts::DeclarativeStackedBarSeries(0x1df550cd830)
qml: null
qrc:/qml/Histogram.qml:27: TypeError: Type error
I update the BarSeries from C++ like this:
void HistogramProvider::updateSeries(QStackedBarSeries *barSeries)
{
[...]
barSeries->clear();
QBarSet* set = new QBarSet("Histogram", barSeries);
set->setBorderColor(QColor("transparent"));
set->setColor(QColor("#6f74dd"));
for(int i = 0; i < bins.size(); i++) {
set->append(bins.at(i));
}
qDebug() << "blubb";
barSeries->append(set);
}
What am I doing wrong here?