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// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only
/*!
\page qtcharts-donutbreakdown-example.html
\title Creating a Donut Breakdown Chart
\brief Shows how to create a donut breakdown chart.
\include gallery.qdocinc
\image examples_donutbreakdown.png {Screenshot showing a donut breakdown chart example}
\section1 Creating Donut Breakdown Charts
Let's start by defining some data for the chart.
\snippet chartsgallery/donutbreakdownwidget.cpp 1
Then we create a chart where we add the data. Note that this is our own chart derived from QChart.
\snippet chartsgallery/donutbreakdownwidget.cpp 2
Our own chart works in such a way that we create a main series in the constructor we create a main series,
which aggregates the data provided by the breakdown series. This is the piechart in the center.
\snippet chartsgallery/donutbreakdownchart.cpp 1
When a breakdown series is added the data is used to create a slice in the main series and the
breakdown series itself is used to create a segment of a donut positioned so that it is aligned
with the corresponding slice in the main series.
\snippet chartsgallery/donutbreakdownchart.cpp 2
Here's how the start and end angles for the donut segments are calculated.
\snippet chartsgallery/donutbreakdownchart.cpp 3
The legend markers are customized to show the breakdown percentage. The markers for the main level slices are hidden.
\snippet chartsgallery/donutbreakdownchart.cpp 4
Instead the main level slices show the percentage on the label.
\snippet chartsgallery/donutbreakdownmainslice.cpp 1
\dots
\snippet chartsgallery/donutbreakdownmainslice.cpp 2
Now that we have our chart defined, we can finally create a QChartView and show the chart.
\snippet chartsgallery/donutbreakdownwidget.cpp 3
*/