pieview.h Example File

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 #ifndef PIEVIEW_H
 #define PIEVIEW_H

 #include <QAbstractItemView>

 class PieView : public QAbstractItemView
 {
     Q_OBJECT

 public:
     PieView(QWidget *parent = nullptr);

     QRect visualRect(const QModelIndex &index) const override;
     void scrollTo(const QModelIndex &index, ScrollHint hint = EnsureVisible) override;
     QModelIndex indexAt(const QPoint &point) const override;

 protected slots:
     void dataChanged(const QModelIndex &topLeft, const QModelIndex &bottomRight,
                      const QVector<int> &roles = QVector<int>()) override;
     void rowsInserted(const QModelIndex &parent, int start, int end) override;
     void rowsAboutToBeRemoved(const QModelIndex &parent, int start, int end) override;

 protected:
     bool edit(const QModelIndex &index, EditTrigger trigger, QEvent *event) override;
     QModelIndex moveCursor(QAbstractItemView::CursorAction cursorAction,
                            Qt::KeyboardModifiers modifiers) override;

     int horizontalOffset() const override;
     int verticalOffset() const override;

     bool isIndexHidden(const QModelIndex &index) const override;

     void setSelection(const QRect&, QItemSelectionModel::SelectionFlags command) override;

     void mousePressEvent(QMouseEvent *event) override;

     void mouseMoveEvent(QMouseEvent *event) override;
     void mouseReleaseEvent(QMouseEvent *event) override;

     void paintEvent(QPaintEvent *event) override;
     void resizeEvent(QResizeEvent *event) override;
     void scrollContentsBy(int dx, int dy) override;

     QRegion visualRegionForSelection(const QItemSelection &selection) const override;

 private:
     QRect itemRect(const QModelIndex &item) const;
     QRegion itemRegion(const QModelIndex &index) const;
     int rows(const QModelIndex &index = QModelIndex()) const;
     void updateGeometries() override;

     int margin = 0;
     int totalSize = 300;
     int pieSize = totalSize - 2 * margin;
     int validItems = 0;
     double totalValue = 0.0;
     QRubberBand *rubberBand = nullptr;
     QPoint origin;
 };

 #endif // PIEVIEW_H