- Qt 5.5
- Qt Widgets
- Chart Example
- pieview.cpp Example File
- Qt 5.5.1 Reference Documentation

# pieview.cpp Example File

itemviews/chart/pieview.cpp

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    #include <QtWidgets>
    #include <cmath>

    #ifndef M_PI
    #define M_PI 3.1415927
    #endif

    #include "pieview.h"

    PieView::PieView(QWidget *parent)
        : QAbstractItemView(parent)
    {
        horizontalScrollBar()->setRange(0, 0);
        verticalScrollBar()->setRange(0, 0);

        margin = 8;
        totalSize = 300;
        pieSize = totalSize - 2 * margin;
        validItems = 0;
        totalValue = 0.0;
        rubberBand = 0;
    }

    void PieView::dataChanged(const QModelIndex &topLeft,
                              const QModelIndex &bottomRight,
                              const QVector<int> &)
    {
        QAbstractItemView::dataChanged(topLeft, bottomRight);

        validItems = 0;
        totalValue = 0.0;

        for (int row = 0; row < model()->rowCount(rootIndex()); ++row) {

            QModelIndex index = model()->index(row, 1, rootIndex());
            double value = model()->data(index).toDouble();

            if (value > 0.0) {
                totalValue += value;
                validItems++;
            }
        }
        viewport()->update();
    }

    bool PieView::edit(const QModelIndex &index, EditTrigger trigger, QEvent *event)
    {
        if (index.column() == 0)
            return QAbstractItemView::edit(index, trigger, event);
        else
            return false;
    }

    /*
        Returns the item that covers the coordinate given in the view.
    */

    QModelIndex PieView::indexAt(const QPoint &point) const
    {
        if (validItems == 0)
            return QModelIndex();

        // Transform the view coordinates into contents widget coordinates.
        int wx = point.x() + horizontalScrollBar()->value();
        int wy = point.y() + verticalScrollBar()->value();

        if (wx < totalSize) {
            double cx = wx - totalSize / 2;
            double cy = totalSize / 2 - wy; // positive cy for items above the center

            // Determine the distance from the center point of the pie chart.
            double d = std::sqrt(std::pow(cx, 2) + std::pow(cy, 2));

            if (d == 0 || d > pieSize / 2)
                return QModelIndex();

            // Determine the angle of the point.
            double angle = (180 / M_PI) * std::acos(cx / d);
            if (cy < 0)
                angle = 360 - angle;

            // Find the relevant slice of the pie.
            double startAngle = 0.0;

            for (int row = 0; row < model()->rowCount(rootIndex()); ++row) {

                QModelIndex index = model()->index(row, 1, rootIndex());
                double value = model()->data(index).toDouble();

                if (value > 0.0) {
                    double sliceAngle = 360 * value / totalValue;

                    if (angle >= startAngle && angle < (startAngle + sliceAngle))
                        return model()->index(row, 1, rootIndex());

                    startAngle += sliceAngle;
                }
            }
        } else {
            double itemHeight = QFontMetrics(viewOptions().font).height();
            int listItem = int((wy - margin) / itemHeight);
            int validRow = 0;

            for (int row = 0; row < model()->rowCount(rootIndex()); ++row) {

                QModelIndex index = model()->index(row, 1, rootIndex());
                if (model()->data(index).toDouble() > 0.0) {

                    if (listItem == validRow)
                        return model()->index(row, 0, rootIndex());

                    // Update the list index that corresponds to the next valid row.
                    ++validRow;
                }
            }
        }

        return QModelIndex();
    }

    bool PieView::isIndexHidden(const QModelIndex & /*index*/) const
    {
        return false;
    }

    /*
        Returns the rectangle of the item at position \a index in the
        model. The rectangle is in contents coordinates.
    */

    QRect PieView::itemRect(const QModelIndex &index) const
    {
        if (!index.isValid())
            return QRect();

        // Check whether the index's row is in the list of rows represented
        // by slices.
        QModelIndex valueIndex;

        if (index.column() != 1)
            valueIndex = model()->index(index.row(), 1, rootIndex());
        else
            valueIndex = index;

        if (model()->data(valueIndex).toDouble() <= 0.0)
            return QRect();

        int listItem = 0;
        for (int row = index.row()-1; row >= 0; --row) {
            if (model()->data(model()->index(row, 1, rootIndex())).toDouble() > 0.0)
                listItem++;
        }

        double itemHeight;

        switch (index.column()) {
        case 0:
            itemHeight = QFontMetrics(viewOptions().font).height();

            return QRect(totalSize,
                         int(margin + listItem*itemHeight),
                         totalSize - margin, int(itemHeight));
        case 1:
            return viewport()->rect();
        }
        return QRect();
    }

    QRegion PieView::itemRegion(const QModelIndex &index) const
    {
        if (!index.isValid())
            return QRegion();

        if (index.column() != 1)
            return itemRect(index);

        if (model()->data(index).toDouble() <= 0.0)
            return QRegion();

        double startAngle = 0.0;
        for (int row = 0; row < model()->rowCount(rootIndex()); ++row) {

            QModelIndex sliceIndex = model()->index(row, 1, rootIndex());
            double value = model()->data(sliceIndex).toDouble();

            if (value > 0.0) {
                double angle = 360 * value / totalValue;

                if (sliceIndex == index) {
                    QPainterPath slicePath;
                    slicePath.moveTo(totalSize / 2, totalSize / 2);
                    slicePath.arcTo(margin, margin, margin+pieSize, margin+pieSize,
                                    startAngle, angle);
                    slicePath.closeSubpath();

                    return QRegion(slicePath.toFillPolygon().toPolygon());
                }

                startAngle += angle;
            }
        }

        return QRegion();
    }

    int PieView::horizontalOffset() const
    {
        return horizontalScrollBar()->value();
    }

    void PieView::mousePressEvent(QMouseEvent *event)
    {
        QAbstractItemView::mousePressEvent(event);
        origin = event->pos();
        if (!rubberBand)
            rubberBand = new QRubberBand(QRubberBand::Rectangle, viewport());
        rubberBand->setGeometry(QRect(origin, QSize()));
        rubberBand->show();
    }

    void PieView::mouseMoveEvent(QMouseEvent *event)
    {
        if (rubberBand)
            rubberBand->setGeometry(QRect(origin, event->pos()).normalized());
        QAbstractItemView::mouseMoveEvent(event);
    }

    void PieView::mouseReleaseEvent(QMouseEvent *event)
    {
        QAbstractItemView::mouseReleaseEvent(event);
        if (rubberBand)
            rubberBand->hide();
        viewport()->update();
    }

    QModelIndex PieView::moveCursor(QAbstractItemView::CursorAction cursorAction,
                                    Qt::KeyboardModifiers /*modifiers*/)
    {
        QModelIndex current = currentIndex();

        switch (cursorAction) {
            case MoveLeft:
            case MoveUp:
                if (current.row() > 0)
                    current = model()->index(current.row() - 1, current.column(),
                                             rootIndex());
                else
                    current = model()->index(0, current.column(), rootIndex());
                break;
            case MoveRight:
            case MoveDown:
                if (current.row() < rows(current) - 1)
                    current = model()->index(current.row() + 1, current.column(),
                                             rootIndex());
                else
                    current = model()->index(rows(current) - 1, current.column(),
                                             rootIndex());
                break;
            default:
                break;
        }

        viewport()->update();
        return current;
    }

    void PieView::paintEvent(QPaintEvent *event)
    {
        QItemSelectionModel *selections = selectionModel();
        QStyleOptionViewItem option = viewOptions();

        QBrush background = option.palette.base();
        QPen foreground(option.palette.color(QPalette::WindowText));

        QPainter painter(viewport());
        painter.setRenderHint(QPainter::Antialiasing);

        painter.fillRect(event->rect(), background);
        painter.setPen(foreground);

        // Viewport rectangles
        QRect pieRect = QRect(margin, margin, pieSize, pieSize);

        if (validItems <= 0)
            return;

        painter.save();
        painter.translate(pieRect.x() - horizontalScrollBar()->value(),
                          pieRect.y() - verticalScrollBar()->value());
        painter.drawEllipse(0, 0, pieSize, pieSize);
        double startAngle = 0.0;
        int row;

        for (row = 0; row < model()->rowCount(rootIndex()); ++row) {
            QModelIndex index = model()->index(row, 1, rootIndex());
            double value = model()->data(index).toDouble();

            if (value > 0.0) {
                double angle = 360*value/totalValue;

                QModelIndex colorIndex = model()->index(row, 0, rootIndex());
                QColor color = QColor(model()->data(colorIndex, Qt::DecorationRole).toString());

                if (currentIndex() == index)
                    painter.setBrush(QBrush(color, Qt::Dense4Pattern));
                else if (selections->isSelected(index))
                    painter.setBrush(QBrush(color, Qt::Dense3Pattern));
                else
                    painter.setBrush(QBrush(color));

                painter.drawPie(0, 0, pieSize, pieSize, int(startAngle*16), int(angle*16));

                startAngle += angle;
            }
        }
        painter.restore();

        int keyNumber = 0;

        for (row = 0; row < model()->rowCount(rootIndex()); ++row) {
            QModelIndex index = model()->index(row, 1, rootIndex());
            double value = model()->data(index).toDouble();

            if (value > 0.0) {
                QModelIndex labelIndex = model()->index(row, 0, rootIndex());

                QStyleOptionViewItem option = viewOptions();
                option.rect = visualRect(labelIndex);
                if (selections->isSelected(labelIndex))
                    option.state |= QStyle::State_Selected;
                if (currentIndex() == labelIndex)
                    option.state |= QStyle::State_HasFocus;
                itemDelegate()->paint(&painter, option, labelIndex);

                ++keyNumber;
            }
        }
    }

    void PieView::resizeEvent(QResizeEvent * /* event */)
    {
        updateGeometries();
    }

    int PieView::rows(const QModelIndex &index) const
    {
        return model()->rowCount(model()->parent(index));
    }

    void PieView::rowsInserted(const QModelIndex &parent, int start, int end)
    {
        for (int row = start; row <= end; ++row) {
            QModelIndex index = model()->index(row, 1, rootIndex());
            double value = model()->data(index).toDouble();

            if (value > 0.0) {
                totalValue += value;
                ++validItems;
            }
        }

        QAbstractItemView::rowsInserted(parent, start, end);
    }

    void PieView::rowsAboutToBeRemoved(const QModelIndex &parent, int start, int end)
    {
        for (int row = start; row <= end; ++row) {
            QModelIndex index = model()->index(row, 1, rootIndex());
            double value = model()->data(index).toDouble();
            if (value > 0.0) {
                totalValue -= value;
                --validItems;
            }
        }

        QAbstractItemView::rowsAboutToBeRemoved(parent, start, end);
    }

    void PieView::scrollContentsBy(int dx, int dy)
    {
        viewport()->scroll(dx, dy);
    }

    void PieView::scrollTo(const QModelIndex &index, ScrollHint)
    {
        QRect area = viewport()->rect();
        QRect rect = visualRect(index);

        if (rect.left() < area.left()) {
            horizontalScrollBar()->setValue(
                horizontalScrollBar()->value() + rect.left() - area.left());
        } else if (rect.right() > area.right()) {
            horizontalScrollBar()->setValue(
                horizontalScrollBar()->value() + qMin(
                    rect.right() - area.right(), rect.left() - area.left()));
        }

        if (rect.top() < area.top()) {
            verticalScrollBar()->setValue(
                verticalScrollBar()->value() + rect.top() - area.top());
        } else if (rect.bottom() > area.bottom()) {
            verticalScrollBar()->setValue(
                verticalScrollBar()->value() + qMin(
                    rect.bottom() - area.bottom(), rect.top() - area.top()));
        }

        update();
    }

    /*
        Find the indices corresponding to the extent of the selection.
    */

    void PieView::setSelection(const QRect &rect, QItemSelectionModel::SelectionFlags command)
    {
        // Use content widget coordinates because we will use the itemRegion()
        // function to check for intersections.

        QRect contentsRect = rect.translated(
                                horizontalScrollBar()->value(),
                                verticalScrollBar()->value()).normalized();

        int rows = model()->rowCount(rootIndex());
        int columns = model()->columnCount(rootIndex());
        QModelIndexList indexes;

        for (int row = 0; row < rows; ++row) {
            for (int column = 0; column < columns; ++column) {
                QModelIndex index = model()->index(row, column, rootIndex());
                QRegion region = itemRegion(index);
                if (region.intersects(contentsRect))
                    indexes.append(index);
            }
        }

        if (indexes.size() > 0) {
            int firstRow = indexes[0].row();
            int lastRow = indexes[0].row();
            int firstColumn = indexes[0].column();
            int lastColumn = indexes[0].column();

            for (int i = 1; i < indexes.size(); ++i) {
                firstRow = qMin(firstRow, indexes[i].row());
                lastRow = qMax(lastRow, indexes[i].row());
                firstColumn = qMin(firstColumn, indexes[i].column());
                lastColumn = qMax(lastColumn, indexes[i].column());
            }

            QItemSelection selection(
                model()->index(firstRow, firstColumn, rootIndex()),
                model()->index(lastRow, lastColumn, rootIndex()));
            selectionModel()->select(selection, command);
        } else {
            QModelIndex noIndex;
            QItemSelection selection(noIndex, noIndex);
            selectionModel()->select(selection, command);
        }

        update();
    }

    void PieView::updateGeometries()
    {
        horizontalScrollBar()->setPageStep(viewport()->width());
        horizontalScrollBar()->setRange(0, qMax(0, 2*totalSize - viewport()->width()));
        verticalScrollBar()->setPageStep(viewport()->height());
        verticalScrollBar()->setRange(0, qMax(0, totalSize - viewport()->height()));
    }

    int PieView::verticalOffset() const
    {
        return verticalScrollBar()->value();
    }

    /*
        Returns the position of the item in viewport coordinates.
    */

    QRect PieView::visualRect(const QModelIndex &index) const
    {
        QRect rect = itemRect(index);
        if (!rect.isValid())
            return rect;

        return QRect(rect.left() - horizontalScrollBar()->value(),
                     rect.top() - verticalScrollBar()->value(),
                     rect.width(), rect.height());
    }

    /*
        Returns a region corresponding to the selection in viewport coordinates.
    */

    QRegion PieView::visualRegionForSelection(const QItemSelection &selection) const
    {
        int ranges = selection.count();

        if (ranges == 0)
            return QRect();

        QRegion region;
        for (int i = 0; i < ranges; ++i) {
            QItemSelectionRange range = selection.at(i);
            for (int row = range.top(); row <= range.bottom(); ++row) {
                for (int col = range.left(); col <= range.right(); ++col) {
                    QModelIndex index = model()->index(row, col, rootIndex());
                    region += visualRect(index);
                }
            }
        }
        return region;
    }