pieview.cpp Example File

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 #include "pieview.h"

 #include <QtWidgets>

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

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

     if (!roles.contains(Qt::DisplayRole))
         return;

     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, Qt::DisplayRole).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 = qRadiansToDegrees(std::atan2(cy, cx));
         if (angle < 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++;
     }

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

         return QRect(totalSize,
                      qRound(margin + listItem * itemHeight),
                      totalSize - margin, qRound(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.at(0).row();
         int lastRow = firstRow;
         int firstColumn = indexes.at(0).column();
         int lastColumn = firstColumn;

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