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pieview.cpp Example File
^{itemviews/chart/pieview.cpp}

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 #include <math.h>
 #include <QtGui>

 #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)
 {
     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 = pow(pow(cx, 2) + pow(cy, 2), 0.5);

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

         // Determine the angle of the point.
         double angle = (180 / M_PI) * 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) {

         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, this);
     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();
     QStyle::State state = option.state;

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

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

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

     // Viewport rectangles
     QRect pieRect = QRect(margin, margin, pieSize, pieSize);
     QPoint keyPoint = QPoint(totalSize - horizontalScrollBar()->value(),
                              margin - verticalScrollBar()->value());

     if (validItems > 0) {

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

 /*
     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;
 }