pixeldelegate.cpp Example File

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 #include <QtWidgets>

 #include "pixeldelegate.h"

 PixelDelegate::PixelDelegate(QObject *parent)
     : QAbstractItemDelegate(parent)
 {
     pixelSize = 12;
 }

 void PixelDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option,
                           const QModelIndex &index) const
 {
     if (option.state & QStyle::State_Selected)
         painter->fillRect(option.rect, option.palette.highlight());

     int size = qMin(option.rect.width(), option.rect.height());
     int brightness = index.model()->data(index, Qt::DisplayRole).toInt();
     double radius = (size/2.0) - (brightness/255.0 * size/2.0);
     if (radius == 0.0)
         return;

     painter->save();
     painter->setRenderHint(QPainter::Antialiasing, true);
     painter->setPen(Qt::NoPen);
     if (option.state & QStyle::State_Selected)
         painter->setBrush(option.palette.highlightedText());
     else
         painter->setBrush(option.palette.text());

     painter->drawEllipse(QRectF(option.rect.x() + option.rect.width()/2 - radius,
                                 option.rect.y() + option.rect.height()/2 - radius,
                                 2*radius, 2*radius));
     painter->restore();
 }

 QSize PixelDelegate::sizeHint(const QStyleOptionViewItem & /* option */,
                               const QModelIndex & /* index */) const
 {
     return QSize(pixelSize, pixelSize);
 }

 void PixelDelegate::setPixelSize(int size)
 {
     pixelSize = size;
 }