Qt 5.11 | Qt Widgets | Drag and Drop Robot Example | coloritem.cpp Example File

Qt 5.11.3 Reference Documentation

# coloritem.cpp Example File

graphicsview/dragdroprobot/coloritem.cpp

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      #include <QtWidgets>

      #include "coloritem.h"

      ColorItem::ColorItem()
          : color(QRandomGenerator::global()->bounded(256), QRandomGenerator::global()->bounded(256), QRandomGenerator::global()->bounded(256))
      {
          setToolTip(QString("QColor(%1, %2, %3)\n%4")
                    .arg(color.red()).arg(color.green()).arg(color.blue())
                    .arg("Click and drag this color onto the robot!"));
          setCursor(Qt::OpenHandCursor);
          setAcceptedMouseButtons(Qt::LeftButton);
      }

      QRectF ColorItem::boundingRect() const
      {
          return QRectF(-15.5, -15.5, 34, 34);
      }

      void ColorItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
      {
          Q_UNUSED(option);
          Q_UNUSED(widget);
          painter->setPen(Qt::NoPen);
          painter->setBrush(Qt::darkGray);
          painter->drawEllipse(-12, -12, 30, 30);
          painter->setPen(QPen(Qt::black, 1));
          painter->setBrush(QBrush(color));
          painter->drawEllipse(-15, -15, 30, 30);
      }

      void ColorItem::mousePressEvent(QGraphicsSceneMouseEvent *)
      {
          setCursor(Qt::ClosedHandCursor);
      }

      void ColorItem::mouseMoveEvent(QGraphicsSceneMouseEvent *event)
      {
          if (QLineF(event->screenPos(), event->buttonDownScreenPos(Qt::LeftButton))
              .length() < QApplication::startDragDistance()) {
              return;
          }

          QDrag *drag = new QDrag(event->widget());
          QMimeData *mime = new QMimeData;
          drag->setMimeData(mime);

          static int n = 0;
          if (n++ > 2 && QRandomGenerator::global()->bounded(3) == 0) {
              QImage image(":/images/head.png");
              mime->setImageData(image);

              drag->setPixmap(QPixmap::fromImage(image).scaled(30, 40));
              drag->setHotSpot(QPoint(15, 30));
          } else {
              mime->setColorData(color);
              mime->setText(QString("#%1%2%3")
                            .arg(color.red(), 2, 16, QLatin1Char('0'))
                            .arg(color.green(), 2, 16, QLatin1Char('0'))
                            .arg(color.blue(), 2, 16, QLatin1Char('0')));

              QPixmap pixmap(34, 34);
              pixmap.fill(Qt::white);

              QPainter painter(&pixmap);
              painter.translate(15, 15);
              painter.setRenderHint(QPainter::Antialiasing);
              paint(&painter, 0, 0);
              painter.end();

              pixmap.setMask(pixmap.createHeuristicMask());

              drag->setPixmap(pixmap);
              drag->setHotSpot(QPoint(15, 20));
          }

          drag->exec();
          setCursor(Qt::OpenHandCursor);
      }

      void ColorItem::mouseReleaseEvent(QGraphicsSceneMouseEvent *)
      {
          setCursor(Qt::OpenHandCursor);
      }