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# renderarea.cpp Example File
painting/transformations/renderarea.cpp

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     #include <QtGui>

     #include "renderarea.h"

     RenderArea::RenderArea(QWidget *parent)
         : QWidget(parent)
     {
         QFont newFont = font();
         newFont.setPixelSize(12);
         setFont(newFont);

         QFontMetrics fontMetrics(newFont);
         xBoundingRect = fontMetrics.boundingRect(tr("x"));
         yBoundingRect = fontMetrics.boundingRect(tr("y"));
     }

     void RenderArea::setOperations(const QList<Operation> &operations)
     {
         this->operations = operations;
         update();
     }

     void RenderArea::setShape(const QPainterPath &shape)
     {
         this->shape = shape;
         update();
     }

     QSize RenderArea::minimumSizeHint() const
     {
         return QSize(182, 182);
     }

     QSize RenderArea::sizeHint() const
     {
         return QSize(232, 232);
     }

     void RenderArea::paintEvent(QPaintEvent *event)
     {
         QPainter painter(this);
         painter.setRenderHint(QPainter::Antialiasing);
         painter.fillRect(event->rect(), QBrush(Qt::white));

         painter.translate(66, 66);

         painter.save();
         transformPainter(painter);
         drawShape(painter);
         painter.restore();

         drawOutline(painter);

         transformPainter(painter);
         drawCoordinates(painter);
     }

     void RenderArea::drawCoordinates(QPainter &painter)
     {
         painter.setPen(Qt::red);

         painter.drawLine(0, 0, 50, 0);
         painter.drawLine(48, -2, 50, 0);
         painter.drawLine(48, 2, 50, 0);
         painter.drawText(60 - xBoundingRect.width() / 2,
                          0 + xBoundingRect.height() / 2, tr("x"));

         painter.drawLine(0, 0, 0, 50);
         painter.drawLine(-2, 48, 0, 50);
         painter.drawLine(2, 48, 0, 50);
         painter.drawText(0 - yBoundingRect.width() / 2,
                          60 + yBoundingRect.height() / 2, tr("y"));
     }

     void RenderArea::drawOutline(QPainter &painter)
     {
         painter.setPen(Qt::darkGreen);
         painter.setPen(Qt::DashLine);
         painter.setBrush(Qt::NoBrush);
         painter.drawRect(0, 0, 100, 100);
     }

     void RenderArea::drawShape(QPainter &painter)
     {
         painter.fillPath(shape, Qt::blue);
     }

     void RenderArea::transformPainter(QPainter &painter)
     {
         for (int i = 0; i < operations.size(); ++i) {
             switch (operations[i]) {
             case Translate:
                 painter.translate(50, 50);
                 break;
             case Scale:
                 painter.scale(0.75, 0.75);
                 break;
             case Rotate:
                 painter.rotate(60);
                 break;
             case NoTransformation:
             default:
                 ;
             }
         }
     }