renderarea.cpp Example File

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  #include "renderarea.h"

  #include <QPainter>
  #include <QPaintEvent>

  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:
              ;
          }
      }
  }