Transformations Example | Qt Widgets 5.13.0

Qt 5.13 | Qt Widgets | Transformations Example

Qt 5.13.0 Reference Documentation

# Transformations Example

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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:
                  ;
              }
          }
      }