Qt 5.9 | Qt Core | Mandelbrot Example | mandelbrotwidget.cpp Example File

Qt 5.9.9 Reference Documentation

# mandelbrotwidget.cpp Example File

threads/mandelbrot/mandelbrotwidget.cpp

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      #include <QPainter>
      #include <QKeyEvent>

      #include <math.h>

      #include "mandelbrotwidget.h"

      const double DefaultCenterX = -0.637011f;
      const double DefaultCenterY = -0.0395159f;
      const double DefaultScale = 0.00403897f;

      const double ZoomInFactor = 0.8f;
      const double ZoomOutFactor = 1 / ZoomInFactor;
      const int ScrollStep = 20;

      MandelbrotWidget::MandelbrotWidget(QWidget *parent)
          : QWidget(parent)
      {
          centerX = DefaultCenterX;
          centerY = DefaultCenterY;
          pixmapScale = DefaultScale;
          curScale = DefaultScale;

          connect(&thread, SIGNAL(renderedImage(QImage,double)), this, SLOT(updatePixmap(QImage,double)));

          setWindowTitle(tr("Mandelbrot"));
      #ifndef QT_NO_CURSOR
          setCursor(Qt::CrossCursor);
      #endif
          resize(550, 400);

      }

      void MandelbrotWidget::paintEvent(QPaintEvent * /* event */)
      {
          QPainter painter(this);
          painter.fillRect(rect(), Qt::black);

          if (pixmap.isNull()) {
              painter.setPen(Qt::white);
              painter.drawText(rect(), Qt::AlignCenter, tr("Rendering initial image, please wait..."));
              return;
          }

          if (curScale == pixmapScale) {
              painter.drawPixmap(pixmapOffset, pixmap);
          } else {
              double scaleFactor = pixmapScale / curScale;
              int newWidth = int(pixmap.width() * scaleFactor);
              int newHeight = int(pixmap.height() * scaleFactor);
              int newX = pixmapOffset.x() + (pixmap.width() - newWidth) / 2;
              int newY = pixmapOffset.y() + (pixmap.height() - newHeight) / 2;

              painter.save();
              painter.translate(newX, newY);
              painter.scale(scaleFactor, scaleFactor);
              QRectF exposed = painter.matrix().inverted().mapRect(rect()).adjusted(-1, -1, 1, 1);
              painter.drawPixmap(exposed, pixmap, exposed);
              painter.restore();
          }

          QString text = tr("Use mouse wheel or the '+' and '-' keys to zoom. "
                            "Press and hold left mouse button to scroll.");
          QFontMetrics metrics = painter.fontMetrics();
          int textWidth = metrics.width(text);

          painter.setPen(Qt::NoPen);
          painter.setBrush(QColor(0, 0, 0, 127));
          painter.drawRect((width() - textWidth) / 2 - 5, 0, textWidth + 10, metrics.lineSpacing() + 5);
          painter.setPen(Qt::white);
          painter.drawText((width() - textWidth) / 2, metrics.leading() + metrics.ascent(), text);
      }

      void MandelbrotWidget::resizeEvent(QResizeEvent * /* event */)
      {
          thread.render(centerX, centerY, curScale, size());
      }

      void MandelbrotWidget::keyPressEvent(QKeyEvent *event)
      {
          switch (event->key()) {
          case Qt::Key_Plus:
              zoom(ZoomInFactor);
              break;
          case Qt::Key_Minus:
              zoom(ZoomOutFactor);
              break;
          case Qt::Key_Left:
              scroll(-ScrollStep, 0);
              break;
          case Qt::Key_Right:
              scroll(+ScrollStep, 0);
              break;
          case Qt::Key_Down:
              scroll(0, -ScrollStep);
              break;
          case Qt::Key_Up:
              scroll(0, +ScrollStep);
              break;
          default:
              QWidget::keyPressEvent(event);
          }
      }

      #if QT_CONFIG(wheelevent)
      void MandelbrotWidget::wheelEvent(QWheelEvent *event)
      {
          int numDegrees = event->delta() / 8;
          double numSteps = numDegrees / 15.0f;
          zoom(pow(ZoomInFactor, numSteps));
      }
      #endif

      void MandelbrotWidget::mousePressEvent(QMouseEvent *event)
      {
          if (event->button() == Qt::LeftButton)
              lastDragPos = event->pos();
      }

      void MandelbrotWidget::mouseMoveEvent(QMouseEvent *event)
      {
          if (event->buttons() & Qt::LeftButton) {
              pixmapOffset += event->pos() - lastDragPos;
              lastDragPos = event->pos();
              update();
          }
      }

      void MandelbrotWidget::mouseReleaseEvent(QMouseEvent *event)
      {
          if (event->button() == Qt::LeftButton) {
              pixmapOffset += event->pos() - lastDragPos;
              lastDragPos = QPoint();

              int deltaX = (width() - pixmap.width()) / 2 - pixmapOffset.x();
              int deltaY = (height() - pixmap.height()) / 2 - pixmapOffset.y();
              scroll(deltaX, deltaY);
          }
      }

      void MandelbrotWidget::updatePixmap(const QImage &image, double scaleFactor)
      {
          if (!lastDragPos.isNull())
              return;

          pixmap = QPixmap::fromImage(image);
          pixmapOffset = QPoint();
          lastDragPos = QPoint();
          pixmapScale = scaleFactor;
          update();
      }

      void MandelbrotWidget::zoom(double zoomFactor)
      {
          curScale *= zoomFactor;
          update();
          thread.render(centerX, centerY, curScale, size());
      }

      void MandelbrotWidget::scroll(int deltaX, int deltaY)
      {
          centerX += deltaX * curScale;
          centerY += deltaY * curScale;
          update();
          thread.render(centerX, centerY, curScale, size());
      }