Qt 5.9 | Qt OpenGL | 2D Painting Example | helper.cpp Example File

Qt 5.9.9 Reference Documentation

# helper.cpp Example File

2dpainting/helper.cpp

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      #include "helper.h"

      #include <QPainter>
      #include <QPaintEvent>
      #include <QWidget>

      Helper::Helper()
      {
          QLinearGradient gradient(QPointF(50, -20), QPointF(80, 20));
          gradient.setColorAt(0.0, Qt::white);
          gradient.setColorAt(1.0, QColor(0xa6, 0xce, 0x39));

          background = QBrush(QColor(64, 32, 64));
          circleBrush = QBrush(gradient);
          circlePen = QPen(Qt::black);
          circlePen.setWidth(1);
          textPen = QPen(Qt::white);
          textFont.setPixelSize(50);
      }

      void Helper::paint(QPainter *painter, QPaintEvent *event, int elapsed)
      {
          painter->fillRect(event->rect(), background);
          painter->translate(100, 100);

          painter->save();
          painter->setBrush(circleBrush);
          painter->setPen(circlePen);
          painter->rotate(elapsed * 0.030);

          qreal r = elapsed / 1000.0;
          int n = 30;
          for (int i = 0; i < n; ++i) {
              painter->rotate(30);
              qreal factor = (i + r) / n;
              qreal radius = 0 + 120.0 * factor;
              qreal circleRadius = 1 + factor * 20;
              painter->drawEllipse(QRectF(radius, -circleRadius,
                                          circleRadius * 2, circleRadius * 2));
          }
          painter->restore();

          painter->setPen(textPen);
          painter->setFont(textFont);
          painter->drawText(QRect(-50, -50, 100, 100), Qt::AlignCenter, QStringLiteral("Qt"));
      }