chasewidget.cpp Example File

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  #include "chasewidget.h"

  #include <QtCore/QPoint>

  #include <QtWidgets/QApplication>
  #include <QtGui/QHideEvent>
  #include <QtGui/QPainter>
  #include <QtGui/QPaintEvent>
  #include <QtGui/QShowEvent>

  ChaseWidget::ChaseWidget(QWidget *parent, QPixmap pixmap, bool pixmapEnabled)
      : QWidget(parent)
      , m_segment(0)
      , m_delay(100)
      , m_step(40)
      , m_timerId(-1)
      , m_animated(false)
      , m_pixmap(pixmap)
      , m_pixmapEnabled(pixmapEnabled)
  {
  }

  void ChaseWidget::setAnimated(bool value)
  {
      if (m_animated == value)
          return;
      m_animated = value;
      if (m_timerId != -1) {
          killTimer(m_timerId);
          m_timerId = -1;
      }
      if (m_animated) {
          m_segment = 0;
          m_timerId = startTimer(m_delay);
      }
      update();
  }

  void ChaseWidget::paintEvent(QPaintEvent *event)
  {
      Q_UNUSED(event);
      QPainter p(this);
      if (m_pixmapEnabled && !m_pixmap.isNull()) {
          p.drawPixmap(0, 0, m_pixmap);
          return;
      }

      const int extent = qMin(width() - 8, height() - 8);
      const int displ = extent / 4;
      const int ext = extent / 4 - 1;

      p.setRenderHint(QPainter::Antialiasing, true);

      if (m_animated)
          p.setPen(Qt::gray);
      else
          p.setPen(QPen(palette().dark().color()));

      p.translate(width() / 2, height() / 2); // center

      for (int segment = 0; segment < segmentCount(); ++segment) {
          p.rotate(QApplication::isRightToLeft() ? m_step : -m_step);
          if (m_animated)
              p.setBrush(colorForSegment(segment));
          else
              p.setBrush(palette().background());
          p.drawEllipse(QRect(displ, -ext / 2, ext, ext));
      }
  }

  QSize ChaseWidget::sizeHint() const
  {
      return QSize(32, 32);
  }

  void ChaseWidget::timerEvent(QTimerEvent *event)
  {
      if (event->timerId() == m_timerId) {
          ++m_segment;
          update();
      }
      QWidget::timerEvent(event);
  }

  QColor ChaseWidget::colorForSegment(int seg) const
  {
      int index = ((seg + m_segment) % segmentCount());
      int comp = qMax(0, 255 - (index * (255 / segmentCount())));
      return QColor(comp, comp, comp, 255);
  }

  int ChaseWidget::segmentCount() const
  {
      return 360 / m_step;
  }

  void ChaseWidget::setPixmapEnabled(bool enable)
  {
      m_pixmapEnabled = enable;
  }