animation.h Example File

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  #ifndef ANIMATION_H
  #define ANIMATION_H

  #include <QtWidgets>

  #include <QtCore/qpropertyanimation.h>

  class Animation : public QPropertyAnimation {
  public:
      enum PathType {
          LinearPath,
          CirclePath,
          NPathTypes
      };
      Animation(QObject *target, const QByteArray &prop)
          : QPropertyAnimation(target, prop)
      {
          setPathType(LinearPath);
      }

      void setPathType(PathType pathType)
      {
          if (pathType >= NPathTypes)
              qWarning("Unknown pathType %d", pathType);

          m_pathType = pathType;
          m_path = QPainterPath();
      }

      void updateCurrentTime(int currentTime) override
      {
          if (m_pathType == CirclePath) {
              if (m_path.isEmpty()) {
                  QPointF to = endValue().toPointF();
                  QPointF from = startValue().toPointF();
                  m_path.moveTo(from);
                  m_path.addEllipse(QRectF(from, to));
              }
              int dura = duration();
              const qreal progress = ((dura == 0) ? 1 : ((((currentTime - 1) % dura) + 1) / qreal(dura)));

              qreal easedProgress = easingCurve().valueForProgress(progress);
              if (easedProgress > 1.0) {
                  easedProgress -= 1.0;
              } else if (easedProgress < 0) {
                  easedProgress += 1.0;
              }
              QPointF pt = m_path.pointAtPercent(easedProgress);
              updateCurrentValue(pt);
              emit valueChanged(pt);
          } else {
              QPropertyAnimation::updateCurrentTime(currentTime);
          }
      }

      QPainterPath m_path;
      PathType m_pathType;
  };

  #endif // ANIMATION_H