qt5base-lts/examples/widgets/animation/easing/animation.h

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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