How to set the duration of a QVariantAnimation constant to different values?

[Kattia]

How to get a constant animation duration time, independent of how small/bigger the frame size is?

For example, when startSize is 900x900, the animation duration time should be the same than when the startSize be 100x100

void ThumbnailFrame::resetSize()
{
    QVariantAnimation* ani = new QVariantAnimation;

    QSize startSize = thumbnailFrame->size();
    QSize endSize(p_ui->displayWidth->text().toInt(),
        p_ui->displayHeight->text().toInt());

    qreal distance = qSqrt(qPow(startSize.width() - endSize.width(), 2) 
        + qPow(startSize.height() - endSize.height(), 2));
    int duration = static_cast<int>(distance / 2); // factor

    ani->setEasingCurve(QEasingCurve::Type::Linear);
    ani->setDuration(duration);
    ani->setStartValue(startSize);
    ani->setEndValue(endSize);

    connect(ani, &QVariantAnimation::valueChanged, thumbnailFrame,
        [=](const QVariant& value)
    {
        thumbnailFrame->setFixedSize(value.toSize());
    });

    ani->start(QAbstractAnimation::DeleteWhenStopped);
}

I tried

qreal distance = qSqrt(qPow(startSize.width() - endSize.width(), 2) 
        + qPow(startSize.height() - endSize.height(), 2));
    int duration = static_cast<int>(distance / 2); // factor

But it aint resulting in a constant duration speed independent of the frame start/end size

[Kattia]

@Pl45m4 yes im a bit confused, but what im trying is to make the animation have the same duration independent of the size

[Pl45m4]

Hi @Kattia ,

I think you're mixing two approaches.

How to get a constant animation duration time, independent of how small/bigger the frame size is?

Here you are asking for "constant time", independent of covered distance, which needs to result in variable speeds.

But it aint resulting in a constant duration speed independent of the frame start/end size

and here you are saying, that you expect the above approach to have constant speed, no matter if you animate from 900x900 or 100x100 to whatever size.

How should this work?! :)
You can't drive 1h with 100km/h twice and expect to cover 100km in the first and 500km in the second run :))

It's either... or...
Either you set a fixed duration and let the QVariantAnimation calculate the step-size from start to end ("speed").
Or you calculate the step-size ("speed") on your own before and set the resulting duration time.

[Kattia]

@Pl45m4 yes im a bit confused, but what im trying is to make the animation have the same duration independent of the size

[Pl45m4]

@Kattia said in How to set the duration of a QVariantAnimation constant to different values?:

ani->setDuration(duration);

If you set this to the time you need, it should be enough.
QVariantAnimation transforms start to end using the curve function given here

ani->setEasingCurve(QEasingCurve::Type::Linear);

in a constant time interval.

[Kattia]

Thankyou! you're correct i was testing it wrong, thats why i was getting a different animation time, sorry my bad!