As for the timer this is where I set it up:

@void CircularList::startSliding(Direction direction)
{
// Immediately mark as animation flowing. Do nothing if an animation is
// currently flowing.
if (isCurrentlyAnimated)
return;
isCurrentlyAnimated = true;

// ...

// Start the timer to proceed with the animation.
currentDirection = direction;
timestampStarted = QDateTime::currentMSecsSinceEpoch();
currentTimerId = startTimer(REFRESH_PERIOD);

for (int i = 0; i < fullList.size(); i++) {
startPositions.append(fullList[i]->pos());
}
}@

The only interesting thing is startTimer I suppose. I tried many refresh rate values to see the difference. This function is invoked when there is a pressEvent.
When the release is called, I simply stop the timer.

@void CircularList::stopSliding()
{
killTimer(currentTimerId);
isCurrentlyAnimated = false;
startPositions.clear();
}@

Any idea why I have those delays? My code is almost all here. Is there any way to check if the delay is caused by the CPU being busy doing something?
Thanks!

Yes, this is my timerEvent method implementation:

@void CircularList::timerEvent(QTimerEvent* event)
{
Q_UNUSED(event);

// I have to compute position according to time.
QPointF pos;
qint64 currentTimestamp = QDateTime::currentMSecsSinceEpoch();
for (int i = 0; i < fullList.size(); i++) {
computeNewPosition(fullList[i], currentTimestamp, startPositions[i], pos);
fullList[i]->setPos(pos);
}
}@

fullList is a QList of items, which are subclasses of QObject and QGraphicsPixmapItem. Those are the objects I want to move.
computeNewPosition is passed the item to move, the timestamp of the update event, the initial position and sets pos as the new position. I tried to do this some other ways but the same behavior is shown.

@inline
void CircularList::computeNewPosition(ListItem* item,
qint64& currentTimestamp,
QPointF& startPos,
QPointF& pos)
{
int direction = (currentDirection == DIRECTION_LEFT) ? -1 : 1;
qint64 elapsedMs = currentTimestamp - timestampStarted;
qreal shift = directionCRUISING_SPEEDelapsedMs/1000.0;
qreal xpos = startPos.x() + shift;
pos.setY(item->pos().y());
pos.setX(xpos);
}@

I start the timer when the user presses a button, then I ignore whatever repetition arrives and I kill the timer when the user releases.
I know this is not the most obvious way to do this, but it was only the last attempt.

Is it normal that there are such irregular calls of the timerEvent method? Can I setPos without triggering an update?
Thanks!