What the use of `_makeRoundTrip` function

[izayl]

  /// Causes the controller to scroll one round.
  Future<void> _makeRoundTrip() async {
    // Reset the controller, then accelerate, move linearly and decelerate.
    _controller.jumpTo(_startPosition);
    if (!_running) return;

    await _accelerate();
    if (!_running) return;

    await _moveLinearly();
    if (!_running) return;

    await _decelerate();
    if (!_running) return;

    await Future.delayed(widget.pauseAfterRound);
  }

I'm confused to this _makeRoundTrip function, why there are three phase: accelerate/ linear/ decelerate?

my version for implement auto scroll is just use a infinite loop:

  @override
  void initState() {
    super.initState();

    _scrollController = ScrollController(initialScrollOffset: 0);
    _initState();

    Future.delayed(Duration(microseconds: 5000), () {
      Future.doWhile(() async {
        await _scroll();
        return true;
      });
    });
  }

  Future<void> _scroll() async {
    await _scrollController.animateTo(_scrollController.offset + (delta * 4),
        curve: Curves.linear, duration: Duration(seconds: 1));
  }

But this loop will cost more CPU load.

[MarcelGarus]

This function scroll only one round trip. If you provide an acceleration or deceleration curve and duration, you'll see that the marquee slowly starts to scroll, then scrolls linearly and then, finally stops. Example:

Marquee(
  text: 'Some sample text that takes some space.',
  pauseAfterRound: Duration(seconds: 1),
  accelerationDuration: Duration(seconds: 1),
  accelerationCurve: Curves.linear,
  decelerationDuration: Duration(milliseconds: 500),
  decelerationCurve: Curves.easeOut,
)