update method

@override (ViewportScrollPane, Cmd?) update(Msg msg)

Updates the component state in response to a message.

Returns the updated component (often this) and an optional command.

Implementation

@override
(ViewportScrollPane, Cmd?) update(Msg msg) {
  if (msg is MouseMsg) {
    final local = _toLocal(msg);
    final candidates = _localCandidates(local);

    if (msg.button == MouseButton.left && _height > 0 && _maxOffset > 0) {
      switch (msg.action) {
        case MouseAction.press:
          if (candidates.any(_isOnBar)) {
            _dragging = true;
            _scrollToCandidateY(candidates);
            return (this, null);
          }
          break;
        case MouseAction.release:
          _dragging = false;
          return (this, null);
        case MouseAction.motion:
          if (_dragging) {
            _scrollToCandidateY(candidates);
            return (this, null);
          }
          break;
        default:
          break;
      }
    }

    // Fall through: let viewport handle clicks/selection, etc.
    final (vp, cmd) = viewport.update(local);
    viewport = vp;
    return (this, cmd);
  }

  final (vp, cmd) = viewport.update(msg);
  viewport = vp;
  return (this, cmd);
}