scrollToVisible method

void scrollToVisible(Rect rect, { AnimationController? animation, })

Scrolls this controller until the scrollOffset is such that the specified rect is fully visible in the viewport.

The coordinates of rect are in the coordinate space of the viewport (the same coordinate space as scrollOffset). So if you call this with Rect.zero, this will scroll to a scroll offset of Offset.zero.

If the animation argument is non-null, the scroll offset will be animated to its destination value. Otherwise, the scroll offset will jump to its destination.

Implementation

void scrollToVisible(Rect rect, {AnimationController? animation}) {
  final Rect viewport = scrollOffset & _viewportSize;

  double deltaX = 0;
  final double leftDisplacement = rect.left - viewport.left;
  final double rightDisplacement = rect.right - viewport.right;
  if (leftDisplacement < 0 && rightDisplacement < 0) {
    // The area lies to the left of our viewport bounds.
    deltaX = max(leftDisplacement, rightDisplacement);
  } else if (leftDisplacement > 0 && rightDisplacement > 0) {
    // The area lies to the right of our viewport bounds.
    deltaX = min(leftDisplacement, rightDisplacement);
  }

  double deltaY = 0;
  final double topDisplacement = rect.top - viewport.top;
  final double bottomDisplacement = rect.bottom - viewport.bottom;
  if (topDisplacement < 0 && bottomDisplacement < 0) {
    // The area lies above our viewport bounds.
    deltaY = max(topDisplacement, bottomDisplacement);
  } else if (topDisplacement > 0 && bottomDisplacement > 0) {
    // The area lies below our viewport bounds.
    deltaY = min(topDisplacement, bottomDisplacement);
  }

  if (deltaX != 0 || deltaY != 0) {
    final Offset target = Offset(
      min(max(scrollOffset.dx + deltaX, 0), max(_viewSize.width - viewport.width, 0)),
      min(max(scrollOffset.dy + deltaY, 0), max(_viewSize.height - viewport.height, 0)),
    );
    if (animation == null) {
      scrollOffset = target;
    } else {
      _animateTo(target, animation);
    }
  }
}