flip static method

Offset flip(Size view, FPortalChildBox child, FPortalBox portal)

Flips the portal to the opposite side of the child if it does not cause the portal to overflow out of the viewport. Otherwise shifts the portal along the child's edge.

Implementation

static Offset flip(Size view, FPortalChildBox child, FPortalBox portal) {
  var anchor = none(view, child, portal).translate(child.offset.dx, child.offset.dy);

  final viewBox = Offset.zero & view;
  final portalBox = anchor & portal.size;

  switch ((viewBox, portalBox)) {
    case _ when portalBox.left < viewBox.left:
      final flipped = _flip(child, portal, x: true);
      if ((flipped & portal.size).right <= viewBox.right) {
        anchor = flipped;
      }

    case _ when viewBox.right < portalBox.right:
      final flipped = _flip(child, portal, x: true);
      if (viewBox.left <= (flipped & portal.size).left) {
        anchor = flipped;
      }
  }

  switch ((viewBox, portalBox)) {
    case _ when portalBox.top < viewBox.top:
      final flipped = _flip(child, portal, x: false);
      if ((flipped & portal.size).bottom <= viewBox.bottom) {
        anchor = flipped;
      }

    case _ when viewBox.bottom < portalBox.bottom:
      final flipped = _flip(child, portal, x: false);
      if (viewBox.top <= (flipped & portal.size).top) {
        anchor = flipped;
      }
  }

  final adjustedAnchor = _along(anchor, viewBox, anchor & portal.size);
  return adjustedAnchor.translate(-child.offset.dx, -child.offset.dy);
}