getOverlayPosition method

RelativeRect getOverlayPosition(BuildContext pContext, MenuAlign? pAlign, BoxConstraints pConstraints)

return overlay position based on different params such, constrains, alignment and screen size

Implementation

RelativeRect getOverlayPosition(
    BuildContext pContext, MenuAlign? pAlign, BoxConstraints pConstraints) {
  final dropdownBox = pContext.findRenderObject() as RenderBox;
  final overlayBox =
      Overlay.of(pContext).context.findRenderObject() as RenderBox;
  var popupSize = computePopupSize(dropdownBox, overlayBox, pConstraints);
  var lAlign = pAlign ?? MenuAlign.bottomCenter;

  final dropDownY =
      dropdownBox.localToGlobal(Offset.zero, ancestor: overlayBox).dy;
  final bottomHeight =
      overlayBox.size.height - dropDownY - dropdownBox.size.height;
  final topHeight = dropDownY;

  //get best orientation
  if (lAlign.isDown && popupSize.height > bottomHeight) {
    //check if there enough space in opposite direction,
    if (popupSize.height <= topHeight) {
      lAlign = lAlign.reverse;
    } else if (topHeight > bottomHeight) {
      //if there is more available space in the opposite direction then use that direction
      lAlign = lAlign.reverse;
      popupSize = Size(popupSize.width, topHeight);
    } else {
      //Other wise minimize the height to max available space
      popupSize = Size(popupSize.width, bottomHeight);
    }
  } else if (lAlign.isUp && popupSize.height > topHeight) {
    //check if there enough space in opposite direction,
    if (popupSize.height <= bottomHeight) {
      lAlign = lAlign.reverse;
    } else if (bottomHeight > topHeight) {
      //if there is more available space in the opposite direction then use that direction
      lAlign = lAlign.reverse;
      popupSize = Size(popupSize.width, bottomHeight);
    } else {
      //Other wise minimize the height to max available space
      popupSize = Size(popupSize.width, topHeight);
    }
  }

  return getPosition(dropdownBox, overlayBox, popupSize, lAlign);
}