If dropModeFlags includes DROP_MODE_INBETWEEN, returns -1 if position is the upper part of a tree item at that position, 1 for the lower part, and additionally 0 for the middle part if dropModeFlags includes DROP_MODE_ON_ITEM.
Otherwise, returns 0. If there are no tree item at position, returns -100.
If dropModeFlags includes DROP_MODE_INBETWEEN, returns -1 if position is the upper part of a tree item at that position, 1 for the lower part, and additionally 0 for the middle part if dropModeFlags includes DROP_MODE_ON_ITEM. Otherwise, returns 0. If there are no tree item at position, returns -100.