void ScrollMoved(Vector2 delta)
{
//Set the size of the content container to match the size of all of its 'children'
AdjustContentSize(ElementSize * _totalNumElements);
//How many elements can fit into the content area
float scrollAreaSize = _scrollRect.vertical ? ((RectTransform)_scrollRect.transform).rect.height : ((RectTransform)_scrollRect.transform).rect.width;
int numElementsVisibleInScrollArea = Mathf.CeilToInt(scrollAreaSize / ElementSize);
//basically the number of elements culled 'above you', clamped between 0 and 'number of total emenents - number of elements that would fit in the display area'
//since there is nothing lower than those last few elements
int numElementsCulledAbove = Mathf.Clamp(Mathf.FloorToInt(GetScrollRectNormalizedPosition() * (_totalNumElements - numElementsVisibleInScrollArea)), 0, Mathf.Clamp(_totalNumElements - (numElementsVisibleInScrollArea + 1), 0, int.MaxValue));
//Adjust the spacers width/height and have it fill the empty space that is supposed to be taken up by all the ui elements that are being culled
AdjustSpacer(numElementsCulledAbove * ElementSize);
int requiredElementsInList = Mathf.Min((numElementsVisibleInScrollArea + 1), _totalNumElements);
bool refreshRequired = _activeElements.Count != requiredElementsInList || _lastCulledAbove != numElementsCulledAbove;
if (refreshRequired)
{
if (_activeElements.Count != requiredElementsInList)
{
InitializeElements(requiredElementsInList, numElementsCulledAbove);
}
else
{
RepurposeMethod repurposeMethod = numElementsCulledAbove > _lastCulledAbove ? RepurposeMethod.TopGoesToBottom : RepurposeMethod.BottomGoesToTop;
RepurposeElement(repurposeMethod, numElementsCulledAbove);
}
}
_lastCulledAbove = numElementsCulledAbove;
}
void RepurposeElement(RepurposeMethod repurposeMethod, int numElementsCulledAbove)
{
if (repurposeMethod == RepurposeMethod.TopGoesToBottom)
{
var top = _activeElements[0];
_activeElements.RemoveAt(0);
_activeElements.Add(top);
top.transform.SetSiblingIndex(_activeElements[_activeElements.Count - 2].transform.GetSiblingIndex() + 1);
top.Setup((numElementsCulledAbove + _activeElements.Count - 1), _scrollListData);
}
else
{
var bottom = _activeElements[_activeElements.Count - 1];
_activeElements.RemoveAt(_activeElements.Count - 1);
_activeElements.Insert(0, bottom);
bottom.transform.SetSiblingIndex(_activeElements[1].transform.GetSiblingIndex());
bottom.Setup((numElementsCulledAbove), _scrollListData);
}
}
