TreeNode::NodeData::updateCache

virtual TreeCacheNode* updateCache(HAL* hal, TreeCacheNode* pparent, TreeCacheNode* pinsert, TreeNode* pnode, UInt16 depth) const = 0;

updateCache is an internal function used for node implementation. This needs to handle 3 cases: 

1. Renderer cache node is not created. Create the proper node and process/cache subtree, adding items into draw primitive (DP). 

2. Render cache node created, but has no parent. This means cached node has been removed and is now being re-added. pParent, pRoot and other variables need to be initialized, DPs inserted. 

3. Render node is created and is part of parent. In this case, we are verifying a child node of a subtree after an ancestor (ex, parent) was re-added. We don't need to do insert/remove, but we do need to update pRoot/Depth and insert DPs.

The updated cache node.