This is a follow-up to further optimize the work done for bug 101857
Because :hover state is not reliable for detecting which node is actually under mouse cursor (or in the chain of parents of that node), there should be another way to detect nodes under mouse cursor.
One possibility is to keep track of the hovered chain in EventHandler.
Other suggestions are welcome.
There are also bugs around for cursor/hover not updating on DOM/layout changes, those cases could probably be handled by the solution too.