How to implement a UI similar to a UML Diagram with connections?

Question

I'm working on an App that has a hierarchy of nodes and connections between them (Similar to Visio, a UML diagram, or Netbeans Visual Library). The nodes can be moved around, connections between nodes are maintained, etc.
The hierarchy of nodes is easily mimicked as JavaFX Nodes in the scene graph. Implementing the UI for the connections however has proved to be trickier. Here are 2 issues I'm trying to solve:
1) Connections need to track the positioning of their 'endpoint' nodes. Let's say a connection is an arrow connecting 2 arbitrary nodes in the hierarchy. The connection is itself a JavaFX node but in a different parent than the endpoint nodes. There doesn't seem to be a way to be notified that the endpoint nodes' location in the scene has changed, only their local bounds. Because there could be a whole sub-hierarchy of nodes being moved at a time, the connections need to reposition themselves whenever one of its endpoint nodes move in the scene (or should I say - move with respect to the common 'root' pane of the nodes and connections). Any ideas on how to implement this would be appreciated!
2) I wanted the connections to 'float' independent of the nodes. I thought the StackPane would be ideal, (back pane for nodes, front pane for connections), however, the front pane "steals" all the mouse events from the back pane! There's an almost useful method called 'setMouseTransparent', but it applies to a Node AND all of its children. Thus calling this on the front pane means the Connections no longer get mouse clicks. Blah... am I missing something here? Why isn't there a setMouseTransparent() method that doesn't apply to the children? I'd like the connections (thin lines using 'Path') to get mouse events, and otherwise nodes in the back plane should get them.
As a workaround to 2, I bailed on StackPane and use a regular Pane to hold both the nodes and connections. But I need to ensure the connections are always at the 'end' of the list of children... But that's an ugly solution. I feel like either I or JavaFX am missing something here.
Thanks for any suggestions,
Craig

Answer 1

So you need to update the connections between nodes when the nodes are moved around?
But because the connections aren't in the same immediate parent as the nodes they are in a different "local" coordinate space... you want to somehow listen to a node's location in terms of the scene coordinates? So even though the nodes local coordinates remain the same the node moves because it's parent moves and there is now way to observe that directly. Is that right.