OK, a user drags our somewhat sizeable nodes around, and he will drop them so that they overlap - which we cannot allow.

So i feed back the cursor based on:

OverrideCursor =
(CanPlaceNode(MousePosition.X, MousePosition.Y, Selection.Nodes.Count)) ? Cursors.Hand : Cursors.No;

..which checks if geometry of the to-be-dropped node or nodes (selection) will overlap with some existing stuff, and shows a NO cursor when he drags.
This is placed in SelectionMoving handler.

===

Now, i noticed that the MousePosition (which we update from mouse moving handler) has an OFFSET to the nodes the user can drag around in diagram, i.e. he can fetch a node low or up, completely left or right and drag it so.

Is there a way to determine deltaX, deltaY difference between node's Upper Left corner & mouse drag point? That would help the CanPlaceNode method to better determine the potential overlap....

Maybe i have to store this deltas on the mouse down on a node (which is the onset of drag)?
Or is there some already better thought up solution?

cheers

so selection.bounds are updated along with the drag, too?

could not use it for drag of multiple nodes, as i arrange them to drop next to each other programatically. But its ok, i solved it per:

_dragGrabPnt = new Point(e.GetPosition(DocumentPlane).X - MouseNode.Bounds.X, e.GetPosition(DocumentPlane).Y - MouseNode.Bounds.Y);

in MousePressed aka drag begin; that way, i know the offset when a node is dragged around.

(pls close the thread )

cheers