Try using Node.setResizeConstraint(Direction.NONE)
OK, we will, but doesn't that only make it impossible to resize the node
after you have drawn it? We want to be sure that the node has the same
size every time such a node is drawn (for example, an initial state should
automatically become an ellipse with dx = 15 and dy = 15 every time it is
drawn).
But maybe this will work. In that case, where/in what file should this be
used?