Selected python box moves to new position by click rather than dragging

[jharaldson]

The phenomena occurs only at startup and the first box that is selected. After being moved this behavior is not seen again. It does not apply to all boxes, seems to apply to Python boxes.

Test case:
Actions:

1. Open Field
2. Click Python box
3. Click with mouse pointer on another part of the Field window
   Results:
4. Box is moved to the position of the mouse pointer

[marcdownie]

I think what's happening here is that the first click on Python box is expensive (that's when all the classes for Jython are loaded). Click and drag over that and it looks like the box isn't moving (because everything is paused waiting for Jython) and then the box jumps somewhere random with the mouse-up. I'll try booting Jython in a background thread on launch.