You should create your own morph subclass to handle mouse events. Or you can use a ready-made HandleMorph:
| line handle |
line := (LineMorph from: 100@100 to: 100@100 color: Color red width: 2) openInWorld.
handle := HandleMorph new forEachPointDo:
[:newPoint | line setVertices: {100@100. newPoint}].
self currentHand attachMorph: handle.
You should create your own morph subclass to handle mouse events. Or you can use a ready-made
HandleMorph
: