[Pharo-users] How does mouseFocus work?

At the moment I do startDrag: evt WorldState addDeferredUIMessage: [ self attachAllSubnodes. evt hand grabMorph: self. evt hand addEventListener: self. ]. with handleListenEvent: anEvent anEvent isMouseUp ifTrue: [ self activeHand removeEventListener: self. self detachAllSubnodes ]. anEvent isMouseMove ifTrue: [ self moved: anEvent ] and moved: anEvent self positionMeInParent: anEvent. self updateParentLine. self nodes do: [ :node | node updateParentLine ] to make sure that I can update the parentLine morph when moving this morph. Is there some documentation on how mouseFocus works? Stephan