The draw-interaction state machine.
The live cursor preview vertex while drawing, else null.
null
'polyline' (distance / profile) or 'polygon' (area).
'polyline'
'polygon'
'idle' (not drawing) → 'drawing' (click adds vertices) → 'done' (shape finished).
'idle'
'drawing'
'done'
The placed vertices, in click order.
The draw-interaction state machine.