The Face Object Field Actors on key

on-key is invoked when a face has focus, and a key is pressed.

The input argument and the return value is the event object.

Examples

Simple keyboard navigation in a street map face:

on-key: [
  dx: dy: 0
  
  if arg/key = 'right [dx: 1]
  if arg/key = 'left  [dx: -1]
  if arg/key = 'up    [dy: 1]
  if arg/key = 'down  [dy: -1]
  
  if find arg/flags 'shift [
    dx: dx * 3
    dy: dy * 3
  ]
  
  move-map as-pair dx dy
  arg
]