Button element `btn`

js

btn(id, r, action)

id (optional): element ID
r (required): display rectangle, type Rect
action (optional): click action; see data types

After definition, the element’s id (besides the Rect) has:

id.pressing: 1 if the button is currently pressed, 0 otherwise
id.last: time of last press in seconds; -1 if never pressed
id.count: number of times the button has been pressed