Procs
proc onPressed(handler: (elem: Element) -> void): Behavior {...}{.raises: [Exception], tags: [RootEffect].}
proc onReleased(handler: (elem: Element) -> void): Behavior {...}{.raises: [Exception], tags: [RootEffect].}
proc onPointerMoved(handler: (elem: Element, pos: Point) -> void): Behavior {...}{. raises: [Exception], tags: [RootEffect].}