Cannot continue drawing when the signature is interrupted

[ChannelYu]

https://user-images.githubusercontent.com/7424823/117410258-c4d71900-af44-11eb-84bd-7fdb940b3849.mov

The user might accidentally touch the status bar like in the video, and the Listener object does not handle the cancellation callback, so the user can not continue drawing while this is happening.

Add Listener.onPointerCancel may solves this problem :

class SignatureState extends State<Signature> {

  @override
  Widget build(BuildContext context) {
    ...
    Listener(
      ...
      onPointerCancel: (PointerCancelEvent event) {
           if (activePointerId == event.pointer) {
              _addPoint(event, PointType.tap);
              widget.controller.onDrawEnd?.call();
              activePointerId = null;
            }
      },
    );
  }
}

Here are the results:

https://user-images.githubusercontent.com/7424823/117412645-97d83580-af47-11eb-938f-7ca3b968c785.mov

[MartinHlavna]

Thanks for the fix!

[MartinHlavna]

Version 4.1.1 is published