onKey method
Implementation
@override
KeyEventResult onKey(KeyEvent event, ToolContext ctx) {
_attach(ctx);
final key = event.logicalKey;
if ((key == LogicalKeyboardKey.shiftLeft ||
key == LogicalKeyboardKey.shiftRight) &&
event is! KeyRepeatEvent) {
_shift = event is KeyDownEvent;
}
return super.onKey(event, ctx);
}