wip: shortcut listener widget.

app/lib/constants/constants.dart

@@ -22,6 +22,8 @@ const double defaultButtonHeight = 36;
 
 const List<String> builtInCommands = [
   'ShowWorkspace',
+  'Handle4Or5FingersSwipeUp',
+  'Handle4Or5FingersSwipeDown',
   'ToggleMaximize',
   'Minimize',
   'ShowWindow',

app/lib/constants/keyboard_mapper.dart

@@ -0,0 +1,11 @@
+import 'package:flutter/services.dart';
+
+/// https://github.com/linuxdeepin/dde-daemon/blob/76be73fbf019cee73983292e1edf47611ed9a219/gesture/manager.go#L386
+final Map<LogicalKeyboardKey, String> keyMapper = {
+  LogicalKeyboardKey.control: 'ctrl',
+  LogicalKeyboardKey.controlLeft: 'ctrl',
+  LogicalKeyboardKey.controlRight: 'ctrl',
+  LogicalKeyboardKey.shift: 'shift',
+  LogicalKeyboardKey.shiftLeft: 'shift',
+  LogicalKeyboardKey.shiftRight: 'shift',
+};