enable backspace for mobile platform.

I think it's bad idea to totally reject key stroke. It made many functional keybinding not
usable. Just accept it as PC does and throw those situation to
application developer is more resonable.

Author: stalin

lib/frontend/input_behavior_mobile.dart

@@ -1,36 +1,15 @@
 import 'package:flutter/services.dart';
-import 'package:flutter/widgets.dart';
 import 'package:xterm/frontend/input_behavior_default.dart';
 import 'package:xterm/input/keys.dart';
 import 'package:xterm/xterm.dart';
 
 class InputBehaviorMobile extends InputBehaviorDefault {
   InputBehaviorMobile();
 
+  @override
   final acceptKeyStroke = false;
 
-  final initEditingState = const TextEditingValue(
-    text: '  ',
-    selection: TextSelection.collapsed(offset: 1),
-  );
-
-  TextEditingValue onTextEdit(
-      TextEditingValue value, TerminalUiInteraction terminal) {
-    if (value.text.length > initEditingState.text.length) {
-      terminal.raiseOnInput(value.text.substring(1, value.text.length - 1));
-    } else if (value.text.length < initEditingState.text.length) {
-      terminal.keyInput(TerminalKey.backspace);
-    } else {
-      if (value.selection.baseOffset < 1) {
-        terminal.keyInput(TerminalKey.arrowLeft);
-      } else if (value.selection.baseOffset > 1) {
-        terminal.keyInput(TerminalKey.arrowRight);
-      }
-    }
-
-    return initEditingState;
-  }
-
+  @override
   void onAction(TextInputAction action, TerminalUiInteraction terminal) {
     print('action $action');
     switch (action) {