starting on configurator for counter and sum

confapp/lib/hcl/view/screen/content_widget.dart

@@ -69,15 +69,13 @@ class _SVGeneratorState extends State<SVGenerator> {
     );
     final key = Key(label);
 
-    if (knob is IntConfigKnob || knob is StringConfigKnob) {
+    if (knob is TextInputConfigKnob) {
       selector = TextFormField(
         key: key,
-        initialValue: (knob is IntConfigKnob && knob.value > 255)
-            ? '0x${knob.value.toRadixString(16)}'
-            : knob.value.toString(),
+        initialValue: knob.valueString,
         decoration: decoration,
         validator: (value) {
-          if (value!.isEmpty) {
+          if (value.isEmpty && !value.allowEmpty) {
             return 'Please enter value';
           }
           return null;

lib/src/component_config/components/config_counter.dart

@@ -0,0 +1,29 @@
+// Copyright (C) 2024 Intel Corporation
+// SPDX-License-Identifier: BSD-3-Clause
+//
+// config_counter.dart
+// Configurator for a Counter.
+//
+// 2024 September 6
+// Author: Max Korbel <[email protected]>
+
+import 'package:rohd_hcl/rohd_hcl.dart';
+
+class SumInterfaceKnob extends GroupOfKnobs {
+  ToggleConfigKnob hasEnableKnob = ToggleConfigKnob(value: false);
+
+  ToggleConfigKnob isFixedValueKnob = ToggleConfigKnob(value: false);
+
+  IntOptionalConfigKnob widthKnob = IntOptionalConfigKnob(value: 8);
+
+  SumInterfaceKnob() : super({});
+
+  @override
+  Map<String, ConfigKnob<dynamic>> get subKnobs => {
+        'Has Enable': hasEnableKnob,
+        'Is Fixed Value': isFixedValueKnob,
+        'Width': widthKnob,
+      };
+}
+
+// class CounterConfigurator extends Configurator {}

lib/src/component_config/config_knobs/config_knobs.dart

@@ -5,6 +5,8 @@ export 'choice_config_knob.dart';
 export 'config_knob.dart';
 export 'group_of_knobs_knob.dart';
 export 'int_config_knob.dart';
+export 'int_optional_config_knob.dart';
 export 'list_of_knobs_knob.dart';
 export 'string_config_knob.dart';
+export 'text_config_knob.dart';
 export 'toggle_config_knob.dart';

lib/src/component_config/config_knobs/int_config_knob.dart

@@ -9,14 +9,18 @@
 import 'package:rohd_hcl/rohd_hcl.dart';
 
 /// A knob to store an [int].
-class IntConfigKnob extends ConfigKnob<int> {
+class IntConfigKnob extends TextConfigKnob<int> {
   /// Creates a new config knob with the specified initial [value].
   IntConfigKnob({required super.value});
 
   @override
   Map<String, dynamic> toJson() =>
       {'value': value > 255 ? '0x${value.toRadixString(16)}' : value};
 
+  @override
+  String get valueString =>
+      value > 255 ? '0x${value.toRadixString(16)}' : value.toString();
+
   @override
   void loadJson(Map<String, dynamic> decodedJson) {
     final val = decodedJson['value'];

lib/src/component_config/config_knobs/int_optional_config_knob.dart

@@ -0,0 +1,50 @@
+// Copyright (C) 2024 Intel Corporation
+// SPDX-License-Identifier: BSD-3-Clause
+//
+// int_optional_config_knob.dart
+// A knob for holding a number or null.
+//
+// 2024 September 9
+
+import 'package:rohd_hcl/rohd_hcl.dart';
+
+/// A knob to store an [int].
+class IntOptionalConfigKnob extends TextConfigKnob<int?> {
+  /// Creates a new config knob with the specified initial [value].
+  IntOptionalConfigKnob({required super.value});
+
+  @override
+  Map<String, dynamic> toJson() => {
+        'value': value == null
+            ? null
+            : value! > 255
+                ? '0x${value!.toRadixString(16)}'
+                : value
+      };
+
+  @override
+  String get valueString => value == null
+      ? ''
+      : value! > 255
+          ? '0x${value!.toRadixString(16)}'
+          : value.toString();
+
+  @override
+  bool get allowEmpty => true;
+
+  @override
+  void loadJson(Map<String, dynamic> decodedJson) {
+    final val = decodedJson['value'];
+    if (val == null) {
+      value = null;
+    } else if (val is String) {
+      if (val.isEmpty) {
+        value = null;
+      } else {
+        value = int.parse(val);
+      }
+    } else {
+      value = val as int;
+    }
+  }
+}

lib/src/component_config/config_knobs/string_config_knob.dart

@@ -9,7 +9,7 @@
 import 'package:rohd_hcl/rohd_hcl.dart';
 
 /// A knob for holding a [String].
-class StringConfigKnob extends ConfigKnob<String> {
+class StringConfigKnob extends TextConfigKnob<String> {
   /// Creates a new knob with the specified initial [value].
   StringConfigKnob({required super.value});
 }

lib/src/component_config/config_knobs/text_config_knob.dart

@@ -0,0 +1,22 @@
+// Copyright (C) 2024 Intel Corporation
+// SPDX-License-Identifier: BSD-3-Clause
+//
+// text_config_knob.dart
+// Definition of a configuration knob which can be configured by parsing text.
+//
+// 2023 December 5
+
+import 'package:rohd_hcl/rohd_hcl.dart';
+
+/// A configuration knob for use in [Configurator]s which can be configured by
+/// text.
+abstract class TextConfigKnob<T> extends ConfigKnob<T> {
+  /// Creates a new knob with an initial [value].
+  TextConfigKnob({required super.value});
+
+  /// A [String] representation of the [value].
+  String get valueString => value.toString();
+
+  /// Whether the knob allows an empty string as input.
+  bool get allowEmpty => false;
+}