From 5b791775b6cdcba5b155c88cf4c8ea754a1604a6 Mon Sep 17 00:00:00 2001
From: Hanny Prastya Hariyadi <p.hanny@allm.inc>
Date: Mon, 2 Oct 2023 16:18:59 +0900
Subject: [PATCH 01/23] Remove locale and lookupFDashLocalizations in view
 layer

---
 lib/extensions/function_extension.dart        | 26 ++++++
 lib/fhir_types/src/date_time_picker.dart      | 12 +--
 .../model/aggregation/src/aggregator.dart     |  8 +-
 .../aggregation/src/narrative_aggregator.dart | 12 ++-
 .../questionnaire_response_aggregator.dart    |  9 +-
 .../src/total_score_aggregator.dart           | 10 ++-
 .../model/item/answer/src/answer_model.dart   | 54 ++++++------
 .../answer/src/attachment_answer_model.dart   | 29 ++++---
 .../item/answer/src/boolean_answer_model.dart |  4 +-
 .../item/answer/src/coding_answer_model.dart  | 38 ++++----
 .../src/coding_answer_option_model.dart       |  3 +-
 .../answer/src/datetime_answer_model.dart     | 27 +++---
 .../answer/src/numerical_answer_model.dart    | 47 +++++-----
 .../item/answer/src/string_answer_model.dart  | 79 +++++++++--------
 .../answer/src/unsupported_answer_model.dart  |  4 +-
 .../model/item/src/question_item_model.dart   | 36 +++-----
 .../model/item/src/response_item_model.dart   | 69 ++++++++-------
 .../src/questionnaire_response_model.dart     | 33 +++----
 .../model/src/rendering_string.dart           |  4 +
 .../answer/src/attachment_answer_filler.dart  |  6 +-
 .../answer/src/boolean_answer_filler.dart     | 14 +--
 .../item/answer/src/coding_answer_filler.dart | 32 ++++---
 .../answer/src/datetime_answer_filler.dart    |  3 +-
 .../answer/src/numerical_answer_filler.dart   | 37 +++++---
 .../item/answer/src/string_answer_filler.dart | 17 +++-
 .../view/item/src/group_item.dart             |  5 +-
 .../src/question_response_item_filler.dart    |  8 +-
 .../item/src/questionnaire_item_filler.dart   | 11 ++-
 .../src/questionnaire_item_filler_title.dart  | 10 ++-
 .../src/questionnaire_complete_button.dart    |  5 +-
 .../view/src/questionnaire_filler.dart        | 60 ++++++-------
 .../view/src/questionnaire_page_scaffold.dart |  3 +-
 .../view/src/questionnaire_scroller.dart      | 87 +++++++++----------
 .../view/src/questionnaire_scroller_page.dart |  3 -
 .../view/src/questionnaire_stepper.dart       |  6 +-
 .../view/src/questionnaire_stepper_page.dart  |  2 -
 .../src/questionnaire_stepper_page_view.dart  | 21 +++--
 .../view/src/questionnaire_theme.dart         | 34 ++++----
 lib/questionnaires/view/src/xhtml.dart        | 11 ++-
 39 files changed, 494 insertions(+), 385 deletions(-)
 create mode 100644 lib/extensions/function_extension.dart

diff --git a/lib/extensions/function_extension.dart b/lib/extensions/function_extension.dart
new file mode 100644
index 00000000..656c0428
--- /dev/null
+++ b/lib/extensions/function_extension.dart
@@ -0,0 +1,26 @@
+/// An extension on [Function] that provides a method to call functions
+/// safely, which means if the function throws an error, it will catch that
+/// error and return `null`, instead of letting the error propagate.
+///
+/// This can be useful when working with functions that may throw exceptions
+/// but you don't want to handle those exceptions explicitly or when you
+/// prefer to deal with a `null` return value in the case of an error.
+extension TryOrNull on Function {
+  /// Calls the function safely and returns the result of the function if it's
+  /// successful, or `null` if an error occurs.
+  ///
+  /// Here, `T` represents the expected return type of the function.
+  ///
+  /// Example:
+  /// ```dart
+  /// Function riskyFunction = () => throw Exception('Oops!');
+  /// final result = riskyFunction.callSafely(); // result will be `null`.
+  /// ```
+  T? callSafely<T>() {
+    try {
+      return this.call() as T;
+    } catch (e) {
+      return null;
+    }
+  }
+}
diff --git a/lib/fhir_types/src/date_time_picker.dart b/lib/fhir_types/src/date_time_picker.dart
index f1bf5769..23b0ad0e 100644
--- a/lib/fhir_types/src/date_time_picker.dart
+++ b/lib/fhir_types/src/date_time_picker.dart
@@ -76,8 +76,8 @@ class _FhirDateTimePickerState extends State<FhirDateTimePicker> {
     if (value == null || dateTime == null) return '';
 
     return (widget.pickerType == Time)
-      ? DateFormat.jm(locale.toString()).format(dateTime)
-      : value.format(locale, withTimeZone: widget.pickerType == FhirDateTime);
+        ? DateFormat.jm(locale.toString()).format(dateTime)
+        : value.format(locale, withTimeZone: widget.pickerType == FhirDateTime);
   }
 
   Future<void> _showPicker(Locale locale) async {
@@ -113,13 +113,15 @@ class _FhirDateTimePickerState extends State<FhirDateTimePicker> {
               // Get new BuildContext with overridden locale
               builder: (context) {
                 // Get time of day format of current locale
-                final timeOfDayFormat = MaterialLocalizations.of(context).timeOfDayFormat();
+                final timeOfDayFormat =
+                    MaterialLocalizations.of(context).timeOfDayFormat();
                 return MediaQuery(
                   data: MediaQuery.of(context).copyWith(
                     // Workaround for time picker validation bug in `input` mode with locales specifying a 24h TimeOfDayFormat.
                     // - https://github.com/sujrd/faiadashu/pull/32#issuecomment-1678639964
                     // - https://github.com/flutter/flutter/issues/85527
-                    alwaysUse24HourFormat: timeOfDay24hFormats.contains(timeOfDayFormat),
+                    alwaysUse24HourFormat:
+                        timeOfDay24hFormats.contains(timeOfDayFormat),
                   ),
                   child: child!,
                 );
@@ -157,7 +159,7 @@ class _FhirDateTimePickerState extends State<FhirDateTimePicker> {
 
   @override
   Widget build(BuildContext context) {
-    final locale = widget.locale ?? Localizations.localeOf(context);
+    final locale = Localizations.localeOf(context);
 
     // There is no Locale in initState.
     if (!_fieldInitialized) {
diff --git a/lib/questionnaires/model/aggregation/src/aggregator.dart b/lib/questionnaires/model/aggregation/src/aggregator.dart
index ac756372..d62cf3c1 100644
--- a/lib/questionnaires/model/aggregation/src/aggregator.dart
+++ b/lib/questionnaires/model/aggregation/src/aggregator.dart
@@ -1,3 +1,4 @@
+import 'package:faiadashu/l10n/l10n.dart';
 import 'package:faiadashu/questionnaires/model/model.dart';
 import 'package:flutter/material.dart';
 
@@ -8,11 +9,16 @@ import 'package:flutter/material.dart';
 abstract class Aggregator<T> extends ValueNotifier<T> {
   late final QuestionnaireResponseModel questionnaireResponseModel;
   late final Locale locale;
+  final FDashLocalizations localizations;
   final bool autoAggregate;
 
   /// [autoAggregate] specifies whether it should attach listeners to the
   /// questionnaire and aggregate when the questionnaire changes.
-  Aggregator(T initialValue, {this.autoAggregate = true}) : super(initialValue);
+  Aggregator(
+    T initialValue, {
+    required this.localizations,
+    this.autoAggregate = true,
+  }) : super(initialValue);
 
   // ignore: use_setters_to_change_properties
   /// Initialize the aggregator.
diff --git a/lib/questionnaires/model/aggregation/src/narrative_aggregator.dart b/lib/questionnaires/model/aggregation/src/narrative_aggregator.dart
index 821cf9c4..c392cc6a 100644
--- a/lib/questionnaires/model/aggregation/src/narrative_aggregator.dart
+++ b/lib/questionnaires/model/aggregation/src/narrative_aggregator.dart
@@ -18,8 +18,12 @@ class NarrativeAggregator extends Aggregator<Narrative> {
     status: NarrativeStatus.empty,
   );
 
-  NarrativeAggregator()
-      : super(NarrativeAggregator.emptyNarrative, autoAggregate: false);
+  NarrativeAggregator({required FDashLocalizations localizations})
+      : super(
+          NarrativeAggregator.emptyNarrative,
+          localizations: localizations,
+          autoAggregate: false,
+        );
 
   @override
   void init(QuestionnaireResponseModel questionnaireResponseModel) {
@@ -121,7 +125,7 @@ class NarrativeAggregator extends Aggregator<Narrative> {
 
     if (invalid) {
       div.write(
-        '<span style="color:red">${lookupFDashLocalizations(locale).dataAbsentReasonAsTextOutput} ',
+        '<span style="color:red">${localizations.dataAbsentReasonAsTextOutput} ',
       );
     }
 
@@ -129,7 +133,7 @@ class NarrativeAggregator extends Aggregator<Narrative> {
       div.write('<p>***</p>');
     } else if (dataAbsentReason == dataAbsentReasonAskedButDeclinedCode) {
       div.write(
-        '<p><i><span style="color:red">X </span>${lookupFDashLocalizations(locale).dataAbsentReasonAskedDeclinedOutput}</i></p>',
+        '<p><i><span style="color:red">X </span>${localizations.dataAbsentReasonAskedDeclinedOutput}</i></p>',
       );
     } else {
       final filledAnswers = itemModel.answeredAnswerModels;
diff --git a/lib/questionnaires/model/aggregation/src/questionnaire_response_aggregator.dart b/lib/questionnaires/model/aggregation/src/questionnaire_response_aggregator.dart
index a5af7688..ea0c811c 100644
--- a/lib/questionnaires/model/aggregation/src/questionnaire_response_aggregator.dart
+++ b/lib/questionnaires/model/aggregation/src/questionnaire_response_aggregator.dart
@@ -1,5 +1,6 @@
 import 'package:faiadashu/coding/coding.dart';
 import 'package:faiadashu/fhir_types/fhir_types.dart';
+import 'package:faiadashu/l10n/l10n.dart';
 import 'package:faiadashu/logging/logging.dart';
 import 'package:faiadashu/questionnaires/questionnaires.dart';
 import 'package:fhir/r4.dart';
@@ -13,8 +14,12 @@ class QuestionnaireResponseAggregator
     extends Aggregator<QuestionnaireResponse> {
   static final Logger _logger = Logger(QuestionnaireResponseAggregator);
 
-  QuestionnaireResponseAggregator()
-      : super(QuestionnaireResponse(), autoAggregate: false);
+  QuestionnaireResponseAggregator({required FDashLocalizations localizations})
+      : super(
+          QuestionnaireResponse(),
+          localizations: localizations,
+          autoAggregate: false,
+        );
 
   QuestionnaireResponseItem? _fromQuestionItem(
     QuestionItemModel itemModel,
diff --git a/lib/questionnaires/model/aggregation/src/total_score_aggregator.dart b/lib/questionnaires/model/aggregation/src/total_score_aggregator.dart
index 313929e2..a1cec24d 100644
--- a/lib/questionnaires/model/aggregation/src/total_score_aggregator.dart
+++ b/lib/questionnaires/model/aggregation/src/total_score_aggregator.dart
@@ -1,4 +1,5 @@
 import 'package:collection/collection.dart';
+import 'package:faiadashu/l10n/l10n.dart';
 import 'package:faiadashu/logging/logging.dart';
 import 'package:faiadashu/questionnaires/model/model.dart';
 import 'package:fhir/r4.dart';
@@ -16,8 +17,13 @@ class TotalScoreAggregator extends Aggregator<Decimal> {
   static final _logger = Logger(TotalScoreAggregator);
 
   late final QuestionItemModel? totalScoreItem;
-  TotalScoreAggregator({bool autoAggregate = true})
-      : super(Decimal(0), autoAggregate: autoAggregate);
+  TotalScoreAggregator(
+      {required FDashLocalizations localizations, bool autoAggregate = true})
+      : super(
+          Decimal(0),
+          localizations: localizations,
+          autoAggregate: autoAggregate,
+        );
 
   @override
   void init(QuestionnaireResponseModel questionnaireResponseModel) {
diff --git a/lib/questionnaires/model/item/answer/src/answer_model.dart b/lib/questionnaires/model/item/answer/src/answer_model.dart
index 70312201..8d9198d0 100644
--- a/lib/questionnaires/model/item/answer/src/answer_model.dart
+++ b/lib/questionnaires/model/item/answer/src/answer_model.dart
@@ -1,5 +1,5 @@
-import 'package:faiadashu/fhir_types/fhir_types.dart';
-import 'package:faiadashu/questionnaires/model/model.dart';
+import 'package:faiadashu/faiadashu.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/validation_error.dart';
 import 'package:fhir/r4.dart';
 import 'package:flutter/material.dart';
 
@@ -74,16 +74,16 @@ abstract class AnswerModel<I, V> extends ResponseNode {
 
   /// Validates a new input value. Does not change the [value].
   ///
-  /// Returns null when [inputValue] is valid, or a localized message when it is not.
-  ///
   /// This is used to validate external input from a view.
-  String? validateInput(I? inputValue);
+  ///
+  /// Throws [ValidationError] when when [inputValue] is invalid.
+  void validateInput(I? inputValue);
 
   /// Validates a value against the constraints of the answer model.
   /// Does not change the [value] of the answer model.
   ///
-  /// Returns null when it is valid, or a localized message when it is not.
-  String? validateValue(V? inputValue);
+  /// Throws [ValidationError] when when [inputValue] is invalid.
+  void validateValue(V? inputValue);
 
   /// Validates whether the current [value] will pass the completeness check.
   ///
@@ -93,29 +93,25 @@ abstract class AnswerModel<I, V> extends ResponseNode {
   /// Since an individual answer does not know whether it is required, this
   /// is not taken into account.
   ///
-  /// Returns null when the answer is valid, or an error text,
-  /// when it is not.
-  ///
-  String? validate({
+  /// Returns an empty list when the answer is valid, otherwise
+  /// Returns a list of [ValidationError].
+  List<ValidationError> validate({
     bool updateErrorText = true,
     bool notifyListeners = false,
   }) {
-    final newErrorText = validateValue(
-      value,
-    );
-
-    if (errorText == newErrorText) {
-      return newErrorText;
+    try {
+      validateValue(value);
+
+      if (notifyListeners) {
+        this.notifyListeners();
+      }
+      return [];
+    } on ValidationError catch (exception) {
+      if (updateErrorText) {
+        _error = exception;
+      }
+      return [exception];
     }
-
-    if (updateErrorText) {
-      errorText = newErrorText;
-    }
-    if (notifyListeners) {
-      this.notifyListeners();
-    }
-
-    return newErrorText;
   }
 
   /// Returns whether any answer (valid or invalid) has been provided.
@@ -124,12 +120,14 @@ abstract class AnswerModel<I, V> extends ResponseNode {
   /// Returns whether this question is unanswered.
   bool get isEmpty;
 
-  String? errorText;
+  ValidationError? _error;
 
   /// Returns an error text for display in the answer's control.
   ///
   /// This might return an error text from the parent [QuestionItemModel].
-  String? get displayErrorText => errorText ?? responseItemModel.errorText;
+  String? displayErrorText(FDashLocalizations localizations) =>
+      _error?.getMessage(localizations) ??
+      responseItemModel.getErrorText(localizations);
 
   /// Returns a [QuestionnaireResponseAnswer] based on the current value.
   ///
diff --git a/lib/questionnaires/model/item/answer/src/attachment_answer_model.dart b/lib/questionnaires/model/item/answer/src/attachment_answer_model.dart
index ffeab84e..abdeae1f 100644
--- a/lib/questionnaires/model/item/answer/src/attachment_answer_model.dart
+++ b/lib/questionnaires/model/item/answer/src/attachment_answer_model.dart
@@ -1,8 +1,8 @@
 import 'package:faiadashu/fhir_types/fhir_types.dart';
-import 'package:faiadashu/l10n/l10n.dart';
 import 'package:faiadashu/questionnaires/model/model.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/max_size_error.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/mime_types_error.dart';
 import 'package:fhir/r4.dart';
-import 'package:filesize/filesize.dart';
 
 class AttachmentAnswerModel extends AnswerModel<Attachment, Attachment> {
   final num maxSize;
@@ -10,14 +10,18 @@ class AttachmentAnswerModel extends AnswerModel<Attachment, Attachment> {
 
   AttachmentAnswerModel(super.responseModel)
       : maxSize = responseModel.questionnaireItem.extension_
-                ?.extensionOrNull('http://hl7.org/fhir/StructureDefinition/maxSize')
+                ?.extensionOrNull(
+                    'http://hl7.org/fhir/StructureDefinition/maxSize')
                 ?.valueDecimal
-                ?.value ?? 0,
+                ?.value ??
+            0,
         mimeTypes = responseModel.questionnaireItem.extension_
-                ?.whereExtensionIs('http://hl7.org/fhir/StructureDefinition/mimeType')
+                ?.whereExtensionIs(
+                    'http://hl7.org/fhir/StructureDefinition/mimeType')
                 ?.map((ext) => ext.valueCode?.value ?? '')
                 .where((mimeType) => mimeType != '')
-                .toList() ?? [];
+                .toList() ??
+            [];
 
   @override
   RenderingString get display => (value != null)
@@ -25,25 +29,26 @@ class AttachmentAnswerModel extends AnswerModel<Attachment, Attachment> {
       : RenderingString.nullText;
 
   @override
-  String? validateInput(Attachment? inValue) {
-    return validateValue(inValue);
+  void validateInput(Attachment? inValue) {
+    validateValue(inValue);
   }
 
   @override
-  String? validateValue(Attachment? inputValue) {
+  void validateValue(Attachment? inputValue) {
     if (inputValue == null) return null;
 
     if (maxSize > 0) {
       final attachmentSize = inputValue.size?.value;
       if (attachmentSize == null || attachmentSize > maxSize) {
-        return lookupFDashLocalizations(locale).validatorMaxSize(filesize(maxSize));
+        throw MaxSizeError(nodeUid, maxSize);
       }
     }
 
     if (mimeTypes.isNotEmpty) {
       final attachmentMimeType = inputValue.contentType?.value;
-      if (attachmentMimeType == null || !mimeTypes.contains(attachmentMimeType)) {
-        return lookupFDashLocalizations(locale).validatorMimeTypes(mimeTypes.join(', '));
+      if (attachmentMimeType == null ||
+          !mimeTypes.contains(attachmentMimeType)) {
+        throw MimeTypesError(nodeUid, mimeTypes);
       }
     }
 
diff --git a/lib/questionnaires/model/item/answer/src/boolean_answer_model.dart b/lib/questionnaires/model/item/answer/src/boolean_answer_model.dart
index 076a379c..f00eaf54 100644
--- a/lib/questionnaires/model/item/answer/src/boolean_answer_model.dart
+++ b/lib/questionnaires/model/item/answer/src/boolean_answer_model.dart
@@ -23,12 +23,12 @@ class BooleanAnswerModel extends AnswerModel<Boolean, Boolean> {
         );
 
   @override
-  String? validateInput(Boolean? inValue) {
+  void validateInput(Boolean? inValue) {
     return null;
   }
 
   @override
-  String? validateValue(Boolean? inputValue) {
+  void validateValue(Boolean? inputValue) {
     return null;
   }
 
diff --git a/lib/questionnaires/model/item/answer/src/coding_answer_model.dart b/lib/questionnaires/model/item/answer/src/coding_answer_model.dart
index b38e86e0..775ab28a 100644
--- a/lib/questionnaires/model/item/answer/src/coding_answer_model.dart
+++ b/lib/questionnaires/model/item/answer/src/coding_answer_model.dart
@@ -3,6 +3,9 @@ import 'package:faiadashu/fhir_types/fhir_types.dart';
 import 'package:faiadashu/l10n/l10n.dart';
 import 'package:faiadashu/logging/logging.dart';
 import 'package:faiadashu/questionnaires/model/model.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/max_occurs_error.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/min_occurs_error.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/single_selection_or_open_string_error.dart';
 import 'package:faiadashu/questionnaires/questionnaires.dart';
 import 'package:fhir/r4.dart';
 
@@ -154,15 +157,6 @@ class CodingAnswerModel extends AnswerModel<OptionsOrString, OptionsOrString> {
 
   bool get isOptionsOrString => qi.type == QuestionnaireItemType.open_choice;
 
-  RenderingString get openLabel => RenderingString.fromText(
-        qi.extension_
-                ?.extensionOrNull(
-                  'http://hl7.org/fhir/uv/sdc/StructureDefinition/questionnaire-sdc-openLabel',
-                )
-                ?.valueString ??
-            lookupFDashLocalizations(locale).fillerOpenCodingOtherLabel,
-      );
-
   String _nextOptionUid() => _answerOptions.length.toString();
 
   void _addAnswerOptionFromValueSetCoding(Coding coding) {
@@ -231,6 +225,17 @@ class CodingAnswerModel extends AnswerModel<OptionsOrString, OptionsOrString> {
     _createAnswerOptions();
   }
 
+  RenderingString getOpenLabel(FDashLocalizations localizations) {
+    return RenderingString.fromText(
+      _openLabel ?? localizations.fillerOpenCodingOtherLabel,
+    );
+  }
+
+  String? get _openLabel => qi.extension_
+      ?.extensionOrNull(
+          'http://hl7.org/fhir/uv/sdc/StructureDefinition/questionnaire-sdc-openLabel')
+      ?.valueString;
+
   Iterable<RenderingString> toDisplay({bool includeMedia = true}) {
     final value = this.value;
     if (value == null) {
@@ -301,14 +306,14 @@ class CodingAnswerModel extends AnswerModel<OptionsOrString, OptionsOrString> {
   }
 
   @override
-  String? validateInput(OptionsOrString? inValue) {
+  void validateInput(OptionsOrString? inValue) {
     return validateValue(inValue);
   }
 
   @override
-  String? validateValue(OptionsOrString? inValue) {
+  void validateValue(OptionsOrString? inValue) {
     if (inValue == null) {
-      return null;
+      return;
     }
 
     final selectedOptionsCount = inValue.selectedOptions?.length ?? 0;
@@ -318,21 +323,18 @@ class CodingAnswerModel extends AnswerModel<OptionsOrString, OptionsOrString> {
 
     if (!(questionnaireItemModel.questionnaireItem.repeats?.value ?? false)) {
       if (totalCount != 1) {
-        return lookupFDashLocalizations(locale)
-            .validatorSingleSelectionOrSingleOpenString(openLabel.plainText);
+        throw SingleSelectionOrOpenStringError(nodeUid, _openLabel);
       }
     }
 
     if (totalCount < minOccurs) {
-      return lookupFDashLocalizations(locale).validatorMinOccurs(minOccurs);
+      throw MinOccursError(nodeUid, minOccurs);
     }
 
     final maxOccurs = this.maxOccurs;
     if (maxOccurs != null && totalCount > maxOccurs) {
-      return lookupFDashLocalizations(locale).validatorMaxOccurs(maxOccurs);
+      throw MaxOccursError(nodeUid, maxOccurs);
     }
-
-    return null;
   }
 
   @override
diff --git a/lib/questionnaires/model/item/answer/src/coding_answer_option_model.dart b/lib/questionnaires/model/item/answer/src/coding_answer_option_model.dart
index e1caa725..20b41ea0 100644
--- a/lib/questionnaires/model/item/answer/src/coding_answer_option_model.dart
+++ b/lib/questionnaires/model/item/answer/src/coding_answer_option_model.dart
@@ -132,7 +132,7 @@ class CodingAnswerOptionModel {
         ?.valueString;
 
     final optionPrefix = (plainOptionPrefix != null)
-        ? RenderingString.fromText(plainOptionPrefix)
+        ? RenderingString.fromText(plainOptionPrefix, extensions: extensions)
         : null;
 
     RenderingString optionText;
@@ -154,6 +154,7 @@ class CodingAnswerOptionModel {
         forDisplay = _createForDisplay(coding, locale, questionnaireItemModel);
         optionText = RenderingString.fromText(
           plainText,
+          extensions: extensions,
         );
       }
     } else {
diff --git a/lib/questionnaires/model/item/answer/src/datetime_answer_model.dart b/lib/questionnaires/model/item/answer/src/datetime_answer_model.dart
index ed56b9bc..541198bd 100644
--- a/lib/questionnaires/model/item/answer/src/datetime_answer_model.dart
+++ b/lib/questionnaires/model/item/answer/src/datetime_answer_model.dart
@@ -1,6 +1,6 @@
 import 'package:faiadashu/fhir_types/fhir_types.dart';
-import 'package:faiadashu/l10n/l10n.dart';
 import 'package:faiadashu/questionnaires/model/model.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/date_time_error.dart';
 import 'package:fhir/r4.dart'
     show
         Date,
@@ -53,15 +53,15 @@ class DateTimeAnswerModel extends AnswerModel<FhirDateTime, FhirDateTime> {
   }
 
   @override
-  String? validateInput(FhirDateTime? inValue) {
+  void validateInput(FhirDateTime? inValue) {
     return validateValue(inValue);
   }
 
   @override
-  String? validateValue(FhirDateTime? inValue) {
-    return inValue == null || inValue.isValid
-        ? null
-        : lookupFDashLocalizations(locale).validatorDateTime;
+  void validateValue(FhirDateTime? inValue) {
+    if (!(inValue == null || inValue.isValid)) {
+      throw DateTimeError(nodeUid);
+    }
   }
 
   @override
@@ -81,13 +81,12 @@ class DateTimeAnswerModel extends AnswerModel<FhirDateTime, FhirDateTime> {
   @override
   void populate(QuestionnaireResponseAnswer answer) {
     // NOTE: Model should probably be populated based on QuestionnaireItemType
-    value = answer.valueDateTime ?? (
-      (answer.valueDate != null)
-      ? FhirDateTime(answer.valueDate)
-      : (answer.valueTime != null)
-      // TODO: Find a better way to convert Time values to FhirDateTime
-      ? FhirDateTime('1970-01-01T${answer.valueTime}')
-      : null
-    );
+    value = answer.valueDateTime ??
+        ((answer.valueDate != null)
+            ? FhirDateTime(answer.valueDate)
+            : (answer.valueTime != null)
+                // TODO: Find a better way to convert Time values to FhirDateTime
+                ? FhirDateTime('1970-01-01T${answer.valueTime}')
+                : null);
   }
 }
diff --git a/lib/questionnaires/model/item/answer/src/numerical_answer_model.dart b/lib/questionnaires/model/item/answer/src/numerical_answer_model.dart
index c307d8de..935a76e7 100644
--- a/lib/questionnaires/model/item/answer/src/numerical_answer_model.dart
+++ b/lib/questionnaires/model/item/answer/src/numerical_answer_model.dart
@@ -1,8 +1,11 @@
 import 'package:faiadashu/coding/coding.dart';
+import 'package:faiadashu/extensions/function_extension.dart';
 import 'package:faiadashu/fhir_types/fhir_types.dart';
-import 'package:faiadashu/l10n/l10n.dart';
 import 'package:faiadashu/logging/logging.dart';
 import 'package:faiadashu/questionnaires/model/model.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/max_value_error.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/min_value_error.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/nan_error.dart';
 import 'package:fhir/r4.dart';
 import 'package:intl/intl.dart';
 
@@ -161,16 +164,21 @@ class NumericalAnswerModel extends AnswerModel<String, Quantity> {
     }
 
     qi.extension_
-      ?.whereExtensionIs('http://hl7.org/fhir/StructureDefinition/questionnaire-unitOption')
-      ?.forEach((extension) {
-        final coding = extension.valueCoding;
-        if (coding == null) return;
-        _units[keyForUnitChoice(coding)] = coding;
-      });
+        ?.whereExtensionIs(
+            'http://hl7.org/fhir/StructureDefinition/questionnaire-unitOption')
+        ?.forEach((extension) {
+      final coding = extension.valueCoding;
+      if (coding == null) return;
+      _units[keyForUnitChoice(coding)] = coding;
+    });
 
     // Using updated usage for questionnaire-unit in R5 (http://hl7.org/fhir/extensions/StructureDefinition-questionnaire-unit.html)
-    final questionnaireUnit = qi.extension_?.extensionOrNull('http://hl7.org/fhir/StructureDefinition/questionnaire-unit')?.valueCoding;
-    if (questionnaireUnit != null && questionnaireUnit.display != null) _units[keyForUnitChoice(questionnaireUnit)] = questionnaireUnit;
+    final questionnaireUnit = qi.extension_
+        ?.extensionOrNull(
+            'http://hl7.org/fhir/StructureDefinition/questionnaire-unit')
+        ?.valueCoding;
+    if (questionnaireUnit != null && questionnaireUnit.display != null)
+      _units[keyForUnitChoice(questionnaireUnit)] = questionnaireUnit;
   }
 
   @override
@@ -181,9 +189,9 @@ class NumericalAnswerModel extends AnswerModel<String, Quantity> {
       : RenderingString.nullText;
 
   @override
-  String? validateInput(String? inputValue) {
+  void validateInput(String? inputValue) {
     if (inputValue == null || inputValue.isEmpty) {
-      return null;
+      return;
     }
     num number = double.nan;
     try {
@@ -191,17 +199,17 @@ class NumericalAnswerModel extends AnswerModel<String, Quantity> {
     } catch (_) {
       // Ignore FormatException, number remains nan.
     }
-    if (number == double.nan) {
-      return lookupFDashLocalizations(locale).validatorNan;
+    if (number.isNaN) {
+      throw NanError(nodeUid);
     }
 
     final quantity = _valueFromNumber(number);
 
-    return validateValue(quantity);
+    validateValue(quantity);
   }
 
   @override
-  String? validateValue(Quantity? inputValue) {
+  void validateValue(Quantity? inputValue) {
     if (inputValue == null) {
       return null;
     }
@@ -213,12 +221,10 @@ class NumericalAnswerModel extends AnswerModel<String, Quantity> {
     }
 
     if (number > _maxValue) {
-      return lookupFDashLocalizations(locale)
-          .validatorMaxValue(Decimal(_maxValue).format(locale));
+      throw MaxValueError(nodeUid, Decimal(_maxValue).format(locale));
     }
     if (number < _minValue) {
-      return lookupFDashLocalizations(locale)
-          .validatorMinValue(Decimal(_minValue).format(locale));
+      throw MinValueError(nodeUid, Decimal(_minValue).format(locale));
     }
 
     return null;
@@ -259,7 +265,8 @@ class NumericalAnswerModel extends AnswerModel<String, Quantity> {
   /// * Updates the numerical value based on text input
   /// * Keeps the unit
   Quantity? copyWithTextInput(String textInput) {
-    final valid = validateInput(textInput) == null;
+    final valid = (() => validateInput(textInput)).callSafely() ?? false;
+
     final dataAbsentReasonExtension = !valid
         ? [
             FhirExtension(
diff --git a/lib/questionnaires/model/item/answer/src/string_answer_model.dart b/lib/questionnaires/model/item/answer/src/string_answer_model.dart
index d8b11ab0..eb7077a3 100644
--- a/lib/questionnaires/model/item/answer/src/string_answer_model.dart
+++ b/lib/questionnaires/model/item/answer/src/string_answer_model.dart
@@ -1,7 +1,10 @@
 import 'package:faiadashu/coding/coding.dart';
 import 'package:faiadashu/fhir_types/fhir_types.dart';
-import 'package:faiadashu/l10n/l10n.dart';
 import 'package:faiadashu/questionnaires/model/model.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/entry_format_error.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/min_length_error.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/regex_error.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/url_error.dart';
 import 'package:fhir/r4.dart';
 
 enum StringAnswerKeyboard { plain, email, phone, number, multiline, url }
@@ -61,73 +64,73 @@ class StringAnswerModel extends AnswerModel<String, String> {
       : RenderingString.nullText;
 
   @override
-  String? validateInput(String? inValue) {
+  void validateInput(String? inValue) {
     final checkValue = inValue?.trim();
 
     return validateValue(checkValue);
   }
 
   @override
-  String? validateValue(String? inputValue) {
+  void validateValue(String? inputValue) {
     if (inputValue == null || inputValue.isEmpty) {
-      return null;
+      return;
     }
 
     if (inputValue.length < minLength) {
-      return lookupFDashLocalizations(locale).validatorMinLength(minLength);
+      throw MinLengthError(nodeUid, minLength);
     }
 
     if (maxLength != null && inputValue.length > maxLength!) {
-      return lookupFDashLocalizations(locale).validatorMaxLength(maxLength!);
+      throw MinLengthError(nodeUid, maxLength!);
     }
 
     if (qi.type == QuestionnaireItemType.url) {
       if (!_urlRegExp.hasMatch(inputValue)) {
-        return lookupFDashLocalizations(locale).validatorUrl;
+        throw UrlError(nodeUid);
       }
     }
 
     if (regExp != null) {
       if (!regExp!.hasMatch(inputValue)) {
-        return (entryFormat != null)
-            ? lookupFDashLocalizations(locale)
-                .validatorEntryFormat(entryFormat!)
-            : lookupFDashLocalizations(locale).validatorRegExp;
+        throw (entryFormat != null)
+            ? EntryFormatError(nodeUid, entryFormat!)
+            : RegexError(nodeUid);
       }
     }
-
-    return null;
   }
 
   @override
   QuestionnaireResponseAnswer? createFhirAnswer(
     List<QuestionnaireResponseItem>? items,
   ) {
-    final value = this.value?.trim();
-
-    final valid = validateInput(value) == null;
-    final dataAbsentReasonExtension = !valid
-        ? [
-            FhirExtension(
-              url: dataAbsentReasonExtensionUrl,
-              valueCode: dataAbsentReasonAsTextCode,
-            ),
-          ]
-        : null;
-
-    return (value != null && value.isNotEmpty)
-        ? (qi.type != QuestionnaireItemType.url)
-            ? QuestionnaireResponseAnswer(
-                valueString: value,
-                extension_: dataAbsentReasonExtension,
-                item: items,
-              )
-            : QuestionnaireResponseAnswer(
-                valueUri: FhirUri(value),
-                extension_: dataAbsentReasonExtension,
-                item: items,
-              )
-        : null;
+    try {
+      final value = this.value?.trim();
+
+      validateInput(value);
+
+      final dataAbsentReasonExtension = [
+        FhirExtension(
+          url: dataAbsentReasonExtensionUrl,
+          valueCode: dataAbsentReasonAsTextCode,
+        ),
+      ];
+
+      return (value != null && value.isNotEmpty)
+          ? (qi.type != QuestionnaireItemType.url)
+              ? QuestionnaireResponseAnswer(
+                  valueString: value,
+                  extension_: dataAbsentReasonExtension,
+                  item: items,
+                )
+              : QuestionnaireResponseAnswer(
+                  valueUri: FhirUri(value),
+                  extension_: dataAbsentReasonExtension,
+                  item: items,
+                )
+          : null;
+    } on Exception {
+      return null;
+    }
   }
 
   @override
diff --git a/lib/questionnaires/model/item/answer/src/unsupported_answer_model.dart b/lib/questionnaires/model/item/answer/src/unsupported_answer_model.dart
index f16712ef..f37c9e60 100644
--- a/lib/questionnaires/model/item/answer/src/unsupported_answer_model.dart
+++ b/lib/questionnaires/model/item/answer/src/unsupported_answer_model.dart
@@ -16,12 +16,12 @@ class UnsupportedAnswerModel extends AnswerModel<Object, Object> {
   RenderingString get display => RenderingString.nullText;
 
   @override
-  String? validateInput(Object? inValue) {
+  void validateInput(Object? inValue) {
     return null;
   }
 
   @override
-  String? validateValue(Object? inputValue) {
+  void validateValue(Object? inputValue) {
     return null;
   }
 
diff --git a/lib/questionnaires/model/item/src/question_item_model.dart b/lib/questionnaires/model/item/src/question_item_model.dart
index 76ed1df1..0f66ed02 100644
--- a/lib/questionnaires/model/item/src/question_item_model.dart
+++ b/lib/questionnaires/model/item/src/question_item_model.dart
@@ -1,10 +1,8 @@
 import 'dart:developer';
 
 import 'package:collection/collection.dart';
-import 'package:faiadashu/coding/coding.dart';
-import 'package:faiadashu/fhir_types/fhir_types.dart';
-import 'package:faiadashu/logging/logging.dart';
-import 'package:faiadashu/questionnaires/questionnaires.dart';
+import 'package:faiadashu/faiadashu.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/validation_error.dart';
 import 'package:fhir/primitive_types/primitive_types.dart';
 import 'package:fhir/r4/r4.dart';
 import 'package:fhir_path/fhir_path.dart';
@@ -172,36 +170,27 @@ class QuestionItemModel extends ResponseItemModel {
   }
 
   @override
-  Map<String, String>? validate({
+  List<ValidationError> validate({
     bool updateErrorText = true,
     bool notifyListeners = false,
   }) {
     // Non-existent answer models can be invalid, e.g. if minOccurs is not met.
     _ensureAnswerModel();
 
-    final responseErrorTexts = super.validate(
-          updateErrorText: updateErrorText,
-          notifyListeners: notifyListeners,
-        ) ??
-        <String, String>{};
+    List<ValidationError> errors = super.validate(
+      updateErrorText: updateErrorText,
+      notifyListeners: notifyListeners,
+    );
 
-    final answersErrorTexts = <String, String>{};
     for (final am in answerModels) {
-      final answerValidationText = am.validate(
+      final amErrors = am.validate(
         updateErrorText: updateErrorText,
         notifyListeners: notifyListeners,
       );
-
-      if (answerValidationText != null) {
-        answersErrorTexts[am.nodeUid] = answerValidationText;
-      }
+      errors.addAll(amErrors);
     }
 
-    final combinedErrorTexts = responseErrorTexts..addAll(answersErrorTexts);
-
-    return responseErrorTexts.isEmpty && answersErrorTexts.isEmpty
-        ? null
-        : combinedErrorTexts;
+    return errors;
   }
 
   @override
@@ -430,8 +419,9 @@ class QuestionItemModel extends ResponseItemModel {
       // Write the value back to the answer model
       firstAnswerModel.populateFromExpression(evaluationResult);
     } catch (ex) {
-      errorText =
-          (ex is FhirPathEvaluationException) ? ex.message : ex.toString();
+      // errorText =
+      //     (ex is FhirPathEvaluationException) ? ex.message : ex.toString();
+      if (ex is FhirPathEvaluationException) {}
       _qimLogger.warn('Calculation problem: $_calculatedExpression', error: ex);
       notifyListeners(); // This could be added to a setter for errorText, but might have side-effects.
     }
diff --git a/lib/questionnaires/model/item/src/response_item_model.dart b/lib/questionnaires/model/item/src/response_item_model.dart
index b48ead2e..0a7c434d 100644
--- a/lib/questionnaires/model/item/src/response_item_model.dart
+++ b/lib/questionnaires/model/item/src/response_item_model.dart
@@ -1,6 +1,8 @@
-import 'package:faiadashu/l10n/l10n.dart';
-import 'package:faiadashu/logging/logging.dart';
-import 'package:faiadashu/questionnaires/model/model.dart';
+import 'package:faiadashu/faiadashu.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/constraint_validation_error.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/custom_validation_error.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/required_item_error.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/validation_error.dart';
 import 'package:fhir/r4.dart';
 
 /// Model a response item
@@ -48,49 +50,45 @@ abstract class ResponseItemModel extends FillerItemModel {
   /// Returns a description of the current error situation with this item.
   ///
   /// Localized text if an error exists. Or null if no error exists.
-  String? errorText;
+  String? getErrorText(FDashLocalizations localizations) {
+    return _exception?.getMessage(localizations);
+  }
+
+  ValidationError? _exception;
 
-  Map<String, String>? validate({
+  List<ValidationError> validate({
     bool updateErrorText = true,
     bool notifyListeners = false,
   }) {
-    String? newErrorText;
-
     if (questionnaireItemModel.isRequired && isUnanswered) {
-      newErrorText = lookupFDashLocalizations(questionnaireResponseModel.locale)
-          .validatorRequiredItem;
+      return [RequiredItemError(nodeUid)];
     }
-
-    final constraintError = validateConstraint();
-    newErrorText ??= constraintError;
-
-    if (errorText != newErrorText) {
-      if (updateErrorText) {
-        errorText = newErrorText;
-      }
-      if (notifyListeners) {
-        this.notifyListeners();
+    try {
+      validateConstraint();
+      _exception = null;
+    } on ValidationError catch (exception) {
+      _exception ??= exception;
+
+      if (_exception != exception) {
+        if (updateErrorText) {
+          _exception = exception;
+        }
+        if (notifyListeners) {
+          this.notifyListeners();
+        }
       }
+      return [_exception!];
     }
-
-    if (newErrorText == null) {
-      return null;
-    } else {
-      final resultMap = <String, String>{};
-      resultMap[nodeUid] = newErrorText;
-
-      return resultMap;
-    }
+    return [];
   }
 
   /// Returns whether the item is satisfying the `questionnaire-constraint`.
   ///
-  /// Returns null if satisfied, or a human-readable text if not satisfied.
-  /// Returns null if no constraint is specified.
-  String? validateConstraint() {
+  /// Throws [CustomValidationError] with human-readable text if not satisfied.
+  void validateConstraint() {
     final constraintExpression = _constraintExpression;
     if (constraintExpression == null) {
-      return null;
+      return;
     }
 
     final isSatisfied = constraintExpression.fetchBoolValue(
@@ -99,6 +97,11 @@ abstract class ResponseItemModel extends FillerItemModel {
       location: nodeUid,
     );
 
-    return isSatisfied ? null : questionnaireItemModel.constraintHuman;
+    if (!isSatisfied) {
+      throw ConstraintValidationError(
+        nodeUid,
+        questionnaireItemModel.constraintHuman,
+      );
+    }
   }
 }
diff --git a/lib/questionnaires/model/src/questionnaire_response_model.dart b/lib/questionnaires/model/src/questionnaire_response_model.dart
index c979c795..f53dd19b 100644
--- a/lib/questionnaires/model/src/questionnaire_response_model.dart
+++ b/lib/questionnaires/model/src/questionnaire_response_model.dart
@@ -1,11 +1,11 @@
-import 'dart:ui';
-
 import 'package:collection/collection.dart';
+import 'package:faiadashu/l10n/l10n.dart';
 import 'package:faiadashu/logging/logging.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/validation_error.dart';
 import 'package:faiadashu/questionnaires/questionnaires.dart';
 import 'package:faiadashu/resource_provider/resource_provider.dart';
 import 'package:fhir/r4.dart';
-import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
 
 /// High-level model of a response to a questionnaire.
 class QuestionnaireResponseModel {
@@ -160,6 +160,7 @@ class QuestionnaireResponseModel {
     List<Aggregator>? aggregators,
     required FhirResourceProvider fhirResourceProvider,
     required LaunchContext launchContext,
+    required FDashLocalizations localizations,
     QuestionnaireModelDefaults questionnaireModelDefaults =
         const QuestionnaireModelDefaults(),
   }) async {
@@ -178,9 +179,9 @@ class QuestionnaireResponseModel {
       questionnaireModel: questionnaireModel,
       aggregators: aggregators ??
           [
-            TotalScoreAggregator(),
-            NarrativeAggregator(),
-            QuestionnaireResponseAggregator(),
+            TotalScoreAggregator(localizations: localizations),
+            NarrativeAggregator(localizations: localizations),
+            QuestionnaireResponseAggregator(localizations: localizations),
           ],
       launchContext: launchContext,
     );
@@ -824,8 +825,10 @@ class QuestionnaireResponseModel {
   ///
   /// Will return the parent [QuestionItemModel] if uid corresponds to an answer.
   FillerItemModel? fillerItemModelByUid(String uid) {
-    final fillerItem =
-        orderedFillerItemModels().firstWhereOrNull((fim) => fim.nodeUid == uid);
+    final fillerItem = orderedFillerItemModels().firstWhereOrNull((fim) {
+      print("UID:" + fim.nodeUid);
+      return fim.nodeUid == uid;
+    });
     if (fillerItem != null) {
       return fillerItem;
     }
@@ -848,20 +851,20 @@ class QuestionnaireResponseModel {
   /// Returns null, if everything is complete.
   /// Returns a map (UID -> error text) with incomplete entries, if items are incomplete.
   Map<String, String>? validate({
+    required FDashLocalizations localizations,
     bool updateErrorText = true,
     bool notifyListeners = false,
   }) {
     final invalidMap = <String, String>{};
 
     for (final itemModel in orderedResponseItemModels()) {
-      final errorTexts = itemModel.validate(
-        updateErrorText: updateErrorText,
-        notifyListeners: notifyListeners,
-      );
-      if (errorTexts != null) {
+      try {
+        itemModel.validate(
+          updateErrorText: updateErrorText,
+          notifyListeners: notifyListeners,
+        );
+      } on ValidationError catch (exception) {
         _logger.debug('$itemModel is invalid.');
-
-        invalidMap.addAll(errorTexts);
       }
     }
 
diff --git a/lib/questionnaires/model/src/rendering_string.dart b/lib/questionnaires/model/src/rendering_string.dart
index 7a05287b..20607959 100644
--- a/lib/questionnaires/model/src/rendering_string.dart
+++ b/lib/questionnaires/model/src/rendering_string.dart
@@ -33,6 +33,8 @@ class RenderingString with Diagnosticable {
   /// The unaltered rendering-markdown extension
   final Markdown? renderingMarkdown;
 
+  final List<FhirExtension>? extensions;
+
   /// Construct an [RenderingString] from the provided attributes.
   ///
   /// No alterations of the attributes will take place, in particular,
@@ -44,6 +46,7 @@ class RenderingString with Diagnosticable {
     this.renderingStyle,
     this.renderingXhtml,
     this.renderingMarkdown,
+    this.extensions,
   });
 
   /// Construct an [RenderingString] from plainText and optional extensions.
@@ -107,6 +110,7 @@ class RenderingString with Diagnosticable {
       renderingStyle: renderingStyle,
       renderingXhtml: renderingXhtml,
       renderingMarkdown: renderingMarkdown,
+      extensions: extensions,
     );
   }
 
diff --git a/lib/questionnaires/view/item/answer/src/attachment_answer_filler.dart b/lib/questionnaires/view/item/answer/src/attachment_answer_filler.dart
index df9c467a..2e4f904b 100644
--- a/lib/questionnaires/view/item/answer/src/attachment_answer_filler.dart
+++ b/lib/questionnaires/view/item/answer/src/attachment_answer_filler.dart
@@ -1,4 +1,5 @@
 import 'package:faiadashu/fhir_types/fhir_types.dart';
+import 'package:faiadashu/l10n/l10n.dart';
 import 'package:faiadashu/questionnaires/questionnaires.dart';
 import 'package:fhir/r4.dart';
 import 'package:flutter/material.dart';
@@ -29,7 +30,8 @@ class _AttachmentAnswerState extends QuestionnaireAnswerFillerState<Attachment,
       );
 }
 
-class _AttachmentInputControl extends AnswerInputControl<AttachmentAnswerModel> {
+class _AttachmentInputControl
+    extends AnswerInputControl<AttachmentAnswerModel> {
   const _AttachmentInputControl(
     AttachmentAnswerModel answerModel, {
     FocusNode? focusNode,
@@ -47,7 +49,7 @@ class _AttachmentInputControl extends AnswerInputControl<AttachmentAnswerModel>
       allowedMimeTypes: answerModel.mimeTypes,
       onChanged: (attachment) => answerModel.value = attachment,
       decoration: InputDecoration(
-        errorText: answerModel.displayErrorText,
+        errorText: answerModel.displayErrorText(FDashLocalizations.of(context)),
       ),
     );
   }
diff --git a/lib/questionnaires/view/item/answer/src/boolean_answer_filler.dart b/lib/questionnaires/view/item/answer/src/boolean_answer_filler.dart
index f924b27a..6426a498 100644
--- a/lib/questionnaires/view/item/answer/src/boolean_answer_filler.dart
+++ b/lib/questionnaires/view/item/answer/src/boolean_answer_filler.dart
@@ -1,3 +1,4 @@
+import 'package:faiadashu/l10n/l10n.dart';
 import 'package:faiadashu/questionnaires/questionnaires.dart';
 import 'package:fhir/r4.dart';
 import 'package:flutter/material.dart';
@@ -47,9 +48,11 @@ class _BooleanInputControl extends AnswerInputControl<BooleanAnswerModel> {
           value: (answerModel.isTriState)
               ? answerModel.value?.value
               : (answerModel.value?.value != null),
-          activeColor: (answerModel.displayErrorText != null)
-              ? Theme.of(context).errorColor
-              : null,
+          activeColor:
+              (answerModel.displayErrorText(FDashLocalizations.of(context)) !=
+                      null)
+                  ? Theme.of(context).errorColor
+                  : null,
           tristate: answerModel.isTriState,
           onChanged: (answerModel.isControlEnabled)
               ? (newValue) {
@@ -62,9 +65,10 @@ class _BooleanInputControl extends AnswerInputControl<BooleanAnswerModel> {
                 }
               : null,
         ),
-        if (answerModel.displayErrorText != null)
+        if (answerModel.displayErrorText(FDashLocalizations.of(context)) !=
+            null)
           Text(
-            answerModel.displayErrorText!,
+            answerModel.displayErrorText(FDashLocalizations.of(context))!,
             style: Theme.of(context)
                 .textTheme
                 .caption!
diff --git a/lib/questionnaires/view/item/answer/src/coding_answer_filler.dart b/lib/questionnaires/view/item/answer/src/coding_answer_filler.dart
index 2507cecd..eb55ff52 100644
--- a/lib/questionnaires/view/item/answer/src/coding_answer_filler.dart
+++ b/lib/questionnaires/view/item/answer/src/coding_answer_filler.dart
@@ -43,13 +43,20 @@ class _CodingInputControl extends AnswerInputControl<CodingAnswerModel> {
 
   @override
   Widget build(BuildContext context) {
-    final errorText = answerModel.displayErrorText;
+    final errorText =
+        answerModel.displayErrorText(FDashLocalizations.of(context));
 
-    return QuestionnaireTheme.of(context).codingControlLayoutBuilder(
-      context,
-      _buildCodingControl(context),
-      openStringInputControlWidget: answerModel.isOptionsOrString ? _OpenStringInputControl(answerModel) : null,
-      errorText: errorText,
+    return Column(
+      children: [
+        QuestionnaireTheme.of(context).codingControlLayoutBuilder(
+          context,
+          _buildCodingControl(context),
+          openStringInputControlWidget: answerModel.isOptionsOrString
+              ? _OpenStringInputControl(answerModel)
+              : null,
+          errorText: errorText,
+        )
+      ],
     );
   }
 
@@ -314,7 +321,7 @@ class _CodingDropdown extends AnswerInputControl<CodingAnswerModel> {
         // Empty error texts triggers red border, but showing text would result in a duplicate.
         errorStyle:
             const TextStyle(height: 0, color: Color.fromARGB(0, 0, 0, 0)),
-        errorText: answerModel.displayErrorText,
+        errorText: answerModel.displayErrorText(FDashLocalizations.of(context)),
       ),
     );
   }
@@ -472,7 +479,9 @@ class _CodingChoiceDecorator extends StatelessWidget {
       child: AnimatedBuilder(
         animation: Focus.of(context),
         builder: (context, child) {
-          final hasError = answerModel.displayErrorText != null;
+          final hasError =
+              answerModel.displayErrorText(FDashLocalizations.of(context)) !=
+                  null;
           final decoTheme = Theme.of(context).inputDecorationTheme;
 
           // TODO: Return something borderless when filled = true
@@ -591,7 +600,7 @@ class _OpenStringInputControlState extends State<_OpenStringInputControl> {
       children: [
         Xhtml.fromRenderingString(
           context,
-          answerModel.openLabel,
+          answerModel.getOpenLabel(FDashLocalizations.of(context)),
           defaultTextStyle: Theme.of(context)
               .textTheme
               .bodyText2
@@ -615,7 +624,8 @@ class _OpenStringInputControlState extends State<_OpenStringInputControl> {
               errorStyle:
                   const TextStyle(height: 0, color: Color.fromARGB(0, 0, 0, 0)),
 
-              errorText: answerModel.displayErrorText,
+              errorText:
+                  answerModel.displayErrorText(FDashLocalizations.of(context)),
             ),
           ),
         ),
@@ -650,7 +660,7 @@ class _FDashAutocompleteField extends StatelessWidget {
         onFieldSubmitted();
       },
       decoration: InputDecoration(
-        errorText: answerModel.displayErrorText,
+        errorText: answerModel.displayErrorText(FDashLocalizations.of(context)),
         hintText: FDashLocalizations.of(context).autoCompleteSearchTermInput,
       ),
     );
diff --git a/lib/questionnaires/view/item/answer/src/datetime_answer_filler.dart b/lib/questionnaires/view/item/answer/src/datetime_answer_filler.dart
index 5c86ceec..910fcf61 100644
--- a/lib/questionnaires/view/item/answer/src/datetime_answer_filler.dart
+++ b/lib/questionnaires/view/item/answer/src/datetime_answer_filler.dart
@@ -1,4 +1,5 @@
 import 'package:faiadashu/fhir_types/fhir_types.dart';
+import 'package:faiadashu/l10n/l10n.dart';
 import 'package:faiadashu/questionnaires/questionnaires.dart';
 import 'package:fhir/r4.dart'
     show Date, FhirDateTime, QuestionnaireItemType, Time;
@@ -65,7 +66,7 @@ class _DateTimeInputControl extends AnswerInputControl<DateTimeAnswerModel> {
       datePickerEntryMode: QuestionnaireTheme.of(context).datePickerEntryMode,
       timePickerEntryMode: QuestionnaireTheme.of(context).timePickerEntryMode,
       decoration: InputDecoration(
-        errorText: answerModel.displayErrorText,
+        errorText: answerModel.displayErrorText(FDashLocalizations.of(context)),
         errorStyle: (itemModel
                 .isCalculated) // Force display of error text on calculated item
             ? TextStyle(
diff --git a/lib/questionnaires/view/item/answer/src/numerical_answer_filler.dart b/lib/questionnaires/view/item/answer/src/numerical_answer_filler.dart
index 09f149c4..6ae3adff 100644
--- a/lib/questionnaires/view/item/answer/src/numerical_answer_filler.dart
+++ b/lib/questionnaires/view/item/answer/src/numerical_answer_filler.dart
@@ -1,4 +1,6 @@
 import 'package:faiadashu/fhir_types/fhir_types.dart';
+import 'package:faiadashu/l10n/l10n.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/custom_validation_error.dart';
 import 'package:faiadashu/questionnaires/questionnaires.dart';
 import 'package:fhir/r4.dart';
 import 'package:flutter/material.dart';
@@ -195,7 +197,8 @@ class _NumberFieldInputControl
             textAlignVertical: TextAlignVertical.center,
             textAlign: TextAlign.end,
             decoration: InputDecoration(
-              errorText: answerModel.displayErrorText,
+              errorText:
+                  answerModel.displayErrorText(FDashLocalizations.of(context)),
               errorStyle: (itemModel
                       .isCalculated) // Force display of error text on calculated item
                   ? TextStyle(
@@ -206,7 +209,9 @@ class _NumberFieldInputControl
               prefixIcon: itemModel.isCalculated
                   ? Icon(
                       Icons.calculate,
-                      color: (answerModel.displayErrorText != null)
+                      color: (answerModel.displayErrorText(
+                                  FDashLocalizations.of(context)) !=
+                              null)
                           ? Theme.of(context).errorColor
                           : null,
                     )
@@ -222,11 +227,16 @@ class _NumberFieldInputControl
               signed: answerModel.minValue < 0,
               decimal: answerModel.maxDecimal > 0,
             ),
-            validator: (itemModel.isCalculated)
-                ? null
-                : (inputValue) {
-                    return answerModel.validateInput(inputValue);
-                  },
+            validator: (inputValue) {
+              try {
+                if (itemModel.isCalculated) {
+                  answerModel.validateInput(inputValue);
+                }
+              } on CustomValidationError catch (exception) {
+                return exception.getMessage(FDashLocalizations.of(context));
+              }
+              return null;
+            },
             autovalidateMode: (itemModel.isCalculated)
                 ? AutovalidateMode.disabled
                 : AutovalidateMode.always,
@@ -237,11 +247,11 @@ class _NumberFieldInputControl
                 // - hasSingleUnitChoice = true (no dropdown shown), or
                 // - user has not interacted with the unit dropdown.
                 value = answerModel
-                  .copyWithUnit(answerModel.unitChoices.first.code?.value)
-                  ?.copyWith(
-                    value: value?.value,
-                    extension_: value?.extension_,
-                  );
+                    .copyWithUnit(answerModel.unitChoices.first.code?.value)
+                    ?.copyWith(
+                      value: value?.value,
+                      extension_: value?.extension_,
+                    );
               }
               answerModel.value = value;
             },
@@ -276,7 +286,8 @@ class _UnitDropDown extends AnswerInputControl<NumericalAnswerModel> {
             width: unitWidth,
             child: DropdownButtonHideUnderline(
               child: DropdownButton<String>(
-                value: answerModel.keyOfUnit ?? answerModel.unitChoices.first.code?.value,
+                value: answerModel.keyOfUnit ??
+                    answerModel.unitChoices.first.code?.value,
                 hint: const NullDashText(),
                 onChanged: (answerModel.isControlEnabled)
                     ? (String? newValue) {
diff --git a/lib/questionnaires/view/item/answer/src/string_answer_filler.dart b/lib/questionnaires/view/item/answer/src/string_answer_filler.dart
index f37ea7e0..e34cb73e 100644
--- a/lib/questionnaires/view/item/answer/src/string_answer_filler.dart
+++ b/lib/questionnaires/view/item/answer/src/string_answer_filler.dart
@@ -1,3 +1,5 @@
+import 'package:faiadashu/l10n/l10n.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/custom_validation_error.dart';
 import 'package:faiadashu/questionnaires/questionnaires.dart';
 import 'package:fhir/r4.dart';
 import 'package:flutter/material.dart';
@@ -94,7 +96,7 @@ class _StringAnswerInputControl extends AnswerInputControl<StringAnswerModel> {
           ? QuestionnaireTheme.of(context).maxLinesForTextItem
           : 1,
       decoration: InputDecoration(
-        errorText: answerModel.displayErrorText,
+        errorText: answerModel.displayErrorText(FDashLocalizations.of(context)),
         errorStyle: (itemModel
                 .isCalculated) // Force display of error text on calculated item
             ? TextStyle(
@@ -105,13 +107,22 @@ class _StringAnswerInputControl extends AnswerInputControl<StringAnswerModel> {
         prefixIcon: itemModel.isCalculated
             ? Icon(
                 Icons.calculate,
-                color: (answerModel.displayErrorText != null)
+                color: (answerModel
+                            .displayErrorText(FDashLocalizations.of(context)) !=
+                        null)
                     ? Theme.of(context).errorColor
                     : null,
               )
             : null,
       ),
-      validator: (inputValue) => answerModel.validateInput(inputValue),
+      validator: (inputValue) {
+        try {
+          answerModel.validateInput(inputValue);
+        } on CustomValidationError catch (exception) {
+          return exception.getMessage(FDashLocalizations.of(context));
+        }
+        return null;
+      },
       autovalidateMode: AutovalidateMode.always,
       onChanged: (content) {
         answerModel.value = content;
diff --git a/lib/questionnaires/view/item/src/group_item.dart b/lib/questionnaires/view/item/src/group_item.dart
index 1f84da43..8274cc26 100644
--- a/lib/questionnaires/view/item/src/group_item.dart
+++ b/lib/questionnaires/view/item/src/group_item.dart
@@ -1,3 +1,4 @@
+import 'package:faiadashu/l10n/l10n.dart';
 import 'package:faiadashu/logging/logging.dart';
 import 'package:faiadashu/questionnaires/questionnaires.dart';
 import 'package:flutter/material.dart';
@@ -30,7 +31,9 @@ class _GroupItemState extends ResponseItemFillerState<GroupItem> {
     return AnimatedBuilder(
       animation: widget.responseItemModel,
       builder: (context, _) {
-        final errorText = widget.responseItemModel.errorText;
+        final errorText = widget.responseItemModel.getErrorText(
+          FDashLocalizations.of(context),
+        );
 
         return widget.responseItemModel.displayVisibility !=
                 DisplayVisibility.hidden
diff --git a/lib/questionnaires/view/item/src/question_response_item_filler.dart b/lib/questionnaires/view/item/src/question_response_item_filler.dart
index ae340549..cc6eaac0 100644
--- a/lib/questionnaires/view/item/src/question_response_item_filler.dart
+++ b/lib/questionnaires/view/item/src/question_response_item_filler.dart
@@ -79,9 +79,8 @@ class QuestionResponseItemFillerState
 
   Widget? _questionSkipperWidget() {
     if (questionnaireTheme.canSkipQuestions &&
-      !widget.questionnaireItemModel.isReadOnly &&
-      !widget.questionnaireItemModel.isRequired
-    ) {
+        !widget.questionnaireItemModel.isReadOnly &&
+        !widget.questionnaireItemModel.isRequired) {
       return Row(
         children: [
           Text(
@@ -121,7 +120,8 @@ class QuestionResponseItemFillerState
               debugDumpFocusTree();
             }, */
             focusNode: focusNode,
-            child: QuestionnaireTheme.of(context).questionResponseItemLayoutBuilder(
+            child: QuestionnaireTheme.of(context)
+                .questionResponseItemLayoutBuilder(
               context,
               widget.responseItemModel as QuestionItemModel,
               _answerFillerWidget(),
diff --git a/lib/questionnaires/view/item/src/questionnaire_item_filler.dart b/lib/questionnaires/view/item/src/questionnaire_item_filler.dart
index 9b6a6a49..c595e392 100644
--- a/lib/questionnaires/view/item/src/questionnaire_item_filler.dart
+++ b/lib/questionnaires/view/item/src/questionnaire_item_filler.dart
@@ -17,7 +17,11 @@ abstract class QuestionnaireItemFiller extends StatefulWidget {
 
 abstract class QuestionnaireItemFillerState<W extends QuestionnaireItemFiller>
     extends State<W> {
-  late final Widget? _titleWidget;
+  late final Widget? _titleWidget = QuestionnaireItemFillerTitle.fromFillerItem(
+    context: context,
+    fillerItem: widget.fillerItemModel,
+    questionnaireTheme: questionnaireTheme,
+  );
   Widget? get titleWidget => _titleWidget;
 
   QuestionnaireFillerData? _questionnaireFiller;
@@ -32,11 +36,6 @@ abstract class QuestionnaireItemFillerState<W extends QuestionnaireItemFiller>
   void initState() {
     super.initState();
     _focusNode = FocusNode(debugLabel: responseUid, skipTraversal: true);
-
-    _titleWidget = QuestionnaireItemFillerTitle.fromFillerItem(
-      fillerItem: widget.fillerItemModel,
-      questionnaireTheme: questionnaireTheme,
-    );
   }
 
   @override
diff --git a/lib/questionnaires/view/item/src/questionnaire_item_filler_title.dart b/lib/questionnaires/view/item/src/questionnaire_item_filler_title.dart
index f0a25ce8..cb8d2015 100644
--- a/lib/questionnaires/view/item/src/questionnaire_item_filler_title.dart
+++ b/lib/questionnaires/view/item/src/questionnaire_item_filler_title.dart
@@ -1,3 +1,4 @@
+import 'package:faiadashu/extensions/string_extension.dart';
 import 'package:faiadashu/fhir_types/fhir_types.dart';
 import 'package:faiadashu/logging/logging.dart';
 import 'package:faiadashu/questionnaires/questionnaires.dart';
@@ -19,6 +20,7 @@ class QuestionnaireItemFillerTitle extends StatelessWidget {
   }) : super(key: key);
 
   static Widget? fromFillerItem({
+    required BuildContext context,
     required FillerItemModel fillerItem,
     required QuestionnaireThemeData questionnaireTheme,
     Key? key,
@@ -48,10 +50,14 @@ class QuestionnaireItemFillerTitle extends StatelessWidget {
               : '</p>';
 
       final prefixText = fillerItem.prefix;
+      final title = text.xhtmlText.translate(
+        questionnaireItemModel.text?.extensions ?? [],
+        Localizations.localeOf(context),
+      );
 
       final htmlTitleText = (prefixText != null)
-          ? '$openStyleTag${prefixText.xhtmlText}&nbsp;${text.xhtmlText}$requiredTag$closeStyleTag'
-          : '$openStyleTag${text.xhtmlText}$requiredTag$closeStyleTag';
+          ? '$openStyleTag${prefixText}&nbsp;${title}$requiredTag$closeStyleTag'
+          : '$openStyleTag${title}$requiredTag$closeStyleTag';
 
       return QuestionnaireItemFillerTitle._(
         htmlTitleText: htmlTitleText,
diff --git a/lib/questionnaires/view/src/questionnaire_complete_button.dart b/lib/questionnaires/view/src/questionnaire_complete_button.dart
index 3c3f0366..eaf36c2d 100644
--- a/lib/questionnaires/view/src/questionnaire_complete_button.dart
+++ b/lib/questionnaires/view/src/questionnaire_complete_button.dart
@@ -31,7 +31,10 @@ class _QuestionnaireCompleteButtonState
         final currentResponseStatus = qrm.responseStatus;
 
         if (currentResponseStatus != QuestionnaireResponseStatus.completed) {
-          final incompleteItems = qrm.validate(notifyListeners: true);
+          final incompleteItems = qrm.validate(
+            localizations: FDashLocalizations.of(context),
+            notifyListeners: true,
+          );
           qrm.invalidityNotifier.value = incompleteItems;
 
           if (incompleteItems != null) {
diff --git a/lib/questionnaires/view/src/questionnaire_filler.dart b/lib/questionnaires/view/src/questionnaire_filler.dart
index babc906d..3a0faca4 100644
--- a/lib/questionnaires/view/src/questionnaire_filler.dart
+++ b/lib/questionnaires/view/src/questionnaire_filler.dart
@@ -1,3 +1,4 @@
+import 'package:faiadashu/l10n/l10n.dart';
 import 'package:faiadashu/logging/logging.dart';
 import 'package:faiadashu/questionnaires/questionnaires.dart';
 import 'package:faiadashu/resource_provider/resource_provider.dart';
@@ -13,7 +14,6 @@ import 'package:flutter/material.dart';
 /// see: [QuestionnaireScrollerPage]
 /// see: [QuestionnaireStepperPage]
 class QuestionnaireResponseFiller extends StatefulWidget {
-  final Locale locale;
   final WidgetBuilder builder;
   final List<Aggregator<dynamic>>? aggregators;
   final void Function(BuildContext context, Uri url)? onLinkTap;
@@ -24,19 +24,19 @@ class QuestionnaireResponseFiller extends StatefulWidget {
   final FhirResourceProvider fhirResourceProvider;
   final LaunchContext launchContext;
 
-  Future<QuestionnaireResponseModel>
-      _createQuestionnaireResponseModel() async =>
-          QuestionnaireResponseModel.fromFhirResourceBundle(
-            locale: locale,
-            aggregators: aggregators,
-            fhirResourceProvider: fhirResourceProvider,
-            launchContext: launchContext,
-            questionnaireModelDefaults: questionnaireModelDefaults,
-          );
+  Future<QuestionnaireResponseModel> _createQuestionnaireResponseModel({
+    required BuildContext context,
+  }) async =>
+      QuestionnaireResponseModel.fromFhirResourceBundle(
+          locale: Localizations.localeOf(context),
+          aggregators: aggregators,
+          fhirResourceProvider: fhirResourceProvider,
+          launchContext: launchContext,
+          questionnaireModelDefaults: questionnaireModelDefaults,
+          localizations: FDashLocalizations.of(context));
 
   const QuestionnaireResponseFiller({
     Key? key,
-    required this.locale,
     required this.builder,
     required this.fhirResourceProvider,
     required this.launchContext,
@@ -65,18 +65,11 @@ class _QuestionnaireResponseFillerState
     extends State<QuestionnaireResponseFiller> {
   static final _logger = Logger(_QuestionnaireResponseFillerState);
 
-  late final Future<QuestionnaireResponseModel> builderFuture;
   QuestionnaireResponseModel? _questionnaireResponseModel;
   VoidCallback? _handleQuestionnaireResponseModelChangeListenerFunction;
   // ignore: use_late_for_private_fields_and_variables
   QuestionnaireFillerData? _questionnaireFillerData;
 
-  @override
-  void initState() {
-    super.initState();
-    builderFuture = widget._createQuestionnaireResponseModel();
-  }
-
   @override
   void didChangeDependencies() {
     super.didChangeDependencies();
@@ -110,7 +103,6 @@ class _QuestionnaireResponseFillerState
         () {
           _questionnaireFillerData = QuestionnaireFillerData._(
             _questionnaireResponseModel!,
-            locale: widget.locale,
             builder: widget.builder,
             onLinkTap: widget.onLinkTap,
             onDataAvailable: widget.onDataAvailable,
@@ -134,7 +126,7 @@ class _QuestionnaireResponseFillerState
     _logger.trace('Enter build()');
 
     return FutureBuilder<QuestionnaireResponseModel>(
-      future: builderFuture,
+      future: widget._createQuestionnaireResponseModel(context: context),
       builder: (context, snapshot) {
         switch (snapshot.connectionState) {
           case ConnectionState.active:
@@ -168,7 +160,6 @@ class _QuestionnaireResponseFillerState
 
                 _questionnaireFillerData = QuestionnaireFillerData._(
                   _questionnaireResponseModel!,
-                  locale: widget.locale,
                   builder: widget.builder,
                   onLinkTap: widget.onLinkTap,
                   onDataAvailable: widget.onDataAvailable,
@@ -191,7 +182,6 @@ class _QuestionnaireResponseFillerState
 class QuestionnaireFillerData extends InheritedWidget {
   static final _logger = Logger(QuestionnaireFillerData);
 
-  final Locale locale;
   final QuestionnaireResponseModel questionnaireResponseModel;
   // TODO: Should this copy exist, or just refer to the qrm as the source of truth?
   final List<FillerItemModel> fillerItemModels;
@@ -206,7 +196,6 @@ class QuestionnaireFillerData extends InheritedWidget {
   QuestionnaireFillerData._(
     this.questionnaireResponseModel, {
     Key? key,
-    required this.locale,
     this.onDataAvailable,
     this.onLinkTap,
     required this.questionnaireTheme,
@@ -258,14 +247,16 @@ class QuestionnaireFillerData extends InheritedWidget {
   /// The [QuestionnaireItemFiller]s are ordered based on 'pre-order'.
   ///
   /// see: https://en.wikipedia.org/wiki/Tree_traversal#Pre-order,_NLR
-  QuestionnaireItemFiller itemFillerAt(int index) {
+  QuestionnaireItemFiller itemFillerAt(BuildContext context, int index) {
     _logger.trace('itemFillerAt $index');
+    final item = _itemFillers[index];
 
-    if (_itemFillers[index] == null) {
+    if (item == null) {
       _logger.debug('itemFillerAt $index will be created.');
       _itemFillers[index] = questionnaireTheme.createQuestionnaireItemFiller(
         this,
         fillerItemModels.elementAt(index),
+        Localizations.localeOf(context),
         key: ValueKey<String>(
           'item-filler-${fillerItemModels.elementAt(index).nodeUid}',
         ),
@@ -284,19 +275,22 @@ class QuestionnaireFillerData extends InheritedWidget {
   /// that is currently visible.
   int indexOfVisibleItemAt(int visibleIndex, {bool rootsOnly = false}) {
     final visibleItems = fillerItemModels
-      .where((item) => item.displayVisibility != DisplayVisibility.hidden)
-      .where((item) => !rootsOnly || item.parentNode == null)
-      .toList(growable: false);
+        .where((item) => item.displayVisibility != DisplayVisibility.hidden)
+        .where((item) => !rootsOnly || item.parentNode == null)
+        .toList(growable: false);
 
-    return visibleItems.length > visibleIndex ? fillerItemModels.indexOf(visibleItems[visibleIndex]) : -1;
+    return visibleItems.length > visibleIndex
+        ? fillerItemModels.indexOf(visibleItems[visibleIndex])
+        : -1;
   }
 
   /// Returns the [QuestionnaireItemFiller] of the [visibleIndex]-th item that is currently
   /// visible.
-  QuestionnaireItemFiller? visibleItemFillerAt(int visibleIndex) {
+  QuestionnaireItemFiller? visibleItemFillerAt(
+      BuildContext context, int visibleIndex) {
     final index = indexOfVisibleItemAt(visibleIndex);
 
-    return index < 0 ? null : itemFillerAt(index);
+    return index < 0 ? null : itemFillerAt(context, index);
   }
 
   /// Returns the integer range of items corresponding to the [visibleRootIndex]-th root item
@@ -306,8 +300,8 @@ class QuestionnaireFillerData extends InheritedWidget {
     if (rootIndex < 0) return [-1, -1];
 
     final descendantsCount = fillerItemModels
-      .where((item) => item.rootNode == fillerItemModels[rootIndex])
-      .length;
+        .where((item) => item.rootNode == fillerItemModels[rootIndex])
+        .length;
 
     return [rootIndex, rootIndex + descendantsCount + 1];
   }
diff --git a/lib/questionnaires/view/src/questionnaire_page_scaffold.dart b/lib/questionnaires/view/src/questionnaire_page_scaffold.dart
index e392c163..3cd4ec87 100644
--- a/lib/questionnaires/view/src/questionnaire_page_scaffold.dart
+++ b/lib/questionnaires/view/src/questionnaire_page_scaffold.dart
@@ -33,11 +33,10 @@ class DefaultQuestionnairePageScaffoldBuilder
   @override
   Widget build(
     BuildContext context, {
-    Locale? locale,
     required void Function(void Function()) setStateCallback,
     required Widget child,
   }) {
-    final theLocale = locale ?? Localizations.localeOf(context);
+    final theLocale = Localizations.localeOf(context);
 
     final questionnaireFiller = QuestionnaireResponseFiller.of(context);
     final questionnaire = questionnaireFiller
diff --git a/lib/questionnaires/view/src/questionnaire_scroller.dart b/lib/questionnaires/view/src/questionnaire_scroller.dart
index 7e94a0a0..4c925cc7 100644
--- a/lib/questionnaires/view/src/questionnaire_scroller.dart
+++ b/lib/questionnaires/view/src/questionnaire_scroller.dart
@@ -26,7 +26,6 @@ import 'package:scrollable_positioned_list/scrollable_positioned_list.dart';
 /// See: [QuestionnaireScrollerPage] for a [QuestionnaireScroller] which already
 /// wraps the list in a ready-made [Scaffold], incl. some commonly used buttons.
 class QuestionnaireScroller extends StatefulWidget {
-  final Locale? locale;
   final FhirResourceProvider fhirResourceProvider;
   final LaunchContext launchContext;
   final List<Aggregator<dynamic>>? aggregators;
@@ -38,7 +37,6 @@ class QuestionnaireScroller extends StatefulWidget {
       onQuestionnaireResponseChanged;
 
   const QuestionnaireScroller({
-    this.locale,
     required this.scaffoldBuilder,
     required this.fhirResourceProvider,
     required this.launchContext,
@@ -153,12 +151,11 @@ class _QuestionnaireScrollerState extends State<QuestionnaireScroller> {
 
   @override
   Widget build(BuildContext context) {
-    final locale = widget.locale ?? Localizations.localeOf(context);
+    final locale = Localizations.localeOf(context);
 
     return QuestionnaireResponseFiller(
       fhirResourceProvider: widget.fhirResourceProvider,
       launchContext: widget.launchContext,
-      locale: locale,
       questionnaireModelDefaults: widget.questionnaireModelDefaults,
       builder: (BuildContext context) {
         _belowFillerContext = context;
@@ -170,50 +167,46 @@ class _QuestionnaireScrollerState extends State<QuestionnaireScroller> {
           'Scroll position: ${_itemPositionsListener.itemPositions.value}',
         );
 
-        return Localizations.override(
-          context: context,
-          locale: locale,
-          child: widget.scaffoldBuilder.build(
-            context,
-            setStateCallback: (fn) {
-              setState(fn);
-            },
-            child: LayoutBuilder(
-              builder: (context, constraints) {
-                const edgeInsets = 8.0;
-                const twice = 2;
-
-                return ScrollablePositionedList.builder(
-                  itemScrollController: _listScrollController,
-                  itemPositionsListener: _itemPositionsListener,
-                  itemCount: totalLength,
-                  padding: const EdgeInsets.all(edgeInsets),
-                  minCacheExtent: 200, // Allow tabbing to prev/next items
-                  itemBuilder: (BuildContext context, int i) {
-                    return Row(
-                      children: [
-                        Container(
-                          constraints: BoxConstraints(
-                            maxWidth: QuestionnaireTheme.of(context)
-                                .maxItemWidth
-                                .clamp(
-                                  constraints.minWidth,
-                                  constraints.maxWidth - twice * edgeInsets,
-                                ),
-                          ),
-                          child: QuestionnaireTheme.of(context).scrollerItemBuilder(
-                            context,
-                            QuestionnaireResponseFiller.of(context),
-                            i,
-                          ),
+        return widget.scaffoldBuilder.build(
+          context,
+          setStateCallback: (fn) {
+            setState(fn);
+          },
+          child: LayoutBuilder(
+            builder: (context, constraints) {
+              const edgeInsets = 8.0;
+              const twice = 2;
+
+              return ScrollablePositionedList.builder(
+                itemScrollController: _listScrollController,
+                itemPositionsListener: _itemPositionsListener,
+                itemCount: totalLength,
+                padding: const EdgeInsets.all(edgeInsets),
+                minCacheExtent: 200, // Allow tabbing to prev/next items
+                itemBuilder: (BuildContext context, int i) {
+                  return Row(
+                    children: [
+                      Container(
+                        constraints: BoxConstraints(
+                          maxWidth:
+                              QuestionnaireTheme.of(context).maxItemWidth.clamp(
+                                    constraints.minWidth,
+                                    constraints.maxWidth - twice * edgeInsets,
+                                  ),
+                        ),
+                        child:
+                            QuestionnaireTheme.of(context).scrollerItemBuilder(
+                          context,
+                          QuestionnaireResponseFiller.of(context),
+                          i,
                         ),
-                        const Spacer(),
-                      ],
-                    );
-                  },
-                );
-              },
-            ),
+                      ),
+                      const Spacer(),
+                    ],
+                  );
+                },
+              );
+            },
           ),
         );
       },
diff --git a/lib/questionnaires/view/src/questionnaire_scroller_page.dart b/lib/questionnaires/view/src/questionnaire_scroller_page.dart
index c3cd388c..4bbc93ef 100644
--- a/lib/questionnaires/view/src/questionnaire_scroller_page.dart
+++ b/lib/questionnaires/view/src/questionnaire_scroller_page.dart
@@ -6,7 +6,6 @@ import 'package:flutter/material.dart';
 ///
 /// Fills up the entire page, provides default navigation, help button.
 class QuestionnaireScrollerPage extends StatelessWidget {
-  final Locale? locale;
   final FhirResourceProvider fhirResourceProvider;
   final LaunchContext launchContext;
   final Widget? floatingActionButton;
@@ -16,7 +15,6 @@ class QuestionnaireScrollerPage extends StatelessWidget {
   final QuestionnaireModelDefaults questionnaireModelDefaults;
 
   const QuestionnaireScrollerPage({
-    this.locale,
     required this.fhirResourceProvider,
     required this.launchContext,
     this.floatingActionButton,
@@ -30,7 +28,6 @@ class QuestionnaireScrollerPage extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     return QuestionnaireScroller(
-      locale: locale,
       scaffoldBuilder: DefaultQuestionnairePageScaffoldBuilder(
         // Progress can only be shown instead of a FAB
         floatingActionButton: floatingActionButton ??
diff --git a/lib/questionnaires/view/src/questionnaire_stepper.dart b/lib/questionnaires/view/src/questionnaire_stepper.dart
index 16ebacbf..c2ec8fd1 100644
--- a/lib/questionnaires/view/src/questionnaire_stepper.dart
+++ b/lib/questionnaires/view/src/questionnaire_stepper.dart
@@ -6,7 +6,6 @@ import 'package:flutter/material.dart';
 
 /// Fill a questionnaire through a wizard-style series of individual questions.
 class QuestionnaireStepper extends StatefulWidget {
-  final Locale? locale;
   final FhirResourceProvider fhirResourceProvider;
   final LaunchContext launchContext;
   final QuestionnairePageScaffoldBuilder scaffoldBuilder;
@@ -23,7 +22,6 @@ class QuestionnaireStepper extends StatefulWidget {
   final void Function(FillerItemModel?)? onVisibleItemUpdated;
 
   const QuestionnaireStepper({
-    this.locale,
     required this.scaffoldBuilder,
     required this.fhirResourceProvider,
     required this.launchContext,
@@ -59,7 +57,6 @@ class QuestionnaireStepperState extends State<QuestionnaireStepper> {
   @override
   Widget build(BuildContext context) {
     return QuestionnaireResponseFiller(
-      locale: widget.locale ?? Localizations.localeOf(context),
       fhirResourceProvider: widget.fhirResourceProvider,
       launchContext: widget.launchContext,
       questionnaireModelDefaults: widget.questionnaireModelDefaults,
@@ -95,7 +92,8 @@ class QuestionnaireStepperState extends State<QuestionnaireStepper> {
                               Decimal value,
                               Widget? child,
                             ) {
-                              final scoreString = value.value!.round().toString();
+                              final scoreString =
+                                  value.value!.round().toString();
 
                               return AnimatedSwitcher(
                                 duration: const Duration(milliseconds: 200),
diff --git a/lib/questionnaires/view/src/questionnaire_stepper_page.dart b/lib/questionnaires/view/src/questionnaire_stepper_page.dart
index 2107bb7e..4b64ead0 100644
--- a/lib/questionnaires/view/src/questionnaire_stepper_page.dart
+++ b/lib/questionnaires/view/src/questionnaire_stepper_page.dart
@@ -8,14 +8,12 @@ import 'package:flutter/material.dart';
 /// see [QuestionnaireScrollerPage]
 class QuestionnaireStepperPage extends QuestionnaireStepper {
   const QuestionnaireStepperPage({
-    Locale? locale,
     required FhirResourceProvider fhirResourceProvider,
     required LaunchContext launchContext,
     QuestionnaireModelDefaults questionnaireModelDefaults =
         const QuestionnaireModelDefaults(),
     Key? key,
   }) : super(
-          locale: locale,
           scaffoldBuilder: const DefaultQuestionnairePageScaffoldBuilder(),
           fhirResourceProvider: fhirResourceProvider,
           launchContext: launchContext,
diff --git a/lib/questionnaires/view/src/questionnaire_stepper_page_view.dart b/lib/questionnaires/view/src/questionnaire_stepper_page_view.dart
index 26265588..b9d90139 100644
--- a/lib/questionnaires/view/src/questionnaire_stepper_page_view.dart
+++ b/lib/questionnaires/view/src/questionnaire_stepper_page_view.dart
@@ -30,8 +30,9 @@ class QuestionnaireStepperPageView extends StatefulWidget {
       _QuestionnaireStepperPageViewState();
 }
 
-class _QuestionnaireStepperPageViewState extends State<QuestionnaireStepperPageView> {
-  PageController _pageController = PageController();
+class _QuestionnaireStepperPageViewState
+    extends State<QuestionnaireStepperPageView> {
+  PageController _pageController = PageController(keepPage: true);
   bool _hasRequestsRunning = false;
   QuestionnaireItemFiller? _currentQuestionnaireItemFiller;
 
@@ -49,6 +50,7 @@ class _QuestionnaireStepperPageViewState extends State<QuestionnaireStepperPageV
     final fillerData = QuestionnaireResponseFiller.of(context);
 
     final nextPageFillerItem = themeData.stepperQuestionnaireItemFiller(
+      context,
       fillerData,
       currentPage + 1,
     );
@@ -74,8 +76,11 @@ class _QuestionnaireStepperPageViewState extends State<QuestionnaireStepperPageV
   void _updateVisibleItem(int index) {
     final responseFiller = QuestionnaireResponseFiller.of(context);
 
-    final data = QuestionnaireTheme.of(context)
-        .stepperQuestionnaireItemFiller(responseFiller, index);
+    final data = QuestionnaireTheme.of(context).stepperQuestionnaireItemFiller(
+      context,
+      responseFiller,
+      index,
+    );
 
     _currentQuestionnaireItemFiller = data;
     widget.onVisibleItemUpdated?.call(data?.fillerItemModel);
@@ -100,8 +105,12 @@ class _QuestionnaireStepperPageViewState extends State<QuestionnaireStepperPageV
       itemBuilder: (BuildContext context, int index) {
         final responseFillerData = QuestionnaireResponseFiller.of(context);
 
-        final data = QuestionnaireTheme.of(context)
-            .stepperQuestionnaireItemFiller(responseFillerData, index);
+        final data =
+            QuestionnaireTheme.of(context).stepperQuestionnaireItemFiller(
+          context,
+          responseFillerData,
+          index,
+        );
 
         _updateVisibleItem(index);
         if (data == null) return null;
diff --git a/lib/questionnaires/view/src/questionnaire_theme.dart b/lib/questionnaires/view/src/questionnaire_theme.dart
index b87c4de8..9ca28a81 100644
--- a/lib/questionnaires/view/src/questionnaire_theme.dart
+++ b/lib/questionnaires/view/src/questionnaire_theme.dart
@@ -1,6 +1,4 @@
-import 'package:faiadashu/l10n/l10n.dart';
-import 'package:faiadashu/logging/logging.dart';
-import 'package:faiadashu/questionnaires/questionnaires.dart';
+import 'package:faiadashu/faiadashu.dart';
 import 'package:flutter/material.dart';
 
 /// Should coding selections be presented in a compact or an expanded format?
@@ -153,6 +151,7 @@ class QuestionnaireThemeData {
   ///
   /// [pageIndex] is the index of the page that's being currently built.
   final QuestionnaireItemFiller? Function(
+    BuildContext context,
     QuestionnaireFillerData responseFiller,
     int pageIndex,
   ) stepperQuestionnaireItemFiller;
@@ -192,7 +191,8 @@ class QuestionnaireThemeData {
   /// Used by [QuestionnaireResponseFiller].
   QuestionnaireItemFiller createQuestionnaireItemFiller(
     QuestionnaireFillerData questionnaireFiller,
-    FillerItemModel fillerItemModel, {
+    FillerItemModel fillerItemModel,
+    Locale locale, {
     Key? key,
   }) {
     if (fillerItemModel is QuestionItemModel) {
@@ -344,14 +344,12 @@ class QuestionnaireThemeData {
             padding: const EdgeInsets.only(top: 8),
             child: titleWidget,
           ),
-        if (promptTextWidget != null)
-          promptTextWidget,
+        if (promptTextWidget != null) promptTextWidget,
         Container(
           padding: const EdgeInsets.only(top: 8),
           child: answerFillerWidget,
         ),
-        if (questionSkipperWidget != null)
-          questionSkipperWidget,
+        if (questionSkipperWidget != null) questionSkipperWidget,
         const SizedBox(height: 16),
       ],
     );
@@ -413,13 +411,14 @@ class QuestionnaireThemeData {
       children: [
         codingControlWidget,
         if (openStringInputControlWidget != null) openStringInputControlWidget,
-        if (errorText != null) Text(
-          errorText,
-          style: Theme.of(context)
-              .textTheme
-              .caption
-              ?.copyWith(color: Theme.of(context).errorColor),
-        ),
+        if (errorText != null)
+          Text(
+            errorText,
+            style: Theme.of(context)
+                .textTheme
+                .caption
+                ?.copyWith(color: Theme.of(context).errorColor),
+          ),
       ],
     );
   }
@@ -429,14 +428,15 @@ class QuestionnaireThemeData {
     QuestionnaireFillerData responseFiller,
     int index,
   ) {
-    return responseFiller.itemFillerAt(index);
+    return responseFiller.itemFillerAt(context, index);
   }
 
   static QuestionnaireItemFiller? _defaultStepperQuestionnaireItemFiller(
+    BuildContext context,
     QuestionnaireFillerData responseFiller,
     int index,
   ) {
-    final itemFiller = responseFiller.visibleItemFillerAt(index);
+    final itemFiller = responseFiller.visibleItemFillerAt(context, index);
     if (itemFiller == null) return null;
 
     return itemFiller;
diff --git a/lib/questionnaires/view/src/xhtml.dart b/lib/questionnaires/view/src/xhtml.dart
index 037a9192..9ebd120f 100644
--- a/lib/questionnaires/view/src/xhtml.dart
+++ b/lib/questionnaires/view/src/xhtml.dart
@@ -1,3 +1,4 @@
+import 'package:faiadashu/extensions/string_extension.dart';
 import 'package:faiadashu/fhir_types/fhir_types.dart';
 import 'package:faiadashu/logging/logging.dart';
 import 'package:faiadashu/questionnaires/model/model.dart';
@@ -54,8 +55,14 @@ class Xhtml extends StatelessWidget {
   }) {
     _logger.trace('enter fromRenderingString $renderingString');
 
-    final xhtml = renderingString.xhtmlText;
-    final plainText = renderingString.plainText;
+    final xhtml = renderingString.xhtmlText.translate(
+      renderingString.extensions,
+      Localizations.localeOf(context),
+    );
+    final plainText = renderingString.plainText.translate(
+      renderingString.extensions,
+      Localizations.localeOf(context),
+    );
 
     if (renderingString.isPlain) {
       return Xhtml._(

From 020a4447724ba611d01507173f015a038e4da005 Mon Sep 17 00:00:00 2001
From: Hanny Prastya Hariyadi <p.hanny@allm.inc>
Date: Mon, 2 Oct 2023 16:21:00 +0900
Subject: [PATCH 02/23] Add validation errors

---
 .../constraint_validation_error.dart            | 13 +++++++++++++
 .../custom_validation_error.dart                | 12 ++++++++++++
 .../src/validation_errors/date_time_error.dart  | 11 +++++++++++
 .../validation_errors/entry_format_error.dart   | 13 +++++++++++++
 .../src/validation_errors/fhir_path_error.dart  | 14 ++++++++++++++
 .../src/validation_errors/max_length_error.dart | 12 ++++++++++++
 .../src/validation_errors/max_occurs_error.dart | 12 ++++++++++++
 .../src/validation_errors/max_size_error.dart   | 13 +++++++++++++
 .../src/validation_errors/max_value_error.dart  | 12 ++++++++++++
 .../src/validation_errors/mime_types_error.dart | 12 ++++++++++++
 .../src/validation_errors/min_length_error.dart | 12 ++++++++++++
 .../src/validation_errors/min_occurs_error.dart | 12 ++++++++++++
 .../src/validation_errors/min_value_error.dart  | 12 ++++++++++++
 .../model/src/validation_errors/nan_error.dart  | 11 +++++++++++
 .../src/validation_errors/regex_error.dart      | 11 +++++++++++
 .../validation_errors/required_item_error.dart  | 11 +++++++++++
 .../single_selection_or_open_string_error.dart  | 17 +++++++++++++++++
 .../model/src/validation_errors/url_error.dart  | 11 +++++++++++
 .../src/validation_errors/validation_error.dart |  9 +++++++++
 19 files changed, 230 insertions(+)
 create mode 100644 lib/questionnaires/model/src/validation_errors/constraint_validation_error.dart
 create mode 100644 lib/questionnaires/model/src/validation_errors/custom_validation_error.dart
 create mode 100644 lib/questionnaires/model/src/validation_errors/date_time_error.dart
 create mode 100644 lib/questionnaires/model/src/validation_errors/entry_format_error.dart
 create mode 100644 lib/questionnaires/model/src/validation_errors/fhir_path_error.dart
 create mode 100644 lib/questionnaires/model/src/validation_errors/max_length_error.dart
 create mode 100644 lib/questionnaires/model/src/validation_errors/max_occurs_error.dart
 create mode 100644 lib/questionnaires/model/src/validation_errors/max_size_error.dart
 create mode 100644 lib/questionnaires/model/src/validation_errors/max_value_error.dart
 create mode 100644 lib/questionnaires/model/src/validation_errors/mime_types_error.dart
 create mode 100644 lib/questionnaires/model/src/validation_errors/min_length_error.dart
 create mode 100644 lib/questionnaires/model/src/validation_errors/min_occurs_error.dart
 create mode 100644 lib/questionnaires/model/src/validation_errors/min_value_error.dart
 create mode 100644 lib/questionnaires/model/src/validation_errors/nan_error.dart
 create mode 100644 lib/questionnaires/model/src/validation_errors/regex_error.dart
 create mode 100644 lib/questionnaires/model/src/validation_errors/required_item_error.dart
 create mode 100644 lib/questionnaires/model/src/validation_errors/single_selection_or_open_string_error.dart
 create mode 100644 lib/questionnaires/model/src/validation_errors/url_error.dart
 create mode 100644 lib/questionnaires/model/src/validation_errors/validation_error.dart

diff --git a/lib/questionnaires/model/src/validation_errors/constraint_validation_error.dart b/lib/questionnaires/model/src/validation_errors/constraint_validation_error.dart
new file mode 100644
index 00000000..c4106738
--- /dev/null
+++ b/lib/questionnaires/model/src/validation_errors/constraint_validation_error.dart
@@ -0,0 +1,13 @@
+import 'package:faiadashu/l10n/src/fdash_localizations.g.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/validation_error.dart';
+
+class ConstraintValidationError extends ValidationError {
+  final String? message;
+  const ConstraintValidationError(String nodeUid, this.message)
+      : super(nodeUid);
+
+  @override
+  String? getMessage(FDashLocalizations localizations) {
+    return message;
+  }
+}
diff --git a/lib/questionnaires/model/src/validation_errors/custom_validation_error.dart b/lib/questionnaires/model/src/validation_errors/custom_validation_error.dart
new file mode 100644
index 00000000..1351d41f
--- /dev/null
+++ b/lib/questionnaires/model/src/validation_errors/custom_validation_error.dart
@@ -0,0 +1,12 @@
+import 'package:faiadashu/l10n/src/fdash_localizations.g.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/validation_error.dart';
+
+class CustomValidationError extends ValidationError {
+  final String? message;
+  const CustomValidationError(String nodeUid, this.message) : super(nodeUid);
+
+  @override
+  String? getMessage(FDashLocalizations localizations) {
+    return message!;
+  }
+}
diff --git a/lib/questionnaires/model/src/validation_errors/date_time_error.dart b/lib/questionnaires/model/src/validation_errors/date_time_error.dart
new file mode 100644
index 00000000..55f8b6f0
--- /dev/null
+++ b/lib/questionnaires/model/src/validation_errors/date_time_error.dart
@@ -0,0 +1,11 @@
+import 'package:faiadashu/l10n/src/fdash_localizations.g.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/validation_error.dart';
+
+class DateTimeError extends ValidationError {
+  DateTimeError(super.nodeUid);
+
+  @override
+  String? getMessage(FDashLocalizations localizations) {
+    return localizations.validatorDateTime;
+  }
+}
diff --git a/lib/questionnaires/model/src/validation_errors/entry_format_error.dart b/lib/questionnaires/model/src/validation_errors/entry_format_error.dart
new file mode 100644
index 00000000..c000bf54
--- /dev/null
+++ b/lib/questionnaires/model/src/validation_errors/entry_format_error.dart
@@ -0,0 +1,13 @@
+import 'package:faiadashu/l10n/src/fdash_localizations.g.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/validation_error.dart';
+
+class EntryFormatError extends ValidationError {
+  final String entryFormat;
+
+  const EntryFormatError(String nodeUid, this.entryFormat) : super(nodeUid);
+
+  @override
+  String? getMessage(FDashLocalizations localizations) {
+    return localizations.validatorEntryFormat(entryFormat);
+  }
+}
diff --git a/lib/questionnaires/model/src/validation_errors/fhir_path_error.dart b/lib/questionnaires/model/src/validation_errors/fhir_path_error.dart
new file mode 100644
index 00000000..52a889ab
--- /dev/null
+++ b/lib/questionnaires/model/src/validation_errors/fhir_path_error.dart
@@ -0,0 +1,14 @@
+import 'package:faiadashu/l10n/src/fdash_localizations.g.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/validation_error.dart';
+import 'package:fhir_path/fhir_path.dart';
+
+class FhirPathError extends ValidationError {
+  final FhirPathEvaluationException exception;
+
+  const FhirPathError(String nodeUid, this.exception) : super(nodeUid);
+
+  @override
+  String? getMessage(FDashLocalizations localizations) {
+    return exception.message;
+  }
+}
diff --git a/lib/questionnaires/model/src/validation_errors/max_length_error.dart b/lib/questionnaires/model/src/validation_errors/max_length_error.dart
new file mode 100644
index 00000000..557fd317
--- /dev/null
+++ b/lib/questionnaires/model/src/validation_errors/max_length_error.dart
@@ -0,0 +1,12 @@
+import 'package:faiadashu/l10n/src/fdash_localizations.g.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/validation_error.dart';
+
+class MaxLengthError extends ValidationError {
+  final int maxLength;
+  MaxLengthError(String nodeUid, this.maxLength) : super(nodeUid);
+
+  @override
+  String? getMessage(FDashLocalizations localizations) {
+    return localizations.validatorMaxLength(maxLength);
+  }
+}
diff --git a/lib/questionnaires/model/src/validation_errors/max_occurs_error.dart b/lib/questionnaires/model/src/validation_errors/max_occurs_error.dart
new file mode 100644
index 00000000..894ed9d1
--- /dev/null
+++ b/lib/questionnaires/model/src/validation_errors/max_occurs_error.dart
@@ -0,0 +1,12 @@
+import 'package:faiadashu/l10n/src/fdash_localizations.g.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/validation_error.dart';
+
+class MaxOccursError extends ValidationError {
+  final int maxOccurs;
+  MaxOccursError(String nodeUid, this.maxOccurs) : super(nodeUid);
+
+  @override
+  String? getMessage(FDashLocalizations localizations) {
+    return localizations.validatorMaxOccurs(maxOccurs);
+  }
+}
diff --git a/lib/questionnaires/model/src/validation_errors/max_size_error.dart b/lib/questionnaires/model/src/validation_errors/max_size_error.dart
new file mode 100644
index 00000000..226608c0
--- /dev/null
+++ b/lib/questionnaires/model/src/validation_errors/max_size_error.dart
@@ -0,0 +1,13 @@
+import 'package:faiadashu/l10n/src/fdash_localizations.g.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/validation_error.dart';
+import 'package:filesize/filesize.dart';
+
+class MaxSizeError extends ValidationError {
+  final size;
+  MaxSizeError(String nodeUid, this.size) : super(nodeUid);
+
+  @override
+  String? getMessage(FDashLocalizations localizations) {
+    return localizations.validatorMaxSize(filesize(size));
+  }
+}
diff --git a/lib/questionnaires/model/src/validation_errors/max_value_error.dart b/lib/questionnaires/model/src/validation_errors/max_value_error.dart
new file mode 100644
index 00000000..387c2067
--- /dev/null
+++ b/lib/questionnaires/model/src/validation_errors/max_value_error.dart
@@ -0,0 +1,12 @@
+import 'package:faiadashu/l10n/src/fdash_localizations.g.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/validation_error.dart';
+
+class MaxValueError extends ValidationError {
+  final String maxValue;
+  MaxValueError(String nodeUid, this.maxValue) : super(nodeUid);
+
+  @override
+  String? getMessage(FDashLocalizations localizations) {
+    return localizations.validatorMaxValue(maxValue);
+  }
+}
diff --git a/lib/questionnaires/model/src/validation_errors/mime_types_error.dart b/lib/questionnaires/model/src/validation_errors/mime_types_error.dart
new file mode 100644
index 00000000..9b4b098a
--- /dev/null
+++ b/lib/questionnaires/model/src/validation_errors/mime_types_error.dart
@@ -0,0 +1,12 @@
+import 'package:faiadashu/l10n/src/fdash_localizations.g.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/validation_error.dart';
+
+class MimeTypesError extends ValidationError {
+  final List<String> mimeTypes;
+  MimeTypesError(String nodeUid, this.mimeTypes) : super(nodeUid);
+
+  @override
+  String? getMessage(FDashLocalizations localizations) {
+    return localizations.validatorMimeTypes(mimeTypes.join(","));
+  }
+}
diff --git a/lib/questionnaires/model/src/validation_errors/min_length_error.dart b/lib/questionnaires/model/src/validation_errors/min_length_error.dart
new file mode 100644
index 00000000..f910f575
--- /dev/null
+++ b/lib/questionnaires/model/src/validation_errors/min_length_error.dart
@@ -0,0 +1,12 @@
+import 'package:faiadashu/l10n/src/fdash_localizations.g.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/validation_error.dart';
+
+class MinLengthError extends ValidationError {
+  final int minLength;
+  MinLengthError(String nodeUid, this.minLength) : super(nodeUid);
+
+  @override
+  String? getMessage(FDashLocalizations localizations) {
+    return localizations.validatorMinLength(minLength);
+  }
+}
diff --git a/lib/questionnaires/model/src/validation_errors/min_occurs_error.dart b/lib/questionnaires/model/src/validation_errors/min_occurs_error.dart
new file mode 100644
index 00000000..68c1bb23
--- /dev/null
+++ b/lib/questionnaires/model/src/validation_errors/min_occurs_error.dart
@@ -0,0 +1,12 @@
+import 'package:faiadashu/l10n/src/fdash_localizations.g.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/validation_error.dart';
+
+class MinOccursError extends ValidationError {
+  final int minOccurs;
+  MinOccursError(String nodeUid, this.minOccurs) : super(nodeUid);
+
+  @override
+  String? getMessage(FDashLocalizations localizations) {
+    return localizations.validatorMinOccurs(minOccurs);
+  }
+}
diff --git a/lib/questionnaires/model/src/validation_errors/min_value_error.dart b/lib/questionnaires/model/src/validation_errors/min_value_error.dart
new file mode 100644
index 00000000..bc6cefc9
--- /dev/null
+++ b/lib/questionnaires/model/src/validation_errors/min_value_error.dart
@@ -0,0 +1,12 @@
+import 'package:faiadashu/l10n/src/fdash_localizations.g.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/validation_error.dart';
+
+class MinValueError extends ValidationError {
+  final String minValue;
+  MinValueError(String nodeUid, this.minValue) : super(nodeUid);
+
+  @override
+  String? getMessage(FDashLocalizations localizations) {
+    return localizations.validatorMinValue(minValue);
+  }
+}
diff --git a/lib/questionnaires/model/src/validation_errors/nan_error.dart b/lib/questionnaires/model/src/validation_errors/nan_error.dart
new file mode 100644
index 00000000..114cb164
--- /dev/null
+++ b/lib/questionnaires/model/src/validation_errors/nan_error.dart
@@ -0,0 +1,11 @@
+import 'package:faiadashu/l10n/src/fdash_localizations.g.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/validation_error.dart';
+
+class NanError extends ValidationError {
+  NanError(super.nodeUid);
+
+  @override
+  String? getMessage(FDashLocalizations localizations) {
+    return localizations.validatorNan;
+  }
+}
diff --git a/lib/questionnaires/model/src/validation_errors/regex_error.dart b/lib/questionnaires/model/src/validation_errors/regex_error.dart
new file mode 100644
index 00000000..5b6451ba
--- /dev/null
+++ b/lib/questionnaires/model/src/validation_errors/regex_error.dart
@@ -0,0 +1,11 @@
+import 'package:faiadashu/l10n/src/fdash_localizations.g.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/validation_error.dart';
+
+class RegexError extends ValidationError {
+  RegexError(super.nodeUid);
+
+  @override
+  String? getMessage(FDashLocalizations localizations) {
+    return localizations.validatorRegExp;
+  }
+}
diff --git a/lib/questionnaires/model/src/validation_errors/required_item_error.dart b/lib/questionnaires/model/src/validation_errors/required_item_error.dart
new file mode 100644
index 00000000..634992d9
--- /dev/null
+++ b/lib/questionnaires/model/src/validation_errors/required_item_error.dart
@@ -0,0 +1,11 @@
+import 'package:faiadashu/l10n/src/fdash_localizations.g.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/validation_error.dart';
+
+class RequiredItemError extends ValidationError {
+  RequiredItemError(super.nodeUid);
+
+  @override
+  String? getMessage(FDashLocalizations localizations) {
+    return localizations.validatorRequiredItem;
+  }
+}
diff --git a/lib/questionnaires/model/src/validation_errors/single_selection_or_open_string_error.dart b/lib/questionnaires/model/src/validation_errors/single_selection_or_open_string_error.dart
new file mode 100644
index 00000000..aee98d8b
--- /dev/null
+++ b/lib/questionnaires/model/src/validation_errors/single_selection_or_open_string_error.dart
@@ -0,0 +1,17 @@
+import 'package:faiadashu/l10n/src/fdash_localizations.g.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/validation_error.dart';
+
+class SingleSelectionOrOpenStringError extends ValidationError {
+  final String? openLabel;
+  SingleSelectionOrOpenStringError(
+    String nodeUid,
+    this.openLabel,
+  ) : super(nodeUid);
+
+  @override
+  String? getMessage(FDashLocalizations localizations) {
+    return localizations.validatorSingleSelectionOrSingleOpenString(
+      openLabel ?? localizations.fillerOpenCodingOtherLabel,
+    );
+  }
+}
diff --git a/lib/questionnaires/model/src/validation_errors/url_error.dart b/lib/questionnaires/model/src/validation_errors/url_error.dart
new file mode 100644
index 00000000..e84dc17d
--- /dev/null
+++ b/lib/questionnaires/model/src/validation_errors/url_error.dart
@@ -0,0 +1,11 @@
+import 'package:faiadashu/l10n/src/fdash_localizations.g.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/validation_error.dart';
+
+class UrlError extends ValidationError {
+  UrlError(super.nodeUid);
+
+  @override
+  String? getMessage(FDashLocalizations localizations) {
+    return localizations.validatorUrl;
+  }
+}
diff --git a/lib/questionnaires/model/src/validation_errors/validation_error.dart b/lib/questionnaires/model/src/validation_errors/validation_error.dart
new file mode 100644
index 00000000..46b50acd
--- /dev/null
+++ b/lib/questionnaires/model/src/validation_errors/validation_error.dart
@@ -0,0 +1,9 @@
+import 'package:faiadashu/l10n/l10n.dart';
+
+abstract class ValidationError {
+  final String nodeUid;
+
+  const ValidationError(this.nodeUid);
+
+  String? getMessage(FDashLocalizations localizations);
+}

From 77d97d371b6bc9c7c0a026c1ea6cf41331ce9de8 Mon Sep 17 00:00:00 2001
From: Hanny Prastya Hariyadi <p.hanny@allm.inc>
Date: Mon, 2 Oct 2023 19:21:58 +0900
Subject: [PATCH 03/23] Update example

---
 .../custom_questionnaire_stepper_page.dart    |  45 ++++-
 example/lib/main.dart                         |  99 +++++++---
 example/lib/questionnaire_launch_tile.dart    | 174 +++++++++---------
 3 files changed, 203 insertions(+), 115 deletions(-)

diff --git a/example/lib/custom_questionnaire_stepper_page.dart b/example/lib/custom_questionnaire_stepper_page.dart
index cc1d9910..e18513a8 100644
--- a/example/lib/custom_questionnaire_stepper_page.dart
+++ b/example/lib/custom_questionnaire_stepper_page.dart
@@ -1,4 +1,6 @@
 import 'package:faiadashu/faiadashu.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/validation_error.dart';
+import 'package:faiadashu_example/main.dart';
 import 'package:flutter/material.dart';
 
 class CustomQuestionnaireStepperPage extends StatefulWidget {
@@ -40,9 +42,11 @@ class _CustomQuestionnaireStepperPageState
       return;
     }
 
-    // Validate the first matching item, and if it's valid, navigate to the next page
-    if (matchingItems.first.validate(notifyListeners: true) == null) {
+    try {
+      matchingItems.first.validate(notifyListeners: true);
       _navigateToNextPage();
+    } on ValidationError {
+      rethrow;
     }
   }
 
@@ -67,8 +71,39 @@ class _CustomQuestionnaireStepperPageState
           children: [
             Expanded(
               child: QuestionnaireStepper(
-                  scaffoldBuilder:
-                      const DefaultQuestionnairePageScaffoldBuilder(),
+                  scaffoldBuilder: DefaultQuestionnairePageScaffoldBuilder(
+                      persistentFooterButtons: [
+                        PopupMenuButton<Locale>(
+                          icon: const Icon(Icons.language),
+                          onSelected: (Locale locale) {
+                            LocaleInheritedWidget.of(context)
+                                .updateLocale(locale);
+                          },
+                          itemBuilder: (BuildContext context) =>
+                              <PopupMenuEntry<Locale>>[
+                            const PopupMenuItem<Locale>(
+                              value: Locale('en'),
+                              child: Text('English'),
+                            ),
+                            const PopupMenuItem<Locale>(
+                              value: Locale('ar'),
+                              child: Text('عَرَبِيّ'),
+                            ),
+                            const PopupMenuItem<Locale>(
+                              value: Locale('de'),
+                              child: Text('Deutsch'),
+                            ),
+                            const PopupMenuItem<Locale>(
+                              value: Locale('es'),
+                              child: Text('Español'),
+                            ),
+                            const PopupMenuItem<Locale>(
+                              value: Locale('ja'),
+                              child: Text('日本語'),
+                            ),
+                          ],
+                        ),
+                      ]),
                   fhirResourceProvider: widget.fhirResourceProvider,
                   launchContext: widget.launchContext,
                   controller: _controller,
@@ -77,8 +112,6 @@ class _CustomQuestionnaireStepperPageState
                   },
                   onPageChanged: _onPageChanged,
                   onBeforePageChanged: (currentItemModel, nextItemModel) async {
-                    /// Adding delay
-                    await Future.delayed(Duration(seconds: 1));
                     return BeforePageChangedData(canProceed: true);
                   },
                   onVisibleItemUpdated: (item) {
diff --git a/example/lib/main.dart b/example/lib/main.dart
index 0019d3c9..a37fd3cf 100644
--- a/example/lib/main.dart
+++ b/example/lib/main.dart
@@ -44,32 +44,73 @@ void main() {
   runApp(const MyApp());
 }
 
-class MyApp extends StatelessWidget {
+class MyApp extends StatefulWidget {
   const MyApp({Key? key}) : super(key: key);
 
+  @override
+  MyAppState createState() => MyAppState();
+}
+
+class MyAppState extends State<MyApp> {
+  Locale _currentLocale = const Locale('en', 'US');
+
+  void _updateLocale(Locale newLocale) {
+    setState(() {
+      _currentLocale = newLocale;
+    });
+  }
+
   @override
   Widget build(BuildContext context) {
-    return MaterialApp(
-      debugShowCheckedModeBanner: false,
-      theme: ThemeData.light(useMaterial3: true).copyWith(
-        colorScheme: ColorScheme.fromSeed(seedColor: Colors.pink),
-        inputDecorationTheme: ThemeData.light(useMaterial3: true).inputDecorationTheme.copyWith(
-              filled: true,
-            ),
+    return LocaleInheritedWidget(
+      updateLocale: _updateLocale,
+      currentLocale: _currentLocale,
+      child: MaterialApp(
+        debugShowCheckedModeBanner: false,
+        theme: ThemeData.light(useMaterial3: true).copyWith(
+          colorScheme: ColorScheme.fromSeed(seedColor: Colors.pink),
+          inputDecorationTheme:
+              ThemeData.light(useMaterial3: true).inputDecorationTheme.copyWith(
+                    filled: true,
+                  ),
+        ),
+        darkTheme: ThemeData.dark(useMaterial3: true),
+        title: 'Faiadashu™ FHIRDash Gallery',
+        localizationsDelegates: const [
+          FDashLocalizations.delegate,
+          GlobalMaterialLocalizations.delegate,
+          GlobalWidgetsLocalizations.delegate,
+          GlobalCupertinoLocalizations.delegate,
+        ],
+        supportedLocales: FDashLocalizations.supportedLocales,
+        locale: _currentLocale,
+        home: const HomePage(),
       ),
-      darkTheme: ThemeData.dark(useMaterial3: true),
-      title: 'Faiadashu™ FHIRDash Gallery',
-      localizationsDelegates: const [
-        FDashLocalizations.delegate,
-        GlobalMaterialLocalizations.delegate,
-        GlobalWidgetsLocalizations.delegate,
-      ],
-      supportedLocales: FDashLocalizations.supportedLocales,
-      home: const HomePage(),
     );
   }
 }
 
+class LocaleInheritedWidget extends InheritedWidget {
+  final Function(Locale) updateLocale;
+  final Locale currentLocale;
+
+  const LocaleInheritedWidget({
+    Key? key,
+    required this.updateLocale,
+    required this.currentLocale,
+    required Widget child,
+  }) : super(key: key, child: child);
+
+  @override
+  bool updateShouldNotify(LocaleInheritedWidget old) {
+    return old.currentLocale != currentLocale;
+  }
+
+  static LocaleInheritedWidget of(BuildContext context) {
+    return context.dependOnInheritedWidgetOfExactType<LocaleInheritedWidget>()!;
+  }
+}
+
 class HomePage extends StatefulWidget {
   const HomePage({Key? key}) : super(key: key);
 
@@ -123,7 +164,6 @@ class _HomePageState extends State<HomePage> {
       clientId: '4564f6f7-335f-43d3-8867-a0f4e6f901d6',
       redirectUri: FhirUri('com.legentix.faiagallery://callback'),
     );
-
   }
 
   @override
@@ -134,7 +174,8 @@ class _HomePageState extends State<HomePage> {
 
   /// Schedules repaint after login / logout.
   void _onLoginChanged() {
-    _logger.debug('_onLoginChanged: ${questionnaireResponseStorage.smartClient.isLoggedIn()}');
+    _logger.debug(
+        '_onLoginChanged: ${questionnaireResponseStorage.smartClient.isLoggedIn()}');
     setState(() {
       // Rebuild
     });
@@ -206,7 +247,8 @@ class _HomePageState extends State<HomePage> {
           ),
         ),
         actions: [
-          SmartLoginButton(questionnaireResponseStorage.smartClient, onLoginChanged: _onLoginChanged)
+          SmartLoginButton(questionnaireResponseStorage.smartClient,
+              onLoginChanged: _onLoginChanged)
         ],
       ),
       body: SafeArea(
@@ -225,7 +267,8 @@ class _HomePageState extends State<HomePage> {
                 launchContext: launchContext,
                 questionnairePath: 'assets/instruments/beverage_ig.json',
                 saveResponseFunction: questionnaireResponseStorage.saveToMemory,
-                restoreResponseFunction: questionnaireResponseStorage.restoreFromMemory,
+                restoreResponseFunction:
+                    questionnaireResponseStorage.restoreFromMemory,
                 uploadResponseFunction: uploadResponseFunction,
                 questionnaireModelDefaults: QuestionnaireModelDefaults(
                   prefixBuilder: (fim) {
@@ -358,7 +401,7 @@ class _HomePageState extends State<HomePage> {
                         child: CustomQuestionnaireStepperPage(
                           fhirResourceProvider: AssetResourceProvider.singleton(
                             questionnaireResourceUri,
-                            'assets/instruments/framingham-hcdc.json',
+                            'assets/instruments/triage.json',
                           ),
                           launchContext: launchContext,
                         ),
@@ -396,7 +439,8 @@ class _HomePageState extends State<HomePage> {
                 launchContext: launchContext,
                 questionnairePath: 'assets/instruments/bluebook.json',
                 saveResponseFunction: questionnaireResponseStorage.saveToMemory,
-                restoreResponseFunction: questionnaireResponseStorage.restoreFromMemory,
+                restoreResponseFunction:
+                    questionnaireResponseStorage.restoreFromMemory,
                 uploadResponseFunction: uploadResponseFunction,
               ),
               _launchQuestionnaire(
@@ -425,7 +469,8 @@ class _HomePageState extends State<HomePage> {
                 launchContext: launchContext,
                 questionnairePath: 'assets/instruments/argonaut_sampler.json',
                 saveResponseFunction: questionnaireResponseStorage.saveToMemory,
-                restoreResponseFunction: questionnaireResponseStorage.restoreFromMemory,
+                restoreResponseFunction:
+                    questionnaireResponseStorage.restoreFromMemory,
                 uploadResponseFunction: uploadResponseFunction,
               ),
               QuestionnaireLaunchTile(
@@ -439,7 +484,8 @@ class _HomePageState extends State<HomePage> {
                 launchContext: launchContext,
                 questionnairePath: 'assets/instruments/argonaut_sampler.json',
                 saveResponseFunction: questionnaireResponseStorage.saveToMemory,
-                restoreResponseFunction: questionnaireResponseStorage.restoreFromMemory,
+                restoreResponseFunction:
+                    questionnaireResponseStorage.restoreFromMemory,
                 uploadResponseFunction: uploadResponseFunction,
               ),
               QuestionnaireLaunchTile(
@@ -453,7 +499,8 @@ class _HomePageState extends State<HomePage> {
                 launchContext: launchContext,
                 questionnairePath: 'assets/instruments/argonaut_sampler.json',
                 saveResponseFunction: questionnaireResponseStorage.saveToMemory,
-                restoreResponseFunction: questionnaireResponseStorage.restoreFromMemory,
+                restoreResponseFunction:
+                    questionnaireResponseStorage.restoreFromMemory,
                 uploadResponseFunction: uploadResponseFunction,
               ),
               _headline(
diff --git a/example/lib/questionnaire_launch_tile.dart b/example/lib/questionnaire_launch_tile.dart
index d8f04e96..cbfe0cec 100644
--- a/example/lib/questionnaire_launch_tile.dart
+++ b/example/lib/questionnaire_launch_tile.dart
@@ -15,11 +15,12 @@ class QuestionnaireLaunchTile extends StatefulWidget {
   final Locale? locale;
   final FhirResourceProvider fhirResourceProvider;
   final LaunchContext launchContext;
-  final void Function(String questionnairePath, QuestionnaireResponse? questionnaireResponse)
-      saveResponseFunction;
-  final void Function(BuildContext context, String questionnairePath, QuestionnaireResponse? questionnaireResponse)?
-      uploadResponseFunction;
-  final QuestionnaireResponse? Function(String questionnairePath) restoreResponseFunction;
+  final void Function(String questionnairePath,
+      QuestionnaireResponse? questionnaireResponse) saveResponseFunction;
+  final void Function(BuildContext context, String questionnairePath,
+      QuestionnaireResponse? questionnaireResponse)? uploadResponseFunction;
+  final QuestionnaireResponse? Function(String questionnairePath)
+      restoreResponseFunction;
 
   final QuestionnaireModelDefaults questionnaireModelDefaults;
 
@@ -45,7 +46,6 @@ class QuestionnaireLaunchTile extends StatefulWidget {
 
 class _QuestionnaireLaunchTileState extends State<QuestionnaireLaunchTile> {
   late final FhirResourceProvider _questionnaireProvider;
-  late Locale _locale;
   late NumberFormat _percentPattern;
   late Future<QuestionnaireResponseModel> _modelFuture;
 
@@ -58,11 +58,13 @@ class _QuestionnaireLaunchTileState extends State<QuestionnaireLaunchTile> {
     );
   }
 
-  Future<QuestionnaireResponseModel> _createModelFuture() {
+  Future<QuestionnaireResponseModel> _createModelFuture(
+      FDashLocalizations localizations) {
     return QuestionnaireResponseModel.fromFhirResourceBundle(
+      localizations: localizations,
       fhirResourceProvider: _questionnaireProvider,
       launchContext: widget.launchContext,
-      locale: _locale,
+      locale: Locale('ja'),
     ).then<QuestionnaireResponseModel>((qrm) {
       qrm.populate(
         widget.restoreResponseFunction.call(widget.questionnairePath),
@@ -74,9 +76,10 @@ class _QuestionnaireLaunchTileState extends State<QuestionnaireLaunchTile> {
   @override
   void didChangeDependencies() {
     super.didChangeDependencies();
-    _locale = widget.locale ?? Localizations.localeOf(context);
-    _percentPattern = NumberFormat.percentPattern(_locale.toString());
-    _modelFuture = _createModelFuture();
+    _percentPattern = NumberFormat.percentPattern(
+      Localizations.localeOf(context).toString(),
+    );
+    _modelFuture = _createModelFuture(FDashLocalizations.of(context));
   }
 
   @override
@@ -134,62 +137,92 @@ class _QuestionnaireLaunchTileState extends State<QuestionnaireLaunchTile> {
         Navigator.push(
           context,
           MaterialPageRoute(
-            builder: (context) => QuestionnaireScrollerPage(
-              locale: _locale,
-              fhirResourceProvider: RegistryFhirResourceProvider([
-                AssetResourceProvider.singleton(
-                  questionnaireResourceUri,
-                  widget.questionnairePath,
-                ),
-                InMemoryResourceProvider.inMemory(
-                  questionnaireResponseResourceUri,
-                  widget.restoreResponseFunction(
+            builder: (context) => Localizations.override(
+              context: context,
+              locale: widget.locale,
+              child: QuestionnaireScrollerPage(
+                fhirResourceProvider: RegistryFhirResourceProvider([
+                  AssetResourceProvider.singleton(
+                    questionnaireResourceUri,
                     widget.questionnairePath,
                   ),
-                ),
-                widget.fhirResourceProvider,
-              ]),
-              launchContext: widget.launchContext,
-              // Callback for supportLink
-              onLinkTap: launchLink,
-              persistentFooterButtons: [
-                Builder(
-                  builder: (context) => const QuestionnaireCompleteButton(),
-                ),
-                if (widget.uploadResponseFunction != null)
+                  InMemoryResourceProvider.inMemory(
+                    questionnaireResponseResourceUri,
+                    widget.restoreResponseFunction(
+                      widget.questionnairePath,
+                    ),
+                  ),
+                  widget.fhirResourceProvider,
+                ]),
+                launchContext: widget.launchContext,
+                // Callback for supportLink
+                onLinkTap: launchLink,
+                persistentFooterButtons: [
+                  Builder(
+                    builder: (context) => const QuestionnaireCompleteButton(),
+                  ),
+                  if (widget.uploadResponseFunction != null)
+                    Builder(
+                      builder: (context) => ElevatedButton.icon(
+                        label: Text(
+                          FDashLocalizations.of(context)
+                              .handlingUploadButtonLabel,
+                        ),
+                        icon: const Icon(Icons.cloud_upload),
+                        onPressed: () {
+                          // Generate a response and upload it to a FHIR server.
+                          // In a real-world scenario this would have more robust state handling.
+                          widget.uploadResponseFunction?.call(
+                            context,
+                            widget.questionnairePath,
+                            QuestionnaireResponseFiller.of(context)
+                                .aggregator<QuestionnaireResponseAggregator>()
+                                .aggregate(
+                                  responseStatus:
+                                      QuestionnaireResponseStatus.completed,
+                                ),
+                          );
+                          ScaffoldMessenger.of(context).showSnackBar(
+                            SnackBar(
+                              content: Row(
+                                mainAxisAlignment:
+                                    MainAxisAlignment.spaceBetween,
+                                children: [
+                                  Text(
+                                    FDashLocalizations.of(context)
+                                        .handlingUploading,
+                                  ),
+                                  SyncIndicator(
+                                    color:
+                                        Theme.of(context).colorScheme.primary,
+                                  )
+                                ],
+                              ),
+                            ),
+                          );
+                          Navigator.pop(context);
+                        },
+                      ),
+                    ),
                   Builder(
                     builder: (context) => ElevatedButton.icon(
                       label: Text(
-                        FDashLocalizations.of(context)
-                            .handlingUploadButtonLabel,
+                        FDashLocalizations.of(context).handlingSaveButtonLabel,
                       ),
-                      icon: const Icon(Icons.cloud_upload),
+                      icon: const Icon(Icons.save_alt),
                       onPressed: () {
-                        // Generate a response and upload it to a FHIR server.
-                        // In a real-world scenario this would have more robust state handling.
-                        widget.uploadResponseFunction?.call(
-                          context,
+                        // Generate a response and store it in-memory.
+                        // In a real-world scenario one would persist or post the response instead.
+                        widget.saveResponseFunction.call(
                           widget.questionnairePath,
                           QuestionnaireResponseFiller.of(context)
                               .aggregator<QuestionnaireResponseAggregator>()
-                              .aggregate(
-                                responseStatus:
-                                    QuestionnaireResponseStatus.completed,
-                              ),
+                              .aggregate(),
                         );
                         ScaffoldMessenger.of(context).showSnackBar(
                           SnackBar(
-                            content: Row(
-                              mainAxisAlignment: MainAxisAlignment.spaceBetween,
-                              children: [
-                                Text(
-                                  FDashLocalizations.of(context)
-                                      .handlingUploading,
-                                ),
-                                SyncIndicator(
-                                  color: Theme.of(context).colorScheme.primary,
-                                )
-                              ],
+                            content: Text(
+                              FDashLocalizations.of(context).handlingSaved,
                             ),
                           ),
                         );
@@ -197,40 +230,15 @@ class _QuestionnaireLaunchTileState extends State<QuestionnaireLaunchTile> {
                       },
                     ),
                   ),
-                Builder(
-                  builder: (context) => ElevatedButton.icon(
-                    label: Text(
-                      FDashLocalizations.of(context).handlingSaveButtonLabel,
-                    ),
-                    icon: const Icon(Icons.save_alt),
-                    onPressed: () {
-                      // Generate a response and store it in-memory.
-                      // In a real-world scenario one would persist or post the response instead.
-                      widget.saveResponseFunction.call(
-                        widget.questionnairePath,
-                        QuestionnaireResponseFiller.of(context)
-                            .aggregator<QuestionnaireResponseAggregator>()
-                            .aggregate(),
-                      );
-                      ScaffoldMessenger.of(context).showSnackBar(
-                        SnackBar(
-                          content: Text(
-                            FDashLocalizations.of(context).handlingSaved,
-                          ),
-                        ),
-                      );
-                      Navigator.pop(context);
-                    },
-                  ),
-                ),
-              ],
-              questionnaireModelDefaults: widget.questionnaireModelDefaults,
+                ],
+                questionnaireModelDefaults: widget.questionnaireModelDefaults,
+              ),
             ),
           ),
         ).then((value) {
           // This triggers after return from questionnaire filler
           setState(() {
-            _modelFuture = _createModelFuture();
+            _modelFuture = _createModelFuture(FDashLocalizations.of(context));
           });
         });
       },

From 38b0c1d334e36cd5ce423b3ec29f9b90a4e4beb3 Mon Sep 17 00:00:00 2001
From: Hanny Prastya Hariyadi <p.hanny@allm.inc>
Date: Mon, 2 Oct 2023 19:23:56 +0900
Subject: [PATCH 04/23] Fix prefix not properly rendered

---
 .../view/item/src/questionnaire_item_filler_title.dart          | 2 +-
 lib/questionnaires/view/src/questionnaire_scroller.dart         | 2 --
 2 files changed, 1 insertion(+), 3 deletions(-)

diff --git a/lib/questionnaires/view/item/src/questionnaire_item_filler_title.dart b/lib/questionnaires/view/item/src/questionnaire_item_filler_title.dart
index cb8d2015..95057a6b 100644
--- a/lib/questionnaires/view/item/src/questionnaire_item_filler_title.dart
+++ b/lib/questionnaires/view/item/src/questionnaire_item_filler_title.dart
@@ -56,7 +56,7 @@ class QuestionnaireItemFillerTitle extends StatelessWidget {
       );
 
       final htmlTitleText = (prefixText != null)
-          ? '$openStyleTag${prefixText}&nbsp;${title}$requiredTag$closeStyleTag'
+          ? '$openStyleTag${prefixText.xhtmlText}&nbsp;${title}$requiredTag$closeStyleTag'
           : '$openStyleTag${title}$requiredTag$closeStyleTag';
 
       return QuestionnaireItemFillerTitle._(
diff --git a/lib/questionnaires/view/src/questionnaire_scroller.dart b/lib/questionnaires/view/src/questionnaire_scroller.dart
index 4c925cc7..3b9d7698 100644
--- a/lib/questionnaires/view/src/questionnaire_scroller.dart
+++ b/lib/questionnaires/view/src/questionnaire_scroller.dart
@@ -151,8 +151,6 @@ class _QuestionnaireScrollerState extends State<QuestionnaireScroller> {
 
   @override
   Widget build(BuildContext context) {
-    final locale = Localizations.localeOf(context);
-
     return QuestionnaireResponseFiller(
       fhirResourceProvider: widget.fhirResourceProvider,
       launchContext: widget.launchContext,

From 5c40a463474fd8c4174ffa06c649b3ae25f11604 Mon Sep 17 00:00:00 2001
From: Hanny Prastya Hariyadi <p.hanny@allm.inc>
Date: Mon, 2 Oct 2023 19:27:43 +0900
Subject: [PATCH 05/23] Remove unintended changes

---
 lib/questionnaires/model/src/questionnaire_response_model.dart | 1 -
 1 file changed, 1 deletion(-)

diff --git a/lib/questionnaires/model/src/questionnaire_response_model.dart b/lib/questionnaires/model/src/questionnaire_response_model.dart
index f53dd19b..fb83cc9b 100644
--- a/lib/questionnaires/model/src/questionnaire_response_model.dart
+++ b/lib/questionnaires/model/src/questionnaire_response_model.dart
@@ -826,7 +826,6 @@ class QuestionnaireResponseModel {
   /// Will return the parent [QuestionItemModel] if uid corresponds to an answer.
   FillerItemModel? fillerItemModelByUid(String uid) {
     final fillerItem = orderedFillerItemModels().firstWhereOrNull((fim) {
-      print("UID:" + fim.nodeUid);
       return fim.nodeUid == uid;
     });
     if (fillerItem != null) {

From 762b5737aca7ee13581d544baf2a4a4eb21fab84 Mon Sep 17 00:00:00 2001
From: Hanny Prastya Hariyadi <p.hanny@allm.inc>
Date: Mon, 2 Oct 2023 19:38:13 +0900
Subject: [PATCH 06/23] Remove Locale from any widget

---
 lib/fhir_types/src/codeable_concept_text.dart                | 5 +----
 lib/fhir_types/src/date_time_picker.dart                     | 2 --
 lib/fhir_types/src/date_time_text.dart                       | 5 +----
 lib/observations/src/observation_value_view.dart             | 4 +---
 lib/observations/src/observation_view.dart                   | 4 ----
 .../view/item/answer/src/datetime_answer_filler.dart         | 1 -
 6 files changed, 3 insertions(+), 18 deletions(-)

diff --git a/lib/fhir_types/src/codeable_concept_text.dart b/lib/fhir_types/src/codeable_concept_text.dart
index 495a72a1..0e0e5b29 100644
--- a/lib/fhir_types/src/codeable_concept_text.dart
+++ b/lib/fhir_types/src/codeable_concept_text.dart
@@ -5,20 +5,17 @@ import 'package:flutter/material.dart';
 class CodeableConceptText extends StatelessWidget {
   final CodeableConcept codeableConcept;
   final TextStyle? style;
-  final Locale? locale;
 
   const CodeableConceptText(
     this.codeableConcept, {
     this.style,
-    this.locale,
     Key? key,
   }) : super(key: key);
 
   @override
   Widget build(BuildContext context) {
     return Text(
-      codeableConcept
-          .localizedDisplay(locale ?? Localizations.localeOf(context)),
+      codeableConcept.localizedDisplay(Localizations.localeOf(context)),
       style: style,
     );
   }
diff --git a/lib/fhir_types/src/date_time_picker.dart b/lib/fhir_types/src/date_time_picker.dart
index 23b0ad0e..d84139f9 100644
--- a/lib/fhir_types/src/date_time_picker.dart
+++ b/lib/fhir_types/src/date_time_picker.dart
@@ -10,7 +10,6 @@ import 'package:intl/intl.dart';
 /// The control is displayed as a text field that can be tapped to open
 /// a picker.
 class FhirDateTimePicker extends StatefulWidget {
-  final Locale? locale;
   final DateTime firstDate;
   final DateTime lastDate;
   final FhirDateTime? initialDateTime;
@@ -31,7 +30,6 @@ class FhirDateTimePicker extends StatefulWidget {
     this.timePickerEntryMode = TimePickerEntryMode.dial,
     this.decoration,
     this.onChanged,
-    this.locale,
     this.focusNode,
     this.enabled = true,
     Key? key,
diff --git a/lib/fhir_types/src/date_time_text.dart b/lib/fhir_types/src/date_time_text.dart
index 703c471a..419cb8e8 100644
--- a/lib/fhir_types/src/date_time_text.dart
+++ b/lib/fhir_types/src/date_time_text.dart
@@ -8,20 +8,17 @@ class FhirDateTimeText extends StatelessWidget {
   final FhirDateTime? dateTime;
   final TextStyle? style;
   final String defaultText;
-  final Locale? locale;
   const FhirDateTimeText(
     this.dateTime, {
     this.style,
     this.defaultText = '',
-    this.locale,
     Key? key,
   }) : super(key: key);
 
   @override
   Widget build(BuildContext context) {
     return Text(
-      dateTime?.format(locale ?? Localizations.localeOf(context)) ??
-          defaultText,
+      dateTime?.format(Localizations.localeOf(context)) ?? defaultText,
       style: style,
     );
   }
diff --git a/lib/observations/src/observation_value_view.dart b/lib/observations/src/observation_value_view.dart
index e634b783..0fc71666 100644
--- a/lib/observations/src/observation_value_view.dart
+++ b/lib/observations/src/observation_value_view.dart
@@ -10,7 +10,6 @@ import 'package:intl/intl.dart';
 /// or components of valueQuantity.
 class ObservationValueView extends StatelessWidget {
   final Observation _observation;
-  final Locale? locale;
   final TextStyle? valueStyle;
   final TextStyle? unitStyle;
   final String componentSeparator;
@@ -20,7 +19,6 @@ class ObservationValueView extends StatelessWidget {
   const ObservationValueView(
     this._observation, {
     super.key,
-    this.locale,
     this.valueStyle,
     this.unitStyle,
     this.componentSeparator = ' | ',
@@ -33,7 +31,7 @@ class ObservationValueView extends StatelessWidget {
     final Widget valueWidget;
 
     final decimalFormat = NumberFormat.decimalPattern(
-      (locale ?? Localizations.localeOf(context)).toString(),
+      (Localizations.localeOf(context)).toString(),
     );
 
     if (_observation.valueQuantity != null) {
diff --git a/lib/observations/src/observation_view.dart b/lib/observations/src/observation_view.dart
index 2b544493..8758a2e0 100644
--- a/lib/observations/src/observation_view.dart
+++ b/lib/observations/src/observation_view.dart
@@ -11,12 +11,10 @@ class ObservationView extends StatelessWidget {
   final Widget _valueWidget;
   final Widget _codeWidget;
   final Widget _dateTimeWidget;
-  final Locale? locale;
 
   ObservationView(
     Observation observation, {
     super.key,
-    this.locale,
     TextStyle? valueStyle,
     TextStyle? unitStyle,
     TextStyle? codeStyle,
@@ -28,7 +26,6 @@ class ObservationView extends StatelessWidget {
           observation,
           valueStyle: valueStyle,
           unitStyle: unitStyle,
-          locale: locale,
           componentSeparator: componentSeparator,
           unknownUnitText: unknownUnitText,
           unknownValueText: unknownValueText,
@@ -37,7 +34,6 @@ class ObservationView extends StatelessWidget {
             CodeableConceptText(observation.code, style: codeStyle, key: key),
         _dateTimeWidget = FhirDateTimeText(
           observation.effectiveDateTime,
-          locale: locale,
           style: dateTimeStyle,
         );
 
diff --git a/lib/questionnaires/view/item/answer/src/datetime_answer_filler.dart b/lib/questionnaires/view/item/answer/src/datetime_answer_filler.dart
index 910fcf61..1b098571 100644
--- a/lib/questionnaires/view/item/answer/src/datetime_answer_filler.dart
+++ b/lib/questionnaires/view/item/answer/src/datetime_answer_filler.dart
@@ -57,7 +57,6 @@ class _DateTimeInputControl extends AnswerInputControl<DateTimeAnswerModel> {
     return FhirDateTimePicker(
       focusNode: focusNode,
       enabled: answerModel.isControlEnabled,
-      locale: locale,
       initialDateTime: initialDate,
       // TODO: This can be specified through minValue / maxValue
       firstDate: DateTime(1860),

From af41121c9ab99f4cf63e244584d0e40798b6a17d Mon Sep 17 00:00:00 2001
From: Hanny Prastya Hariyadi <p.hanny@allm.inc>
Date: Mon, 2 Oct 2023 19:38:29 +0900
Subject: [PATCH 07/23] Update example

---
 example/lib/observation_page.dart | 18 ++++++++----
 example/lib/primitive_page.dart   | 48 +++++++++++++++++++++++--------
 2 files changed, 48 insertions(+), 18 deletions(-)

diff --git a/example/lib/observation_page.dart b/example/lib/observation_page.dart
index c103a23d..55ffb8cf 100644
--- a/example/lib/observation_page.dart
+++ b/example/lib/observation_page.dart
@@ -119,12 +119,18 @@ class ObservationPage extends ExhibitPage {
         const SizedBox(
           height: 16,
         ),
-        ObservationView(
-          bpObservationWHR,
-          valueStyle: Theme.of(context).textTheme.headline4,
-          codeStyle: Theme.of(context).textTheme.subtitle2,
-          dateTimeStyle: Theme.of(context).textTheme.caption,
-          locale: const Locale.fromSubtags(languageCode: 'ar', countryCode: 'BH'),
+        Localizations.override(
+          context: context,
+          locale: const Locale.fromSubtags(
+            languageCode: 'ar',
+            countryCode: 'BH',
+          ),
+          child: ObservationView(
+            bpObservationWHR,
+            valueStyle: Theme.of(context).textTheme.headline4,
+            codeStyle: Theme.of(context).textTheme.subtitle2,
+            dateTimeStyle: Theme.of(context).textTheme.caption,
+          ),
         ),
       ],
     );
diff --git a/example/lib/primitive_page.dart b/example/lib/primitive_page.dart
index d267357e..dcb1e356 100644
--- a/example/lib/primitive_page.dart
+++ b/example/lib/primitive_page.dart
@@ -17,25 +17,49 @@ class PrimitivePage extends ExhibitPage {
         FhirDateTimeText(FhirDateTime('2010-02')),
         const Spacer(),
         Text('Germany', style: Theme.of(context).textTheme.headline6),
-        FhirDateTimeText(
-          FhirDateTime('2010-02-05 14:02'),
-          locale: const Locale.fromSubtags(languageCode: 'de', countryCode: 'DE'),
+        Localizations.override(
+          context: context,
+          locale: const Locale.fromSubtags(
+            languageCode: 'de',
+            countryCode: 'DE',
+          ),
+          child: FhirDateTimeText(
+            FhirDateTime('2010-02-05 14:02'),
+          ),
         ),
         const Spacer(),
         Text('Japan', style: Theme.of(context).textTheme.headline6),
-        FhirDateTimeText(
-          FhirDateTime('2010-02'),
-          locale: const Locale.fromSubtags(languageCode: 'ja', countryCode: 'JP'),
+        Localizations.override(
+          context: context,
+          locale: const Locale.fromSubtags(
+            languageCode: 'ja',
+            countryCode: 'JP',
+          ),
+          child: FhirDateTimeText(
+            FhirDateTime('2010-02'),
+          ),
         ),
-        FhirDateTimeText(
-          FhirDateTime('2010-02-05 14:02'),
-          locale: const Locale.fromSubtags(languageCode: 'ja', countryCode: 'JP'),
+        Localizations.override(
+          context: context,
+          locale: const Locale.fromSubtags(
+            languageCode: 'ja',
+            countryCode: 'JP',
+          ),
+          child: FhirDateTimeText(
+            FhirDateTime('2010-02-05 14:02'),
+          ),
         ),
         const Spacer(),
         Text('Bahrain', style: Theme.of(context).textTheme.headline6),
-        FhirDateTimeText(
-          FhirDateTime('2010-02-05 14:02'),
-          locale: const Locale.fromSubtags(languageCode: 'ar', countryCode: 'BH'),
+        Localizations.override(
+          context: context,
+          locale: const Locale.fromSubtags(
+            languageCode: 'ar',
+            countryCode: 'BH',
+          ),
+          child: FhirDateTimeText(
+            FhirDateTime('2010-02-05 14:02'),
+          ),
         ),
       ],
     );

From 65c0a0526bd5e921e37bfb1c92341caa62a5298a Mon Sep 17 00:00:00 2001
From: Hanny Prastya Hariyadi <p.hanny@allm.inc>
Date: Tue, 3 Oct 2023 13:36:06 +0900
Subject: [PATCH 08/23] Fix validation not working

---
 .../custom_questionnaire_stepper_page.dart    |  7 ++---
 .../model/item/src/response_item_model.dart   | 28 +++++++++----------
 .../src/questionnaire_response_model.dart     | 25 ++++++++---------
 .../src/questionnaire_complete_button.dart    | 13 +++++----
 4 files changed, 33 insertions(+), 40 deletions(-)

diff --git a/example/lib/custom_questionnaire_stepper_page.dart b/example/lib/custom_questionnaire_stepper_page.dart
index e18513a8..5487fb97 100644
--- a/example/lib/custom_questionnaire_stepper_page.dart
+++ b/example/lib/custom_questionnaire_stepper_page.dart
@@ -1,5 +1,4 @@
 import 'package:faiadashu/faiadashu.dart';
-import 'package:faiadashu/questionnaires/model/src/validation_errors/validation_error.dart';
 import 'package:faiadashu_example/main.dart';
 import 'package:flutter/material.dart';
 
@@ -42,11 +41,9 @@ class _CustomQuestionnaireStepperPageState
       return;
     }
 
-    try {
-      matchingItems.first.validate(notifyListeners: true);
+    final errors = matchingItems.first.validate(notifyListeners: true);
+    if (errors.isEmpty) {
       _navigateToNextPage();
-    } on ValidationError {
-      rethrow;
     }
   }
 
diff --git a/lib/questionnaires/model/item/src/response_item_model.dart b/lib/questionnaires/model/item/src/response_item_model.dart
index 0a7c434d..708f98c4 100644
--- a/lib/questionnaires/model/item/src/response_item_model.dart
+++ b/lib/questionnaires/model/item/src/response_item_model.dart
@@ -1,6 +1,5 @@
 import 'package:faiadashu/faiadashu.dart';
 import 'package:faiadashu/questionnaires/model/src/validation_errors/constraint_validation_error.dart';
-import 'package:faiadashu/questionnaires/model/src/validation_errors/custom_validation_error.dart';
 import 'package:faiadashu/questionnaires/model/src/validation_errors/required_item_error.dart';
 import 'package:faiadashu/questionnaires/model/src/validation_errors/validation_error.dart';
 import 'package:fhir/r4.dart';
@@ -60,31 +59,30 @@ abstract class ResponseItemModel extends FillerItemModel {
     bool updateErrorText = true,
     bool notifyListeners = false,
   }) {
-    if (questionnaireItemModel.isRequired && isUnanswered) {
-      return [RequiredItemError(nodeUid)];
-    }
+    _exception = questionnaireItemModel.isRequired && isUnanswered
+        ? RequiredItemError(nodeUid)
+        : null;
+
     try {
       validateConstraint();
-      _exception = null;
     } on ValidationError catch (exception) {
       _exception ??= exception;
 
-      if (_exception != exception) {
-        if (updateErrorText) {
-          _exception = exception;
-        }
-        if (notifyListeners) {
-          this.notifyListeners();
-        }
+      if (_exception != exception && updateErrorText) {
+        _exception = exception;
       }
-      return [_exception!];
     }
-    return [];
+
+    if (notifyListeners) {
+      this.notifyListeners();
+    }
+
+    return _exception != null ? [_exception!] : [];
   }
 
   /// Returns whether the item is satisfying the `questionnaire-constraint`.
   ///
-  /// Throws [CustomValidationError] with human-readable text if not satisfied.
+  /// Throws [ValidationError] if not satisfied.
   void validateConstraint() {
     final constraintExpression = _constraintExpression;
     if (constraintExpression == null) {
diff --git a/lib/questionnaires/model/src/questionnaire_response_model.dart b/lib/questionnaires/model/src/questionnaire_response_model.dart
index fb83cc9b..3dbb181b 100644
--- a/lib/questionnaires/model/src/questionnaire_response_model.dart
+++ b/lib/questionnaires/model/src/questionnaire_response_model.dart
@@ -847,27 +847,24 @@ class QuestionnaireResponseModel {
   /// * All filled fields are valid
   /// * All expression-based constraints are satisfied
   ///
-  /// Returns null, if everything is complete.
-  /// Returns a map (UID -> error text) with incomplete entries, if items are incomplete.
-  Map<String, String>? validate({
-    required FDashLocalizations localizations,
+  /// Returns an empty list if everything is complete; otherwise,
+  /// returns a list of [ValidationError], resulting from validation
+  /// for each [ResponseItemModel.validate].
+  List<ValidationError> validate({
     bool updateErrorText = true,
     bool notifyListeners = false,
   }) {
-    final invalidMap = <String, String>{};
+    List<ValidationError> validationErrors = [];
 
     for (final itemModel in orderedResponseItemModels()) {
-      try {
-        itemModel.validate(
-          updateErrorText: updateErrorText,
-          notifyListeners: notifyListeners,
-        );
-      } on ValidationError catch (exception) {
-        _logger.debug('$itemModel is invalid.');
-      }
+      final errors = itemModel.validate(
+        updateErrorText: updateErrorText,
+        notifyListeners: notifyListeners,
+      );
+      validationErrors.addAll(errors);
     }
 
-    return invalidMap.isNotEmpty ? invalidMap : null;
+    return validationErrors;
   }
 
   /// A map of UIDs -> error texts of invalid [ResponseNode]s.
diff --git a/lib/questionnaires/view/src/questionnaire_complete_button.dart b/lib/questionnaires/view/src/questionnaire_complete_button.dart
index eaf36c2d..dbd1266b 100644
--- a/lib/questionnaires/view/src/questionnaire_complete_button.dart
+++ b/lib/questionnaires/view/src/questionnaire_complete_button.dart
@@ -31,15 +31,16 @@ class _QuestionnaireCompleteButtonState
         final currentResponseStatus = qrm.responseStatus;
 
         if (currentResponseStatus != QuestionnaireResponseStatus.completed) {
-          final incompleteItems = qrm.validate(
-            localizations: FDashLocalizations.of(context),
+          final validationErrors = qrm.validate(
             notifyListeners: true,
           );
-          qrm.invalidityNotifier.value = incompleteItems;
+          qrm.invalidityNotifier.value = {
+            for (var validation in validationErrors)
+              validation.nodeUid:
+                  validation.getMessage(FDashLocalizations.of(context)) ?? ""
+          };
 
-          if (incompleteItems != null) {
-            return;
-          }
+          return;
         }
 
         final newResponseStatus =

From 98b2524af9b986443fe7b93d7033cc3de082e406 Mon Sep 17 00:00:00 2001
From: Hanny Prastya Hariyadi <p.hanny@allm.inc>
Date: Wed, 4 Oct 2023 17:08:04 +0900
Subject: [PATCH 09/23] Add CommonValidationError

---
 ...ion_error.dart => common_validation_error.dart} |  4 ++--
 .../src/validation_errors/fhir_path_error.dart     | 14 --------------
 2 files changed, 2 insertions(+), 16 deletions(-)
 rename lib/questionnaires/model/src/validation_errors/{custom_validation_error.dart => common_validation_error.dart} (71%)
 delete mode 100644 lib/questionnaires/model/src/validation_errors/fhir_path_error.dart

diff --git a/lib/questionnaires/model/src/validation_errors/custom_validation_error.dart b/lib/questionnaires/model/src/validation_errors/common_validation_error.dart
similarity index 71%
rename from lib/questionnaires/model/src/validation_errors/custom_validation_error.dart
rename to lib/questionnaires/model/src/validation_errors/common_validation_error.dart
index 1351d41f..77b3dbab 100644
--- a/lib/questionnaires/model/src/validation_errors/custom_validation_error.dart
+++ b/lib/questionnaires/model/src/validation_errors/common_validation_error.dart
@@ -1,9 +1,9 @@
 import 'package:faiadashu/l10n/src/fdash_localizations.g.dart';
 import 'package:faiadashu/questionnaires/model/src/validation_errors/validation_error.dart';
 
-class CustomValidationError extends ValidationError {
+class CommonValidationError extends ValidationError {
   final String? message;
-  const CustomValidationError(String nodeUid, this.message) : super(nodeUid);
+  const CommonValidationError(String nodeUid, this.message) : super(nodeUid);
 
   @override
   String? getMessage(FDashLocalizations localizations) {
diff --git a/lib/questionnaires/model/src/validation_errors/fhir_path_error.dart b/lib/questionnaires/model/src/validation_errors/fhir_path_error.dart
deleted file mode 100644
index 52a889ab..00000000
--- a/lib/questionnaires/model/src/validation_errors/fhir_path_error.dart
+++ /dev/null
@@ -1,14 +0,0 @@
-import 'package:faiadashu/l10n/src/fdash_localizations.g.dart';
-import 'package:faiadashu/questionnaires/model/src/validation_errors/validation_error.dart';
-import 'package:fhir_path/fhir_path.dart';
-
-class FhirPathError extends ValidationError {
-  final FhirPathEvaluationException exception;
-
-  const FhirPathError(String nodeUid, this.exception) : super(nodeUid);
-
-  @override
-  String? getMessage(FDashLocalizations localizations) {
-    return exception.message;
-  }
-}

From 4924422b0d709f09726961a199af981fc367d50a Mon Sep 17 00:00:00 2001
From: Hanny Prastya Hariyadi <p.hanny@allm.inc>
Date: Wed, 4 Oct 2023 17:14:23 +0900
Subject: [PATCH 10/23] Remove throwing and catching ValidationError

---
 .../model/item/answer/src/answer_model.dart   | 40 ++++++-----
 .../answer/src/attachment_answer_model.dart   | 11 +--
 .../item/answer/src/boolean_answer_model.dart |  5 +-
 .../item/answer/src/coding_answer_model.dart  | 15 ++--
 .../answer/src/datetime_answer_model.dart     |  8 ++-
 .../answer/src/numerical_answer_model.dart    | 20 +++---
 .../item/answer/src/string_answer_model.dart  | 71 ++++++++++---------
 .../answer/src/unsupported_answer_model.dart  |  5 +-
 .../model/item/src/question_item_model.dart   |  8 ++-
 .../model/item/src/response_item_model.dart   | 14 ++--
 .../answer/src/numerical_answer_filler.dart   | 13 ++--
 .../item/answer/src/string_answer_filler.dart | 12 +---
 lib/questionnaires/view/src/xhtml.dart        |  6 +-
 13 files changed, 118 insertions(+), 110 deletions(-)

diff --git a/lib/questionnaires/model/item/answer/src/answer_model.dart b/lib/questionnaires/model/item/answer/src/answer_model.dart
index 8d9198d0..4678c53b 100644
--- a/lib/questionnaires/model/item/answer/src/answer_model.dart
+++ b/lib/questionnaires/model/item/answer/src/answer_model.dart
@@ -76,14 +76,16 @@ abstract class AnswerModel<I, V> extends ResponseNode {
   ///
   /// This is used to validate external input from a view.
   ///
-  /// Throws [ValidationError] when when [inputValue] is invalid.
-  void validateInput(I? inputValue);
+  /// Returns null when [inputValue] is invalid; otherwise
+  /// Returns [ValidationError].
+  ValidationError? validateInput(I? inputValue);
 
   /// Validates a value against the constraints of the answer model.
   /// Does not change the [value] of the answer model.
   ///
-  /// Throws [ValidationError] when when [inputValue] is invalid.
-  void validateValue(V? inputValue);
+  /// Returns null when [inputValue] is invalid; otherwise
+  /// Returns [ValidationError].
+  ValidationError? validateValue(V? inputValue);
 
   /// Validates whether the current [value] will pass the completeness check.
   ///
@@ -99,19 +101,21 @@ abstract class AnswerModel<I, V> extends ResponseNode {
     bool updateErrorText = true,
     bool notifyListeners = false,
   }) {
-    try {
-      validateValue(value);
-
-      if (notifyListeners) {
-        this.notifyListeners();
-      }
-      return [];
-    } on ValidationError catch (exception) {
-      if (updateErrorText) {
-        _error = exception;
-      }
-      return [exception];
+    final validationError = validateValue(value);
+
+    if (_validationError == validationError && validationError != null) {
+      return [validationError];
+    }
+
+    if (updateErrorText) {
+      _validationError = validationError;
     }
+
+    if (notifyListeners) {
+      this.notifyListeners();
+    }
+
+    return _validationError != null ? [_validationError!] : [];
   }
 
   /// Returns whether any answer (valid or invalid) has been provided.
@@ -120,13 +124,13 @@ abstract class AnswerModel<I, V> extends ResponseNode {
   /// Returns whether this question is unanswered.
   bool get isEmpty;
 
-  ValidationError? _error;
+  ValidationError? _validationError;
 
   /// Returns an error text for display in the answer's control.
   ///
   /// This might return an error text from the parent [QuestionItemModel].
   String? displayErrorText(FDashLocalizations localizations) =>
-      _error?.getMessage(localizations) ??
+      _validationError?.getMessage(localizations) ??
       responseItemModel.getErrorText(localizations);
 
   /// Returns a [QuestionnaireResponseAnswer] based on the current value.
diff --git a/lib/questionnaires/model/item/answer/src/attachment_answer_model.dart b/lib/questionnaires/model/item/answer/src/attachment_answer_model.dart
index abdeae1f..5eb32e91 100644
--- a/lib/questionnaires/model/item/answer/src/attachment_answer_model.dart
+++ b/lib/questionnaires/model/item/answer/src/attachment_answer_model.dart
@@ -2,6 +2,7 @@ import 'package:faiadashu/fhir_types/fhir_types.dart';
 import 'package:faiadashu/questionnaires/model/model.dart';
 import 'package:faiadashu/questionnaires/model/src/validation_errors/max_size_error.dart';
 import 'package:faiadashu/questionnaires/model/src/validation_errors/mime_types_error.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/validation_error.dart';
 import 'package:fhir/r4.dart';
 
 class AttachmentAnswerModel extends AnswerModel<Attachment, Attachment> {
@@ -29,18 +30,18 @@ class AttachmentAnswerModel extends AnswerModel<Attachment, Attachment> {
       : RenderingString.nullText;
 
   @override
-  void validateInput(Attachment? inValue) {
-    validateValue(inValue);
+  ValidationError? validateInput(Attachment? inValue) {
+    return validateValue(inValue);
   }
 
   @override
-  void validateValue(Attachment? inputValue) {
+  ValidationError? validateValue(Attachment? inputValue) {
     if (inputValue == null) return null;
 
     if (maxSize > 0) {
       final attachmentSize = inputValue.size?.value;
       if (attachmentSize == null || attachmentSize > maxSize) {
-        throw MaxSizeError(nodeUid, maxSize);
+        return MaxSizeError(nodeUid, maxSize);
       }
     }
 
@@ -48,7 +49,7 @@ class AttachmentAnswerModel extends AnswerModel<Attachment, Attachment> {
       final attachmentMimeType = inputValue.contentType?.value;
       if (attachmentMimeType == null ||
           !mimeTypes.contains(attachmentMimeType)) {
-        throw MimeTypesError(nodeUid, mimeTypes);
+        return MimeTypesError(nodeUid, mimeTypes);
       }
     }
 
diff --git a/lib/questionnaires/model/item/answer/src/boolean_answer_model.dart b/lib/questionnaires/model/item/answer/src/boolean_answer_model.dart
index f00eaf54..28e633a8 100644
--- a/lib/questionnaires/model/item/answer/src/boolean_answer_model.dart
+++ b/lib/questionnaires/model/item/answer/src/boolean_answer_model.dart
@@ -1,4 +1,5 @@
 import 'package:faiadashu/questionnaires/model/model.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/validation_error.dart';
 import 'package:fhir/r4.dart';
 
 class BooleanAnswerModel extends AnswerModel<Boolean, Boolean> {
@@ -23,12 +24,12 @@ class BooleanAnswerModel extends AnswerModel<Boolean, Boolean> {
         );
 
   @override
-  void validateInput(Boolean? inValue) {
+  ValidationError? validateInput(Boolean? inValue) {
     return null;
   }
 
   @override
-  void validateValue(Boolean? inputValue) {
+  ValidationError? validateValue(Boolean? inputValue) {
     return null;
   }
 
diff --git a/lib/questionnaires/model/item/answer/src/coding_answer_model.dart b/lib/questionnaires/model/item/answer/src/coding_answer_model.dart
index 775ab28a..c6709511 100644
--- a/lib/questionnaires/model/item/answer/src/coding_answer_model.dart
+++ b/lib/questionnaires/model/item/answer/src/coding_answer_model.dart
@@ -6,6 +6,7 @@ import 'package:faiadashu/questionnaires/model/model.dart';
 import 'package:faiadashu/questionnaires/model/src/validation_errors/max_occurs_error.dart';
 import 'package:faiadashu/questionnaires/model/src/validation_errors/min_occurs_error.dart';
 import 'package:faiadashu/questionnaires/model/src/validation_errors/single_selection_or_open_string_error.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/validation_error.dart';
 import 'package:faiadashu/questionnaires/questionnaires.dart';
 import 'package:fhir/r4.dart';
 
@@ -306,14 +307,14 @@ class CodingAnswerModel extends AnswerModel<OptionsOrString, OptionsOrString> {
   }
 
   @override
-  void validateInput(OptionsOrString? inValue) {
+  ValidationError? validateInput(OptionsOrString? inValue) {
     return validateValue(inValue);
   }
 
   @override
-  void validateValue(OptionsOrString? inValue) {
+  ValidationError? validateValue(OptionsOrString? inValue) {
     if (inValue == null) {
-      return;
+      return null;
     }
 
     final selectedOptionsCount = inValue.selectedOptions?.length ?? 0;
@@ -323,18 +324,20 @@ class CodingAnswerModel extends AnswerModel<OptionsOrString, OptionsOrString> {
 
     if (!(questionnaireItemModel.questionnaireItem.repeats?.value ?? false)) {
       if (totalCount != 1) {
-        throw SingleSelectionOrOpenStringError(nodeUid, _openLabel);
+        return SingleSelectionOrOpenStringError(nodeUid, _openLabel);
       }
     }
 
     if (totalCount < minOccurs) {
-      throw MinOccursError(nodeUid, minOccurs);
+      return MinOccursError(nodeUid, minOccurs);
     }
 
     final maxOccurs = this.maxOccurs;
     if (maxOccurs != null && totalCount > maxOccurs) {
-      throw MaxOccursError(nodeUid, maxOccurs);
+      return MaxOccursError(nodeUid, maxOccurs);
     }
+
+    return null;
   }
 
   @override
diff --git a/lib/questionnaires/model/item/answer/src/datetime_answer_model.dart b/lib/questionnaires/model/item/answer/src/datetime_answer_model.dart
index 541198bd..711ae212 100644
--- a/lib/questionnaires/model/item/answer/src/datetime_answer_model.dart
+++ b/lib/questionnaires/model/item/answer/src/datetime_answer_model.dart
@@ -1,6 +1,7 @@
 import 'package:faiadashu/fhir_types/fhir_types.dart';
 import 'package:faiadashu/questionnaires/model/model.dart';
 import 'package:faiadashu/questionnaires/model/src/validation_errors/date_time_error.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/validation_error.dart';
 import 'package:fhir/r4.dart'
     show
         Date,
@@ -53,15 +54,16 @@ class DateTimeAnswerModel extends AnswerModel<FhirDateTime, FhirDateTime> {
   }
 
   @override
-  void validateInput(FhirDateTime? inValue) {
+  ValidationError? validateInput(FhirDateTime? inValue) {
     return validateValue(inValue);
   }
 
   @override
-  void validateValue(FhirDateTime? inValue) {
+  ValidationError? validateValue(FhirDateTime? inValue) {
     if (!(inValue == null || inValue.isValid)) {
-      throw DateTimeError(nodeUid);
+      return DateTimeError(nodeUid);
     }
+    return null;
   }
 
   @override
diff --git a/lib/questionnaires/model/item/answer/src/numerical_answer_model.dart b/lib/questionnaires/model/item/answer/src/numerical_answer_model.dart
index 935a76e7..0b72417d 100644
--- a/lib/questionnaires/model/item/answer/src/numerical_answer_model.dart
+++ b/lib/questionnaires/model/item/answer/src/numerical_answer_model.dart
@@ -1,11 +1,11 @@
 import 'package:faiadashu/coding/coding.dart';
-import 'package:faiadashu/extensions/function_extension.dart';
 import 'package:faiadashu/fhir_types/fhir_types.dart';
 import 'package:faiadashu/logging/logging.dart';
 import 'package:faiadashu/questionnaires/model/model.dart';
 import 'package:faiadashu/questionnaires/model/src/validation_errors/max_value_error.dart';
 import 'package:faiadashu/questionnaires/model/src/validation_errors/min_value_error.dart';
 import 'package:faiadashu/questionnaires/model/src/validation_errors/nan_error.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/validation_error.dart';
 import 'package:fhir/r4.dart';
 import 'package:intl/intl.dart';
 
@@ -189,9 +189,9 @@ class NumericalAnswerModel extends AnswerModel<String, Quantity> {
       : RenderingString.nullText;
 
   @override
-  void validateInput(String? inputValue) {
+  ValidationError? validateInput(String? inputValue) {
     if (inputValue == null || inputValue.isEmpty) {
-      return;
+      return null;
     }
     num number = double.nan;
     try {
@@ -200,16 +200,16 @@ class NumericalAnswerModel extends AnswerModel<String, Quantity> {
       // Ignore FormatException, number remains nan.
     }
     if (number.isNaN) {
-      throw NanError(nodeUid);
+      return NanError(nodeUid);
     }
 
     final quantity = _valueFromNumber(number);
 
-    validateValue(quantity);
+    return validateValue(quantity);
   }
 
   @override
-  void validateValue(Quantity? inputValue) {
+  ValidationError? validateValue(Quantity? inputValue) {
     if (inputValue == null) {
       return null;
     }
@@ -221,10 +221,10 @@ class NumericalAnswerModel extends AnswerModel<String, Quantity> {
     }
 
     if (number > _maxValue) {
-      throw MaxValueError(nodeUid, Decimal(_maxValue).format(locale));
+      return MaxValueError(nodeUid, Decimal(_maxValue).format(locale));
     }
     if (number < _minValue) {
-      throw MinValueError(nodeUid, Decimal(_minValue).format(locale));
+      return MinValueError(nodeUid, Decimal(_minValue).format(locale));
     }
 
     return null;
@@ -265,9 +265,9 @@ class NumericalAnswerModel extends AnswerModel<String, Quantity> {
   /// * Updates the numerical value based on text input
   /// * Keeps the unit
   Quantity? copyWithTextInput(String textInput) {
-    final valid = (() => validateInput(textInput)).callSafely() ?? false;
+    final valid = validateInput(textInput);
 
-    final dataAbsentReasonExtension = !valid
+    final dataAbsentReasonExtension = valid != null
         ? [
             FhirExtension(
               url: dataAbsentReasonExtensionUrl,
diff --git a/lib/questionnaires/model/item/answer/src/string_answer_model.dart b/lib/questionnaires/model/item/answer/src/string_answer_model.dart
index eb7077a3..d0b48dfd 100644
--- a/lib/questionnaires/model/item/answer/src/string_answer_model.dart
+++ b/lib/questionnaires/model/item/answer/src/string_answer_model.dart
@@ -5,6 +5,7 @@ import 'package:faiadashu/questionnaires/model/src/validation_errors/entry_forma
 import 'package:faiadashu/questionnaires/model/src/validation_errors/min_length_error.dart';
 import 'package:faiadashu/questionnaires/model/src/validation_errors/regex_error.dart';
 import 'package:faiadashu/questionnaires/model/src/validation_errors/url_error.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/validation_error.dart';
 import 'package:fhir/r4.dart';
 
 enum StringAnswerKeyboard { plain, email, phone, number, multiline, url }
@@ -64,73 +65,73 @@ class StringAnswerModel extends AnswerModel<String, String> {
       : RenderingString.nullText;
 
   @override
-  void validateInput(String? inValue) {
+  ValidationError? validateInput(String? inValue) {
     final checkValue = inValue?.trim();
 
     return validateValue(checkValue);
   }
 
   @override
-  void validateValue(String? inputValue) {
+  ValidationError? validateValue(String? inputValue) {
     if (inputValue == null || inputValue.isEmpty) {
-      return;
+      return null;
     }
 
     if (inputValue.length < minLength) {
-      throw MinLengthError(nodeUid, minLength);
+      return MinLengthError(nodeUid, minLength);
     }
 
     if (maxLength != null && inputValue.length > maxLength!) {
-      throw MinLengthError(nodeUid, maxLength!);
+      return MinLengthError(nodeUid, maxLength!);
     }
 
     if (qi.type == QuestionnaireItemType.url) {
       if (!_urlRegExp.hasMatch(inputValue)) {
-        throw UrlError(nodeUid);
+        return UrlError(nodeUid);
       }
     }
 
     if (regExp != null) {
       if (!regExp!.hasMatch(inputValue)) {
-        throw (entryFormat != null)
+        return (entryFormat != null)
             ? EntryFormatError(nodeUid, entryFormat!)
             : RegexError(nodeUid);
       }
     }
+
+    return null;
   }
 
   @override
   QuestionnaireResponseAnswer? createFhirAnswer(
     List<QuestionnaireResponseItem>? items,
   ) {
-    try {
-      final value = this.value?.trim();
-
-      validateInput(value);
-
-      final dataAbsentReasonExtension = [
-        FhirExtension(
-          url: dataAbsentReasonExtensionUrl,
-          valueCode: dataAbsentReasonAsTextCode,
-        ),
-      ];
-
-      return (value != null && value.isNotEmpty)
-          ? (qi.type != QuestionnaireItemType.url)
-              ? QuestionnaireResponseAnswer(
-                  valueString: value,
-                  extension_: dataAbsentReasonExtension,
-                  item: items,
-                )
-              : QuestionnaireResponseAnswer(
-                  valueUri: FhirUri(value),
-                  extension_: dataAbsentReasonExtension,
-                  item: items,
-                )
-          : null;
-    } on Exception {
-      return null;
-    }
+    final value = this.value?.trim();
+
+    final valid = validateInput(value) == null;
+
+    final dataAbsentReasonExtension = !valid
+        ? [
+            FhirExtension(
+              url: dataAbsentReasonExtensionUrl,
+              valueCode: dataAbsentReasonAsTextCode,
+            ),
+          ]
+        : null;
+
+    return (value != null && value.isNotEmpty)
+        ? (qi.type != QuestionnaireItemType.url)
+            ? QuestionnaireResponseAnswer(
+                valueString: value,
+                extension_: dataAbsentReasonExtension,
+                item: items,
+              )
+            : QuestionnaireResponseAnswer(
+                valueUri: FhirUri(value),
+                extension_: dataAbsentReasonExtension,
+                item: items,
+              )
+        : null;
   }
 
   @override
diff --git a/lib/questionnaires/model/item/answer/src/unsupported_answer_model.dart b/lib/questionnaires/model/item/answer/src/unsupported_answer_model.dart
index f37c9e60..2b5a0c08 100644
--- a/lib/questionnaires/model/item/answer/src/unsupported_answer_model.dart
+++ b/lib/questionnaires/model/item/answer/src/unsupported_answer_model.dart
@@ -1,4 +1,5 @@
 import 'package:faiadashu/questionnaires/model/model.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/validation_error.dart';
 import 'package:fhir/r4.dart';
 
 /// A pseudo-model for a questionnaire item of an unsupported type.
@@ -16,12 +17,12 @@ class UnsupportedAnswerModel extends AnswerModel<Object, Object> {
   RenderingString get display => RenderingString.nullText;
 
   @override
-  void validateInput(Object? inValue) {
+  ValidationError? validateInput(Object? inValue) {
     return null;
   }
 
   @override
-  void validateValue(Object? inputValue) {
+  ValidationError? validateValue(Object? inputValue) {
     return null;
   }
 
diff --git a/lib/questionnaires/model/item/src/question_item_model.dart b/lib/questionnaires/model/item/src/question_item_model.dart
index 0f66ed02..163168b1 100644
--- a/lib/questionnaires/model/item/src/question_item_model.dart
+++ b/lib/questionnaires/model/item/src/question_item_model.dart
@@ -2,6 +2,7 @@ import 'dart:developer';
 
 import 'package:collection/collection.dart';
 import 'package:faiadashu/faiadashu.dart';
+import 'package:faiadashu/questionnaires/model/src/validation_errors/common_validation_error.dart';
 import 'package:faiadashu/questionnaires/model/src/validation_errors/validation_error.dart';
 import 'package:fhir/primitive_types/primitive_types.dart';
 import 'package:fhir/r4/r4.dart';
@@ -419,9 +420,10 @@ class QuestionItemModel extends ResponseItemModel {
       // Write the value back to the answer model
       firstAnswerModel.populateFromExpression(evaluationResult);
     } catch (ex) {
-      // errorText =
-      //     (ex is FhirPathEvaluationException) ? ex.message : ex.toString();
-      if (ex is FhirPathEvaluationException) {}
+      validationError = CommonValidationError(
+        nodeUid,
+        ex is FhirPathEvaluationException ? ex.message : ex.toString(),
+      );
       _qimLogger.warn('Calculation problem: $_calculatedExpression', error: ex);
       notifyListeners(); // This could be added to a setter for errorText, but might have side-effects.
     }
diff --git a/lib/questionnaires/model/item/src/response_item_model.dart b/lib/questionnaires/model/item/src/response_item_model.dart
index 708f98c4..ade3abc3 100644
--- a/lib/questionnaires/model/item/src/response_item_model.dart
+++ b/lib/questionnaires/model/item/src/response_item_model.dart
@@ -50,26 +50,26 @@ abstract class ResponseItemModel extends FillerItemModel {
   ///
   /// Localized text if an error exists. Or null if no error exists.
   String? getErrorText(FDashLocalizations localizations) {
-    return _exception?.getMessage(localizations);
+    return validationError?.getMessage(localizations);
   }
 
-  ValidationError? _exception;
+  ValidationError? validationError;
 
   List<ValidationError> validate({
     bool updateErrorText = true,
     bool notifyListeners = false,
   }) {
-    _exception = questionnaireItemModel.isRequired && isUnanswered
+    validationError = questionnaireItemModel.isRequired && isUnanswered
         ? RequiredItemError(nodeUid)
         : null;
 
     try {
       validateConstraint();
     } on ValidationError catch (exception) {
-      _exception ??= exception;
+      validationError ??= exception;
 
-      if (_exception != exception && updateErrorText) {
-        _exception = exception;
+      if (exception != exception && updateErrorText) {
+        validationError = exception;
       }
     }
 
@@ -77,7 +77,7 @@ abstract class ResponseItemModel extends FillerItemModel {
       this.notifyListeners();
     }
 
-    return _exception != null ? [_exception!] : [];
+    return validationError != null ? [validationError!] : [];
   }
 
   /// Returns whether the item is satisfying the `questionnaire-constraint`.
diff --git a/lib/questionnaires/view/item/answer/src/numerical_answer_filler.dart b/lib/questionnaires/view/item/answer/src/numerical_answer_filler.dart
index 6ae3adff..6dd98aa1 100644
--- a/lib/questionnaires/view/item/answer/src/numerical_answer_filler.dart
+++ b/lib/questionnaires/view/item/answer/src/numerical_answer_filler.dart
@@ -1,6 +1,5 @@
 import 'package:faiadashu/fhir_types/fhir_types.dart';
 import 'package:faiadashu/l10n/l10n.dart';
-import 'package:faiadashu/questionnaires/model/src/validation_errors/custom_validation_error.dart';
 import 'package:faiadashu/questionnaires/questionnaires.dart';
 import 'package:fhir/r4.dart';
 import 'package:flutter/material.dart';
@@ -228,14 +227,12 @@ class _NumberFieldInputControl
               decimal: answerModel.maxDecimal > 0,
             ),
             validator: (inputValue) {
-              try {
-                if (itemModel.isCalculated) {
-                  answerModel.validateInput(inputValue);
-                }
-              } on CustomValidationError catch (exception) {
-                return exception.getMessage(FDashLocalizations.of(context));
+              if (!itemModel.isCalculated) {
+                return null;
               }
-              return null;
+              return answerModel
+                  .validateInput(inputValue)
+                  ?.getMessage(FDashLocalizations.of(context));
             },
             autovalidateMode: (itemModel.isCalculated)
                 ? AutovalidateMode.disabled
diff --git a/lib/questionnaires/view/item/answer/src/string_answer_filler.dart b/lib/questionnaires/view/item/answer/src/string_answer_filler.dart
index e34cb73e..a88b958f 100644
--- a/lib/questionnaires/view/item/answer/src/string_answer_filler.dart
+++ b/lib/questionnaires/view/item/answer/src/string_answer_filler.dart
@@ -1,5 +1,4 @@
 import 'package:faiadashu/l10n/l10n.dart';
-import 'package:faiadashu/questionnaires/model/src/validation_errors/custom_validation_error.dart';
 import 'package:faiadashu/questionnaires/questionnaires.dart';
 import 'package:fhir/r4.dart';
 import 'package:flutter/material.dart';
@@ -115,14 +114,9 @@ class _StringAnswerInputControl extends AnswerInputControl<StringAnswerModel> {
               )
             : null,
       ),
-      validator: (inputValue) {
-        try {
-          answerModel.validateInput(inputValue);
-        } on CustomValidationError catch (exception) {
-          return exception.getMessage(FDashLocalizations.of(context));
-        }
-        return null;
-      },
+      validator: (inputValue) => answerModel
+          .validateInput(inputValue)
+          ?.getMessage(FDashLocalizations.of(context)),
       autovalidateMode: AutovalidateMode.always,
       onChanged: (content) {
         answerModel.value = content;
diff --git a/lib/questionnaires/view/src/xhtml.dart b/lib/questionnaires/view/src/xhtml.dart
index 9ebd120f..c3b46d83 100644
--- a/lib/questionnaires/view/src/xhtml.dart
+++ b/lib/questionnaires/view/src/xhtml.dart
@@ -29,8 +29,10 @@ class Xhtml extends StatelessWidget {
     TextStyle? defaultTextStyle,
     Key? key,
   }) {
-    final xhtmlString =
-        RenderingString.fromText(plainText, extensions: extensions);
+    final xhtmlString = RenderingString.fromText(
+      plainText,
+      extensions: extensions,
+    );
 
     return Xhtml.fromRenderingString(
       context,

From c98aee0b2e108635a4f225fec9066132c3f0d175 Mon Sep 17 00:00:00 2001
From: Hanny Prastya Hariyadi <p.hanny@allm.inc>
Date: Wed, 4 Oct 2023 17:15:24 +0900
Subject: [PATCH 11/23] Remove unintended changes

---
 example/lib/main.dart                          |  2 +-
 example/lib/questionnaire_launch_tile.dart     | 11 ++++++-----
 .../item/answer/src/coding_answer_filler.dart  | 18 +++++++-----------
 3 files changed, 14 insertions(+), 17 deletions(-)

diff --git a/example/lib/main.dart b/example/lib/main.dart
index a37fd3cf..29851e01 100644
--- a/example/lib/main.dart
+++ b/example/lib/main.dart
@@ -401,7 +401,7 @@ class _HomePageState extends State<HomePage> {
                         child: CustomQuestionnaireStepperPage(
                           fhirResourceProvider: AssetResourceProvider.singleton(
                             questionnaireResourceUri,
-                            'assets/instruments/triage.json',
+                            'assets/instruments/framingham-hcdc.json',
                           ),
                           launchContext: launchContext,
                         ),
diff --git a/example/lib/questionnaire_launch_tile.dart b/example/lib/questionnaire_launch_tile.dart
index cbfe0cec..a296285a 100644
--- a/example/lib/questionnaire_launch_tile.dart
+++ b/example/lib/questionnaire_launch_tile.dart
@@ -59,12 +59,13 @@ class _QuestionnaireLaunchTileState extends State<QuestionnaireLaunchTile> {
   }
 
   Future<QuestionnaireResponseModel> _createModelFuture(
-      FDashLocalizations localizations) {
+    BuildContext context,
+  ) {
     return QuestionnaireResponseModel.fromFhirResourceBundle(
-      localizations: localizations,
+      localizations: FDashLocalizations.of(context),
       fhirResourceProvider: _questionnaireProvider,
       launchContext: widget.launchContext,
-      locale: Locale('ja'),
+      locale: Localizations.localeOf(context),
     ).then<QuestionnaireResponseModel>((qrm) {
       qrm.populate(
         widget.restoreResponseFunction.call(widget.questionnairePath),
@@ -79,7 +80,7 @@ class _QuestionnaireLaunchTileState extends State<QuestionnaireLaunchTile> {
     _percentPattern = NumberFormat.percentPattern(
       Localizations.localeOf(context).toString(),
     );
-    _modelFuture = _createModelFuture(FDashLocalizations.of(context));
+    _modelFuture = _createModelFuture(context);
   }
 
   @override
@@ -238,7 +239,7 @@ class _QuestionnaireLaunchTileState extends State<QuestionnaireLaunchTile> {
         ).then((value) {
           // This triggers after return from questionnaire filler
           setState(() {
-            _modelFuture = _createModelFuture(FDashLocalizations.of(context));
+            _modelFuture = _createModelFuture(context);
           });
         });
       },
diff --git a/lib/questionnaires/view/item/answer/src/coding_answer_filler.dart b/lib/questionnaires/view/item/answer/src/coding_answer_filler.dart
index eb55ff52..0490f22d 100644
--- a/lib/questionnaires/view/item/answer/src/coding_answer_filler.dart
+++ b/lib/questionnaires/view/item/answer/src/coding_answer_filler.dart
@@ -46,17 +46,13 @@ class _CodingInputControl extends AnswerInputControl<CodingAnswerModel> {
     final errorText =
         answerModel.displayErrorText(FDashLocalizations.of(context));
 
-    return Column(
-      children: [
-        QuestionnaireTheme.of(context).codingControlLayoutBuilder(
-          context,
-          _buildCodingControl(context),
-          openStringInputControlWidget: answerModel.isOptionsOrString
-              ? _OpenStringInputControl(answerModel)
-              : null,
-          errorText: errorText,
-        )
-      ],
+    return QuestionnaireTheme.of(context).codingControlLayoutBuilder(
+      context,
+      _buildCodingControl(context),
+      openStringInputControlWidget: answerModel.isOptionsOrString
+          ? _OpenStringInputControl(answerModel)
+          : null,
+      errorText: errorText,
     );
   }
 

From 5def257e223d04d936a9611cace5473f74c63f33 Mon Sep 17 00:00:00 2001
From: Hanny Prastya Hariyadi <p.hanny@allm.inc>
Date: Wed, 4 Oct 2023 20:37:43 +0900
Subject: [PATCH 12/23] Remove `callSafely`

---
 lib/extensions/function_extension.dart | 26 --------------------------
 1 file changed, 26 deletions(-)
 delete mode 100644 lib/extensions/function_extension.dart

diff --git a/lib/extensions/function_extension.dart b/lib/extensions/function_extension.dart
deleted file mode 100644
index 656c0428..00000000
--- a/lib/extensions/function_extension.dart
+++ /dev/null
@@ -1,26 +0,0 @@
-/// An extension on [Function] that provides a method to call functions
-/// safely, which means if the function throws an error, it will catch that
-/// error and return `null`, instead of letting the error propagate.
-///
-/// This can be useful when working with functions that may throw exceptions
-/// but you don't want to handle those exceptions explicitly or when you
-/// prefer to deal with a `null` return value in the case of an error.
-extension TryOrNull on Function {
-  /// Calls the function safely and returns the result of the function if it's
-  /// successful, or `null` if an error occurs.
-  ///
-  /// Here, `T` represents the expected return type of the function.
-  ///
-  /// Example:
-  /// ```dart
-  /// Function riskyFunction = () => throw Exception('Oops!');
-  /// final result = riskyFunction.callSafely(); // result will be `null`.
-  /// ```
-  T? callSafely<T>() {
-    try {
-      return this.call() as T;
-    } catch (e) {
-      return null;
-    }
-  }
-}

From f660a742e870b9417cc668dc7db0dbd5cb9f57fb Mon Sep 17 00:00:00 2001
From: Hanny Prastya Hariyadi <p.hanny@allm.inc>
Date: Wed, 4 Oct 2023 21:25:49 +0900
Subject: [PATCH 13/23] Prevent xHtmlText from being replaced by tanslation
 extension

---
 lib/questionnaires/view/src/xhtml.dart | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/lib/questionnaires/view/src/xhtml.dart b/lib/questionnaires/view/src/xhtml.dart
index c3b46d83..c882f157 100644
--- a/lib/questionnaires/view/src/xhtml.dart
+++ b/lib/questionnaires/view/src/xhtml.dart
@@ -57,10 +57,7 @@ class Xhtml extends StatelessWidget {
   }) {
     _logger.trace('enter fromRenderingString $renderingString');
 
-    final xhtml = renderingString.xhtmlText.translate(
-      renderingString.extensions,
-      Localizations.localeOf(context),
-    );
+    final xhtml = renderingString.xhtmlText;
     final plainText = renderingString.plainText.translate(
       renderingString.extensions,
       Localizations.localeOf(context),

From 2c54bad5d857cd29d599ce00ec037e30aea4ab02 Mon Sep 17 00:00:00 2001
From: Hanny <prastya.hanny@gmail.com>
Date: Thu, 5 Oct 2023 18:17:55 +0900
Subject: [PATCH 14/23] Update lib/observations/src/observation_value_view.dart

Co-authored-by: fjwong <fjwong@users.noreply.github.com>
---
 lib/observations/src/observation_value_view.dart | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/observations/src/observation_value_view.dart b/lib/observations/src/observation_value_view.dart
index 0fc71666..c40679f6 100644
--- a/lib/observations/src/observation_value_view.dart
+++ b/lib/observations/src/observation_value_view.dart
@@ -31,7 +31,7 @@ class ObservationValueView extends StatelessWidget {
     final Widget valueWidget;
 
     final decimalFormat = NumberFormat.decimalPattern(
-      (Localizations.localeOf(context)).toString(),
+      Localizations.localeOf(context).toString(),
     );
 
     if (_observation.valueQuantity != null) {

From 0962199475ed76c89a402f3516ddce83471e7980 Mon Sep 17 00:00:00 2001
From: Hanny Prastya Hariyadi <p.hanny@allm.inc>
Date: Wed, 11 Oct 2023 07:55:55 +0900
Subject: [PATCH 15/23] Refactor validateConstraint to return ValidationError?

---
 .../model/item/src/response_item_model.dart   | 46 +++++++++----------
 1 file changed, 23 insertions(+), 23 deletions(-)

diff --git a/lib/questionnaires/model/item/src/response_item_model.dart b/lib/questionnaires/model/item/src/response_item_model.dart
index ade3abc3..b069b2b7 100644
--- a/lib/questionnaires/model/item/src/response_item_model.dart
+++ b/lib/questionnaires/model/item/src/response_item_model.dart
@@ -59,34 +59,34 @@ abstract class ResponseItemModel extends FillerItemModel {
     bool updateErrorText = true,
     bool notifyListeners = false,
   }) {
-    validationError = questionnaireItemModel.isRequired && isUnanswered
-        ? RequiredItemError(nodeUid)
-        : null;
-
-    try {
-      validateConstraint();
-    } on ValidationError catch (exception) {
-      validationError ??= exception;
+    ValidationError? newValidationError;
 
-      if (exception != exception && updateErrorText) {
-        validationError = exception;
-      }
+    if (questionnaireItemModel.isRequired && isUnanswered) {
+      newValidationError = RequiredItemError(nodeUid);
     }
 
-    if (notifyListeners) {
-      this.notifyListeners();
+    final constraintError = validateConstraint();
+    newValidationError ??= constraintError;
+
+    if (validationError != newValidationError) {
+      if (updateErrorText) {
+        validationError = newValidationError;
+      }
+      if (notifyListeners) {
+        this.notifyListeners();
+      }
     }
 
-    return validationError != null ? [validationError!] : [];
+    return newValidationError != null ? [newValidationError] : [];
   }
 
   /// Returns whether the item is satisfying the `questionnaire-constraint`.
   ///
-  /// Throws [ValidationError] if not satisfied.
-  void validateConstraint() {
+  /// Returns [ValidationError] if not satisfied; otherwise null
+  ValidationError? validateConstraint() {
     final constraintExpression = _constraintExpression;
     if (constraintExpression == null) {
-      return;
+      return null;
     }
 
     final isSatisfied = constraintExpression.fetchBoolValue(
@@ -95,11 +95,11 @@ abstract class ResponseItemModel extends FillerItemModel {
       location: nodeUid,
     );
 
-    if (!isSatisfied) {
-      throw ConstraintValidationError(
-        nodeUid,
-        questionnaireItemModel.constraintHuman,
-      );
-    }
+    return isSatisfied
+        ? null
+        : ConstraintValidationError(
+            nodeUid,
+            questionnaireItemModel.constraintHuman,
+          );
   }
 }

From 47debb7ee4dbaf646adac98ebf9e8ec26256cf75 Mon Sep 17 00:00:00 2001
From: Hanny Prastya Hariyadi <p.hanny@allm.inc>
Date: Wed, 11 Oct 2023 07:56:58 +0900
Subject: [PATCH 16/23] Fix calculation not triggered

---
 .../answer/src/numerical_answer_filler.dart   | 29 +++++++++----------
 1 file changed, 14 insertions(+), 15 deletions(-)

diff --git a/lib/questionnaires/view/item/answer/src/numerical_answer_filler.dart b/lib/questionnaires/view/item/answer/src/numerical_answer_filler.dart
index 6dd98aa1..457ec33a 100644
--- a/lib/questionnaires/view/item/answer/src/numerical_answer_filler.dart
+++ b/lib/questionnaires/view/item/answer/src/numerical_answer_filler.dart
@@ -185,6 +185,8 @@ class _NumberFieldInputControl
       );
     }
 
+    final localizations = FDashLocalizations.of(context);
+
     return Row(
       crossAxisAlignment: CrossAxisAlignment.start,
       children: [
@@ -196,8 +198,7 @@ class _NumberFieldInputControl
             textAlignVertical: TextAlignVertical.center,
             textAlign: TextAlign.end,
             decoration: InputDecoration(
-              errorText:
-                  answerModel.displayErrorText(FDashLocalizations.of(context)),
+              errorText: answerModel.displayErrorText(localizations),
               errorStyle: (itemModel
                       .isCalculated) // Force display of error text on calculated item
                   ? TextStyle(
@@ -208,11 +209,10 @@ class _NumberFieldInputControl
               prefixIcon: itemModel.isCalculated
                   ? Icon(
                       Icons.calculate,
-                      color: (answerModel.displayErrorText(
-                                  FDashLocalizations.of(context)) !=
-                              null)
-                          ? Theme.of(context).errorColor
-                          : null,
+                      color:
+                          (answerModel.displayErrorText(localizations) != null)
+                              ? Theme.of(context).errorColor
+                              : null,
                     )
                   : null,
               suffixIcon: (answerModel.hasUnitChoices)
@@ -226,14 +226,13 @@ class _NumberFieldInputControl
               signed: answerModel.minValue < 0,
               decimal: answerModel.maxDecimal > 0,
             ),
-            validator: (inputValue) {
-              if (!itemModel.isCalculated) {
-                return null;
-              }
-              return answerModel
-                  .validateInput(inputValue)
-                  ?.getMessage(FDashLocalizations.of(context));
-            },
+            validator: (itemModel.isCalculated)
+                ? null
+                : (inputValue) {
+                    return answerModel
+                        .validateInput(inputValue)
+                        ?.getMessage(localizations);
+                  },
             autovalidateMode: (itemModel.isCalculated)
                 ? AutovalidateMode.disabled
                 : AutovalidateMode.always,

From 9bbea4e66ffdea6082a831bfd31c47102a2a606a Mon Sep 17 00:00:00 2001
From: Hanny Prastya Hariyadi <p.hanny@allm.inc>
Date: Wed, 11 Oct 2023 12:34:50 +0900
Subject: [PATCH 17/23] Improve localization by doing translation in
 RenderingString

---
 .../item/answer/src/coding_answer_option_model.dart    | 10 +++++++++-
 .../model/src/questionnaire_item_model.dart            |  2 ++
 lib/questionnaires/model/src/questionnaire_model.dart  |  1 +
 lib/questionnaires/model/src/rendering_string.dart     |  8 ++++++--
 .../view/item/src/questionnaire_item_filler_title.dart |  6 +-----
 lib/questionnaires/view/src/questionnaire_filler.dart  |  3 +++
 lib/questionnaires/view/src/xhtml.dart                 |  7 ++-----
 7 files changed, 24 insertions(+), 13 deletions(-)

diff --git a/lib/questionnaires/model/item/answer/src/coding_answer_option_model.dart b/lib/questionnaires/model/item/answer/src/coding_answer_option_model.dart
index 20b41ea0..7c37bccd 100644
--- a/lib/questionnaires/model/item/answer/src/coding_answer_option_model.dart
+++ b/lib/questionnaires/model/item/answer/src/coding_answer_option_model.dart
@@ -75,6 +75,7 @@ class CodingAnswerOptionModel {
       final plainText = coding.localizedDisplay(locale);
       optionText = RenderingString.fromText(
         plainText,
+        locale: locale,
         extensions: coding.displayElement?.extension_,
       );
       forDisplay = plainText;
@@ -132,7 +133,11 @@ class CodingAnswerOptionModel {
         ?.valueString;
 
     final optionPrefix = (plainOptionPrefix != null)
-        ? RenderingString.fromText(plainOptionPrefix, extensions: extensions)
+        ? RenderingString.fromText(
+            plainOptionPrefix,
+            locale: locale,
+            extensions: extensions,
+          )
         : null;
 
     RenderingString optionText;
@@ -146,6 +151,7 @@ class CodingAnswerOptionModel {
         forDisplay = plainText;
         optionText = RenderingString.fromText(
           plainText,
+          locale: locale,
           extensions: xhtmlExtensions,
         );
       } else {
@@ -154,6 +160,7 @@ class CodingAnswerOptionModel {
         forDisplay = _createForDisplay(coding, locale, questionnaireItemModel);
         optionText = RenderingString.fromText(
           plainText,
+          locale: locale,
           extensions: extensions,
         );
       }
@@ -170,6 +177,7 @@ class CodingAnswerOptionModel {
       forDisplay = plainText;
       optionText = RenderingString.fromText(
         plainText,
+        locale: locale,
         extensions: xhtmlExtensions,
       );
     }
diff --git a/lib/questionnaires/model/src/questionnaire_item_model.dart b/lib/questionnaires/model/src/questionnaire_item_model.dart
index cf4b105c..a7e07567 100644
--- a/lib/questionnaires/model/src/questionnaire_item_model.dart
+++ b/lib/questionnaires/model/src/questionnaire_item_model.dart
@@ -273,6 +273,7 @@ class QuestionnaireItemModel with Diagnosticable {
     return (plainText != null)
         ? RenderingString.fromText(
             plainText,
+            locale: questionnaireModel.locale,
             extensions: questionnaireItem.textElement?.extension_,
           )
         : null;
@@ -290,6 +291,7 @@ class QuestionnaireItemModel with Diagnosticable {
     return (plainPrefix != null)
         ? RenderingString.fromText(
             plainPrefix,
+            locale: questionnaireModel.locale,
             extensions: questionnaireItem.prefixElement?.extension_,
           )
         : null;
diff --git a/lib/questionnaires/model/src/questionnaire_model.dart b/lib/questionnaires/model/src/questionnaire_model.dart
index a4d470ea..7a401e02 100644
--- a/lib/questionnaires/model/src/questionnaire_model.dart
+++ b/lib/questionnaires/model/src/questionnaire_model.dart
@@ -113,6 +113,7 @@ class QuestionnaireModel {
     return (plainTitle != null)
         ? RenderingString.fromText(
             plainTitle,
+            locale: locale,
             extensions: questionnaire.titleElement?.extension_,
           )
         : null;
diff --git a/lib/questionnaires/model/src/rendering_string.dart b/lib/questionnaires/model/src/rendering_string.dart
index 20607959..c0494f30 100644
--- a/lib/questionnaires/model/src/rendering_string.dart
+++ b/lib/questionnaires/model/src/rendering_string.dart
@@ -1,8 +1,10 @@
 import 'dart:convert';
 
+import 'package:faiadashu/extensions/string_extension.dart';
 import 'package:faiadashu/fhir_types/fhir_types.dart';
 import 'package:fhir/r4.dart';
 import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
 import 'package:markdown/markdown.dart';
 
 /// Representation of a Fhir string which is plain text with optional
@@ -62,6 +64,7 @@ class RenderingString with Diagnosticable {
   /// * rendering-xhtml
   factory RenderingString.fromText(
     String plainText, {
+    Locale? locale,
     List<FhirExtension>? extensions,
     String? xhtmlText,
   }) {
@@ -83,7 +86,8 @@ class RenderingString with Diagnosticable {
         )
         ?.valueMarkdown;
 
-    final escapedPlainText = _htmlEscape.convert(plainText);
+    final text = plainText.translate(extensions, locale);
+    final escapedPlainText = _htmlEscape.convert(text);
 
     final outputXhtmlText = (xhtmlText != null)
         ? xhtmlText
@@ -98,7 +102,7 @@ class RenderingString with Diagnosticable {
                   )
                 : (renderingStyle != null)
                     ? '<span style="$renderingStyle">$escapedPlainText</span>'
-                    : plainText;
+                    : text;
 
     return RenderingString._(
       plainText,
diff --git a/lib/questionnaires/view/item/src/questionnaire_item_filler_title.dart b/lib/questionnaires/view/item/src/questionnaire_item_filler_title.dart
index 95057a6b..89904ca2 100644
--- a/lib/questionnaires/view/item/src/questionnaire_item_filler_title.dart
+++ b/lib/questionnaires/view/item/src/questionnaire_item_filler_title.dart
@@ -1,4 +1,3 @@
-import 'package:faiadashu/extensions/string_extension.dart';
 import 'package:faiadashu/fhir_types/fhir_types.dart';
 import 'package:faiadashu/logging/logging.dart';
 import 'package:faiadashu/questionnaires/questionnaires.dart';
@@ -50,10 +49,7 @@ class QuestionnaireItemFillerTitle extends StatelessWidget {
               : '</p>';
 
       final prefixText = fillerItem.prefix;
-      final title = text.xhtmlText.translate(
-        questionnaireItemModel.text?.extensions ?? [],
-        Localizations.localeOf(context),
-      );
+      final title = text.xhtmlText;
 
       final htmlTitleText = (prefixText != null)
           ? '$openStyleTag${prefixText.xhtmlText}&nbsp;${title}$requiredTag$closeStyleTag'
diff --git a/lib/questionnaires/view/src/questionnaire_filler.dart b/lib/questionnaires/view/src/questionnaire_filler.dart
index 3a0faca4..163a76ae 100644
--- a/lib/questionnaires/view/src/questionnaire_filler.dart
+++ b/lib/questionnaires/view/src/questionnaire_filler.dart
@@ -144,6 +144,9 @@ class _QuestionnaireResponseFillerState
 
               return QuestionnaireLoadingIndicator(snapshot);
             }
+            if (_questionnaireResponseModel?.locale != snapshot.data?.locale) {
+              _handleQuestionnaireResponseModelChangeListenerFunction = null;
+            }
             if (snapshot.hasData) {
               _logger.debug('FutureBuilder hasData');
               _questionnaireResponseModel = snapshot.data;
diff --git a/lib/questionnaires/view/src/xhtml.dart b/lib/questionnaires/view/src/xhtml.dart
index c882f157..382534cf 100644
--- a/lib/questionnaires/view/src/xhtml.dart
+++ b/lib/questionnaires/view/src/xhtml.dart
@@ -1,4 +1,3 @@
-import 'package:faiadashu/extensions/string_extension.dart';
 import 'package:faiadashu/fhir_types/fhir_types.dart';
 import 'package:faiadashu/logging/logging.dart';
 import 'package:faiadashu/questionnaires/model/model.dart';
@@ -31,6 +30,7 @@ class Xhtml extends StatelessWidget {
   }) {
     final xhtmlString = RenderingString.fromText(
       plainText,
+      locale: Localizations.localeOf(context),
       extensions: extensions,
     );
 
@@ -58,10 +58,7 @@ class Xhtml extends StatelessWidget {
     _logger.trace('enter fromRenderingString $renderingString');
 
     final xhtml = renderingString.xhtmlText;
-    final plainText = renderingString.plainText.translate(
-      renderingString.extensions,
-      Localizations.localeOf(context),
-    );
+    final plainText = renderingString.plainText;
 
     if (renderingString.isPlain) {
       return Xhtml._(

From e9bb381294b3621f403e3bbfb8af7210db3ed8d0 Mon Sep 17 00:00:00 2001
From: Hanny Prastya Hariyadi <p.hanny@allm.inc>
Date: Wed, 11 Oct 2023 12:49:59 +0900
Subject: [PATCH 18/23] Revert changes and remove unneeded parameters

---
 .../item/answer/src/string_answer_filler.dart     | 12 +++++-------
 .../view/item/src/questionnaire_item_filler.dart  | 11 ++++++-----
 .../item/src/questionnaire_item_filler_title.dart |  1 -
 .../view/src/questionnaire_complete_button.dart   |  4 +++-
 .../view/src/questionnaire_filler.dart            |  8 +++-----
 .../view/src/questionnaire_stepper_page_view.dart |  3 ---
 .../view/src/questionnaire_theme.dart             | 15 +++++++--------
 7 files changed, 24 insertions(+), 30 deletions(-)

diff --git a/lib/questionnaires/view/item/answer/src/string_answer_filler.dart b/lib/questionnaires/view/item/answer/src/string_answer_filler.dart
index a88b958f..7e072838 100644
--- a/lib/questionnaires/view/item/answer/src/string_answer_filler.dart
+++ b/lib/questionnaires/view/item/answer/src/string_answer_filler.dart
@@ -61,6 +61,7 @@ class _StringAnswerInputControl extends AnswerInputControl<StringAnswerModel> {
   @override
   Widget build(BuildContext context) {
     final answerModel = this.answerModel;
+    final locale = FDashLocalizations.of(context);
 
     // FIXME: What should be the repaint mechanism for calculated items?
     // (it is getting repainted currently, but further optimization might break that)
@@ -95,7 +96,7 @@ class _StringAnswerInputControl extends AnswerInputControl<StringAnswerModel> {
           ? QuestionnaireTheme.of(context).maxLinesForTextItem
           : 1,
       decoration: InputDecoration(
-        errorText: answerModel.displayErrorText(FDashLocalizations.of(context)),
+        errorText: answerModel.displayErrorText(locale),
         errorStyle: (itemModel
                 .isCalculated) // Force display of error text on calculated item
             ? TextStyle(
@@ -106,17 +107,14 @@ class _StringAnswerInputControl extends AnswerInputControl<StringAnswerModel> {
         prefixIcon: itemModel.isCalculated
             ? Icon(
                 Icons.calculate,
-                color: (answerModel
-                            .displayErrorText(FDashLocalizations.of(context)) !=
-                        null)
+                color: (answerModel.displayErrorText(locale) != null)
                     ? Theme.of(context).errorColor
                     : null,
               )
             : null,
       ),
-      validator: (inputValue) => answerModel
-          .validateInput(inputValue)
-          ?.getMessage(FDashLocalizations.of(context)),
+      validator: (inputValue) =>
+          answerModel.validateInput(inputValue)?.getMessage(locale),
       autovalidateMode: AutovalidateMode.always,
       onChanged: (content) {
         answerModel.value = content;
diff --git a/lib/questionnaires/view/item/src/questionnaire_item_filler.dart b/lib/questionnaires/view/item/src/questionnaire_item_filler.dart
index c595e392..9b6a6a49 100644
--- a/lib/questionnaires/view/item/src/questionnaire_item_filler.dart
+++ b/lib/questionnaires/view/item/src/questionnaire_item_filler.dart
@@ -17,11 +17,7 @@ abstract class QuestionnaireItemFiller extends StatefulWidget {
 
 abstract class QuestionnaireItemFillerState<W extends QuestionnaireItemFiller>
     extends State<W> {
-  late final Widget? _titleWidget = QuestionnaireItemFillerTitle.fromFillerItem(
-    context: context,
-    fillerItem: widget.fillerItemModel,
-    questionnaireTheme: questionnaireTheme,
-  );
+  late final Widget? _titleWidget;
   Widget? get titleWidget => _titleWidget;
 
   QuestionnaireFillerData? _questionnaireFiller;
@@ -36,6 +32,11 @@ abstract class QuestionnaireItemFillerState<W extends QuestionnaireItemFiller>
   void initState() {
     super.initState();
     _focusNode = FocusNode(debugLabel: responseUid, skipTraversal: true);
+
+    _titleWidget = QuestionnaireItemFillerTitle.fromFillerItem(
+      fillerItem: widget.fillerItemModel,
+      questionnaireTheme: questionnaireTheme,
+    );
   }
 
   @override
diff --git a/lib/questionnaires/view/item/src/questionnaire_item_filler_title.dart b/lib/questionnaires/view/item/src/questionnaire_item_filler_title.dart
index 89904ca2..c0f4f76f 100644
--- a/lib/questionnaires/view/item/src/questionnaire_item_filler_title.dart
+++ b/lib/questionnaires/view/item/src/questionnaire_item_filler_title.dart
@@ -19,7 +19,6 @@ class QuestionnaireItemFillerTitle extends StatelessWidget {
   }) : super(key: key);
 
   static Widget? fromFillerItem({
-    required BuildContext context,
     required FillerItemModel fillerItem,
     required QuestionnaireThemeData questionnaireTheme,
     Key? key,
diff --git a/lib/questionnaires/view/src/questionnaire_complete_button.dart b/lib/questionnaires/view/src/questionnaire_complete_button.dart
index dbd1266b..665106b2 100644
--- a/lib/questionnaires/view/src/questionnaire_complete_button.dart
+++ b/lib/questionnaires/view/src/questionnaire_complete_button.dart
@@ -40,7 +40,9 @@ class _QuestionnaireCompleteButtonState
                   validation.getMessage(FDashLocalizations.of(context)) ?? ""
           };
 
-          return;
+          if (validationErrors.isNotEmpty) {
+            return;
+          }
         }
 
         final newResponseStatus =
diff --git a/lib/questionnaires/view/src/questionnaire_filler.dart b/lib/questionnaires/view/src/questionnaire_filler.dart
index 163a76ae..78f28ad8 100644
--- a/lib/questionnaires/view/src/questionnaire_filler.dart
+++ b/lib/questionnaires/view/src/questionnaire_filler.dart
@@ -250,7 +250,7 @@ class QuestionnaireFillerData extends InheritedWidget {
   /// The [QuestionnaireItemFiller]s are ordered based on 'pre-order'.
   ///
   /// see: https://en.wikipedia.org/wiki/Tree_traversal#Pre-order,_NLR
-  QuestionnaireItemFiller itemFillerAt(BuildContext context, int index) {
+  QuestionnaireItemFiller itemFillerAt(int index) {
     _logger.trace('itemFillerAt $index');
     final item = _itemFillers[index];
 
@@ -259,7 +259,6 @@ class QuestionnaireFillerData extends InheritedWidget {
       _itemFillers[index] = questionnaireTheme.createQuestionnaireItemFiller(
         this,
         fillerItemModels.elementAt(index),
-        Localizations.localeOf(context),
         key: ValueKey<String>(
           'item-filler-${fillerItemModels.elementAt(index).nodeUid}',
         ),
@@ -289,11 +288,10 @@ class QuestionnaireFillerData extends InheritedWidget {
 
   /// Returns the [QuestionnaireItemFiller] of the [visibleIndex]-th item that is currently
   /// visible.
-  QuestionnaireItemFiller? visibleItemFillerAt(
-      BuildContext context, int visibleIndex) {
+  QuestionnaireItemFiller? visibleItemFillerAt(int visibleIndex) {
     final index = indexOfVisibleItemAt(visibleIndex);
 
-    return index < 0 ? null : itemFillerAt(context, index);
+    return index < 0 ? null : itemFillerAt(index);
   }
 
   /// Returns the integer range of items corresponding to the [visibleRootIndex]-th root item
diff --git a/lib/questionnaires/view/src/questionnaire_stepper_page_view.dart b/lib/questionnaires/view/src/questionnaire_stepper_page_view.dart
index b9d90139..999b664b 100644
--- a/lib/questionnaires/view/src/questionnaire_stepper_page_view.dart
+++ b/lib/questionnaires/view/src/questionnaire_stepper_page_view.dart
@@ -50,7 +50,6 @@ class _QuestionnaireStepperPageViewState
     final fillerData = QuestionnaireResponseFiller.of(context);
 
     final nextPageFillerItem = themeData.stepperQuestionnaireItemFiller(
-      context,
       fillerData,
       currentPage + 1,
     );
@@ -77,7 +76,6 @@ class _QuestionnaireStepperPageViewState
     final responseFiller = QuestionnaireResponseFiller.of(context);
 
     final data = QuestionnaireTheme.of(context).stepperQuestionnaireItemFiller(
-      context,
       responseFiller,
       index,
     );
@@ -107,7 +105,6 @@ class _QuestionnaireStepperPageViewState
 
         final data =
             QuestionnaireTheme.of(context).stepperQuestionnaireItemFiller(
-          context,
           responseFillerData,
           index,
         );
diff --git a/lib/questionnaires/view/src/questionnaire_theme.dart b/lib/questionnaires/view/src/questionnaire_theme.dart
index 9ca28a81..9047d299 100644
--- a/lib/questionnaires/view/src/questionnaire_theme.dart
+++ b/lib/questionnaires/view/src/questionnaire_theme.dart
@@ -151,7 +151,6 @@ class QuestionnaireThemeData {
   ///
   /// [pageIndex] is the index of the page that's being currently built.
   final QuestionnaireItemFiller? Function(
-    BuildContext context,
     QuestionnaireFillerData responseFiller,
     int pageIndex,
   ) stepperQuestionnaireItemFiller;
@@ -177,12 +176,14 @@ class QuestionnaireThemeData {
     this.datePickerEntryMode = DatePickerEntryMode.calendar,
     this.timePickerEntryMode = TimePickerEntryMode.dial,
     this.createQuestionnaireAnswerFiller = _createDefaultAnswerFiller,
-    this.questionResponseItemLayoutBuilder = _defaultQuestionResponseItemLayoutBuilder,
+    this.questionResponseItemLayoutBuilder =
+        _defaultQuestionResponseItemLayoutBuilder,
     this.groupItemLayoutBuilder = _defaultGroupItemLayoutBuilder,
     this.displayItemLayoutBuilder = _defaultDisplayItemLayoutBuilder,
     this.codingControlLayoutBuilder = _defaultCodingControlLayoutBuilder,
     this.scrollerItemBuilder = _defaultScrollerItemBuilder,
-    this.stepperQuestionnaireItemFiller = _defaultStepperQuestionnaireItemFiller,
+    this.stepperQuestionnaireItemFiller =
+        _defaultStepperQuestionnaireItemFiller,
     this.stepperPageItemBuilder = _defaultStepperPageItemBuilder,
   });
 
@@ -191,8 +192,7 @@ class QuestionnaireThemeData {
   /// Used by [QuestionnaireResponseFiller].
   QuestionnaireItemFiller createQuestionnaireItemFiller(
     QuestionnaireFillerData questionnaireFiller,
-    FillerItemModel fillerItemModel,
-    Locale locale, {
+    FillerItemModel fillerItemModel, {
     Key? key,
   }) {
     if (fillerItemModel is QuestionItemModel) {
@@ -428,15 +428,14 @@ class QuestionnaireThemeData {
     QuestionnaireFillerData responseFiller,
     int index,
   ) {
-    return responseFiller.itemFillerAt(context, index);
+    return responseFiller.itemFillerAt(index);
   }
 
   static QuestionnaireItemFiller? _defaultStepperQuestionnaireItemFiller(
-    BuildContext context,
     QuestionnaireFillerData responseFiller,
     int index,
   ) {
-    final itemFiller = responseFiller.visibleItemFillerAt(context, index);
+    final itemFiller = responseFiller.visibleItemFillerAt(index);
     if (itemFiller == null) return null;
 
     return itemFiller;

From 3598028e169d969b943d32e8b739ed21aebcca11 Mon Sep 17 00:00:00 2001
From: Hanny Prastya Hariyadi <p.hanny@allm.inc>
Date: Wed, 11 Oct 2023 20:57:04 +0900
Subject: [PATCH 19/23] Revert changes

---
 .../item/answer/src/coding_answer_option_model.dart | 13 ++-----------
 1 file changed, 2 insertions(+), 11 deletions(-)

diff --git a/lib/questionnaires/model/item/answer/src/coding_answer_option_model.dart b/lib/questionnaires/model/item/answer/src/coding_answer_option_model.dart
index 7c37bccd..9ba3117f 100644
--- a/lib/questionnaires/model/item/answer/src/coding_answer_option_model.dart
+++ b/lib/questionnaires/model/item/answer/src/coding_answer_option_model.dart
@@ -133,11 +133,7 @@ class CodingAnswerOptionModel {
         ?.valueString;
 
     final optionPrefix = (plainOptionPrefix != null)
-        ? RenderingString.fromText(
-            plainOptionPrefix,
-            locale: locale,
-            extensions: extensions,
-          )
+        ? RenderingString.fromText(plainOptionPrefix)
         : null;
 
     RenderingString optionText;
@@ -151,18 +147,13 @@ class CodingAnswerOptionModel {
         forDisplay = plainText;
         optionText = RenderingString.fromText(
           plainText,
-          locale: locale,
           extensions: xhtmlExtensions,
         );
       } else {
         final plainText =
             _createMultiColumn(coding, locale, questionnaireItemModel);
         forDisplay = _createForDisplay(coding, locale, questionnaireItemModel);
-        optionText = RenderingString.fromText(
-          plainText,
-          locale: locale,
-          extensions: extensions,
-        );
+        optionText = RenderingString.fromText(plainText);
       }
     } else {
       // The spec only allows valueCoding, but valueString occurs in the real world

From 0f82ef052054f94c403434c34b87bc37010ec48d Mon Sep 17 00:00:00 2001
From: Hanny Prastya Hariyadi <p.hanny@allm.inc>
Date: Wed, 11 Oct 2023 20:57:29 +0900
Subject: [PATCH 20/23] Remove unused parameter

---
 lib/questionnaires/model/src/rendering_string.dart | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/lib/questionnaires/model/src/rendering_string.dart b/lib/questionnaires/model/src/rendering_string.dart
index c0494f30..1388235d 100644
--- a/lib/questionnaires/model/src/rendering_string.dart
+++ b/lib/questionnaires/model/src/rendering_string.dart
@@ -35,8 +35,6 @@ class RenderingString with Diagnosticable {
   /// The unaltered rendering-markdown extension
   final Markdown? renderingMarkdown;
 
-  final List<FhirExtension>? extensions;
-
   /// Construct an [RenderingString] from the provided attributes.
   ///
   /// No alterations of the attributes will take place, in particular,
@@ -48,7 +46,6 @@ class RenderingString with Diagnosticable {
     this.renderingStyle,
     this.renderingXhtml,
     this.renderingMarkdown,
-    this.extensions,
   });
 
   /// Construct an [RenderingString] from plainText and optional extensions.
@@ -114,7 +111,6 @@ class RenderingString with Diagnosticable {
       renderingStyle: renderingStyle,
       renderingXhtml: renderingXhtml,
       renderingMarkdown: renderingMarkdown,
-      extensions: extensions,
     );
   }
 

From 7c47cf7fd771fec2eb05b81c9c9a8f47eb5c6a16 Mon Sep 17 00:00:00 2001
From: Hanny Prastya Hariyadi <p.hanny@allm.inc>
Date: Wed, 11 Oct 2023 20:57:55 +0900
Subject: [PATCH 21/23] Add inline documentation

---
 example/lib/custom_questionnaire_stepper_page.dart | 1 +
 1 file changed, 1 insertion(+)

diff --git a/example/lib/custom_questionnaire_stepper_page.dart b/example/lib/custom_questionnaire_stepper_page.dart
index 5487fb97..44bb981e 100644
--- a/example/lib/custom_questionnaire_stepper_page.dart
+++ b/example/lib/custom_questionnaire_stepper_page.dart
@@ -41,6 +41,7 @@ class _CustomQuestionnaireStepperPageState
       return;
     }
 
+    // Validate the first matching item, and if it's valid, navigate to the next page
     final errors = matchingItems.first.validate(notifyListeners: true);
     if (errors.isEmpty) {
       _navigateToNextPage();

From 33aae122977430f71d8f89271e0a1f560a518856 Mon Sep 17 00:00:00 2001
From: Hanny Prastya Hariyadi <p.hanny@allm.inc>
Date: Thu, 12 Oct 2023 15:27:00 +0900
Subject: [PATCH 22/23] Remove unnecessary changes

---
 .../view/src/questionnaire_stepper_page_view.dart               | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/questionnaires/view/src/questionnaire_stepper_page_view.dart b/lib/questionnaires/view/src/questionnaire_stepper_page_view.dart
index 999b664b..aa9274a8 100644
--- a/lib/questionnaires/view/src/questionnaire_stepper_page_view.dart
+++ b/lib/questionnaires/view/src/questionnaire_stepper_page_view.dart
@@ -32,7 +32,7 @@ class QuestionnaireStepperPageView extends StatefulWidget {
 
 class _QuestionnaireStepperPageViewState
     extends State<QuestionnaireStepperPageView> {
-  PageController _pageController = PageController(keepPage: true);
+  PageController _pageController = PageController();
   bool _hasRequestsRunning = false;
   QuestionnaireItemFiller? _currentQuestionnaireItemFiller;
 

From e4c6b15a894b0a10e10a198dd7a4b166c4e8ebf9 Mon Sep 17 00:00:00 2001
From: Hanny Prastya Hariyadi <p.hanny@allm.inc>
Date: Thu, 12 Oct 2023 15:28:38 +0900
Subject: [PATCH 23/23] Add documentation

---
 lib/questionnaires/view/src/questionnaire_filler.dart | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lib/questionnaires/view/src/questionnaire_filler.dart b/lib/questionnaires/view/src/questionnaire_filler.dart
index 78f28ad8..1e5f3b33 100644
--- a/lib/questionnaires/view/src/questionnaire_filler.dart
+++ b/lib/questionnaires/view/src/questionnaire_filler.dart
@@ -144,6 +144,10 @@ class _QuestionnaireResponseFillerState
 
               return QuestionnaireLoadingIndicator(snapshot);
             }
+            // If the locale of `_questionnaireResponseModel` doesn't match the locale of `snapshot.data`,
+            // reset `_handleQuestionnaireResponseModelChangeListenerFunction` to null.
+            // This ensures that `_questionnaireFillerData` will be re-initialized
+            // using the most recent questionnaire response model that has the updated locale
             if (_questionnaireResponseModel?.locale != snapshot.data?.locale) {
               _handleQuestionnaireResponseModelChangeListenerFunction = null;
             }