settings: added coordinate format example

lib/utils/constants.dart

@@ -1,5 +1,6 @@
 import 'package:flutter/material.dart';
 import 'package:flutter/painting.dart';
+import 'package:tuple/tuple.dart';
 
 class Constants {
   // as of Flutter v1.11.0, overflowing `Text` miscalculates height and some text (e.g. 'Å') is clipped
@@ -17,6 +18,8 @@ class Constants {
     offset: Offset(0.5, 1.0),
   );
 
+  static const pointNemo = Tuple2(-48.876667, -123.393333);
+
   static const List<Dependency> androidDependencies = [
     Dependency(
       name: 'CWAC-Document',

lib/widgets/common/aves_selection_dialog.dart

@@ -3,14 +3,18 @@ import 'package:flutter/widgets.dart';
 
 import 'aves_dialog.dart';
 
+typedef TextBuilder<T> = String Function(T value);
+
 class AvesSelectionDialog<T> extends StatefulWidget {
   final T initialValue;
   final Map<T, String> options;
+  final TextBuilder<T> optionSubtitleBuilder;
   final String title;
 
   const AvesSelectionDialog({
     @required this.initialValue,
     @required this.options,
+    this.optionSubtitleBuilder,
     @required this.title,
   });
 
@@ -41,20 +45,30 @@ class _AvesSelectionDialogState<T> extends State<AvesSelectionDialog> {
     );
   }
 
-  Widget _buildRadioListTile(T value, String title) => RadioListTile<T>(
-        key: Key(value.toString()),
-        value: value,
-        groupValue: _selectedValue,
-        onChanged: (v) {
-          _selectedValue = v;
-          Navigator.pop(context, _selectedValue);
-          setState(() {});
-        },
-        title: Text(
-          title,
-          softWrap: false,
-          overflow: TextOverflow.fade,
-          maxLines: 1,
-        ),
-      );
+  Widget _buildRadioListTile(T value, String title) {
+    return RadioListTile<T>(
+      key: Key(value.toString()),
+      value: value,
+      groupValue: _selectedValue,
+      onChanged: (v) {
+        _selectedValue = v;
+        Navigator.pop(context, _selectedValue);
+        setState(() {});
+      },
+      title: Text(
+        title,
+        softWrap: false,
+        overflow: TextOverflow.fade,
+        maxLines: 1,
+      ),
+      subtitle: widget.optionSubtitleBuilder != null
+          ? Text(
+              widget.optionSubtitleBuilder(value),
+              softWrap: false,
+              overflow: TextOverflow.fade,
+              maxLines: 1,
+            )
+          : null,
+    );
+  }
 }

lib/widgets/settings/settings_page.dart

@@ -2,6 +2,7 @@ import 'package:aves/model/settings/coordinate_format.dart';
 import 'package:aves/model/settings/home_page.dart';
 import 'package:aves/model/settings/screen_on.dart';
 import 'package:aves/model/settings/settings.dart';
+import 'package:aves/utils/constants.dart';
 import 'package:aves/widgets/common/aves_selection_dialog.dart';
 import 'package:aves/widgets/common/data_providers/media_query_data_provider.dart';
 import 'package:aves/widgets/common/highlight_title.dart';
@@ -80,6 +81,11 @@ class SettingsPage extends StatelessWidget {
                         builder: (context) => AvesSelectionDialog<CoordinateFormat>(
                           initialValue: settings.coordinateFormat,
                           options: Map.fromEntries(CoordinateFormat.values.map((v) => MapEntry(v, v.name))),
+                          optionSubtitleBuilder: (dynamic value) {
+                            // dynamic declaration followed by cast, as workaround for generics limitation
+                            final formatter = (value as CoordinateFormat);
+                            return formatter.format(Constants.pointNemo);
+                          },
                           title: 'Coordinate Format',
                         ),
                       );