model [nfc]: Remove StreamColorSwatch; just use ColorSwatch<StreamColorVariant>

lib/api/model/model.dart

@@ -416,16 +416,17 @@ class Subscription extends ZulipStream {
     return 0xff000000 | int.parse(str.substring(1), radix: 16);
   }
 
-  StreamColorSwatch? _swatch;
-  /// A [StreamColorSwatch] for the subscription, memoized.
+  ColorSwatch<StreamColor>? _swatch;
+  /// A [ColorSwatch<StreamColorVariant>] for the subscription, memoized.
   // TODO I'm not sure this is the right home for this; it seems like we might
   //   instead have chosen to put it in more UI-centered code, like in a custom
   //   material [ColorScheme] class or something. But it works for now.
-  StreamColorSwatch colorSwatch() => _swatch ??= StreamColorSwatch(color);
+  ColorSwatch<StreamColor> colorSwatch() =>
+    _swatch ??= streamColorSwatch(color);
 
   @visibleForTesting
   @JsonKey(includeToJson: false)
-  StreamColorSwatch? get debugCachedSwatchValue => _swatch;
+  ColorSwatch<StreamColor>? get debugCachedSwatchValue => _swatch;
 
   Subscription({
     required super.streamId,
@@ -462,86 +463,79 @@ class Subscription extends ZulipStream {
 ///
 /// Use this in UI code for colors related to [Subscription.color],
 /// such as the background of an unread count badge.
-class StreamColorSwatch extends ColorSwatch<_StreamColorVariant> {
-  StreamColorSwatch(int base) : super(base, _compute(base));
+ColorSwatch<StreamColor> streamColorSwatch(int base) {
+  final baseAsColor = Color(base);
+
+  final clamped20to75 = clampLchLightness(baseAsColor, 20, 75);
+  final clamped20to75AsHsl = HSLColor.fromColor(clamped20to75);
+
+  final map = {
+    StreamColor.base: baseAsColor,
+
+    // Follows `.unread-count` in Vlad's replit:
+    //   <https://replit.com/@VladKorobov/zulip-sidebar#script.js>
+    //   <https://chat.zulip.org/#narrow/stream/243-mobile-team/topic/design.3A.20.23F117.20.22Inbox.22.20screen/near/1624484>
+    //
+    // TODO fix bug where our results differ from the replit's (see unit tests)
+    StreamColor.unreadCountBadgeBackground:
+      clampLchLightness(baseAsColor, 30, 70)
+        .withOpacity(0.3),
+
+    // Follows `.sidebar-row__icon` in Vlad's replit:
+    //   <https://replit.com/@VladKorobov/zulip-topic-feed-colors#script.js>
+    //
+    // TODO fix bug where our results differ from the replit's (see unit tests)
+    StreamColor.iconOnPlainBackground: clamped20to75,
+
+    // Follows `.recepeient__icon` in Vlad's replit:
+    //   <https://replit.com/@VladKorobov/zulip-topic-feed-colors#script.js>
+    //   <https://chat.zulip.org/#narrow/stream/243-mobile-team/topic/design.3A.20.23F117.20.22Inbox.22.20screen/near/1624484>
+    //
+    // TODO fix bug where our results differ from the replit's (see unit tests)
+    StreamColor.iconOnBarBackground:
+      clamped20to75AsHsl
+        .withLightness(clamped20to75AsHsl.lightness - 0.12)
+        .toColor(),
+
+    // Follows `.recepient` in Vlad's replit:
+    //   <https://replit.com/@VladKorobov/zulip-topic-feed-colors#script.js>
+    //
+    // TODO I think [LabColor.interpolate] doesn't actually do LAB mixing;
+    //   it just calls up to the superclass method [ColorModel.interpolate]:
+    //     <https://pub.dev/documentation/flutter_color_models/latest/flutter_color_models/ColorModel/interpolate.html>
+    //   which does ordinary RGB mixing. Investigate and send a PR?
+    // TODO fix bug where our results differ from the replit's (see unit tests)
+    StreamColor.barBackground:
+      LabColor.fromColor(const Color(0xfff9f9f9))
+        .interpolate(LabColor.fromColor(clamped20to75), 0.22)
+        .toColor(),
+  };
+
+  return ColorSwatch<StreamColor>(base, map);
+}
 
-  Color get base => this[_StreamColorVariant.base]!;
+enum StreamColor {
+  /// The [Subscription.color] int that the swatch is based on.
+  base,
 
-  Color get unreadCountBadgeBackground => this[_StreamColorVariant.unreadCountBadgeBackground]!;
+  unreadCountBadgeBackground,
 
   /// The stream icon on a plain-colored surface, such as white.
   ///
   /// For the icon on a [barBackground]-colored surface,
   /// use [iconOnBarBackground] instead.
-  Color get iconOnPlainBackground => this[_StreamColorVariant.iconOnPlainBackground]!;
+  iconOnPlainBackground,
 
   /// The stream icon on a [barBackground]-colored surface.
   ///
   /// For the icon on a plain surface, use [iconOnPlainBackground] instead.
   /// This color is chosen to enhance contrast with [barBackground]:
   ///   <https://github.com/zulip/zulip/pull/27485>
-  Color get iconOnBarBackground => this[_StreamColorVariant.iconOnBarBackground]!;
+  iconOnBarBackground,
 
   /// The background color of a bar representing a stream, like a recipient bar.
   ///
   /// Use this in the message list, the "Inbox" view, and the "Streams" view.
-  Color get barBackground => this[_StreamColorVariant.barBackground]!;
-
-  static Map<_StreamColorVariant, Color> _compute(int base) {
-    final baseAsColor = Color(base);
-
-    final clamped20to75 = clampLchLightness(baseAsColor, 20, 75);
-    final clamped20to75AsHsl = HSLColor.fromColor(clamped20to75);
-
-    return {
-      _StreamColorVariant.base: baseAsColor,
-
-      // Follows `.unread-count` in Vlad's replit:
-      //   <https://replit.com/@VladKorobov/zulip-sidebar#script.js>
-      //   <https://chat.zulip.org/#narrow/stream/243-mobile-team/topic/design.3A.20.23F117.20.22Inbox.22.20screen/near/1624484>
-      //
-      // TODO fix bug where our results differ from the replit's (see unit tests)
-      _StreamColorVariant.unreadCountBadgeBackground:
-        clampLchLightness(baseAsColor, 30, 70)
-          .withOpacity(0.3),
-
-      // Follows `.sidebar-row__icon` in Vlad's replit:
-      //   <https://replit.com/@VladKorobov/zulip-topic-feed-colors#script.js>
-      //
-      // TODO fix bug where our results differ from the replit's (see unit tests)
-      _StreamColorVariant.iconOnPlainBackground: clamped20to75,
-
-      // Follows `.recepeient__icon` in Vlad's replit:
-      //   <https://replit.com/@VladKorobov/zulip-topic-feed-colors#script.js>
-      //   <https://chat.zulip.org/#narrow/stream/243-mobile-team/topic/design.3A.20.23F117.20.22Inbox.22.20screen/near/1624484>
-      //
-      // TODO fix bug where our results differ from the replit's (see unit tests)
-      _StreamColorVariant.iconOnBarBackground:
-        clamped20to75AsHsl
-          .withLightness(clamped20to75AsHsl.lightness - 0.12)
-          .toColor(),
-
-      // Follows `.recepient` in Vlad's replit:
-      //   <https://replit.com/@VladKorobov/zulip-topic-feed-colors#script.js>
-      //
-      // TODO I think [LabColor.interpolate] doesn't actually do LAB mixing;
-      //   it just calls up to the superclass method [ColorModel.interpolate]:
-      //     <https://pub.dev/documentation/flutter_color_models/latest/flutter_color_models/ColorModel/interpolate.html>
-      //   which does ordinary RGB mixing. Investigate and send a PR?
-      // TODO fix bug where our results differ from the replit's (see unit tests)
-      _StreamColorVariant.barBackground:
-        LabColor.fromColor(const Color(0xfff9f9f9))
-          .interpolate(LabColor.fromColor(clamped20to75), 0.22)
-          .toColor(),
-    };
-  }
-}
-
-enum _StreamColorVariant {
-  base,
-  unreadCountBadgeBackground,
-  iconOnPlainBackground,
-  iconOnBarBackground,
   barBackground,
 }
 

lib/widgets/inbox.dart

@@ -410,12 +410,14 @@ class _StreamHeaderItem extends _HeaderItem {
 
   @override get title => subscription.name;
   @override get icon => iconDataForStream(subscription);
-  @override get collapsedIconColor => subscription.colorSwatch().iconOnPlainBackground;
-  @override get uncollapsedIconColor => subscription.colorSwatch().iconOnBarBackground;
+  @override get collapsedIconColor =>
+    subscription.colorSwatch()[StreamColor.iconOnPlainBackground]!;
+  @override get uncollapsedIconColor =>
+    subscription.colorSwatch()[StreamColor.iconOnBarBackground]!;
   @override get uncollapsedBackgroundColor =>
-    subscription.colorSwatch().barBackground;
+    subscription.colorSwatch()[StreamColor.barBackground]!;
   @override get unreadCountBadgeBackgroundColor =>
-    subscription.colorSwatch().unreadCountBadgeBackground;
+    subscription.colorSwatch()[StreamColor.unreadCountBadgeBackground]!;
 
   @override get onCollapseButtonTap => () async {
     await super.onCollapseButtonTap();

lib/widgets/message_list.dart

@@ -66,7 +66,8 @@ class _MessageListPageState extends State<MessageListPage> {
 
       case StreamNarrow(:final streamId):
       case TopicNarrow(:final streamId):
-        backgroundColor = store.subscriptions[streamId]?.colorSwatch().barBackground
+        backgroundColor =
+          store.subscriptions[streamId]?.colorSwatch()[StreamColor.barBackground]!
           ?? _kUnsubscribedStreamRecipientHeaderColor;
         // All recipient headers will match this color; remove distracting line
         // (but are recipient headers even needed for topic narrows?)
@@ -655,12 +656,12 @@ class StreamMessageRecipientHeader extends StatelessWidget {
     final Color iconColor;
     if (subscription != null) {
       final swatch = subscription.colorSwatch();
-      backgroundColor = swatch.barBackground;
+      backgroundColor = swatch[StreamColor.barBackground]!;
       contrastingColor =
-        (ThemeData.estimateBrightnessForColor(swatch.barBackground) == Brightness.dark)
+        (ThemeData.estimateBrightnessForColor(backgroundColor) == Brightness.dark)
           ? Colors.white
           : Colors.black;
-      iconColor = swatch.iconOnBarBackground;
+      iconColor = swatch[StreamColor.iconOnBarBackground]!;
     } else {
       backgroundColor = _kUnsubscribedStreamRecipientHeaderColor;
       contrastingColor = Colors.black;

lib/widgets/subscription_list.dart

@@ -208,7 +208,7 @@ class SubscriptionItem extends StatelessWidget {
           const SizedBox(width: 16),
           Padding(
             padding: const EdgeInsets.symmetric(vertical: 11),
-            child: Icon(size: 18, color: swatch.iconOnPlainBackground,
+            child: Icon(size: 18, color: swatch[StreamColor.iconOnPlainBackground]!,
               iconDataForStream(subscription))),
           const SizedBox(width: 5),
           Expanded(

lib/widgets/unread_count_badge.dart

@@ -21,16 +21,18 @@ class UnreadCountBadge extends StatelessWidget {
 
   /// The badge's background color.
   ///
-  /// Pass a [StreamColorSwatch] if this badge represents messages in one
-  /// specific stream. The appropriate color from the swatch will be used.
+  /// Pass a [ColorSwatch<StreamColorVariant>] if this badge represents messages
+  /// in one specific stream. The appropriate color from the swatch will be used.
   ///
   /// If null, the default neutral background will be used.
   final Color? backgroundColor;
 
   @override
   Widget build(BuildContext context) {
+    final backgroundColor = this.backgroundColor;
     final effectiveBackgroundColor = switch (backgroundColor) {
-      StreamColorSwatch(unreadCountBadgeBackground: var color) => color,
+      ColorSwatch<StreamColor>() =>
+        backgroundColor[StreamColor.unreadCountBadgeBackground]!,
       Color() => backgroundColor,
       null => const Color.fromRGBO(102, 102, 153, 0.15),
     };

test/api/model/model_checks.dart

@@ -1,5 +1,3 @@
-import 'dart:ui';
-
 import 'package:checks/checks.dart';
 import 'package:zulip/api/model/model.dart';
 
@@ -29,14 +27,6 @@ extension ZulipStreamChecks on Subject<ZulipStream> {
   Subject<int?> get canRemoveSubscribersGroup => has((e) => e.canRemoveSubscribersGroup, 'canRemoveSubscribersGroup');
 }
 
-extension StreamColorSwatchChecks on Subject<StreamColorSwatch> {
-  Subject<Color> get base => has((s) => s.base, 'base');
-  Subject<Color> get unreadCountBadgeBackground => has((s) => s.unreadCountBadgeBackground, 'unreadCountBadgeBackground');
-  Subject<Color> get iconOnPlainBackground => has((s) => s.iconOnPlainBackground, 'iconOnPlainBackground');
-  Subject<Color> get iconOnBarBackground => has((s) => s.iconOnBarBackground, 'iconOnBarBackground');
-  Subject<Color> get barBackground => has((s) => s.barBackground, 'barBackground');
-}
-
 extension MessageChecks on Subject<Message> {
   Subject<int> get id => has((e) => e.id, 'id');
   Subject<String> get content => has((e) => e.content, 'content');

test/api/model/model_test.dart

@@ -5,6 +5,7 @@ import 'package:checks/checks.dart';
 import 'package:test/scaffolding.dart';
 import 'package:zulip/api/model/model.dart';
 
+import '../../flutter_checks.dart';
 import '../../example_data.dart' as eg;
 import '../../stdlib_checks.dart';
 import 'model_checks.dart';
@@ -120,21 +121,25 @@ void main() {
       final sub = eg.subscription(eg.stream(), color: 0xffffffff);
       check(sub.debugCachedSwatchValue).isNull();
       sub.colorSwatch();
-      check(sub.debugCachedSwatchValue).isNotNull().base.equals(const Color(0xffffffff));
+      check(sub.debugCachedSwatchValue).isNotNull()
+        [StreamColor.base].equals(const Color(0xffffffff));
       sub.color = 0xffff0000;
       check(sub.debugCachedSwatchValue).isNull();
       sub.colorSwatch();
-      check(sub.debugCachedSwatchValue).isNotNull().base.equals(const Color(0xffff0000));
+      check(sub.debugCachedSwatchValue).isNotNull()
+        [StreamColor.base].equals(const Color(0xffff0000));
     });
 
-    group('StreamColorSwatch', () {
+    group('streamColorSwatch', () {
       test('base', () {
-        check(StreamColorSwatch(0xffffffff)).base.equals(const Color(0xffffffff));
+        check(streamColorSwatch(0xffffffff))[StreamColor.base]
+          .equals(const Color(0xffffffff));
       });
 
       test('unreadCountBadgeBackground', () {
         void runCheck(int base, Color expected) {
-          check(StreamColorSwatch(base)).unreadCountBadgeBackground.equals(expected);
+          check(streamColorSwatch(base))
+            [StreamColor.unreadCountBadgeBackground].equals(expected);
         }
 
         // Check against everything in ZULIP_ASSIGNMENT_COLORS and EXTREME_COLORS
@@ -196,7 +201,8 @@ void main() {
 
       test('iconOnPlainBackground', () {
         void runCheck(int base, Color expected) {
-          check(StreamColorSwatch(base)).iconOnPlainBackground.equals(expected);
+          check(streamColorSwatch(base))
+            [StreamColor.iconOnPlainBackground].equals(expected);
         }
 
         // Check against everything in ZULIP_ASSIGNMENT_COLORS
@@ -237,7 +243,8 @@ void main() {
 
       test('iconOnBarBackground', () {
         void runCheck(int base, Color expected) {
-          check(StreamColorSwatch(base)).iconOnBarBackground.equals(expected);
+          check(streamColorSwatch(base))
+            [StreamColor.iconOnBarBackground].equals(expected);
         }
 
         // Check against everything in ZULIP_ASSIGNMENT_COLORS
@@ -278,7 +285,8 @@ void main() {
 
       test('barBackground', () {
         void runCheck(int base, Color expected) {
-          check(StreamColorSwatch(base)).barBackground.equals(expected);
+          check(streamColorSwatch(base))
+            [StreamColor.barBackground].equals(expected);
         }
 
         // Check against everything in ZULIP_ASSIGNMENT_COLORS

test/flutter_checks.dart

@@ -5,6 +5,10 @@ import 'package:checks/checks.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 
+extension ColorSwatchChecks<T> on Subject<ColorSwatch<T>> {
+  Subject<Color?> operator [](T index) => has((x) => x[index], '[$index]');
+}
+
 extension RectChecks on Subject<Rect> {
   Subject<double> get top => has((d) => d.top, 'top');
   Subject<double> get bottom => has((d) => d.bottom, 'bottom');

test/widgets/inbox_test.dart

@@ -411,7 +411,8 @@ void main() {
           final collapseIcon = findHeaderCollapseIcon(tester, headerRow!);
           check(collapseIcon).icon.equals(ZulipIcons.arrow_down);
           final streamIcon = findStreamHeaderIcon(tester, streamId);
-          check(streamIcon).color.equals(subscription.colorSwatch().iconOnBarBackground);
+          check(streamIcon).color
+            .equals(subscription.colorSwatch()[StreamColor.iconOnBarBackground]!);
           // TODO check bar background color
           check(tester.widgetList(findSectionContent)).isNotEmpty();
         }
@@ -432,7 +433,8 @@ void main() {
           final collapseIcon = findHeaderCollapseIcon(tester, headerRow!);
           check(collapseIcon).icon.equals(ZulipIcons.arrow_right);
           final streamIcon = findStreamHeaderIcon(tester, streamId);
-          check(streamIcon).color.equals(subscription.colorSwatch().iconOnPlainBackground);
+          check(streamIcon).color
+            .equals(subscription.colorSwatch()[StreamColor.iconOnPlainBackground]!);
           // TODO check bar background color
           check(tester.widgetList(findSectionContent)).isEmpty();
         }

test/widgets/message_list_test.dart

@@ -282,7 +282,7 @@ void main() {
           find.descendant(
             of: find.byType(StreamMessageRecipientHeader),
             matching: find.byType(ColoredBox),
-        ))).color.equals(swatch.barBackground);
+        ))).color.equals(swatch[StreamColor.barBackground]!);
       });
 
       testWidgets('color of stream icon', (tester) async {
@@ -294,7 +294,7 @@ void main() {
           subscriptions: [subscription]);
         await tester.pump();
         check(tester.widget<Icon>(find.byIcon(ZulipIcons.globe)))
-          .color.equals(swatch.iconOnBarBackground);
+          .color.equals(swatch[StreamColor.iconOnBarBackground]!);
       });
 
       testWidgets('normal streams show hash icon', (tester) async {

test/widgets/subscription_list_test.dart

@@ -186,7 +186,7 @@ void main() {
     ], unreadMsgs: unreadMsgs);
     check(getItemCount()).equals(1);
     check(tester.widget<Icon>(find.byType(Icon)).color)
-      .equals(swatch.iconOnPlainBackground);
+      .equals(swatch[StreamColor.iconOnPlainBackground]!);
     check(tester.widget<UnreadCountBadge>(find.byType(UnreadCountBadge)).backgroundColor)
       .equals(swatch);
   });