inbox [nfc]: Pull out _AtMentionMarker

Author: sirpengi

lib/widgets/inbox.dart

@@ -468,15 +468,25 @@ class _TopicItem extends StatelessWidget {
                 overflow: TextOverflow.ellipsis,
                 topic))),
             const SizedBox(width: 12),
-            // Design for at-mention marker based on Figma screen:
-            //   https://www.figma.com/file/1JTNtYo9memgW7vV6d0ygq/Zulip-Mobile?type=design&node-id=224-16386&mode=design&t=JsNndFQ8fKFH0SjS-0
-            if (hasMention) Padding(
-              padding: const EdgeInsetsDirectional.only(end: 4),
-              child: Icon(ZulipIcons.at_sign, size: 14, color:
-                const HSLColor.fromAHSL(0.5, 0, 0, 0.2).toColor())),
+            if (hasMention) const _AtMentionMarker(),
             Padding(padding: const EdgeInsetsDirectional.only(end: 16),
               child: UnreadCountBadge(backgroundColor: subscription.colorSwatch(),
                 count: count)),
           ]))));
   }
 }
+
+class _AtMentionMarker extends StatelessWidget {
+  const _AtMentionMarker();
+
+  static final markerColor = const HSLColor.fromAHSL(0.5, 0, 0, 0.2).toColor();
+
+  @override
+  Widget build(BuildContext context) {
+    // Design for at-mention marker based on Figma screen:
+    //   https://www.figma.com/file/1JTNtYo9memgW7vV6d0ygq/Zulip-Mobile?type=design&node-id=224-16386&mode=design&t=JsNndFQ8fKFH0SjS-0
+    return Padding(
+      padding: const EdgeInsetsDirectional.only(end: 4),
+      child: Icon(ZulipIcons.at_sign, size: 14, color: markerColor));
+  }
+}