From 06c0bb0d1bab3e3abecef52736a607b372886923 Mon Sep 17 00:00:00 2001
From: Tom Brow <tomb@block.xyz>
Date: Sun, 18 Oct 2026 12:32:57 -0700
Subject: [PATCH] perf(mobile): skip unchanged message footer layout

Signed-off-by: Tom Brow <tomb@block.xyz>
---
 .../channels/message_footer_layout.dart       | 14 +++--
 .../channels/message_footer_layout_test.dart  | 57 +++++++++++++++++++
 2 files changed, 66 insertions(+), 5 deletions(-)

diff --git a/mobile/lib/features/channels/message_footer_layout.dart b/mobile/lib/features/channels/message_footer_layout.dart
index a35409a9e2..6668b8a8f6 100644
--- a/mobile/lib/features/channels/message_footer_layout.dart
+++ b/mobile/lib/features/channels/message_footer_layout.dart
@@ -54,9 +54,7 @@ class _FooterLayout extends MultiChildRenderObjectWidget {
     BuildContext context,
     covariant RenderBox renderObject,
   ) {
-    (renderObject as _RenderMessageFooter)
-      ..overlap = overlap
-      ..markNeedsLayout();
+    (renderObject as _RenderMessageFooter).overlap = overlap;
   }
 }
 
@@ -70,9 +68,15 @@ class _RenderMessageFooter extends RenderBox
           RenderBox,
           ContainerBoxParentData<RenderBox>
         > {
-  _RenderMessageFooter(this.overlap);
+  _RenderMessageFooter(this._overlap);
 
-  double overlap;
+  double _overlap;
+  double get overlap => _overlap;
+  set overlap(double value) {
+    if (_overlap == value) return;
+    _overlap = value;
+    markNeedsLayout();
+  }
 
   @override
   void setupParentData(RenderBox child) {
diff --git a/mobile/test/features/channels/message_footer_layout_test.dart b/mobile/test/features/channels/message_footer_layout_test.dart
index 39b1cf3bf0..22f950dd82 100644
--- a/mobile/test/features/channels/message_footer_layout_test.dart
+++ b/mobile/test/features/channels/message_footer_layout_test.dart
@@ -1,8 +1,47 @@
 import 'package:buzz/features/channels/message_footer_layout.dart';
 import 'package:flutter/material.dart';
+import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 void main() {
+  testWidgets('unchanged footer geometry does not relayout its timeline row', (
+    tester,
+  ) async {
+    var layouts = 0;
+    final overlap = ValueNotifier(8.0);
+    addTearDown(overlap.dispose);
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Align(
+          alignment: Alignment.topLeft,
+          child: _LayoutCounter(
+            onLayout: () => layouts++,
+            child: ValueListenableBuilder(
+              valueListenable: overlap,
+              builder: (context, value, child) => MessageFooterLayout(
+                overlap: value,
+                footer: const SizedBox(width: 100, height: 32),
+                child: const SizedBox(width: 200, height: 60),
+              ),
+            ),
+          ),
+        ),
+      ),
+    );
+    final initialLayouts = layouts;
+    tester.element(find.byType(MessageFooterLayout)).markNeedsBuild();
+    await tester.pump();
+    expect(
+      layouts,
+      initialLayouts,
+      reason: 'Rebuilding unchanged reactions must not dirty the row layout',
+    );
+    overlap.value = 12;
+    await tester.pump();
+    expect(layouts, greaterThan(initialLayouts));
+    expect(tester.getSize(find.byType(MessageFooterLayout)).height, 80);
+  });
+
   testWidgets('footer global transforms and semantics include overlap offset', (
     tester,
   ) async {
@@ -118,3 +157,21 @@ void main() {
     },
   );
 }
+
+class _LayoutCounter extends SingleChildRenderObjectWidget {
+  const _LayoutCounter({required this.onLayout, required super.child});
+  final VoidCallback onLayout;
+  @override
+  RenderObject createRenderObject(BuildContext context) =>
+      _CountLayouts(onLayout);
+}
+
+class _CountLayouts extends RenderProxyBox {
+  _CountLayouts(this.onLayout);
+  final VoidCallback onLayout;
+  @override
+  void performLayout() {
+    onLayout();
+    super.performLayout();
+  }
+}