---

name: Flutter Performance description: Optimization standards for rebuilds and memory. metadata: labels: [performance] triggers: files: ['lib/presentation/**', 'pubspec.yaml'] keywords: [const, buildWhen, ListView.builder, Isolate, RepaintBoundary]

Performance

Priority: P1 (OPERATIONAL)

Performance optimization techniques for smooth 60fps Flutter applications.

• Rebuilds: Use const widgets and buildWhen / select for granular updates.
• Lists: Always use ListView.builder for item recycling.
• Heavy Tasks: Use compute() or Isolates for parsing/logic.
• Repaints: Use RepaintBoundary for complex animations. Use debugRepaintRainbowEnabled to debug.
• Images: Use CachedNetworkImage + memCacheWidth. precachePicture for SVGs.

🚫 Anti-Patterns

• Large Rebuilds: **No SetState at Root**: Use granular builders (BlocBuilder, Consumer).
• Logic in Build: **No Heavy Work in body**: Perform parsing/sorting in the Business Layer.
• Missing Const: **No Dynamic Leaf Widgets**: Use const where possible.

CopyBlocBuilder<UserBloc, UserState>(
  buildWhen: (p, c) => p.id != c.id,
  builder: (context, state) => Text(state.name),
)