---
name: flutter-idiomatic-flutter
description: "Modern layout and widget composition standards. Use when composing Flutter widget trees, managing layout constraints, or following idiomatic Flutter patterns. (triggers: lib/presentation/**/*.dart, context.mounted, SizedBox, Gap, composition, shrink)"
---

# Idiomatic Flutter

## **Priority: P1 (OPERATIONAL)**

Modern Flutter layout patterns and composition techniques.

- **Async Gaps**: Check `if (context.mounted)` before using `BuildContext` after `await`.
- **Composition**: Extract complex UI into small widgets. Avoid deep nesting or large helper methods.
- **Layout**:
  - Spacing: Use `Gap(n)` or `SizedBox` over `Padding` for simple gaps.
  - Empty UI: Use `const SizedBox.shrink()`.
  - Intrinsic: Avoid `IntrinsicWidth/Height`; use `Stack` + `FractionallySizedBox` for overlays.
- **Optimization**: Use `ColoredBox`/`Padding`/`DecoratedBox` instead of `Container` when possible.
- **Themes**: Use extensions for `Theme.of(context)` access.

## Anti-Patterns

- ❌ No `if (context.mounted)` after `await` — using BuildContext across async gaps causes crashes
- ❌ `Widget _buildHeader() { … }` helper methods — extract to a `const StatelessWidget` for proper rebuild control and DevTools profiling
- ❌ Accessing a controller or state directly in a widget (`_controller.data`) — use BLoC/Signals to decouple UI from state
- ❌ `Container(width: 0, height: 0)` for empty space — use `const SizedBox.shrink()`



---
Source attribution: HoangNguyen0403
Original project: https://github.com/HoangNguyen0403/agent-skills-standard
License: MIT
License information: https://opensource.org/license/mit
Original upstream instructions; downloaded from Mega AI Hub.

## Upstream license notice

MIT License

Copyright (c) 2026 SkillsHub Contributors

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.



# Mega AI Hub resource metadata

Creator / publisher: HoangNguyen0403
Original project: https://github.com/HoangNguyen0403/agent-skills-standard
Attribution basis: Original repository namespace preserved by package mirror

Fields of work: Development & Engineering
Roles: Frontend Developer, Mobile Developer
Specialties: Frontend, Mobile
Tools: Tool not specified
Country applicability: Country not specified
Classification basis: Source catalog labels
Instruction SHA-256: 202b6903ec99621c9716919598b1f2d8b25bad70651f08402ea59a9b26bb1343
Metadata reviewed: 2026-10-27
This metadata supersedes earlier Mega AI Hub catalog attribution. Original instruction and supporting files are preserved.