A custom `RenderBox` that implements sticky header behavior by reordering children during layout. It is self-contained (depends only on `flutter/rendering.dart`) and demonstrates advanced Flutter rendering—non-trivial skill in overriding `performLayout` and `paint` to pin a child at the top while scrolling. This pattern can be extracted and reused in any Flutter project needing a sticky header without third-party packages.

Implements a shimmer loading effect via `GFShimmerFilter`, a custom `RenderProxyBox` that paints a gradient mask over its child and animates its position. The effect is achieved by overriding `paint` and using `addListener` with an `AnimationController`. This component is isolated (only imports `dart:ui` and `package:flutter/rendering.dart`) and can be dropped into any Flutter app to add shimmer loaders without additional dependencies.

Provides a centralized form state management system using `ChangeNotifier` providers (`GfFormHandler`). It aggregates multiple field providers (`GfFormFieldData`, `GfFormDropdownData`, etc.) and exposes `getFormValues()` for validation and submission. This pattern is decoupled from the widget tree and can be extracted cleanly—it demonstrates a reusable approach to form state in Flutter without external state management libraries.

Contains `_InputPadding`, a custom `RenderShiftedBox` that increases the button's tap target area without visually altering its size. This is achieved by overriding `hitTest` and `paint` to expand the hit region while keeping the painted area unchanged. Though defined within the GFButton file, this render object is a self-contained, reusable pattern for Flutter developers needing to improve touch accessibility without changing visual layout.