Anatomy of an app

The following diagram gives an overview of the pieces
that make up a regular Flutter app generated by flutter create.
It shows where the Flutter Engine sits in this stack,
highlights API boundaries, and identifies the repositories
where the individual pieces live. The legend below clarifies
some of the terminology commonly used to describe the
pieces of a Flutter app.

Dart App

Composes widgets into the desired UI.

Implements business logic.

Owned by app developer.

Framework (source code)

Provides higher-level API to build high-quality apps
(for example, widgets, hit-testing, gesture detection,
accessibility, text input).

Composites the app’s widget tree into a scene.

Engine (source code)

Responsible for rasterizing composited scenes.