Flutter: Why Choose It, Overview, and Rendering Architecture

This article explains why Flutter is chosen as a cross‑platform solution, provides a brief introduction, and describes its runtime principles.

It compares Flutter with other cross‑platform technologies: Hybrid solutions such as Ionic/Cordova rely on a JSBridge and suffer from performance and dependency issues; React Native/Weex improve by converting JavaScript UI to native widgets but still incur JIT communication overhead. Flutter combines the advantages of these approaches while adding a self‑rendering engine, resulting in better performance and a more consistent experience.

Flutter is a mobile application framework that uses a single Dart codebase to generate high‑performance, high‑fidelity apps for both iOS and Android. Its goal is to let developers deliver natural, smooth experiences across platforms.

Unlike native frameworks, Flutter implements its own rendering pipeline. The CPU calculates UI data, the GPU renders it, and the display shows the final image. The process follows the VSync signal, with frames written to a buffer and then presented at 60 Hz.

The architecture is layered: Embedder adapts to the operating system (surface, threads, plugins); Engine includes Skia, Dart, and Text, providing rendering, typography, event handling, and the Dart runtime; Framework is a Dart‑based UI SDK offering widgets, animations, gestures, and Material/Cupertino component libraries.

During layout, Flutter performs a depth‑first traversal of the render‑object tree, applying constraints from parent to child and using relayout boundaries to isolate layout changes.

In the painting phase, each node draws itself and its children in depth‑first order. Repaint boundaries create separate layers so that unrelated parts of the UI are not repainted, improving performance (e.g., in ScrollViews).

After painting, the layer tree is composited: layers are merged based on size, order, and opacity, then Skia rasterizes the result into GPU commands for final rendering.

Understanding Flutter’s design, its use of Skia and Dart, and its rendering pipeline provides a solid foundation for building efficient cross‑platform mobile applications.