How does Compose’s rendering pipeline work under the hood?

Jetpack Compose’s rendering pipeline is one of the biggest shifts from the traditional Android View system. Under the hood, it’s a declarative, state-driven UI engine that efficiently updates only what changed — not the whole screen.

🧠 Big Picture: How Compose Thinks About UI

Compose does NOT redraw the entire UI like Views.

Instead:

UI = Function(State)
When state changes → Compose recomposes only affected parts → updates only necessary pixels.

🏗️ Compose Rendering Pipeline — Step by Step

1️⃣ Composition — Building the UI Tree

@Composable
fun Greeting(name: String) {
    Text("Hello $name")
}

This creates a Composition Tree, not Views.

📌 This tree describes:

• What UI should exist
• How it’s structured
• What depends on what state

2️⃣ Slot Table — Tracking UI Structure

Compose stores the UI structure in a Slot Table:

• Tracks composables
• Tracks state dependencies