How is Compose detecting that a new render needs to be done? For example, when a state changes, but ...

# compose-android

[louiscad]

How is Compose detecting that a new render needs to be done?
For example, when a state changes, but doesn't lead to changes in the tree. Which APIs let Compose UI for Android know that it needs to ask the system to redraw (calling invalidate)?

[shikasd]

Usually state updates, most modifiers use observerReads to track layout/draw changes

[louiscad]

What is observerReads? Where does it come from?

[louiscad]

Digging deep, I found about the SnapshotStateObserver class, which has an observeReads function that executes a block and calls a callback when one of the states read inside said block was changed.

[Zach Klippenstein (he/him) [MOD]]

draw is invalidated based on:
1. state reads inside draw* modifiers
2. changes in composition/layout phases
3. Modifier.Node invalidate calls
Maybe I forgot something, but i think those are the main paths