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kotlinlang

I want to implement mechanism to force select app day-night theme. For example: if set returns it, else returns `isSystemInDarkTheme()` . For example this fun will be called `isAppInDarkTheme()` . I also want to recompose all dependent composables.

Which parts and mechanism of compose is better to use to achieve behavior like it?

Just replace the `isSystemInDarkTheme()` in compose project template with your `isAppInDarkTheme()` and it’ll work.

I mean something different:
`isAppInDarkTheme()`  returns some nullable boolean (for example). Returns it when it is set or `isSystemInDarkTheme()`  if doesn’t. This boolean - where must i store it? state, local provider, something different? When it changes how the composition three will know about it? I must notify something or whatever?

If a parameter of a composable function is observable and it changes, the function will automatically be recomposed. What you need is just a observable value (such as a `State` or a `StateFlow`) which stores the user preference. As for what you use as the store, it has nothing to do with Compose.