After days of research, I think that it's impossib...

# compose-desktop

[Pablo]

After days of research, I think that it's impossible to share navigation between MenuBar (desktopMain) and the screens on commonMain. It's a lack of an important thing for compose desktop. Being capable of select current creen using the MenuBar of a desktop app is a common functionality. Has anyone achieved it with compose desktop?

[Alex Styl]

why is it impossible? havent used the api

[Pablo]

All the screens of my application and navigation logic are on my commonMain module. Navigation logic needs to be also present on my commonMain screens because they can also navigate between them with buttons, the same navigation that must have the MenuBar should be shared between MenuBar and the screens buttons navigation. This is like when you access the "Window" or "Screen" sections of a windows app top menu bar, they allow you navigate, but you also can switch screens with some buttons in the UI of the windows application.

MenuBar is a desktop only composable, so it must be created on the Window of the desktopMain module, before displaying any ui screen placed on the commonMain module. If it needs to execute navigation, it need to hold a instance of the navcontroller, and to pass the navcontroller down in the appstateholder to the commonMain module screens. I followed the pattern in nowinandroid app:
https://github.com/android/nowinandroid/blob/d15c739812f25401b21614fe0f7e18534d285921/app/src/main/kotlin/com/google/samples/apps/nowinandroid/ui/NiaAppState.kt#L54
I created an appstateholder class with the navcontroller, and I instantiated that in the commonMain package:

@Stable
class AppStateHolder(
    val navController: NavHostController = NavHostController()
) {
    // UI State
    val currentDestination: NavDestination?
        @Composable get() = navController
            .currentBackStackEntryAsState().value?.destination

    // UI logic
    fun navigate(route: String) {
        navController.navigate(route)
    }
}

This is my desktopMain window:

fun main() = application {
    initKoin(
        databaseBuilder = createDatabaseBuilder(),
    )

    val windowState = rememberWindowState(
        size = DpSize(1200.dp, 900.dp),
        position = WindowPosition(Alignment.Center)
    )

    val appStateHolder= remember { AppStateHolder() }

    Window(
        onCloseRequest = ::exitApplication,
        title = stringResource(Res.string.app_name),
        state = windowState
    ) {
        WindowsMenuBar(
            onNavigation = { route -> appStateHolder.navigate(route) },
            onExitEvent = ::exitApplication
        )

        MyApplicationTheme {
            App(appStateHolder)
        }
    }
}

Then, in my commonMain package I receive that appStateHolder and use it for navigation:

@Composable
fun App(appStateHolder: AppStateHolder) {

    NavHost(
        navController = appStateHolder.navController,
        startDestination = ScreenRoute.MainScreen.name
    ) {
        composable(ScreenRoute.MainScreen.name) {
            MainScreen(
                modifier = Modifier.padding(16.dp),
                onBusStopsDBButtonClicked = { appStateHolder.navigate(ScreenRoute.BusStopsDB.name) }
            )
        }

Well, this doesn't work, and gives me this runtime error on composable(ScreenRoute.MainScreen.name) line of my desktopMain module:
> Navigator with class "class androidx.navigation.compose.ComposeNavigator". You must call NavController.addNavigator() for each navigation type.

[Chrimaeon]

maybe an important part you are missing. you set the navcontroller but don’t remember it
https://github.com/android/nowinandroid/blob/d15c739812f25401b21614fe0f7e18534d285[…]n/kotlin/com/google/samples/apps/nowinandroid/ui/NiaAppState.kt

[Sanlorng]

Implement a PlatformState that handle menu bar items data as a parameter of App function ，Create a composable function that add menu bar items to PlatformState and remove these when it became disposed. In your desktopMain，binding menu bar items with DesktopPlatformState

[Pablo]

Christian I'm remembering the full App state which contains the navcontroller: val appStateHolder= remember { AppStateHolder() }

[Sanlorng]

This prototype looks like what context menu provider do

[Chrimaeon]

but the rememberNavController is doing some initialisation https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:navigati[…]vigation/compose/NavHostController.kt?q=rememberNavController

[Chrimaeon]

it adds the “navigators” your error requests.

[Chrimaeon]

https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:navigati[…]NavHostController.kt;l=70;bpv=1;bpt=1?q=rememberNavController

[Sanlorng]

Sorry, I just remembered it wrong.

[Pablo]

omg Christian... it worked, thank you soo much, hours and hours stuck with this, can't believe it was that

[Chrimaeon]

💪🏼💯