IssueTracker

Hm, interesting, form the quick looks it seems like nothing changed in scaffold in alpha08. The only thing we've done around alpha07 is migrated scaffold to subcompose and it directly affects the padding parameter.

Louis, do you have any ideas is that might've caused the problem?

Hm, I can't immediately reproduce with an example locally so not sure what's going on, might be related to how / when subcomposition invalidates

Hi just another update, I updated to 1.0.0-alpha10 but still experiencing the same result.

Same issue on beta01.

The issue is inside NavHost.

        val modifier = Modifier.padding(padding)
        NavHost(navController, startDestination = FIRST_SCREEN) {
            composable(FIRST_SCREEN) {
                MyScreen(modifier, Color.Blue) {
                    navController.navigate(SECOND_SCREEN)
                }
            }
            composable(SECOND_SCREEN) {
                MyScreen(modifier, Color.Red) {
                    navController.navigate(FIRST_SCREEN)
                }
            }
        }

When the size has been changed the first line is recomposed and the new modifier object is constructed. Then NavHost is reinvoked with a new builder which contains new lambdas which captures a new modifier. But currently NavHost is not supporting nav graph updates so the new lambdas are ignored. As a result we end up using the initial value of the captured modifier object forever which had size 0. The current workaround would be something like

        val modifier = rememberUpdatedState(Modifier.padding(padding))
        NavHost(navController, startDestination = FIRST_SCREEN) {
            composable(FIRST_SCREEN) {
                MyScreen(modifier.value, Color.Blue) {
                    navController.navigate(SECOND_SCREEN)
                }
            }
            composable(SECOND_SCREEN) {
                MyScreen(modifier.value, Color.Red) {
                    navController.navigate(FIRST_SCREEN)
                }
            }
        }

In this case we wrap the value inside the state object so we can update the state and the old lambda would still use the correct modifier.

Jeremy, assigning it to you as the only correct solution is to support graph updates

So I believe this is related to this as well right?

https://kotlinlang.slack.com/archives/CJLTWPH7S/p1614342645375500

oh sorry about that i linked the wrong thread..

https://kotlinlang.slack.com/archives/CJLTWPH7S/p1610188317341100

its this instead..

Alright. I guess this would hit two issues at the same time then. Thank you!

Note that if you want to pad in all screens, you should passing the padding directly to NavHost rather than manually to each screen:

) { padding ->
        NavHost(navController, startDestination = FIRST_SCREEN, Modifier.padding(padding)) {
            composable(FIRST_SCREEN) {
                MyScreen(Color.Blue) {
                    navController.navigate(SECOND_SCREEN)
                }
            }
            composable(SECOND_SCREEN) {
                MyScreen(Color.Red) {
                    navController.navigate(FIRST_SCREEN)
                }
            }
        }
    }
}

This was made possible in b/175125483 and was part of Navigation Compose 1.0.0-alpha10.

This has been fixed internally and will be part of the Navigation 2.4.0-alpha05 release.