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Merge pull request #3778 from vitorpamplona/claude/back-arrow-responsiveness-sz40m9

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Fix back arrow visibility during predictive back-swipe animations
This commit is contained in:
Vitor Pamplona
2026-07-28 16:09:35 -04:00
committed by GitHub
parent ab5a59a106 88ee46df05
commit af04267f9a
1 changed files with 30 additions and 13 deletions
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amethyst/src/main/java/com/vitorpamplona/amethyst/ui/navigation/navs/Nav.kt
+30 -13
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@@ -28,9 +28,10 @@ import androidx.compose.runtime.Stable
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.setValue
import androidx.lifecycle.viewmodel.compose.LocalViewModelStoreOwner
import androidx.navigation.NavBackStackEntry
import androidx.navigation.NavGraph.Companion.findStartDestination
import androidx.navigation.NavHostController
import androidx.navigation.compose.currentBackStackEntryAsState
import com.vitorpamplona.amethyst.ui.navigation.BOTTOM_NAV_ROOT_KEY
import com.vitorpamplona.amethyst.ui.navigation.isBottomNavRoot
import com.vitorpamplona.amethyst.ui.navigation.routes.Route
@@ -115,19 +116,35 @@ class Nav(
@Composable
override fun canPop(): Boolean {
// Observe the current entry as State so consumers recompose when the
// back stack settles after a navigation or back-swipe transition.
// A non-reactive read would leave a stale value behind: e.g. on
// back-swipe to Home, previousBackStackEntry is still the popping
// entry until the gesture finishes, and nothing would re-evaluate
// canPop afterwards.
val current by controller.currentBackStackEntryAsState()
val entry = current ?: return false
// Decide the back arrow / bottom-bar visibility from THIS screen's own
// back-stack entry — the one the NavHost hands to each destination
// through LocalViewModelStoreOwner — instead of the globally-current
// entry.
//
// A pop commits the moment it is accepted (most visibly during a
// predictive back-swipe, whose exit animation is long and finger-driven):
// controller.currentBackStackEntry flips to the destination while the
// screen being dismissed is still on screen, sliding out and still
// composing its top bar. Reading the global entry there re-evaluated
// canPop against the incoming destination and dropped the arrow before
// the outgoing screen had finished leaving. An entry is intrinsic to its
// screen and never changes for the life of that composition, so the arrow
// now stays put until the screen itself is gone.
//
// Outside a NavHost destination (shell chrome, drawer) the current owner
// is the account-scoped ViewModelStoreOwner, not an entry; fall back to
// the globally-current entry so those callers keep their prior behavior.
val entry =
(LocalViewModelStoreOwner.current as? NavBackStackEntry)
?: controller.currentBackStackEntry
?: return false
// Hidden on tab roots (reached via the bottom nav) and on Home (the
// graph's start destination): nothing sits below either that a back
// arrow could return to. Every other entry is a push on top of Home,
// so it can always pop.
if (entry.isBottomNavRoot()) return false
// Home is the graph's start destination and nothing can sit below
// it, so a back arrow there is never meaningful.
if (entry.destination.id == controller.graph.findStartDestination().id) return false
return controller.previousBackStackEntry != null
return entry.destination.id != controller.graph.findStartDestination().id
}
override fun popBack() {