Solving the issue of a BackArrow on the Home Screen after a back press

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/navigation/navs/BouncingIntentNav.kt

@@ -25,6 +25,7 @@ import android.content.Intent
 import android.net.Uri
 import androidx.compose.material3.DrawerState
 import androidx.compose.material3.DrawerValue
+import androidx.compose.runtime.Composable
 import androidx.compose.runtime.Stable
 import com.vitorpamplona.amethyst.ui.MainActivity
 import com.vitorpamplona.amethyst.ui.navigation.routes.Route
@@ -98,6 +99,7 @@ class BouncingIntentNav(
 
     override fun navBottomBar(route: Route) = nav(route)
 
+    @Composable
     override fun canPop(): Boolean = false
 
     override fun popBack() {

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/navigation/navs/EmptyNav.kt

@@ -22,6 +22,7 @@ package com.vitorpamplona.amethyst.ui.navigation.navs
 
 import androidx.compose.material3.DrawerState
 import androidx.compose.material3.DrawerValue
+import androidx.compose.runtime.Composable
 import androidx.compose.runtime.Stable
 import com.vitorpamplona.amethyst.ui.navigation.routes.Route
 import kotlinx.coroutines.CoroutineScope
@@ -46,6 +47,7 @@ class EmptyNav : INav {
 
     override fun navBottomBar(route: Route) {}
 
+    @Composable
     override fun canPop(): Boolean = false
 
     override fun popBack() {}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/navigation/navs/INav.kt

@@ -21,6 +21,7 @@
 package com.vitorpamplona.amethyst.ui.navigation.navs
 
 import androidx.compose.material3.DrawerState
+import androidx.compose.runtime.Composable
 import androidx.compose.runtime.Stable
 import com.vitorpamplona.amethyst.ui.navigation.routes.Route
 import kotlinx.coroutines.CoroutineScope
@@ -43,6 +44,7 @@ interface INav {
 
     fun navBottomBar(route: Route)
 
+    @Composable
     fun canPop(): Boolean
 
     fun popBack()

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/navigation/navs/Nav.kt

@@ -23,8 +23,12 @@ package com.vitorpamplona.amethyst.ui.navigation.navs
 import android.annotation.SuppressLint
 import androidx.compose.material3.DrawerState
 import androidx.compose.material3.DrawerValue
+import androidx.compose.runtime.Composable
 import androidx.compose.runtime.Stable
+import androidx.compose.runtime.getValue
+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
@@ -93,9 +97,20 @@ class Nav(
         }
     }
 
+    @Composable
     override fun canPop(): Boolean {
-        val current = controller.currentBackStackEntry ?: return false
+        // Observe the current entry as State so consumers recompose when the
-        if (current.isBottomNavRoot()) return false
+        // 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
+        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
     }