From 081347f31b4fcc919720a5e120b6025f09a6704a Mon Sep 17 00:00:00 2001
From: Ashin Walpola <ashin.walpola@haw-hamburg.de>
Date: Wed, 26 Aug 2026 17:12:46 +0200
Subject: [PATCH] Tapping the active bottom-nav tab returns to that tab's root
 screen

Tapping Settings while on Settings > Connection appeared to do nothing. The tab
navigated to its own route, but restoreState = true then restored that tab's
saved back stack, putting the sub-screen straight back on top. The only way out
was the back button or a back swipe.

When the tap targets the tab already in use and the current destination is deeper
inside it, pop back to the tab's own screen instead of navigating. Only entries
above the tab root are removed, so Back and back-swipe behave exactly as before -
both routes out of a sub-screen now work.

The tab also stayed unhighlighted while any sub-screen was open, because selected
compared the current route for equality with the tab's route. Ownership is now
derived from the existing route naming convention, so settings/connection belongs
to Settings and trip_review/{tripId} belongs to Trips. A new settings/* screen is
picked up automatically; a sub-screen named outside its tab's prefix would need a
line in ownsRoute.
---
 .../micr0bu/ui/navigation/AppNavigation.kt    | 38 ++++++++++++++++---
 1 file changed, 33 insertions(+), 5 deletions(-)

diff --git a/app/src/main/java/com/hawhamburg/micr0bu/ui/navigation/AppNavigation.kt b/app/src/main/java/com/hawhamburg/micr0bu/ui/navigation/AppNavigation.kt
index 8b0763f..e7cf0f4 100644
--- a/app/src/main/java/com/hawhamburg/micr0bu/ui/navigation/AppNavigation.kt
+++ b/app/src/main/java/com/hawhamburg/micr0bu/ui/navigation/AppNavigation.kt
@@ -63,6 +63,23 @@ private val bottomNavItems = listOf(
     Screen.Settings,
 )
 
+/**
+ * True if [route] is this tab's own screen or one of its sub-screens.
+ *
+ * The graph is flat, so ownership is derived from the route naming convention: every Settings
+ * sub-screen is "settings/...", and a trip review is "trip_review/{tripId}" belonging to Trips.
+ * Without this, a tab stops looking selected the moment you open anything inside it.
+ */
+private fun Screen.ownsRoute(route: String?): Boolean {
+    if (route == null) return false
+    if (route == this.route) return true
+    return when (this) {
+        Screen.Settings    -> route.startsWith("settings/")
+        Screen.TripHistory -> route.startsWith("trip_review")
+        else               -> false
+    }
+}
+
 @Composable
 fun BottomNavBar(navController: NavController) {
     val backStackEntry by navController.currentBackStackEntryAsState()
@@ -70,13 +87,24 @@ fun BottomNavBar(navController: NavController) {
 
     NavigationBar {
         bottomNavItems.forEach { screen ->
+            val onThisTab = screen.ownsRoute(currentRoute)
             NavigationBarItem(
-                selected = currentRoute == screen.route,
+                selected = onThisTab,
                 onClick = {
-                    navController.navigate(screen.route) {
-                        popUpTo(Screen.Dashboard.route) { saveState = true }
-                        launchSingleTop = true
-                        restoreState = true
+                    if (onThisTab && currentRoute != screen.route) {
+                        // Already inside this tab, just deeper in: pop back to the tab's own
+                        // screen. Navigating instead would restoreState the saved back stack and
+                        // land straight back on the sub-screen, which reads as the tap doing
+                        // nothing - the reason Settings > Connection could not be left by tapping
+                        // Settings. Leaves the rest of the stack intact, so Back still works
+                        // exactly as before.
+                        navController.popBackStack(screen.route, inclusive = false)
+                    } else {
+                        navController.navigate(screen.route) {
+                            popUpTo(Screen.Dashboard.route) { saveState = true }
+                            launchSingleTop = true
+                            restoreState = true
+                        }
                     }
                 },
                 icon = {