Car apps opened from the launcher show no back arrow on their first screen, where the close button already is

gearslip/src/main/java/app/seb3thehacker/gearslip/car/TemplateParts.kt

@@ -363,6 +363,10 @@ internal fun ActionButton(action: Action, large: Boolean = false, modifier: Modi
         AppIconBadge()
         return
     }
+    // On an app's first screen, opened from the launcher, Gearslip's own close button is already
+    // the way out; a back arrow beside it did the same thing twice. Deeper in, it stays.
+    val atRoot by connection.atRoot.collectAsState()
+    if (action.type == Action.TYPE_BACK && atRoot && connection === CarServices.browse) return
     val dark = MaterialTheme.colorScheme.surface.luminanceIsDark()
     val title = action.title.text()
     val panOn by connection.panMode.collectAsState()

gearslip/src/main/java/app/seb3thehacker/gearslip/host/CarAppConnection.kt

@@ -451,12 +451,19 @@ class CarAppConnection(private val context: Context, private val session: Sessio
                 return@call
             }
             GearslipLog.i("host: template = ${template.javaClass.simpleName}")
+            // The app's ScreenManager lists every screen on its stack; one or none is its first.
+            _atRoot.value = ((value as? TemplateWrapper)?.templateInfosForScreenStack?.size ?: 1) <= 1
             _template.value = template
             update { it.copy(template = template.javaClass.simpleName) }
             autoRoute.onTemplate(template)
         }) { manager.getTemplate(it) }
     }
 
+    private val _atRoot = MutableStateFlow(true)
+
+    /** True while the app shows its first screen, where its own back would only close it. */
+    val atRoot: StateFlow<Boolean> = _atRoot
+
     private val _panMode = MutableStateFlow(false)
 
     /**