HERD-35 Wide-screen sidebar switches to the tapped space (#101)

app/src/main/kotlin/com/makefunstuff/herdr/AppNav.kt

@@ -274,10 +274,10 @@ private fun AppNav(nav: NavHostController, startSpace: String? = null) {
         val panes = remember(wide) { Panes(wide) }
         val current by rememberUpdatedState(panes)
         LaunchedEffect(nav) { Links.flow.collect { current.link(nav, it) } }
-        // A space picked in the drawer shows in the Chat tab.
+        // A space picked in the drawer (or the sidebar) shows in the Chat tab.
         fun pick(slot: SpaceSlot) {
             space.key = slot.key
-            nav.goTop(Routes.CHAT)
+            nav.showSpace()
         }
         val openDrawer: () -> Unit = { scope.launch { drawer.open() } }
         val lineColor = Herdr.colors.lineStrong
@@ -445,6 +445,22 @@ private fun PaneEdge() {
     Box(Modifier.width(1.dp).fillMaxHeight().background(Herdr.colors.line))
 }
 
+/**
+ * The Chat tab's own screen, for a space just picked: not what the tab had open over it (that was the last space's
+ * terminal or chat). A phone's drawer opens only over a tab's own screen; the sidebar is there over any (issue #101).
+ */
+private fun NavHostController.showSpace() {
+    if (currentDestination?.route == Routes.CHAT) return
+    val open = currentBackStack.value.any { it.destination.route == Routes.CHAT }
+    // Left for another tab, the Chat tab's screens were kept to come back to: they go.
+    if (!open) clearBackStack(Routes.CHAT)
+    navigate(Routes.CHAT) {
+        // Open, they go too; another tab's are kept, as a tab's switch keeps them.
+        popUpTo(graph.findStartDestination().id) { saveState = !open }
+        launchSingleTop = true
+    }
+}
+
 private fun NavHostController.goTop(route: String) {
     navigate(route) {
         popUpTo(graph.findStartDestination().id) { saveState = true }

tools/ui-preview/src/main/kotlin/preview/Main.kt

@@ -329,6 +329,16 @@ private fun ComposeUiTest.node(matcher: SemanticsMatcher) = onAllNodes(matcher,
 /** Taps the first element showing [text] (exactly, or as its start when it is longer). */
 fun ComposeUiTest.tapText(text: String) { tap(node(hasText(text, substring = true))) }
 
+/** Fails the scene unless an element shows [text]: a scene that checks what a tap leads to. */
+fun ComposeUiTest.expectText(text: String) {
+    check(onAllNodes(hasText(text, substring = true), useUnmergedTree = true).fetchSemanticsNodes().isNotEmpty()) { "\"$text\" isn't shown" }
+}
+
+/** Fails the scene if an element shows [text]: a screen a tap should have taken away. */
+fun ComposeUiTest.expectNoText(text: String) {
+    check(onAllNodes(hasText(text, substring = true), useUnmergedTree = true).fetchSemanticsNodes().isEmpty()) { "\"$text\" is still shown" }
+}
+
 /** Scrolls [text] into view in its list or strip (a tab off the strip's edge), then taps it. */
 fun ComposeUiTest.scrollToText(text: String) {
     runOnUiThread { node(hasText(text, substring = true)).performScrollTo() }

tools/ui-preview/src/main/kotlin/preview/Scenes.kt

@@ -885,6 +885,11 @@ fun scenes(): List<Scene> = listOf(
     Scene("wide-empty", widthDp = 1280, heightDp = 800, setup = { home() }),
     Scene("wide", widthDp = 1280, heightDp = 800, setup = { home() }, actions = { tapText("Speed up /jobs") }),
     Scene("wide-terminal", route = Routes.terminal(DEVBOX, APP_SHELL), widthDp = 840, heightDp = 940),
+    // A space tapped in the sidebar shows in the Chat tab, also from a screen the tab had open (issue #101: the
+    // terminal opened from herdr-android's chat stayed, though website was marked as picked).
+    Scene("wide-pick", widthDp = 1280, heightDp = 800, setup = { home() }, actions = {
+        tapLabel("Chat"); tapText("Terminal"); tapText("website"); expectText("Rewrite the install page"); expectNoText("146×42")
+    }),
     Scene("wide-machines", widthDp = 1280, heightDp = 800, setup = { home() }, actions = { tapLabel("Chat") }),
     // Rotating across the line keeps what is open as it was: a chat with its key row shown, turned from a phone
     // to a tablet's width and from the tablet back to the phone.