fix(ui): fetch the outer thread again when unwinding to it

CHANGELOG.md

@@ -9,6 +9,7 @@ the GitHub release notes, so keep the `## [x.y.z] - date` headings exact.
 
 ### Fixed
 
+- Going back to a thread fetches its conversation again. The return stack remembers which thread each screen showed, so after a nested unwind the outer thread no longer shows the inner conversation. (#110)
 - Backing out of a thread opened from a profile that was itself opened from a thread no longer bounces between the profile and the outer thread. Each screen returns to the one it came from, down to the timeline, through a return stack in place of the single return slots. The snapshot suite now walks that chain. (#110)
 
 ## [0.11.1] - 2026-10-16

docs/PARITY.md

@@ -70,7 +70,7 @@ These are Wii U specific and have no row in the other clients.
 |---|---|---|
 | GamePad touch coverage of the popup and header pills | issue #112 | |
 | TV layout uses the extra space | issue #111 | |
-| Remember scroll position when returning from a thread or profile | partial #110 | The timeline keeps its cursor and scroll across a thread and across a profile, and notifications across a thread or profile; snapshot checks in `tests/snapshot_main.c` assert it on the host. A nested chain (timeline, thread, profile, thread) used to loop between the profile and the outer thread on B, and now unwinds one screen at a time through a return stack; `tests/snapshot_main.c` asserts it. I could not reproduce a timeline rewind and have not seen it on a console, so issue #110 stays open for the owner to confirm. |
+| Remember scroll position when returning from a thread or profile | partial #110 | The timeline keeps its cursor and scroll across a thread and across a profile, and notifications across a thread or profile; snapshot checks in `tests/snapshot_main.c` assert it on the host. A nested chain (timeline, thread, profile, thread) used to loop between the profile and the outer thread on B, and now unwinds one screen at a time through a return stack. Going back to a thread fetches it again, so the outer conversation is the one shown; `tests/snapshot_main.c` asserts both. I could not reproduce a timeline rewind and have not seen it on a console, so issue #110 stays open for the owner to confirm. |
 | More menu unified with the thread and profile screens | implemented | Y opens it on the timeline, thread, notifications and profile. The profile's X, Y and + moved into it; notifications get profile, post and refresh. Snapshot checks in `tests/snapshot_main.c`; search results are the timeline screen and already had it. Host only. |
 | User guide with controls per screen and screenshots | implemented | `docs/guide.md`, checked by `tools/check-guide.py`. |
 | First on-console acceptance pass | issue #24 | Needs the owner's console. |

src/app/app.c

@@ -90,9 +90,33 @@ cobalt_app_create(void)
 /* A thread or profile opened from `from` pushes it, so B from the new screen
  * goes back to it. When the stack is full the oldest return is dropped rather
  * than the newest, which is the one B is about to need. */
+/* The uri of the post the thread on screen was opened on, which is what
+ * cobalt_session_begin_thread takes to fetch that conversation again. Empty
+ * when no thread is loaded. Read it before a new thread is requested, since
+ * the request replaces the one on screen. */
 void
-cobalt_app_push_return(cobalt_app *app, cobalt_screen from)
+cobalt_app_current_thread_uri(char *out, size_t cap)
 {
+   const cobalt_thread *thread = cobalt_session_thread();
+
+   if (!out || cap == 0) {
+      return;
+   }
+   out[0] = '\0';
+   if (thread->focus >= 0 && thread->focus < thread->count) {
+      snprintf(out, cap, "%s", thread->posts[thread->focus].uri);
+   }
+}
+
+/* A thread or profile opened from `from` pushes it, so B from the new screen
+ * goes back to it. `thread_uri` is the conversation `from` showed, when it was
+ * a thread. When the stack is full the oldest return is dropped rather than the
+ * newest, which is the one B is about to need. */
+void
+cobalt_app_push_return(cobalt_app *app, cobalt_screen from, const char *thread_uri)
+{
+   cobalt_return *entry;
+
    if (!app) {
       return;
    }
@@ -101,16 +125,26 @@ cobalt_app_push_return(cobalt_app *app, cobalt_screen from)
               (COBALT_RETURN_DEPTH - 1) * sizeof(app->return_stack[0]));
       app->return_depth--;
    }
-   app->return_stack[app->return_depth++] = from;
+   entry = &app->return_stack[app->return_depth++];
+   entry->screen = from;
+   snprintf(entry->thread_uri, sizeof entry->thread_uri, "%s", thread_uri ? thread_uri : "");
 }
 
+/* Returns the screen to go back to. Going back to a thread also fetches that
+ * conversation again, since the session may hold another one by now. */
 cobalt_screen
 cobalt_app_pop_return(cobalt_app *app)
 {
+   const cobalt_return *entry;
+
    if (!app || app->return_depth == 0) {
       return COBALT_SCREEN_HOME;
    }
-   return app->return_stack[--app->return_depth];
+   entry = &app->return_stack[--app->return_depth];
+   if (entry->screen == COBALT_SCREEN_THREAD && entry->thread_uri[0]) {
+      cobalt_session_begin_thread(entry->thread_uri);
+   }
+   return entry->screen;
 }
 
 cobalt_screen
@@ -625,7 +659,7 @@ app_update_inner(cobalt_app *app, const cobalt_input *in, uint32_t now_ms)
                break;
             case COBALT_PROFILE_VIEW_OPEN_THREAD:
                cobalt_thread_view_reset(&app->thread);
-               cobalt_app_push_return(app, COBALT_SCREEN_PROFILE);
+               cobalt_app_push_return(app, COBALT_SCREEN_PROFILE, NULL);
                app->screen = COBALT_SCREEN_THREAD;
                break;
             case COBALT_PROFILE_VIEW_MENU:
@@ -645,12 +679,12 @@ app_update_inner(cobalt_app *app, const cobalt_input *in, uint32_t now_ms)
                break;
             case COBALT_TIMELINE_OPEN_THREAD:
                cobalt_thread_view_reset(&app->thread);
-               cobalt_app_push_return(app, COBALT_SCREEN_TIMELINE);
+               cobalt_app_push_return(app, COBALT_SCREEN_TIMELINE, NULL);
                app->screen = COBALT_SCREEN_THREAD;
                break;
             case COBALT_TIMELINE_OPEN_PROFILE:
                cobalt_profile_view_rewind(&app->profile);
-               cobalt_app_push_return(app, COBALT_SCREEN_TIMELINE);
+               cobalt_app_push_return(app, COBALT_SCREEN_TIMELINE, NULL);
                app->screen = COBALT_SCREEN_PROFILE;
                break;
             case COBALT_TIMELINE_COMPOSE:
@@ -718,12 +752,12 @@ app_update_inner(cobalt_app *app, const cobalt_input *in, uint32_t now_ms)
                break;
             case COBALT_NOTIFY_OPEN_THREAD:
                cobalt_thread_view_reset(&app->thread);
-               cobalt_app_push_return(app, COBALT_SCREEN_NOTIFICATIONS);
+               cobalt_app_push_return(app, COBALT_SCREEN_NOTIFICATIONS, NULL);
                app->screen = COBALT_SCREEN_THREAD;
                break;
             case COBALT_NOTIFY_OPEN_PROFILE:
                cobalt_profile_view_rewind(&app->profile);
-               cobalt_app_push_return(app, COBALT_SCREEN_NOTIFICATIONS);
+               cobalt_app_push_return(app, COBALT_SCREEN_NOTIFICATIONS, NULL);
                app->screen = COBALT_SCREEN_PROFILE;
                break;
             case COBALT_NOTIFY_MENU: {
@@ -878,7 +912,7 @@ app_update_inner(cobalt_app *app, const cobalt_input *in, uint32_t now_ms)
                break;
             case COBALT_GRAPH_VIEW_OPEN_PROFILE:
                cobalt_profile_view_rewind(&app->profile);
-               cobalt_app_push_return(app, COBALT_SCREEN_FOLLOWS_LIST);
+               cobalt_app_push_return(app, COBALT_SCREEN_FOLLOWS_LIST, NULL);
                app->screen = COBALT_SCREEN_PROFILE;
                break;
             case COBALT_GRAPH_VIEW_STAY:
@@ -894,7 +928,7 @@ app_update_inner(cobalt_app *app, const cobalt_input *in, uint32_t now_ms)
                break;
             case COBALT_GRAPH_VIEW_OPEN_PROFILE:
                cobalt_profile_view_rewind(&app->profile);
-               cobalt_app_push_return(app, COBALT_SCREEN_LIKES_LIST);
+               cobalt_app_push_return(app, COBALT_SCREEN_LIKES_LIST, NULL);
                app->screen = COBALT_SCREEN_PROFILE;
                break;
             case COBALT_GRAPH_VIEW_STAY:
@@ -910,7 +944,7 @@ app_update_inner(cobalt_app *app, const cobalt_input *in, uint32_t now_ms)
                break;
             case COBALT_SEARCH_VIEW_OPEN_PROFILE:
                cobalt_profile_view_rewind(&app->profile);
-               cobalt_app_push_return(app, COBALT_SCREEN_SEARCH);
+               cobalt_app_push_return(app, COBALT_SCREEN_SEARCH, NULL);
                app->screen = COBALT_SCREEN_PROFILE;
                break;
             case COBALT_SEARCH_VIEW_OPEN_POSTS:
@@ -931,7 +965,7 @@ app_update_inner(cobalt_app *app, const cobalt_input *in, uint32_t now_ms)
                break;
             case COBALT_LISTS_VIEW_OPEN_PROFILE:
                cobalt_profile_view_rewind(&app->profile);
-               cobalt_app_push_return(app, COBALT_SCREEN_LISTS);
+               cobalt_app_push_return(app, COBALT_SCREEN_LISTS, NULL);
                app->screen = COBALT_SCREEN_PROFILE;
                break;
             case COBALT_LISTS_VIEW_STAY:

src/app/app_home.c

@@ -382,7 +382,7 @@ cobalt_app_update_account(cobalt_app *app, const cobalt_input *in)
          if (self[0]) {
             cobalt_session_begin_profile(self);
             cobalt_profile_view_rewind(&app->profile);
-            cobalt_app_push_return(app, COBALT_SCREEN_ACCOUNT);
+            cobalt_app_push_return(app, COBALT_SCREEN_ACCOUNT, NULL);
             app->screen = COBALT_SCREEN_PROFILE;
             COBALT_LOGI("account: opened own profile");
          }

src/app/app_internal.h

@@ -51,6 +51,14 @@
  * return is dropped. */
 #define COBALT_RETURN_DEPTH 16
 
+/* A screen to return to, with the conversation it showed when it was left.
+ * The session keeps only the last thread it fetched, so returning to a thread
+ * fetches it again from this uri rather than showing whatever came after. */
+typedef struct {
+   cobalt_screen screen;
+   char thread_uri[COBALT_POST_URI_MAX];
+} cobalt_return;
+
 struct cobalt_app {
    cobalt_screen screen;
    cobalt_display_mode display;
@@ -99,7 +107,7 @@ struct cobalt_app {
    /* Where B from the thread or profile screen returns to. Each screen that
     * opens a thread or profile pushes the one it came from, so a chain such as
     * timeline -> thread -> profile -> thread unwinds one step at a time. */
-   cobalt_screen return_stack[COBALT_RETURN_DEPTH];
+   cobalt_return return_stack[COBALT_RETURN_DEPTH];
    int return_depth;
    /* Where B from a likes/reposts list returns to — the timeline or the
     * thread. The post it belongs to is already in app->graph.actor. */
@@ -142,8 +150,9 @@ void cobalt_app_draw_tv_idle(cobalt_render *r);
 /* app_menus.c */
 void cobalt_app_open_post_menu(cobalt_app *app, const cobalt_post *post, bool in_thread);
 void cobalt_app_open_profile_menu(cobalt_app *app);
-void cobalt_app_push_return(cobalt_app *app, cobalt_screen from);
+void cobalt_app_push_return(cobalt_app *app, cobalt_screen from, const char *thread_uri);
 cobalt_screen cobalt_app_pop_return(cobalt_app *app);
+void cobalt_app_current_thread_uri(char *out, size_t cap);
 void cobalt_app_open_notification_menu(cobalt_app *app, const cobalt_notification *item);
 void cobalt_app_popup_choose(cobalt_app *app, int index);
 

src/app/app_menus.c

@@ -118,12 +118,14 @@ void
 cobalt_app_popup_choose(cobalt_app *app, int index)
 {
    const cobalt_popup_item *it = &app->popup.items[index];
+   char outer[COBALT_POST_URI_MAX];
    switch (it->kind) {
       case COBALT_POPUP_PROFILE:
       case COBALT_POPUP_MENTION:
          if (cobalt_session_begin_profile(it->arg)) {
             cobalt_profile_view_rewind(&app->profile);
-            cobalt_app_push_return(app, app->popup_screen);
+            cobalt_app_current_thread_uri(outer, sizeof outer);
+            cobalt_app_push_return(app, app->popup_screen, outer);
             app->screen = COBALT_SCREEN_PROFILE;
             cobalt_popup_close(&app->popup);
          }
@@ -216,9 +218,11 @@ cobalt_app_popup_choose(cobalt_app *app, int index)
          }
          break;
       case COBALT_POPUP_THREAD:
+         /* Read the conversation on screen before the request replaces it. */
+         cobalt_app_current_thread_uri(outer, sizeof outer);
          if (cobalt_session_begin_thread(it->arg)) {
             cobalt_thread_view_reset(&app->thread);
-            cobalt_app_push_return(app, app->popup_screen);
+            cobalt_app_push_return(app, app->popup_screen, outer);
             app->screen = COBALT_SCREEN_THREAD;
             cobalt_popup_close(&app->popup);
          }

src/atproto/session.h

@@ -214,6 +214,7 @@ const cobalt_feed *cobalt_session_feed(void);
  * Fetch the conversation around `uri`. Replaces whatever thread was loaded.
  */
 bool cobalt_session_begin_thread(const char *uri);
+int cobalt_session_thread_requests(void);
 
 /* The thread as last fetched; never NULL. */
 const cobalt_thread *cobalt_session_thread(void);

src/atproto/session_read.c

@@ -794,6 +794,10 @@ cobalt_session_chat_started_convo(void)
    return g_session.chat_started;
 }
 
+/* How many thread requests were accepted, so a test can see a conversation was
+ * fetched again without depending on when the network answers. */
+static int g_thread_requests;
+
 bool
 cobalt_session_begin_thread(const char *uri)
 {
@@ -804,5 +808,15 @@ cobalt_session_begin_thread(const char *uri)
    cobalt_job_input in;
    memset(&in, 0, sizeof(in));
    snprintf(in.uri, sizeof(in.uri), "%s", uri);
-   return cobalt_session_submit(COBALT_JOB_THREAD, &in);
+   if (!cobalt_session_submit(COBALT_JOB_THREAD, &in)) {
+      return false;
+   }
+   g_thread_requests++;
+   return true;
+}
+
+int
+cobalt_session_thread_requests(void)
+{
+   return g_thread_requests;
 }

tests/snapshot_main.c

@@ -375,7 +375,12 @@ main(int argc, char **argv)
       CHECK(cobalt_app_screen(g_app) == COBALT_SCREEN_THREAD);
       frame(COBALT_BTN_BACK); settle(10);
       CHECK(cobalt_app_screen(g_app) == COBALT_SCREEN_PROFILE);
-      frame(COBALT_BTN_BACK); settle(10);
+      /* Going back to the outer thread fetches it again: the session held the
+       * inner conversation, so without the refetch the outer screen showed it. */
+      const int requests = cobalt_session_thread_requests();
+      frame(COBALT_BTN_BACK);
+      CHECK(cobalt_session_thread_requests() == requests + 1);
+      settle(10);
       CHECK(cobalt_app_screen(g_app) == COBALT_SCREEN_THREAD);
       frame(COBALT_BTN_BACK); settle(10);
       CHECK(cobalt_app_screen(g_app) == COBALT_SCREEN_TIMELINE);