fix: small QoL: return to the last selected menu location (#1629)

## Summary

* **What is the goal of this PR?** Small UX improvement to the Home
screen by preserving the last selected cursor position when returning to
it.

It supersedes #985 and #1103, which are both significantly outdated and
hundreds of commits behind master.

---

### AI Usage

Did you use AI tools to help write this code? _**< YES >**_

src/activities/Activity.cpp

@@ -10,7 +10,7 @@ void Activity::requestUpdate(bool immediate) { activityManager.requestUpdate(imm
 
 void Activity::requestUpdateAndWait() { activityManager.requestUpdateAndWait(); }
 
-void Activity::onGoHome() { activityManager.goHome(); }
+void Activity::onGoHome(HomeMenuItem item) { activityManager.goHome(item); }
 
 void Activity::onSelectBook(const std::string& path) { activityManager.goToReader(path); }
 

src/activities/Activity.h

@@ -58,6 +58,6 @@ class Activity {
 
   // Convenience method to facilitate API transition to ActivityManager
   // TODO: remove this in near future
-  void onGoHome();
+  void onGoHome(HomeMenuItem item = HomeMenuItem::NONE);
   void onSelectBook(const std::string& path);
 };

src/activities/ActivityManager.cpp

@@ -207,10 +207,25 @@ void ActivityManager::goToFullScreenMessage(std::string message, EpdFontFamily::
   replaceActivity(std::make_unique<FullScreenMessageActivity>(renderer, mappedInput, std::move(message), style));
 }
 
+void ActivityManager::goHome(HomeMenuItem initialMenuItem) {
+  if (initialMenuItem == HomeMenuItem::NONE && currentActivity) {
+    const auto& activityName = currentActivity->name;
+    if (activityName == "FileBrowser") {
+      initialMenuItem = HomeMenuItem::FILE_BROWSER;
+    } else if (activityName == "RecentBooks") {
+      initialMenuItem = HomeMenuItem::RECENTS;
+    } else if (activityName == "OpdsBookBrowser") {
+      initialMenuItem = HomeMenuItem::OPDS_BROWSER;
+    } else if (activityName == "CrossPointWebServer") {
+      initialMenuItem = HomeMenuItem::FILE_TRANSFER;
+    } else if (activityName == "Settings") {
+      initialMenuItem = HomeMenuItem::SETTINGS_MENU;
+    }
+  }
+  replaceActivity(std::make_unique<HomeActivity>(renderer, mappedInput, initialMenuItem));
+}
 void ActivityManager::goToCrashReport() { replaceActivity(std::make_unique<CrashActivity>(renderer, mappedInput)); }
 
-void ActivityManager::goHome() { replaceActivity(std::make_unique<HomeActivity>(renderer, mappedInput)); }
-
 void ActivityManager::pushActivity(std::unique_ptr<Activity>&& activity) {
   if (pendingActivity) {
     // Should never happen in practice

src/activities/ActivityManager.h

@@ -16,6 +16,8 @@
 class Activity;    // forward declaration
 class RenderLock;  // forward declaration
 
+enum class HomeMenuItem { NONE, FILE_BROWSER, RECENTS, OPDS_BROWSER, FILE_TRANSFER, SETTINGS_MENU };
+
 /**
  * ActivityManager
  *
@@ -88,7 +90,7 @@ class ActivityManager {
   void goToBoot();
   void goToFullScreenMessage(std::string message, EpdFontFamily::Style style = EpdFontFamily::REGULAR);
   void goToCrashReport();
-  void goHome();
+  void goHome(HomeMenuItem initialMenuItem = HomeMenuItem::NONE);
 
   // This will move current activity to stack instead of deleting it
   void pushActivity(std::unique_ptr<Activity>&& activity);

src/activities/home/HomeActivity.cpp

@@ -113,11 +113,12 @@ void HomeActivity::onEnter() {
 
   hasOpdsServers = OPDS_STORE.hasServers();
 
-  selectorIndex = 0;
-
   const auto& metrics = UITheme::getInstance().getMetrics();
   loadRecentBooks(metrics.homeRecentBooksCount);
 
+  const auto base = static_cast<int>(recentBooks.size());
+  selectorIndex = initialMenuItem == HomeMenuItem::NONE ? 0 : base + menuItemToIndex(initialMenuItem, hasOpdsServers);
+
   // Trigger first update
   requestUpdate();
 }
@@ -179,27 +180,29 @@ void HomeActivity::loop() {
   });
 
   if (mappedInput.wasReleased(MappedInputManager::Button::Confirm)) {
-    // Calculate dynamic indices based on which options are available
-    int idx = 0;
-    int menuSelectedIndex = selectorIndex - static_cast<int>(recentBooks.size());
-    const int fileBrowserIdx = idx++;
-    const int recentsIdx = idx++;
-    const int opdsLibraryIdx = hasOpdsServers ? idx++ : -1;
-    const int fileTransferIdx = idx++;
-    const int settingsIdx = idx;
-
     if (selectorIndex < recentBooks.size()) {
       onSelectBook(recentBooks[selectorIndex].path);
-    } else if (menuSelectedIndex == fileBrowserIdx) {
+    } else {
+      const int menuIndex = selectorIndex - static_cast<int>(recentBooks.size());
+      switch (indexToMenuItem(menuIndex, hasOpdsServers)) {
+        case HomeMenuItem::FILE_BROWSER:
           onFileBrowserOpen();
-    } else if (menuSelectedIndex == recentsIdx) {
+          break;
+        case HomeMenuItem::RECENTS:
           onRecentsOpen();
-    } else if (menuSelectedIndex == opdsLibraryIdx) {
+          break;
+        case HomeMenuItem::OPDS_BROWSER:
           onOpdsBrowserOpen();
-    } else if (menuSelectedIndex == fileTransferIdx) {
+          break;
+        case HomeMenuItem::FILE_TRANSFER:
           onFileTransferOpen();
-    } else if (menuSelectedIndex == settingsIdx) {
+          break;
+        case HomeMenuItem::SETTINGS_MENU:
           onSettingsOpen();
+          break;
+        default:
+          break;
+      }
     }
   }
 }

src/activities/home/HomeActivity.h

@@ -28,6 +28,33 @@ class HomeActivity final : public Activity {
   int coverRectW = 0;
   int coverRectH = 0;
   std::vector<RecentBook> recentBooks;
+  const HomeMenuItem initialMenuItem;
+
+  // Convert HomeMenuItem to menu index (used in onEnter)
+  static int menuItemToIndex(HomeMenuItem item, bool hasOpdsUrl) {
+    int i = 0;
+    if (item == HomeMenuItem::FILE_BROWSER) return i;
+    ++i;
+    if (item == HomeMenuItem::RECENTS) return i;
+    ++i;
+    if (item == HomeMenuItem::OPDS_BROWSER) return hasOpdsUrl ? i : 0;
+    if (hasOpdsUrl) ++i;
+    if (item == HomeMenuItem::FILE_TRANSFER) return i;
+    ++i;
+    if (item == HomeMenuItem::SETTINGS_MENU) return i;
+    return 0;
+  }
+
+  // Convert menu index to HomeMenuItem (used in loop)
+  static HomeMenuItem indexToMenuItem(int idx, bool hasOpdsUrl) {
+    int i = 0;
+    if (idx == i++) return HomeMenuItem::FILE_BROWSER;
+    if (idx == i++) return HomeMenuItem::RECENTS;
+    if (hasOpdsUrl && idx == i++) return HomeMenuItem::OPDS_BROWSER;
+    if (idx == i++) return HomeMenuItem::FILE_TRANSFER;
+    if (idx == i) return HomeMenuItem::SETTINGS_MENU;
+    return HomeMenuItem::NONE;
+  }
   void onSelectBook(const std::string& path);
   void onFileBrowserOpen();
   void onRecentsOpen();
@@ -43,8 +70,9 @@ class HomeActivity final : public Activity {
   void loadRecentCovers(int coverHeight);
 
  public:
-  explicit HomeActivity(GfxRenderer& renderer, MappedInputManager& mappedInput)
+  explicit HomeActivity(GfxRenderer& renderer, MappedInputManager& mappedInput,
-      : Activity("Home", renderer, mappedInput) {}
+                        HomeMenuItem initialMenuItemValue = HomeMenuItem::NONE)
+      : Activity("Home", renderer, mappedInput), initialMenuItem(initialMenuItemValue) {}
   void onEnter() override;
   void onExit() override;
   void loop() override;

src/activities/settings/OpdsServerListActivity.cpp

@@ -34,7 +34,7 @@ void OpdsServerListActivity::onExit() { Activity::onExit(); }
 void OpdsServerListActivity::loop() {
   if (mappedInput.wasPressed(MappedInputManager::Button::Back)) {
     if (pickerMode) {
-      activityManager.goHome();
+      activityManager.goHome(HomeMenuItem::OPDS_BROWSER);
     } else {
       finish();
     }