Refactor ActivityManager calls

src/activities/ActivityManager.h

@@ -15,6 +15,21 @@
 class Activity;    // forward declaration
 class RenderLock;  // forward declaration
 
+// Where a "child" activity (launched via one of the replaceWith* helpers) should route
+// control when it exits successfully. See ActivityManager::returnFromChild().
+enum class ReturnTo : uint8_t { Home, FileBrowser, RecentBooks };
+
+// Minimal state the returning parent needs to restore its previous view (directory,
+// focused item, list index). Kept as a plain struct stored by value on the
+// ActivityManager — single instance, overwritten per transition, no heap churn
+// beyond the two small std::strings.
+struct ReturnHint {
+  ReturnTo target = ReturnTo::Home;
+  std::string path;        // FileBrowser directory to restore
+  std::string selectName;  // item to re-focus in a list (file name, book title)
+  int selectIndex = -1;    // e.g. Recents index
+};
+
 /**
  * ActivityManager
  *
@@ -68,6 +83,12 @@ class ActivityManager {
   // into the next one.
   bool drainInput = false;
 
+  // Where returnFromChild() should route to. Set by replaceWith*() helpers, cleared
+  // in returnFromChild(). Cleared on any manual goHome()/goTo*() to avoid stale hints
+  // outliving the flow they were recorded for.
+  ReturnHint returnHint;
+  bool hasReturnHint = false;
+
  public:
   explicit ActivityManager(GfxRenderer& renderer, MappedInputManager& mappedInput)
       : renderer(renderer), mappedInput(mappedInput), renderingMutex(xSemaphoreCreateMutex()) {
@@ -85,18 +106,29 @@ class ActivityManager {
   // goTo... functions are convenient wrapper for replaceActivity()
   void goToFileTransfer();
   void goToSettings();
-  void goToFileBrowser(std::string path = {});
-  void goToRecentBooks();
+  void goToFileBrowser(std::string path = {}, std::string focusName = {});
+  void goToRecentBooks(int focusIndex = -1);
   void goToGlobalBookmarks();
   void goToBrowser();
   void goToReader(std::string path);
   void goToKOReaderSync();
-  void pushReader(std::string path);
   void goToSleep();
   void goToBoot();
   void goToFullScreenMessage(std::string message, EpdFontFamily::Style style = EpdFontFamily::REGULAR);
   void goToWeather();
-  void goHome();
+  void goHome(std::string focusBookPath = {});
+
+  // Replace-with-hint helpers: destroy the current activity before launching the new
+  // one (freeing its memory) and record where to route control when the new activity
+  // exits. Consumed by returnFromChild().
+  void replaceWithReader(std::string path, ReturnHint hint);
+  void replaceWithFileBrowser(std::string path, ReturnHint hint, std::string focusName = {});
+  void replaceWithRecentBooks(ReturnHint hint);
+
+  // Called by a "child" activity on successful exit. Consults the stored ReturnHint,
+  // clears it, and dispatches to the corresponding parent with restoration args. If
+  // no hint is set, defaults to goHome().
+  void returnFromChild();
 
   // This will move current activity to stack instead of deleting it
   void pushActivity(std::unique_ptr<Activity>&& activity);