[apps] Container::switchTo returns a bool (false if could not switch)

apps/apps_container.cpp

@@ -152,18 +152,19 @@ bool AppsContainer::dispatchEvent(Ion::Events::Event event) {
   if (event == Ion::Events::USBEnumeration) {
     if (Ion::USB::isPlugged()) {
       App::Snapshot * activeSnapshot = (activeApp() == nullptr ? appSnapshotAtIndex(0) : activeApp()->snapshot());
-      if (activeApp() == nullptr || activeApp()->prepareForExit()) {
+      if (switchTo(usbConnectedAppSnapshot())) {
         /* Just after a software update, the battery timer does not have time to
          * fire before the calculator enters DFU mode. As the DFU mode blocks the
          * event loop, we update the battery state "manually" here. */
         updateBatteryState();
-        switchTo(usbConnectedAppSnapshot());
         Ion::USB::DFU();
-        switchTo(activeSnapshot);
+        bool switched = switchTo(activeSnapshot);
+        assert(switched);
+        (void) switched; // Silence compilation warning about unused variable.
         didProcessEvent = true;
       } else {
-        /* activeApp()->prepareForExit() returned false, which means that the
-         * app needs another event loop to prepare for being switched off.
+        /* We could not switch apps, which means that the current app needs
+         * another event loop to prepare for being switched off.
          * Discard the current enumeration interruption.
          * The USB host tries a few times in a row to enumerate the device, so
          * hopefully the device will get another enumeration event soon and this
@@ -222,7 +223,7 @@ bool AppsContainer::processEvent(Ion::Events::Event event) {
   return false;
 }
 
-void AppsContainer::switchTo(App::Snapshot * snapshot) {
+bool AppsContainer::switchTo(App::Snapshot * snapshot) {
   if (activeApp() && snapshot != activeApp()->snapshot()) {
     resetShiftAlphaStatus();
   }
@@ -234,7 +235,7 @@ void AppsContainer::switchTo(App::Snapshot * snapshot) {
   if (snapshot) {
     m_window.setTitle(snapshot->descriptor()->upperName());
   }
-  Container::switchTo(snapshot);
+  return Container::switchTo(snapshot);
 }
 
 void AppsContainer::run() {
@@ -251,15 +252,14 @@ void AppsContainer::run() {
     /* Normal execution. The exception checkpoint must be created before
      * switching to the first app, because the first app might create nodes on
      * the pool. */
+     bool switched =
 #if EPSILON_ONBOARDING_APP
-    switchTo(onBoardingAppSnapshot());
+       switchTo(onBoardingAppSnapshot());
 #else
-    if (numberOfApps() == 2) {
-      switchTo(appSnapshotAtIndex(1));
-    } else {
-      switchTo(appSnapshotAtIndex(0));
-    }
+       switchTo(appSnapshotAtIndex(numberOfApps() == 2 ? 1 : 0));
 #endif
+    assert(switched);
+    (void) switched; // Silence compilation warning about unused variable.
   } else {
     // Exception
     if (activeApp() != nullptr) {
@@ -276,7 +276,9 @@ void AppsContainer::run() {
        * history here, we will be stuck outside the calculation app. */
       activeApp()->snapshot()->reset();
     }
-    switchTo(appSnapshotAtIndex(0));
+    bool switched = switchTo(appSnapshotAtIndex(0));
+    assert(switched);
+    (void) switched; // Silence compilation warning about unused variable.
     Poincare::Tidy();
     activeApp()->displayWarning(I18n::Message::PoolMemoryFull1, I18n::Message::PoolMemoryFull2, true);
   }

apps/apps_container.h

@@ -42,7 +42,7 @@ public:
   VariableBoxController * variableBoxController();
   void suspend(bool checkIfPowerKeyReleased = false);
   virtual bool dispatchEvent(Ion::Events::Event event) override;
-  void switchTo(App::Snapshot * snapshot) override;
+  bool switchTo(App::Snapshot * snapshot) override;
   void run() override;
   bool updateBatteryState();
   void refreshPreferences();

apps/hardware_test/pop_up_controller.cpp

@@ -41,7 +41,9 @@ PopUpController::ContentView::ContentView(Responder * parentResponder) :
   m_okButton(this, I18n::Message::Ok, Invocation([](void * context, void * sender) {
     PopUpController::ContentView * view = (PopUpController::ContentView *)context;
     AppsContainer * appsContainer = (AppsContainer *)view->app()->container();
-    appsContainer->switchTo(appsContainer->hardwareTestAppSnapshot());
+    bool switched = appsContainer->switchTo(appsContainer->hardwareTestAppSnapshot());
+    assert(switched);
+    (void) switched; // Silence compilation warning about unused variable.
     return true;
   }, this), KDFont::SmallFont),
   m_warningTextView(KDFont::SmallFont, I18n::Message::Warning, 0.5, 0.5, KDColorWhite, KDColorBlack),

apps/home/controller.cpp

@@ -58,7 +58,9 @@ Controller::Controller(Responder * parentResponder, ::AppsContainer * container,
 
 bool Controller::handleEvent(Ion::Events::Event event) {
   if (event == Ion::Events::OK || event == Ion::Events::EXE) {
-    m_container->switchTo(m_container->appSnapshotAtIndex(m_selectionDataSource->selectedRow()*k_numberOfColumns+m_selectionDataSource->selectedColumn()+1));
+    bool switched = m_container->switchTo(m_container->appSnapshotAtIndex(m_selectionDataSource->selectedRow()*k_numberOfColumns+m_selectionDataSource->selectedColumn()+1));
+    assert(switched);
+    (void) switched; // Silence compilation warning about unused variable.
     return true;
   }
 

apps/on_boarding/pop_up_controller.cpp

@@ -55,7 +55,9 @@ bool PopUpController::handleEvent(Ion::Events::Event event) {
     app()->dismissModalViewController();
     AppsContainer * appsContainer = (AppsContainer *)app()->container();
     if (appsContainer->activeApp()->snapshot() == appsContainer->onBoardingAppSnapshot()) {
-      appsContainer->switchTo(appsContainer->appSnapshotAtIndex(0));
+      bool switched = appsContainer->switchTo(appsContainer->appSnapshotAtIndex(0));
+      assert(switched);
+      (void) switched; // Silence compilation warning about unused variable.
     }
     return true;
   }

escher/include/escher/container.h

@@ -27,7 +27,7 @@ public:
   virtual void run();
   App * activeApp();
   virtual bool dispatchEvent(Ion::Events::Event event) override;
-  virtual void switchTo(App::Snapshot * snapshot);
+  virtual bool switchTo(App::Snapshot * snapshot);
 protected:
   virtual Window * window() = 0;
 private:

escher/src/container.cpp

@@ -13,14 +13,14 @@ Container::~Container() {
   }
 }
 
-void Container::switchTo(App::Snapshot * snapshot) {
+bool Container::switchTo(App::Snapshot * snapshot) {
   if (m_activeApp && snapshot == m_activeApp->snapshot()) {
-    return;
+    return true;
   }
   if (m_activeApp && !m_activeApp->prepareForExit()) {
     /* activeApp()->prepareForExit() returned false, which means that the app
      * needs another event loop to prepare for being switched off. */
-    return;
+    return false;
   }
   if (m_activeApp) {
     m_activeApp->willBecomeInactive();
@@ -34,6 +34,7 @@ void Container::switchTo(App::Snapshot * snapshot) {
     m_activeApp->didBecomeActive(window());
     window()->redraw();
   }
+  return true;
 }
 
 App * Container::activeApp() {