timer: Fix undefined behavior when capturing expiry time

The timer was calling xTimerGetExpiryTime() after the FreeRTOS timer had
expired, which results in undefined behavior according to the FreeRTOS
documentation.

This change captures the expiry time in the TimerCallback when the timer
expires, using xTaskGetTickCount() instead of the undefined
xTimerGetExpiryTime() on a stopped timer. The expiry time is now
captured before the timer stops running.

Author: vkareh

src/components/timer/Timer.cpp

@@ -30,7 +30,7 @@ bool Timer::IsRunning() {
 }
 
 void Timer::SetExpiredTime() {
-  expired = xTimerGetExpiryTime(timer);
+  expired = xTaskGetTickCount();
 }
 
 void Timer::ResetExpiredTime() {

src/displayapp/DisplayApp.cpp

@@ -67,6 +67,7 @@ namespace {
 
   void TimerCallback(TimerHandle_t xTimer) {
     auto* dispApp = static_cast<DisplayApp*>(pvTimerGetTimerID(xTimer));
+    dispApp->SetTimerExpired();
     dispApp->PushMessage(Display::Messages::TimerDone);
   }
 }
@@ -364,22 +365,21 @@ void DisplayApp::Refresh() {
       case Messages::NewNotification:
         LoadNewScreen(Apps::NotificationsPreview, DisplayApp::FullRefreshDirections::Down);
         break;
-      case Messages::TimerDone:
+      case Messages::TimerDone: {
         if (state != States::Running) {
           PushMessageToSystemTask(System::Messages::GoToRunning);
         }
         // Load timer app if not loaded
         if (currentApp != Apps::Timer) {
           LoadNewScreen(Apps::Timer, DisplayApp::FullRefreshDirections::Up);
         }
-        // Once loaded, set the timer to ringing mode
-        if (currentApp == Apps::Timer) {
-          lv_disp_trig_activity(nullptr);
-          auto* timer = static_cast<Screens::Timer*>(currentScreen.get());
-          timer->SetTimerRinging();
-        }
+        // Set the timer to ringing mode
+        lv_disp_trig_activity(nullptr);
+        auto* timerScreen = static_cast<Screens::Timer*>(currentScreen.get());
+        timerScreen->SetTimerRinging();
         motorController.StartRinging();
         break;
+      }
       case Messages::AlarmTriggered:
         if (currentApp == Apps::Alarm) {
           auto* alarm = static_cast<Screens::Alarm*>(currentScreen.get());
@@ -725,6 +725,10 @@ void DisplayApp::Register(Pinetime::Controllers::NavigationService* NavigationSe
   this->controllers.navigationService = NavigationService;
 }
 
+void DisplayApp::SetTimerExpired() {
+  timer.SetExpiredTime();
+}
+
 void DisplayApp::ApplyBrightness() {
   auto brightness = settingsController.GetBrightness();
   if (brightness != Controllers::BrightnessController::Levels::Low && brightness != Controllers::BrightnessController::Levels::Medium &&

src/displayapp/DisplayApp.h

@@ -80,6 +80,8 @@ namespace Pinetime {
       void Register(Pinetime::Controllers::MusicService* musicService);
       void Register(Pinetime::Controllers::NavigationService* NavigationService);
 
+      void SetTimerExpired();
+
     private:
       Pinetime::Drivers::St7789& lcd;
       const Pinetime::Drivers::Cst816S& touchPanel;

src/displayapp/screens/Timer.cpp

@@ -165,7 +165,6 @@ void Timer::SetTimerRinging() {
   secondCounter.HideControls();
   lv_label_set_text_static(txtPlayPause, "Reset");
   lv_obj_set_style_local_bg_color(btnPlayPause, LV_BTN_PART_MAIN, LV_STATE_DEFAULT, LV_COLOR_RED);
-  timer.SetExpiredTime();
 }
 
 void Timer::ToggleRunning() {