Don't let a notification cancel a ringing alarm

src/displayapp/DisplayApp.cpp

@@ -367,7 +367,12 @@ void DisplayApp::Refresh() {
         // Only used for recovery firmware
         break;
       case Messages::NewNotification:
-        LoadNewScreen(Apps::NotificationsPreview, DisplayApp::FullRefreshDirections::Down);
+        // Loading the preview destroys the current screen. While the alarm or an expired timer is
+        // ringing, ~Alarm() and ~Timer() stop the ringing, so the alert would be cancelled instead
+        // of just being hidden. The notification is still stored and can be read from the list.
+        if (!IsAlerting()) {
+          LoadNewScreen(Apps::NotificationsPreview, DisplayApp::FullRefreshDirections::Down);
+        }
         break;
       case Messages::TimerDone: {
         if (state != States::Running) {
@@ -684,6 +689,14 @@ void DisplayApp::PushMessage(Messages msg) {
   }
 }
 
+bool DisplayApp::IsAlerting() {
+  if (alarmController.IsAlerting()) {
+    return true;
+  }
+  auto timerState = timer.GetTimerState();
+  return timerState && timerState->expired;
+}
+
 void DisplayApp::SetFullRefresh(DisplayApp::FullRefreshDirections direction) {
   switch (direction) {
     case DisplayApp::FullRefreshDirections::Down:

src/displayapp/DisplayApp.h

@@ -128,6 +128,8 @@ namespace Pinetime {
       void Refresh();
       void LoadNewScreen(Apps app, DisplayApp::FullRefreshDirections direction);
       void LoadScreen(Apps app, DisplayApp::FullRefreshDirections direction);
+      /// Is the watch itself alerting the user (alarm or expired timer)?
+      bool IsAlerting();
       void PushMessageToSystemTask(Pinetime::System::Messages message);
 
       Apps nextApp = Apps::None;