Added conditional intermediate back-off

app/src/main/java/eu/faircode/email/AlarmManagerCompatEx.java

@@ -33,11 +33,7 @@ public class AlarmManagerCompatEx {
     static void setAndAllowWhileIdle(
             @NonNull Context context, @NonNull AlarmManager am,
             int type, long trigger, @NonNull PendingIntent pi) {
-        SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
-        boolean exact_alarms = prefs.getBoolean("exact_alarms", true);
-
-        // https://developer.android.com/about/versions/12/behavior-changes-12#exact-alarm-permission
-        if (exact_alarms && canScheduleExactAlarms(context))
+        if (hasExactAlarms(context))
             try {
                 AlarmManagerCompat.setExactAndAllowWhileIdle(am, type, trigger, pi);
             } catch (SecurityException ex) {
@@ -48,10 +44,17 @@ public class AlarmManagerCompatEx {
             AlarmManagerCompat.setAndAllowWhileIdle(am, type, trigger, pi);
     }
 
+    static boolean hasExactAlarms(Context context){
+        SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
+        boolean exact_alarms = prefs.getBoolean("exact_alarms", true);
+        return (exact_alarms && canScheduleExactAlarms(context));
+    }
+
     static boolean canScheduleExactAlarms(Context context) {
         if (Build.VERSION.SDK_INT <= Build.VERSION_CODES.R)
             return true;
         else {
+            // https://developer.android.com/about/versions/12/behavior-changes-12#exact-alarm-permission
             AlarmManager am = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE);
             return am.canScheduleExactAlarms();
         }

app/src/main/java/eu/faircode/email/Log.java

@@ -1729,8 +1729,11 @@ public class Log {
                 .append(" night=").append(Helper.isNight(context))
                 .append("\r\n");
 
-        sb.append("canScheduleExactAlarms=")
+        sb.append("ExactAlarms")
+                .append(" can=")
                 .append(AlarmManagerCompatEx.canScheduleExactAlarms(context))
+                .append(" has=")
+                .append(AlarmManagerCompatEx.hasExactAlarms(context))
                 .append("\r\n");
 
         sb.append("Transliterate: ")

app/src/main/java/eu/faircode/email/ServiceSynchronize.java

@@ -121,6 +121,7 @@ public class ServiceSynchronize extends ServiceBase implements SharedPreferences
     private static final int OPTIMIZE_POLL_INTERVAL = 15; // minutes
     private static final int CONNECT_BACKOFF_START = 8; // seconds
     private static final int CONNECT_BACKOFF_MAX = 8; // seconds (totally 8+2x20=48 seconds)
+    private static final int CONNECT_BACKOFF_INTERMEDIATE = 5; // minutes
     private static final int CONNECT_BACKOFF_ALARM_START = 15; // minutes
     private static final int CONNECT_BACKOFF_ALARM_MAX = 60; // minutes
     private static final long CONNECT_BACKOFF_GRACE = 2 * 60 * 1000L; // milliseconds
@@ -2153,6 +2154,11 @@ public class ServiceSynchronize extends ServiceBase implements SharedPreferences
                     if (backoff < CONNECT_BACKOFF_MAX)
                         state.setBackoff(backoff * 2);
                     else if (backoff == CONNECT_BACKOFF_MAX)
+                        if (AlarmManagerCompatEx.hasExactAlarms(this))
+                            state.setBackoff(CONNECT_BACKOFF_INTERMEDIATE * 60);
+                        else
+                            state.setBackoff(CONNECT_BACKOFF_ALARM_START * 60);
+                    else if (backoff == CONNECT_BACKOFF_INTERMEDIATE * 60)
                         state.setBackoff(CONNECT_BACKOFF_ALARM_START * 60);
                     else if (backoff < CONNECT_BACKOFF_ALARM_MAX * 60) {
                         int b = backoff * 2;