Copter: rewrite gcs-failsafe check for clarity

ArduCopter/events.cpp

@@ -87,17 +87,26 @@ void Copter::handle_battery_failsafe(const char *type_str, const int8_t action)
 // failsafe_gcs_check - check for ground station failsafe
 void Copter::failsafe_gcs_check()
 {
-    uint32_t last_gcs_update_ms;
-
-    // return immediately if gcs failsafe is disabled, gcs has never been connected or we are not overriding rc controls from the gcs and we are not in guided mode
-    // this also checks to see if we have a GCS failsafe active, if we do, then must continue to process the logic for recovery from this state.
-    if ((!failsafe.gcs)&&(g.failsafe_gcs == FS_GCS_DISABLED || failsafe.last_heartbeat_ms == 0 || (!RC_Channels::has_active_overrides() && control_mode != GUIDED))) {
+    if (failsafe.gcs) {
+        // we must run the failsafe checks if we are in failsafe -
+        // otherwise we will never leave failsafe
+    } else if (g.failsafe_gcs == FS_GCS_DISABLED) {
+        // simply disabled
+        return;
+    } else if (failsafe.last_heartbeat_ms == 0) {
+        // GCS has never connected
+        return;
+    } else if (RC_Channels::has_active_overrides()) {
+        // GCS is currently telling us what to do!
+    } else if (control_mode == GUIDED) {
+        // GCS is currently telling us what to do!
+    } else {
         return;
     }
 
     // calc time since last gcs update
     // note: this only looks at the heartbeat from the device id set by g.sysid_my_gcs
-    last_gcs_update_ms = millis() - failsafe.last_heartbeat_ms;
+    const uint32_t last_gcs_update_ms = millis() - failsafe.last_heartbeat_ms;
 
     // check if all is well
     if (last_gcs_update_ms < FS_GCS_TIMEOUT_MS) {