frontend/qt: react to change in connectivity status.

Instead of relying on a polling mechanism, we use QT's signals
to monitor the  connectivity status and react when this changes
by showing a banner. When the connectivity is resumed, we trigger a
reconnect to our nodes.

Author: bznein

backend/backend.go

@@ -279,6 +279,9 @@ func NewBackend(arguments *arguments.Arguments, environment Environment) (*Backe
 		log: log,
 
 		testing: backendConfig.AppConfig().Backend.StartInTestnet || arguments.Testing(),
+
+		// TODO: remove when connectivity check is present on all platforms
+		isOnline: true,
 	}
 	// TODO: remove when connectivity check is present on all platforms
 	backend.isOnline.Store(true)

frontends/qt/network.cpp

@@ -1,29 +1,41 @@
 #include <QNetworkInformation>
 #include "libserver.h"
+<<<<<<< HEAD
 #include "network.h"
+=======
+>>>>>>> b8afb2139 (frontend/qt: react to change in connectivity status.)
 
 void setupReachabilityNotifier() {
     auto loaded = QNetworkInformation::loadBackendByFeatures(QNetworkInformation::Feature::Reachability);
     if (!loaded) {
+<<<<<<< HEAD
         goLog("can't load QNetworkInformation backend");
         // If we can't load the backend, we can't determine whether or not to show the banner.
         setOnline(true);
+=======
+>>>>>>> b8afb2139 (frontend/qt: react to change in connectivity status.)
         return;
     }
     QNetworkInformation* info = QNetworkInformation::instance();
     if (info) {
       QObject::connect(info, &QNetworkInformation::reachabilityChanged, [](QNetworkInformation::Reachability reachability){
+<<<<<<< HEAD
           // We include Reachability::Unknown here as we prefer not include false positives. If QT can't determine whether
           // we are online, we do not show the banner.
           bool isReachable = (reachability == QNetworkInformation::Reachability::Online || reachability == QNetworkInformation::Reachability::Unknown);
           setOnline(isReachable);
+=======
+        bool isReachable = (reachability == QNetworkInformation::Reachability::Online);
+        onlineStatusChanged(isReachable);
+>>>>>>> b8afb2139 (frontend/qt: react to change in connectivity status.)
       });
     }
 }
 
 bool isReachable() {
     auto loaded = QNetworkInformation::loadBackendByFeatures(QNetworkInformation::Feature::Reachability);
     if (!loaded) {
+<<<<<<< HEAD
         goLog("can't load QNetworkInformation backend");
         return true;
     }
@@ -33,4 +45,14 @@ bool isReachable() {
     }
     // Same as above, if we can't obtain information, we don't show any banner at all.
     return true;
+=======
+        return false;
+    }
+    QNetworkInformation* info = QNetworkInformation::instance();
+    if (info) {
+        return info->reachability() == QNetworkInformation::Reachability::Online;
+    } else {
+        return false;
+    }
+>>>>>>> b8afb2139 (frontend/qt: react to change in connectivity status.)
 }