[welcome] Use QNetworkAccessManager in checkHasInternet.

Use QNetworkAccessManager instead of raw QtDBus queries to
NetworkManager in RequirementsChecker::checkHasInternet(). This is much
simpler (i.e., less error-prone) and should be more portable (to, e.g.,
ConnMan).

src/modules/welcome/CMakeLists.txt

@@ -1,7 +1,7 @@
 include_directories( ${PROJECT_BINARY_DIR}/src/libcalamaresui )
 set( CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} ${CMAKE_CURRENT_SOURCE_DIR}/CMakeModules )
 find_package( LIBPARTED REQUIRED )
-find_package( Qt5 ${QT_VERSION} CONFIG REQUIRED DBus )
+find_package( Qt5 ${QT_VERSION} CONFIG REQUIRED DBus Network )
 
 set_source_files_properties( checker/partman_devices.c PROPERTIES LANGUAGE CXX )
 
@@ -14,6 +14,7 @@ set( CHECKER_SOURCES
 set( CHECKER_LINK_LIBRARIES
     ${LIBPARTED_LIBS}
     Qt5::DBus
+    Qt5::Network
 )
 
 calamares_add_plugin( welcome

src/modules/welcome/checker/RequirementsChecker.cpp

@@ -36,6 +36,7 @@
 #include <QFile>
 #include <QFileInfo>
 #include <QLabel>
+#include <QNetworkAccessManager>
 #include <QProcess>
 #include <QTimer>
 
@@ -336,32 +337,8 @@ RequirementsChecker::checkHasPower()
 bool
 RequirementsChecker::checkHasInternet()
 {
-    const QString NM_SVC_NAME( "org.freedesktop.NetworkManager" );
-    const QString NM_INTF_NAME( "org.freedesktop.NetworkManager" );
-    const QString NM_PATH( "/org/freedesktop/NetworkManager" );
-    const int NM_STATE_CONNECTED_GLOBAL = 70;
-
-    QDBusInterface nmIntf( NM_SVC_NAME,
-                           NM_PATH,
-                           NM_INTF_NAME,
-                           QDBusConnection::systemBus(), 0 );
-
-    bool ok = false;
-    int nmState = nmIntf.property( "State" ).toInt( &ok );
-
-    if ( !ok || !nmIntf.isValid() )
-    {
-        // We can't talk to NM, so no idea.  Wild guess: we're connected
-        // using ssh with X forwarding, and are therefore connected.  This
-        // allows us to proceed with a minimum of complaint.
-        Calamares::JobQueue::instance()->globalStorage()->insert( "hasInternet", true );
-        return true;
-    }
-
-    bool hasInternet = nmState == NM_STATE_CONNECTED_GLOBAL;
-
-    Calamares::JobQueue::instance()->globalStorage()->insert( "hasInternet", hasInternet );
-    return hasInternet;
+    // default to true in the QNetworkAccessManager::UnknownAccessibility case
+    return QNetworkAccessManager(this).networkAccessible() != QNetworkAccessManager::NotAccessible;
 }