Add QDBusMessage::createTargetedSignal()

The QDBusMessage::createSignal() static method doesn't take a parameter
for specifying the destination service of the signal. While this is not
a widely used feature, it can be useful to avoid waking up all connected
clients when the service knows what are the clients which are interested
in the signal.

This commit adds a QDBusMessage::createTargetedSignal() method which
also takes the destination service as its first parameter.

Change-Id: I9fdca53673a6944c39c93c1efd69a9d02859684e
Task-number: QTBUG-44704
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

4 files changed, 78 insertions, 2 deletions

diff --git a/src/dbus/qdbusintegrator.cpp b/src/dbus/qdbusintegrator.cpp
index a95d96e526..6a2a657714 100644
--- a/src/dbus/qdbusintegrator.cpp
+++ b/src/dbus/qdbusintegrator.cpp
@@ -1904,7 +1904,8 @@ int QDBusConnectionPrivate::send(const QDBusMessage& message)
                      qPrintable(message.interface()), qPrintable(message.member()),
                      qPrintable(error.message()));
         else if (message.type() == QDBusMessage::SignalMessage)
-            qWarning("QDBusConnection: error: could not send signal path \"%s\" interface \"%s\" member \"%s\": %s",
+            qWarning("QDBusConnection: error: could not send signal to service \"%s\" path \"%s\" interface \"%s\" member \"%s\": %s",
+                     qPrintable(message.service()),
                      qPrintable(message.path()), qPrintable(message.interface()),
                      qPrintable(message.member()),
                      qPrintable(error.message()));
diff --git a/src/dbus/qdbusmessage.cpp b/src/dbus/qdbusmessage.cpp
index 491e1273e7..76e994bbcf 100644
--- a/src/dbus/qdbusmessage.cpp
+++ b/src/dbus/qdbusmessage.cpp
@@ -153,8 +153,10 @@ DBusMessage *QDBusMessagePrivate::toDBusMessage(const QDBusMessage &message, QDB
         }
         break;
     case QDBusMessage::SignalMessage:
-        // nothing can be empty here
+        // only the service name can be empty here
         if (!d_ptr->parametersValidated) {
+            if (!QDBusUtil::checkBusName(d_ptr->service, QDBusUtil::EmptyAllowed, error))
+                return 0;
             if (!QDBusUtil::checkObjectPath(d_ptr->path, QDBusUtil::EmptyNotAllowed, error))
                 return 0;
             if (!QDBusUtil::checkInterfaceName(d_ptr->interface, QDBusUtil::EmptyAllowed, error))
@@ -165,6 +167,7 @@ DBusMessage *QDBusMessagePrivate::toDBusMessage(const QDBusMessage &message, QDB
 
         msg = q_dbus_message_new_signal(d_ptr->path.toUtf8(), d_ptr->interface.toUtf8(),
                                         d_ptr->name.toUtf8());
+        q_dbus_message_set_destination(msg, data(d_ptr->service.toUtf8()));
         break;
     }
 
@@ -372,6 +375,31 @@ QDBusMessage QDBusMessage::createSignal(const QString &path, const QString &inte
 }
 
 /*!
+    \since 5.6
+
+    Constructs a new DBus message with the given \a path, \a interface
+    and \a name, representing a signal emission to \a destination.
+
+    A DBus signal is emitted from one application and is received only by
+    the application owning the destination service name.
+
+    The QDBusMessage object that is returned can be sent using the
+    QDBusConnection::send() function.
+*/
+QDBusMessage QDBusMessage::createTargetedSignal(const QString &service, const QString &path,
+                                                const QString &interface, const QString &name)
+{
+    QDBusMessage message;
+    message.d_ptr->type = SignalMessage;
+    message.d_ptr->service = service;
+    message.d_ptr->path = path;
+    message.d_ptr->interface = interface;
+    message.d_ptr->name = name;
+
+    return message;
+}
+
+/*!
     Constructs a new DBus message representing a method call.
     A method call always informs its destination address
     (\a service, \a path, \a interface and \a method).
diff --git a/src/dbus/qdbusmessage.h b/src/dbus/qdbusmessage.h
index 77f34ec5e2..640226e77a 100644
--- a/src/dbus/qdbusmessage.h
+++ b/src/dbus/qdbusmessage.h
@@ -67,6 +67,8 @@ public:
 
     static QDBusMessage createSignal(const QString &path, const QString &interface,
                                      const QString &name);
+    static QDBusMessage createTargetedSignal(const QString &service, const QString &path,
+                                             const QString &interface, const QString &name);
     static QDBusMessage createMethodCall(const QString &destination, const QString &path,
                                          const QString &interface, const QString &method);
     static QDBusMessage createError(const QString &name, const QString &msg);
diff --git a/tests/auto/dbus/qdbusconnection/tst_qdbusconnection.cpp b/tests/auto/dbus/qdbusconnection/tst_qdbusconnection.cpp
index 32c228c186..d85e842a23 100644
--- a/tests/auto/dbus/qdbusconnection/tst_qdbusconnection.cpp
+++ b/tests/auto/dbus/qdbusconnection/tst_qdbusconnection.cpp
@@ -105,6 +105,8 @@ private slots:
     void sendWithGui();
     void sendAsync();
     void sendSignal();
+    void sendSignalToName();
+    void sendSignalToOtherName();
 
     void registerObject_data();
     void registerObject();
@@ -189,6 +191,49 @@ void tst_QDBusConnection::sendSignal()
     QTest::qWait(1000);
 }
 
+void tst_QDBusConnection::sendSignalToName()
+{
+    QDBusSpy spy;
+
+    QDBusConnection con = QDBusConnection::sessionBus();
+
+    con.connect(con.baseService(), "/org/kde/selftest", "org.kde.selftest", "ping", &spy,
+                SLOT(handlePing(QString)));
+
+    QDBusMessage msg =
+        QDBusMessage::createTargetedSignal(con.baseService(), "/org/kde/selftest",
+                                           "org.kde.selftest", "ping");
+    msg << QLatin1String("ping");
+
+    QVERIFY(con.send(msg));
+
+    QTest::qWait(1000);
+
+    QCOMPARE(spy.args.count(), 1);
+    QCOMPARE(spy.args.at(0).toString(), QString("ping"));
+}
+
+void tst_QDBusConnection::sendSignalToOtherName()
+{
+    QDBusSpy spy;
+
+    QDBusConnection con = QDBusConnection::sessionBus();
+
+    con.connect(con.baseService(), "/org/kde/selftest", "org.kde.selftest", "ping", &spy,
+                SLOT(handlePing(QString)));
+
+    QDBusMessage msg =
+        QDBusMessage::createTargetedSignal("some.other.service", "/org/kde/selftest",
+                                           "org.kde.selftest", "ping");
+    msg << QLatin1String("ping");
+
+    QVERIFY(con.send(msg));
+
+    QTest::qWait(1000);
+
+    QCOMPARE(spy.args.count(), 0);
+}
+
 void tst_QDBusConnection::send()
 {
     QDBusConnection con = QDBusConnection::sessionBus();