Use QDBusServiceWatcher in QDBusAbstractInterface to track the owner

Instead of connecting to the "NameOwnerChanged" signal. This has better
performance, is simpler to implement and is future-proof: when we switch
to kdbus, there won't be a "NameOwnerChanged" signal to connect to. On
the drawback side, this will use slightly more memory.

Change-Id: I5801b8027949f041309567a493000fe7de9bf227
Reviewed-by: Alex Blasche <alexander.blasche@theqtcompany.com>
Reviewed-by: Albert Astals Cid <aacid@kde.org>

2 files changed, 19 insertions, 28 deletions

diff --git a/src/dbus/qdbusabstractinterface.cpp b/src/dbus/qdbusabstractinterface.cpp
index a7c70bce70..5ccd8c8d83 100644
--- a/src/dbus/qdbusabstractinterface.cpp
+++ b/src/dbus/qdbusabstractinterface.cpp
@@ -1,6 +1,7 @@
 /****************************************************************************
 **
 ** Copyright (C) 2015 The Qt Company Ltd.
+** Copyright (C) 2015 Intel Corporation.
 ** Contact: http://www.qt.io/licensing/
 **
 ** This file is part of the QtDBus module of the Qt Toolkit.
@@ -41,6 +42,7 @@
 #include "qdbusmessage_p.h"
 #include "qdbusmetaobject_p.h"
 #include "qdbusmetatype_p.h"
+#include "qdbusservicewatcher.h"
 #include "qdbusutil_p.h"
 
 #include <qdebug.h>
@@ -97,6 +99,17 @@ QDBusAbstractInterfacePrivate::QDBusAbstractInterfacePrivate(const QString &serv
     }
 }
 
+void QDBusAbstractInterfacePrivate::initOwnerTracking()
+{
+    if (!isValid || !connection.isConnected() || connectionPrivate()->mode == QDBusConnectionPrivate::PeerMode)
+        return;
+    if (service.isEmpty() || service.startsWith(QLatin1Char(':')))
+        return;
+    QObject::connect(new QDBusServiceWatcher(service, connection, QDBusServiceWatcher::WatchForOwnerChange, q_func()),
+                     SIGNAL(serviceOwnerChanged(QString,QString,QString)),
+                     q_func(), SLOT(_q_serviceOwnerChanged(QString,QString,QString)));
+}
+
 bool QDBusAbstractInterfacePrivate::canMakeCalls() const
 {
     // recheck only if we have a wildcard (i.e. empty) service or path
@@ -218,9 +231,8 @@ void QDBusAbstractInterfacePrivate::_q_serviceOwnerChanged(const QString &name,
     Q_UNUSED(oldOwner);
     Q_UNUSED(name);
     //qDebug() << "QDBusAbstractInterfacePrivate serviceOwnerChanged" << name << oldOwner << newOwner;
-    if (name == service) {
-        currentOwner = newOwner;
-    }
+    Q_ASSERT(name == service);
+    currentOwner = newOwner;
 }
 
 QDBusAbstractInterfaceBase::QDBusAbstractInterfaceBase(QDBusAbstractInterfacePrivate &d, QObject *parent)
@@ -285,19 +297,7 @@ int QDBusAbstractInterfaceBase::qt_metacall(QMetaObject::Call _c, int _id, void
 QDBusAbstractInterface::QDBusAbstractInterface(QDBusAbstractInterfacePrivate &d, QObject *parent)
     : QDBusAbstractInterfaceBase(d, parent)
 {
-    // keep track of the service owner
-    if (d.isValid &&
-        d.connection.isConnected()
-        && !d.service.isEmpty()
-        && !d.service.startsWith(QLatin1Char(':'))
-        && d.connectionPrivate()->mode != QDBusConnectionPrivate::PeerMode)
-        d_func()->connection.connect(QDBusUtil::dbusService(), // service
-                                     QString(), // path
-                                     QDBusUtil::dbusInterface(), // interface
-                                     QDBusUtil::nameOwnerChanged(),
-                                     QStringList() << d.service,
-                                     QString(), // signature
-                                     this, SLOT(_q_serviceOwnerChanged(QString,QString,QString)));
+    d.initOwnerTracking();
 }
 
 /*!
@@ -312,18 +312,7 @@ QDBusAbstractInterface::QDBusAbstractInterface(const QString &service, const QSt
                                                  con, false), parent)
 {
     // keep track of the service owner
-    if (d_func()->isValid &&
-        d_func()->connection.isConnected()
-        && !service.isEmpty()
-        && !service.startsWith(QLatin1Char(':'))
-        && d_func()->connectionPrivate()->mode != QDBusConnectionPrivate::PeerMode)
-        d_func()->connection.connect(QDBusUtil::dbusService(), // service
-                                     QString(), // path
-                                     QDBusUtil::dbusInterface(), // interface
-                                     QDBusUtil::nameOwnerChanged(),
-                                     QStringList() << service,
-                                     QString(), //signature
-                                     this, SLOT(_q_serviceOwnerChanged(QString,QString,QString)));
+    d_func()->initOwnerTracking();
 }
 
 /*!
diff --git a/src/dbus/qdbusabstractinterface_p.h b/src/dbus/qdbusabstractinterface_p.h
index ba2bcadfb0..1ce457d94b 100644
--- a/src/dbus/qdbusabstractinterface_p.h
+++ b/src/dbus/qdbusabstractinterface_p.h
@@ -1,6 +1,7 @@
 /****************************************************************************
 **
 ** Copyright (C) 2015 The Qt Company Ltd.
+** Copyright (C) 2015 Intel Corporation.
 ** Contact: http://www.qt.io/licensing/
 **
 ** This file is part of the QtDBus module of the Qt Toolkit.
@@ -78,6 +79,7 @@ public:
     QDBusAbstractInterfacePrivate(const QString &serv, const QString &p,
                                   const QString &iface, const QDBusConnection& con, bool dynamic);
     virtual ~QDBusAbstractInterfacePrivate() { }
+    void initOwnerTracking();
     bool canMakeCalls() const;
 
     // these functions do not check if the property is valid