Add a set of connection capabilities to QDBusConnection

The capabilities are negotiated with the D-Bus peer or bus at
connection time and may include extra features not available when
D-Bus 1.0 was released.

Currently (as of D-Bus 1.4), the only additional feature is Unix file
descriptor passing.

Proposed features are "maybe types" and single-precision floating
point. They may be added to D-Bus 1.6.

Task-number: QTBUG-17478

4 files changed, 31 insertions, 2 deletions

diff --git a/src/dbus/qdbusconnection.cpp b/src/dbus/qdbusconnection.cpp
index 1fb11bc..4883a4d 100644
--- a/src/dbus/qdbusconnection.cpp
+++ b/src/dbus/qdbusconnection.cpp
@@ -248,6 +248,17 @@ void QDBusConnectionManager::setConnection(const QString &name, QDBusConnectionP
 */
 
 /*!
+    \since 4.8
+    \enum QDBusConnection::ConnectionCapabilities
+    The available capabilities for a D-Bus connection.
+
+    \value UnixFileDescriptorPassing        passing of Unix file descriptors to other processes
+                                            (see QDBusUnixFileDescriptor)
+
+    \sa connectionCapabilities()
+*/
+
+/*!
     Creates a QDBusConnection object attached to the connection with name \a name.
 
     This does not open the connection. You have to call connectToBus() to open it.
@@ -948,6 +959,18 @@ QString QDBusConnection::name() const
 }
 
 /*!
+    \since 4.8
+
+    Returns the capabilities of this connection as negotiated with the bus
+    server or peer. If this QDBusConnection is not connected, this function
+    returns no capabilities.
+*/
+QDBusConnection::ConnectionCapabilities QDBusConnection::connectionCapabilities() const
+{
+    return d ? d->capabilities : ConnectionCapabilities(0);
+}
+
+/*!
     Attempts to register the \a serviceName on the D-Bus server and
     returns true if the registration succeeded. The registration will
     fail if the name is already registered by another application.
diff --git a/src/dbus/qdbusconnection.h b/src/dbus/qdbusconnection.h
index c0b9905..6ab0ea2 100644
--- a/src/dbus/qdbusconnection.h
+++ b/src/dbus/qdbusconnection.h
@@ -111,9 +111,13 @@ public:
         UnregisterNode,
         UnregisterTree
     };
-
     Q_DECLARE_FLAGS(RegisterOptions, RegisterOption)
 
+    enum ConnectionCapability {
+        UnixFileDescriptorPassing = 0x0001
+    };
+    Q_DECLARE_FLAGS(ConnectionCapabilities, ConnectionCapability)
+
     QDBusConnection(const QString &name);
     QDBusConnection(const QDBusConnection &other);
     ~QDBusConnection();
@@ -124,6 +128,7 @@ public:
     QString baseService() const;
     QDBusError lastError() const;
     QString name() const;
+    ConnectionCapabilities connectionCapabilities() const;
 
     bool send(const QDBusMessage &message) const;
     bool callWithCallback(const QDBusMessage &message, QObject *receiver,
diff --git a/src/dbus/qdbusconnection_p.h b/src/dbus/qdbusconnection_p.h
index 85308c1..36f7c53 100644
--- a/src/dbus/qdbusconnection_p.h
+++ b/src/dbus/qdbusconnection_p.h
@@ -262,6 +262,7 @@ signals:
 
 public:
     QAtomicInt ref;
+    QDBusConnection::ConnectionCapabilities capabilities;
     QString name;               // this connection's name
     QString baseService;        // this connection's base service
 
diff --git a/src/dbus/qdbusintegrator.cpp b/src/dbus/qdbusintegrator.cpp
index 14138e0..77c4223 100644
--- a/src/dbus/qdbusintegrator.cpp
+++ b/src/dbus/qdbusintegrator.cpp
@@ -967,7 +967,7 @@ void QDBusConnectionPrivate::deliverCall(QObject *object, int /*flags*/, const Q
 extern bool qDBusInitThreads();
 
 QDBusConnectionPrivate::QDBusConnectionPrivate(QObject *p)
-    : QObject(p), ref(1), mode(InvalidMode), connection(0), server(0), busService(0),
+    : QObject(p), ref(1), capabilities(0), mode(InvalidMode), connection(0), server(0), busService(0),
       watchAndTimeoutLock(QMutex::Recursive),
       rootNode(QString(QLatin1Char('/')))
 {