Re: NetworkManager D-Bus Interface in C++ and Qt

[Chris Hessing <chris hessing cloudpath net>]

> Hello, I want to add NetworkManager D-Bus Interface to my project 
> (http://gitorious.org/yeos).
> I saw the official specification 
> (http://projects.gnome.org/NetworkManager/developers/spec.html) and I 
> made tests, but I can't use the NetworkManager D-Bus Interface in my 
> project.
> I have the NetworkManager libs installed on Ubuntu 9.04 Jaunty, and I am 
> working in C++ with the Qt libraries.
> I saw the code of nm-applet and KNetworkManager but they need other 
> extra libraries.
> Can you put me a code example of how use the NetworkManager D-Bus 
> Interface in C++ with Qt libraries?
> Thanks for your attention,
> Luis Iv?n Cuende
>
>   



Luis -

Depending on what you want to do, it can be really easy, or really 
painful.  A good place to start is the qdbusxml2cpp tool that is 
included with Qt when it is built with support for DBus.   Using that 
tool, you can generate a lot of the code you need by using the 
introspection files that are included in the network manager source 
code.   Once those classes are generated, they are easy to use.   DBus 
events show up as Qt signals.  DBus calls are method calls.  All the 
DBus work happens behind the scenes.

However, you will probably run in to some issues right off the bat with 
a lot of the introspection files in NetworkManager.   The qdbusxml2cpp 
program is pretty simple minded when it comes to the signatures that it 
supports.   As soon as you hit a signature of any complexity the tool 
will error out.  If you don't need the method that has the complex 
signature, you can comment it out, and run the tool again.

For the more complex ones, you are going to have to put the code 
together yourself.  Fortunately, making the DBus calls isn't terribly 
difficult.   Building the queries and parsing the responses is a 
different story.

Unfortunately, it seems to be difficult to find any useful information 
on the net about how to do what you want to do.  I managed to figure 
some of it out with a significant amount of trial and error.

Here is a bit of code that gets a list of devices from Network Manager 
using Qt.  (The hard way.)   I have removed most of the error checking 
to make the code a little easier to follow  -- hope this helps :

QStringList *NetworkManager::getDevices()
{
   QStringList *myList = NULL;
   QDBusConnection bus = QDBusConnection::systemBus();
   QDBusInterface dbus_interface("org.freedesktop.NetworkManager", 
"/org/freedesktop/NetworkManager",
                                 "org.freedesktop.NetworkManager", bus);
   QDBusMessage reply = dbus_interface.call("GetDevices");

   // Make sure that result contains a reply.
   if (reply.type() == QDBusMessage::ReplyMessage)
   {
       // If it is the reply we expect, it should be a QDBusArgument
       if (reply.arguments().at(0).canConvert<QDBusArgument>())
       {
           // That contains an Array of QStrings holding our Device list.
           QDBusArgument myArg = 
reply.arguments().at(0).value<QDBusArgument>();
           if (myArg.currentType() == QDBusArgument::ArrayType)
           {
               myArg.beginArray();

               // Get memory for our resulting string list.
               myList = new QStringList();
               myList->clear();             // It should already be 
clear, but just to be safe.

               while (!myArg.atEnd())
               {
                   QString myElement = qdbus_cast<QString>(myArg);
                   myList->append(myElement);
               }
               myArg.endArray();
           }
       }
   }
   return myList;
}