[fpc-pascal] D-Bus. Non blocking listening for signals

[Henry Vermaak]

On 13/01/11 15:00, Henry Vermaak wrote:
> On 13/01/11 12:24, dibo20 at wp.pl wrote:
>>
>> "integrate the GLib event loop with an external event loop" - I think
>> this is what I want.
>
> What you want to do is to integrate the dbus connection into your main
> loop (in this case glib). Let me quote from the documentation:
>
> "If you're using GLib or Qt add-on libraries for D-Bus, there are
> special convenience APIs in those libraries that hide all the details of
> dispatch and watch/timeout monitoring. For example,
> dbus_connection_setup_with_g_main().
>
> "If you aren't using these add-on libraries, but want to process
> messages asynchronously, you must manually call
> dbus_connection_set_dispatch_status_function(),
> dbus_connection_set_watch_functions(),
> dbus_connection_set_timeout_functions() providing appropriate functions
> to integrate the connection with your application's main loop. This can
> be tricky to get right; main loops are not simple."
>
> If you look at the dbus_connection_set_watch_functions documentation:
>
> http://dbus.freedesktop.org/doc/api/html/group__DBusConnection.html#gaebf031eb444b4f847606aa27daa3d8e6
>
>
> You'll see that this will provide you will file descriptors that you can
> add to your main loop to watch for the dbus events.
>
> This is all _much_ simpler if you use the dbus-glib functions:
>
> http://www.ibm.com/developerworks/linux/library/l-dbus.html
>
> It doesn't look like that header has been translated to pascal, yet.
> That doesn't matter, since it's now considered obsolete, since glib has
> dbus support now:
>
> http://www.freedesktop.org/wiki/Software/DBusBindings
>
> fpc doesn't seem to have bindings for that, either...

Having said all of this, you can get around this by calling blocking 
dbus calls in a thread and notifying the user interface by virtue of 
Synchronize, PostMessage and QueueAsycCall.

Henry