4 replies to this topic

[theonejb]

I'm trying to program an application that activates when ever the charging status of my laptop changes (from charging to discharging or vice versa). Is there any way in which I can make my application get notified of the event?

I'd like to program in C++, but if thats not possible, I'd be happy to do so in some other language as well.

[CallBackGuy]

Here some python code that uses dbus/HAL to connect to your laptops ac_adapter and receives a signal when it's unplugged/plugged in.
Maybe you can try to port it to C++, I'm sure there is dbus/gobject header files for C++?

import gobject
import dbus, dbus.service, dbus.mainloop.glib

def on_device_event (arg, dbarry):
    if dev.GetProperty ('ac_adapter.present'):
        print "Battery is charging"
    else:
        print "Battery is discharging"

dbus.mainloop.glib.DBusGMainLoop (set_as_default=True)
bus = dbus.SystemBus ()
hal_obj = bus.get_object ('org.freedesktop.Hal', '/org/freedesktop/Hal/Manager')
hal = dbus.Interface (hal_obj, 'org.freedesktop.Hal.Manager')
   
dev_obj = bus.get_object("org.freedesktop.Hal", hal.FindDeviceByCapability("ac_adapter")[0])
dev = dbus.Interface(dev_obj, "org.freedesktop.Hal.Device")
dev.connect_to_signal("PropertyModified", on_device_event)

mainloop = gobject.MainLoop()
mainloop.run()

EDIT: Oh. A bit late of a reply, hopefully this is still helpful for him or someone else.

[theonejb]

Thanks for the reply, I however have already solved the problem. I used the EXACT same technique as you, just in C++. :thumbup:
Still, thnx...

[chili5]

Neat, how did you do it in C++?

[theonejb]

Here's the code snippet for connecting to the DBus and registering a call back. It uses the PowerManagement app. for the callback:

 g_type_init();


  // connect to the DBus

  DBusGConnection *connection;

  GError *error;


  error = NULL;

  connection = dbus_g_bus_get(DBUS_BUS_SESSION, &error);


  // if failed, display error and quit

  if (connection == NULL) {

    g_printerr("ERROR: Unable to connect to DBus.\n");

    g_error_free(error);

    exit(1);

  } else {

    g_print("Success: Connection to DBus succeeded. Proceeding...\n");

  }


  // connect to the PowerManager

  DBusGProxy *proxy;

  const char *name = "org.freedesktop.PowerManagement";

  const char *path = "/org/freedesktop/PowerManagement";

  const char *interface = "org.freedesktop.PowerManagement";


  error = NULL;

  proxy = dbus_g_proxy_new_for_name(connection, name, path, interface);


  // check for errors

  if (proxy == NULL) {

    g_printerr("ERROR: Unable to connect to the PowerManagement Applet.\n");

    g_error_free(error);

    exit(1);

  } else {

    g_print("Success: Connected to PowerManagement Applet. Proceeding...\n");

  }


  // connect to the OnBatteryChanged signal

  GMainLoop *loop = g_main_loop_new(NULL, FALSE);

  const char *sName = "OnBatteryChanged";

  dbus_g_proxy_add_signal(proxy, sName,G_TYPE_BOOLEAN, G_TYPE_INVALID);

  dbus_g_proxy_connect_signal(proxy, sName, G_CALLBACK(onBatCh), NULL, NULL);

  g_print("Success: Connected callback to signal.\n");

Heres the link to the complete application that I needed to implement the DBus connection in:

~surfer-a1/wateen-manager/origin : contents of AC.c at revision 1