power-manager-button.c

        if (button->priv->range)
            gtk_range_set_value (GTK_RANGE (button->priv->range), level);
    }
}

static gboolean
brightness_set_level_with_timeout (PowerManagerButton *button)
{
    gint32 range_level, hw_level;

    TRACE("entering");

    range_level = (gint32) gtk_range_get_value (GTK_RANGE (button->priv->range));

    xfpm_brightness_get_level (button->priv->brightness, &hw_level);

    if ( hw_level != range_level )
    {
        xfpm_brightness_set_level (button->priv->brightness, range_level);
    }

    if (button->priv->set_level_timeout)
    {
        g_source_remove(button->priv->set_level_timeout);
        button->priv->set_level_timeout = 0;
    }

    return FALSE;
}

static void
range_value_changed_cb (PowerManagerButton *button, GtkWidget *widget)
{
    TRACE("entering");

    if (button->priv->set_level_timeout)
        return;

    button->priv->set_level_timeout =
        g_timeout_add(SET_LEVEL_TIMEOUT,
                      (GSourceFunc) brightness_set_level_with_timeout, button);
}

static void
range_scroll_cb (GtkWidget *widget, GdkEvent *event, PowerManagerButton *button)
{
    GdkEventScroll *scroll_event;

    TRACE("entering");

    scroll_event = (GdkEventScroll*)event;

    if (scroll_event->direction == GDK_SCROLL_UP)
        increase_brightness (button);
    else if (scroll_event->direction == GDK_SCROLL_DOWN)
        decrease_brightness (button);
}

static void
range_show_cb (GtkWidget *widget, PowerManagerButton *button)
{
    TRACE("entering");
    /* Release these grabs they will cause a lockup if pkexec is called
     * for the brightness helper */
    gdk_pointer_ungrab(GDK_CURRENT_TIME);
    gdk_keyboard_ungrab(GDK_CURRENT_TIME);
    gtk_grab_remove(widget);
}

static void
power_manager_button_show_menu (PowerManagerButton *button)
{
    GtkWidget *menu, *mi, *img = NULL;
    GdkScreen *gscreen;
    GList *item;
    gboolean show_separator_flag = FALSE;
    gint32 max_level, current_level = 0;

    if(gtk_widget_has_screen(GTK_WIDGET(button)))
        gscreen = gtk_widget_get_screen(GTK_WIDGET(button));
    else
        gscreen = gdk_display_get_default_screen(gdk_display_get_default());

    menu = gtk_menu_new ();
    gtk_menu_set_screen(GTK_MENU(menu), gscreen);
    /* keep track of the menu while it's being displayed */
    button->priv->menu = menu;
    g_signal_connect(GTK_MENU_SHELL(menu), "deactivate", G_CALLBACK(menu_destroyed_cb), button);

    for (item = g_list_first (button->priv->devices); item != NULL; item = g_list_next (item))
    {
        BatteryDevice *battery_device = item->data;

        power_manager_button_menu_add_device (button, battery_device, TRUE);
        /* If we add an item to the menu, show the separator */
        show_separator_flag = TRUE;
    }

    if (show_separator_flag)
    {
        /* separator */
        mi = gtk_separator_menu_item_new();
        gtk_widget_show(mi);
        gtk_menu_shell_append(GTK_MENU_SHELL(menu), mi);
    }

    /* Display brightness slider - show if there's hardware support for it */
    if ( xfpm_brightness_has_hw (button->priv->brightness) )
    {
        GdkPixbuf *pix;

        max_level = xfpm_brightness_get_max_level (button->priv->brightness);

        mi = scale_menu_item_new_with_range (button->priv->brightness_min_level, max_level, 1);

        /* attempt to load and display the brightness icon */
        pix = gtk_icon_theme_load_icon (gtk_icon_theme_get_default (),
                                       XFPM_DISPLAY_BRIGHTNESS_ICON,
                                       32,
                                       GTK_ICON_LOOKUP_GENERIC_FALLBACK,
                                       NULL);
        if (pix)
        {
            img = gtk_image_new_from_pixbuf (pix);
            gtk_image_menu_item_set_image (GTK_IMAGE_MENU_ITEM(mi), img);
        }

        scale_menu_item_set_description_label (SCALE_MENU_ITEM(mi), _("<b>Display brightness</b>"));

        /* range slider */
        button->priv->range = scale_menu_item_get_scale (SCALE_MENU_ITEM (mi));

        /* update the slider to the current brightness level */
        xfpm_brightness_get_level (button->priv->brightness, &current_level);
        gtk_range_set_value (GTK_RANGE(button->priv->range), current_level);

        g_signal_connect_swapped (mi, "value-changed", G_CALLBACK (range_value_changed_cb), button);
        g_signal_connect (mi, "scroll-event", G_CALLBACK (range_scroll_cb), button);
        g_signal_connect (menu, "show", G_CALLBACK (range_show_cb), button);

        gtk_widget_show_all (mi);
        gtk_menu_shell_append(GTK_MENU_SHELL(menu), mi);
    }

    /* Presentation mode checkbox */
    mi = gtk_check_menu_item_new_with_mnemonic (_("Presentation _mode"));
    gtk_widget_set_sensitive (mi, TRUE);
    gtk_widget_show (mi);
    gtk_menu_shell_append(GTK_MENU_SHELL(menu), mi);
    xfconf_g_property_bind(button->priv->channel,
                           PROPERTIES_PREFIX PRESENTATION_MODE,
                           G_TYPE_BOOLEAN, G_OBJECT(mi), "active");

    /* Power manager settings */
    mi = gtk_menu_item_new_with_mnemonic (_("_Power manager settings..."));
    gtk_widget_show(mi);
    gtk_menu_shell_append(GTK_MENU_SHELL(menu), mi);
    g_signal_connect(G_OBJECT(mi), "activate", G_CALLBACK(xfpm_preferences), NULL);

    gtk_menu_popup (GTK_MENU (menu),
                    NULL,
                    NULL,
#ifdef XFCE_PLUGIN
                    xfce_panel_plugin_position_menu,
#else
                    NULL,
#endif
                    button->priv->plugin,
                    0,
                    gtk_get_current_event_time ());
}