Code snippets demonstrating how to send a notification to the user in GNOME-shell 3.2, 3.4 and 3.6

3.2_3.4_icon_in_notification.js

/** GNOME 3.2 and 3.4: sending a notification to the user.
 * In this example we provide the Source's icon through the notification rather than the source
 * (note the 'icon:' property in the object provided as the fourth parameter to the Notification.)
 */
// 1. Make a source
let source = new MessageTray.Source("source title");
// 2. Make a notification
let notification = new MessageTray.Notification(source,
                                                "notification title",
                                                "notification message",
                                                {icon: new St.Icon({
                                                    icon_name: 'avatar-default',
                                                    icon_size: source.ICON_SIZE
                                                })});
// 3. Add the source to the message tray
Main.messageTray.add(source);
// 4. notify!
source.notify(notification);

3.2_3.4_icon_in_source.js

/** GNOME 3.2 and 3.4: sending a notification to the user.
 * In this example we provide the Source's icon by subclassing Source and implementiong createNotificationIcon.
 * Once this is done, sending the ntification is quite simple.
 */
const MySource = new Lang.Class({
    Name: 'MySource',
    Extends: MessageTray.Source,
    _init: function (title) {
        // call the parent constructor
        this.parent(title); 
        // set our icon
        this._setSummaryIcon(this.createNotificationIcon());
    },

    // this should return an icon to show in the message tray. You can use
    // this.ICON_SIZE for a default icon size if you want.
    createNotificationIcon: function () {
        return new St.Icon({
            icon_name: 'avatar-default',
            icon_size: this.ICON_SIZE
        });
    }
}); 

/** Send the notification with our new source! */
// 1. Make a source
let source = new MySource("source title");
// 2. Make a notification
let notification = new MessageTray.Notification(source,
                                                "notification title",
                                                "notification message");
// 3. Add the source to the message tray
Main.messageTray.add(source);
// 4. notify!
source.notify(notification);

3.6_send_notification.js

/** GNOME 3.6: sending a notification to the user.
 * In GNOME 3.6 one can provide the Source and Notification icons by passing in
 * the icon name to the Source constructor.
 * Much simpler than GNOME 3.2 or GNOME 3.4.
 */
// 1. Make a source
let source = new MessageTray.Source("source title", 'avatar-default');
// 2. Make a notification
let notification = new MessageTray.Notification(source,
                                                "notification title",
                                                "notification message");
// 3. Add the source to the message tray
Main.messageTray.add(source);
// 4. notify!
source.notify(notification);