In an earlier post I looked at how I could add my own icon to the Gnome Notification area from my Mono C# applications. The next thing I wanted to do was to show a notification in the taskbar to the user when something truly important happens. If you are running Ubuntu Intrepid (8.10) then its easy to create them from Mono. As I found out, Hoary (8.04) doesn’t include the required libraries.

The standard Mono distribution does not include support for showing Notifications as this functionality is not part of the Gnome standard distribution. Instead Ubuntu and others depend on DBUS and libnotify to deliver their messages. Sebastian Dröge has created the necessary bindings for Mono/C# in libnotify-sharp and these are contained in the Debian/Ubuntu library libnotify0.4-cil.

To install them run:

sudo apt-get install libnotify0.4-cil

There is also a documentation package called monodoc-notify-sharp-manual which you could install it is however completely empty.

To run the demo code (below) simply create a new empty GTK solution in MonoDevelop. You will need to include a reference to libnotify-sharp. In the “Solution” pane, right click “References” and add the “notify-sharp” binding as shown below.

Creating a simple notification is straightforward:

        using Notifications;
        ....
        Notification myNote = new Notification();

        // Use a stock icon, and set the title (summary) and message (body)
        myNote.IconName = Stock.Harddisk;
        myNote.Summary  = "Harddisk fatal error";
        myNote.Body        = "Internal moist levels critical, please man the pumps!";

Each notification has a title (called the summary) and a body. We can also optionally specify an icon and in the code above I have used a stock Gnome icon.

The “AddAction” method allows you to specify one or more actions for a user to click on when the notification is displayed. As the notifications are only displayed for a very short period of time this is probably not such a good place if the required action is truly important.

        // Add an action the user can take to remedy the situation
        myNote.AddAction("DoPump","Start Pump",OnDoSomething);
        myNote.AddAction("DoRun","Run!",OnDoSomething);

The first parameter is passed to the user specified handling function. The second is the name of the action as displayed on the notification.

There are three levels of urgency for our notifications: Low, Normal and Critical. The difference to your user is probably just in the color of the notification.

        // The color of the notification changes depending on urgency
        myNote.Urgency = Urgency.Critical;

Finally we need to show the notification:

        // Show the notification on the desktop
        myNote.Show();

Wrapping up

Unrelated to displaying notification messages from Mono I came across a post by Luc Castera showing how you can simply show these notifications from a shell script:

• Install libnotify-bin: sudo aptitude install libnotify-bin
• From a script, call it: notify-send ‘title of notification’ ‘body of notification’

Source Code

If you created an empty GTK project from MonoDevelop then the following should replace MainWindow.CS:

// MainWindow.cs created with MonoDevelop
// User: martijn at 10:04 AM 1/5/2009
//
// To change standard headers go to Edit->Preferences->Coding->Standard Headers
//
using System;
using Gtk;
using Notifications;

public partial class MainWindow: Gtk.Window
{
    public MainWindow (): base (Gtk.WindowType.Toplevel)
    {
        Build ();

        Button myButton = new Button("Send Notification");
        myButton.Clicked += OnButtonClickedEvent;
        myButton.Show();

        Add(myButton);

    }

    protected void OnDeleteEvent (object sender, DeleteEventArgs a)
    {
        Application.Quit ();
        a.RetVal = true;
    }

    protected void OnButtonClickedEvent (object sender, EventArgs a)
    {
        Notification myNote = new Notification();

        // Use a stock icon, and set the title (summary) and message (body)
        myNote.IconName = Stock.Harddisk;
        myNote.Summary  = "Harddisk fatal error";
        myNote.Body     = "Internal moist levels critical, please man the pumps!";

        // Add an action the user can take to remedy the situation
        myNote.AddAction("DoPump","Start Pump",OnDoSomething);
        myNote.AddAction("DoRun","Run!",OnDoSomething);

        // The color of the notification changes depending on urgency
        myNote.Urgency = Urgency.Critical;  

        // Show the notification on the desktop
        myNote.Show();

    }

    protected void OnDoSomething( object sender, ActionArgs args )
    {
        string TheResult = "";

        switch((string)args.Action)
        {
            case "DoPump" : TheResult = "Pumping failed, head for the hills!"; break;
            case "DoRun"  : TheResult = "Hiding is fine, come back later!"; break;
            default:         TheResult = "Not supposed to happen!"; break;
        }

        MessageDialog myDialog = new MessageDialog(this,
                                                   DialogFlags.DestroyWithParent,
                                                   MessageType.Error,
                                                   ButtonsType.Ok,
                                                   TheResult );

        myDialog.Run();
        myDialog.Destroy();
    }
}

This is a post from Martijn's C# Coding Blog.

Cool (Linux) applications have their own icon in the notification area. To add my own icon in the Gnome notification area using Mono only took a few lines of code. In the post below I show how you can add your icon and associate a tooltip and right click menu to it.

GTK provides the StatusIcon class to register your own icon in the notification area.

    StatusIcon  myStatusIcon;

You can provide and load your own icon, but for this example I used one of the GTK stock icons.

     myStatusIcon = StatusIcon.NewFromStock(Stock.Harddisk);  // I use a stock icon from Stock.*
                                                                                          // to avoid having to include an icon file
     myStatusIcon.Visible = true;                                             // Make sure we are displayed

Adding or changing a tooltip is as straighforward as assigning it:

      myStatusIcon.Tooltip = "Hello World ToolTip";                      // The message to show when the mouse hovers over the icon

To create a rightclick menu we need to register the PopupMenu event handler:

     myStatusIcon.PopupMenu += OnStatusIconPopupMenu;         // Link in the right click popup menu
     ...
     ...

    /* The Status Popup menu is shown when the user right clicks on the toolbar icon */

    protected void OnStatusIconPopupMenu(object sender, EventArgs e)
    {
        Menu popupMenu = new Menu();

        MenuItem helloItem = new MenuItem("About Hello World");
        helloItem.Show();
        helloItem.Activated += new EventHandler(OnHelloAboutActivated);

        popupMenu.Append(helloItem);
        popupMenu.Popup(null,null,null,3,Gtk.Global.CurrentEventTime);
    }

And that is really all there is to it. I have included the complete code below. If you create a new GTK solution in MonoDevelop you will end up with two files, Main.cs and MainWindows.Cs. Replace the MainWindow.CS file with the content below:

using System;
using Gtk;

public partial class MainWindow: Gtk.Window
{
	StatusIcon  myStatusIcon;
	AboutDialog aboutDialog;

	public MainWindow (): base (Gtk.WindowType.Toplevel)
	{

		/* The following lines create the notification area status icon */
		/* Make it visible and link in the right click popup menu       */ 

		myStatusIcon = StatusIcon.NewFromStock(Stock.Harddisk);  // I use a stock icon from Stock.*
		                                                         // to avoid having to include an icon file
		myStatusIcon.Tooltip = "Hello World ToolTip";            // The message to show when the mouse hovers over the icon
		myStatusIcon.Visible = true;                             // Make sure we are displayed
		myStatusIcon.PopupMenu += OnStatusIconPopupMenu;         // Link in the right click popup menu 

		/* Not necessary */
		Label AppWindowLabel = new Label("Hello World");
		this.Add(AppWindowLabel);

		Build ();
	}

	/* Called when the main application closes */

	protected void OnDeleteEvent (object sender, DeleteEventArgs a)
	{
		Application.Quit ();
		a.RetVal = true;
	}

	/* The Status Popup menu is shown when the user right clicks on the toolbar icon */

	protected void OnStatusIconPopupMenu(object sender, EventArgs e)
	{
		Menu popupMenu = new Menu();

		MenuItem helloItem = new MenuItem("About Hello World");
		helloItem.Show();
		helloItem.Activated += new EventHandler(OnHelloAboutActivated);

		popupMenu.Append(helloItem);
		popupMenu.Popup(null,null,null,3,Gtk.Global.CurrentEventTime);
	}

	/* If the user select the "About Hello World" menu option, we show the about dialog */

	protected void OnHelloAboutActivated(object sender, EventArgs e)
	{
		aboutDialog = new AboutDialog();

		aboutDialog.ProgramName = "The About Dialog Popup Demo";
		aboutDialog.Version = "1.0beta";
		aboutDialog.Comments = "The best things in life are simple!";
		aboutDialog.License = "Creative Commons";
		aboutDialog.Authors = new string[] { "Martijn Dijksterhuis" };
		aboutDialog.Website = "http://www.dijksterhuis.org";
		aboutDialog.Response += new ResponseHandler(OnHelloAboutClose);

		aboutDialog.Run();
	}

	/* Catch the "Close" and "X" button event from the about dialog box */

	protected void OnHelloAboutClose(object sender, ResponseArgs e)
	{
		if (e.ResponseId==ResponseType.Cancel || e.ResponseId==ResponseType.DeleteEvent)
		 aboutDialog.Destroy();
	}

}

This is a post from Martijn's C# Coding Blog.