Archive for the ‘Gnome’ Tag

gnome-shell: first impressions

I’ve been trying out gnome-shell for the last week. My impression so far:

* As to be expected it feels very rough
* It needs more keyboard bindings (e.g. in the Activities tab)
* Why is the clock the only interface element in the middle of the top-bar? Put that space to use, for Darwin’s sake! What about putting the applications menu bar up there? 😀
* Unusable without proprietary drivers, at least on NVidia hardware. Didn’t try it on AMD or Intel hardware

Now, that all sounds terrible negative. But in the end I’m quite optimistic. By being willing to break with the traditional desktop paradigm, the gnome-shell people are able to experiment with a plethora of new ideas. Finally workspaces are being put to use as a central metaphor not only as an afterthought. I also think that by using workspaces, MDI applications finally could get useful. I’m also looking forward to the integration of application notification and communication (through telepathy). The design document was very promising, I wonder how it all works out.

Application development with Vala – First Steps: Getting the Vala feeling

Thanks to undeconstructed from #vala at

In the last few weeks I’ve been playing around with Vala, and enjoying it. “What the heck is Vala”, you might ask, and of course you will get an explanation. Not only because Vala, though still in its infancy, hasn’t gotten the attention it deserves.

Vala is, in some sense, a new programming language. It’s syntax and structure leans heavily towards C#. As Jürg Billeter, the mastermind behind Vala, likes to put it; Vala is an amalgam of different C inspired languages, mostly C++ and C#. An though there is no mercury in this mixture, you’ll find many a gold nugget in Vala.

“Why another programming language? Aren’t there enough out there yet?” might be your next question. And of course this also deserves an explanation. Yes, there is an awful lot of programming languages out there. But what makes Vala special is it’s unique combination of high-level programming and low-level interface. You see; even though Vala supports modern programming language features like objects, foreach-loops, generics, annotations, memory management and exception handling, Vala is very slim. It doesn’t require a virtual machine. Indeed; Vala compiles are binary compatible to C. You can use C libraries from within Vala, you can even use Vala libraries from C. That’s because Vala, at it’s core, still builds upon the foundations of C. But more on that later. First, let’s take a look at a piece of Vala code.

int main (string[] argv) {
        stdout.printf ("Hello, World!\n");
        return (0);

Well, that does look familiar, doesn’t it? All control structures (for-loop, while-loop, switch/case, if/else, …) behave like their C counterparts. Vala is very much like C, although there are some peculiarities. Like that string-datatype, and that stdout-whatsit.

Having stored this piece of code in a file called hello0.vala, it can be compiled:

valac hello0.vala

No rocket science thus far. The resulting binary can be executed and will result in following output:

Hello, World!

Now that we have made ourselves a little bit comfortable with the Vala tool chain, let’s take a look at some of the more interesting features Vala has to offer. That string data type, for example.
In our main function, we’ve defined a single input parameter. string[] argv; an array of strings. But other than simple C arrays, this is not only a block of continuous memory. It’s an object by itself and thus has properties we can inspect. It’s length, for example.

int main (string[] argv) {
	stdout.printf ("Argument vector length: %i\n", argv.length);
	return (0);

There is more. Using the foreach-loop we can even iterate over this array.

int main (string[] argv) {
	foreach (string arg in argv) {
		stdout.printf ("Argument: %s", arg);
	return (0);

Neat, isn’t it? But Vala has even more to offer. Like Classes. Everyone likes classes, so let’s make some! Animals are always good for examples, so I’ll use them as well.

public class Animal {
	public string name;
	public bool can_fly;
	public bool can_swim;
	public bool can_walk;
	public string noise;

	public string make_noise () {
		return (this.noise);

int main (string[] argv) {
	Animal dog0 = new Animal ();
	dog0.can_fly = false;
	dog0.can_walk = true;
	dog0.can_swim = true;
	dog0.noise = "Whuff";

	dog1.can_fly = false;
	dog1.can_walk = true;
	dog1.can_swim = true;
	dog1.noise = "Whuff";

	stdout.printf ("dog0: %s", dog1.make_noise ());
	stdout.printf ("dog1: %s", dog1.make_noise ());

This little example already shows some features of Vala. Obviously there are classes, with members and methods. But this example isn’t very sophisticated. Let’s try something more interesting. For example, let’s replace those booleans with a bitmap, bring in some generics and inheritance.

public enum Locomotion {
	NONE =  0,
	WALK =  1,
	SWIM =  2,
	FLY  =  4,
	EVERYTHING = Locomotion.WALK | Locomotion.SWIM | Locomotion.FLY

public abstract class Animal : Object {
	public string noise		{ public get; construct; }
	public Locomotion locomotion	{ public get; construct; }
	public string make_noise () {
		return this.noise;
	construct {
		this.locomotion = Locomotion.NONE;
		this.noise = "";
	public abstract string introduce ();

public class Dog : Animal {
	public string name { private get; construct; }
	Dog (string name) { = name;
	construct {
		this.locomotion = Locomotion.WALK | Locomotion.SWIM;
		this.noise = "Whuff";

	public override string introduce () {
		return ("My name is " +;

public class Finch : Animal {
	construct {
		this.locomotion = Locomotion.WALK | Locomotion.FLY;
		this.noise = "Tchirp";
	public override string introduce () {
		return ("Buggeroff");
public class Fish : Animal {
	construct {
		this.locomotion = Locomotion.SWIM;
		this.noise = "Blubb";
	public override string introduce () {
		return (this.noise);
public class Bass : Fish {
	public string name { public get; construct; }

	Bass (string name) { = name;
	public override string introduce () {
		return ("I am " +;

int main (string[] argv) {
	List<Animal> a_list = new List<Animal> ();
	Dog wulfie = new Dog ("Wulfie");
	Finch bert = new Finch ();
	Bass bob = new Bass("Bob");
	a_list.append (wulfie);
	a_list.append (bert);
	a_list.append (bob);

	foreach (Animal a in a_list) {
		string loc = "i can";
		if ((a.locomotion & Locomotion.FLY) == Locomotion.FLY )
			loc = loc + " fly";
			loc = loc + "'t fly";
		stdout.printf ("(%s)\t%s: %s, %s \n", a.get_type ().name (),  a.make_noise (),  a.introduce (), loc);
	return (0);

As you can see, Vala supports all features you’d expect from a modern programming language. Classes, abstract classes, inheritance, generics, method overloading and so on. And still there are many features I didn’t touch in this essay, like interfaces, signals, exceptions, namespaces, access level modifiers, lambda functions and packages. And most important; Vala provides memory management, freeing the developers of most the hassles usually associated with low-level application programming.

So with all those fancy features, how can Vala still be compatible to C? It’s because valac, the Vala compiler, uses the GLib type system for its underlying framework; Vala code is translated to plain C code with hooks to GLib and (if one uses GLib.Object as superclass) GObject. This generated code in turn is compiled by GCC. Vala applications thus are native binaries, requiring neither an interpreter nor a virtual machine.

Vala provides (very) complete mappings to many important Unix C libraries, such as stdlib, D-Bus, Cairo, SDL, Poppler. And of course, with its roots deep in GLib, Vala also supports the Gtk+ framework and all related libraries. The excellent libgee, also developed in Vala, provides array lists, hashes, sets and collections. Use of the pkg-config system makes using libraries very easy. And as soon as GObject introspection is in place, bindings to all kinds of scripting languages come with the package for free.

Vala, now at version 0.3.4, is still under heavy development. My first experiments have already uncovered some bugs, which got fixed immediately. Vala might still need some time to come of age, but already it is picking up momentum, as the first projects start to use it. Especially developers with an aversion towards C++ might find Vala interesting, for it links the solid GLib type and event system with an elegant syntax, providing all the necessary tools for rapid application development on a stable foundation.


Vala (Project site)

GTK+ 3.0: Getting serious.

GTK+ has come a long way. From its humble beginnings as “The GIMP ToolKit”, it is now used in a plethora of applications. In fact, GTK+ is very popular. GNOME, one of the leading desktop environment on Unix systems, uses GTK+ almost exclusively. The Gimp is built upon GTK+, of course. And there are many commercial software developers like Adobe, NVidia and VMware that decided to use it as a base for their products.

Still, there are several shortcomings with GTK+. Development of the 2.x series started back in 2002. Since then, GTK+ has ripened and aged. It has aged well, but still: its age shows.  Throughout the 2.x cycle, several years now, the developers have kept GTK+ ABI compatible. This keeps application developers depending on GTK+ very happy:  they can be sure that code linked to an older version of GTK+ continues to work with newer releases. Packages released back in 2002 will continue to work with new library releases. That’s great, because no third-party application developer likes to rebuild and repackage the whole product line, just because a new version of the underlying libraries got released and all the distribution start packaging that version. It causes work and trouble. And for commercial/proprietary developers that means costs.

The commitment not to break ABI made a lot of people very happy. But it also put very tight constraints on the GTK+ developers. It’s not that easy to add new features and remain ABI compatible. Minor features, yes. But as soon as you want to make radical improvements and need to change the exposed data structures, you run into serious trouble. It just not possible beyond a certain point.

On the 2008 GTK+ Hackfest in Berlin, Imendio’s GTK+ hackers presented their vision [1] of GTK+’s future and the reasons why they think that GTK+ has to make a step forward, embrace change and break ABI compatibility. Other GTK+ developers [2] have also voiced their opinions, listing parts of GTK+ that need serious love, but state that they don’t require breakage.
Whether or not these are the things that will mark the road to GTK+ 3.0, almost all of them need attention. And give hints to the shape of things to come.

Theming is one major aspect of GTK+ that needs a serious overhaul. Theming in GTK+ sucks and blows big time. The initial concept of how theming works in GTK+ stems from the very first releases and never received serious love. As a result it is very difficult to do fancy graphic things in GTK+ or to make custom widgets that fit into the rest of the desktop. The funny look of Evolution’s tree headers in some themes is one symptom, but every developer with the need to write custom widgets is looking for a hard time.
There have been several suggestions on how to do that, some of them involving CSS-style theming [3]. CSS would be nice, for sure. But even the ability to paint one widget to mimick another would be a huge gain. Application-specific theming and custom layouts? Delicious.

Although it is possible to create animations in plain GTK+, it’s not very easy to do. Out of the desire to create fancy interfaces in the image of the iPhone interface arose several GLib/GTK+ inspired libraries; Clutter, Pigment and Moonlight. All of those have drawbacks, however: Clutter doesn’t use the GLib event system, Moonlight is written in C++ (a no-go for a GTK+ library) and Pigment is in a very rough state. Still, there are very solid plans to what extent a scene-graph library might interact with GTK+ and what requirements such a library has to fulfill [4].

GTK+ has no standard Canvas. There is a GnomeCanvas, but it’s deprecated, not very popular and lacks some key features, like drawing GUI. Many developers resort to plain Cairo when it comes to custom graphics, but Cairo is lacking a way to draw GUI elements also. Nothing gained. There are some possible candidates [5] for a possible GTKCanvas, but none of them seems to be the right candidate. And then there is the question, if a specialised canvas is a good idea at all.
This problem might be solved with the emergence of the aforementioned scene-graph library; instead of introducing a specialised library for custom paint operations, make that library the standard way.

OS integration:
GTK+ is not limited to X11 systems anymore. There are many GTK+ applications that have been ported to Windows and enjoy a surprising popularity there; Inkscape for example has a significant Windows user base. And OS X gets more important with every passing month. Some of these applications make extensive use of operating system features. Up to now, GTK+ featured only a limited set of functions to provide access to operating system functions, but the first solutions addressing this problem are starting to appear [6].

One of the GTK+ buzzwords of the last few month has been introspection. Introspection allows to, well, inspect an object, its methods, public members and its inheritance. This is not only very comfortable for debugging, it also allows for very easy bindings: automated bindings for your favourite programming language? Here it comes. It might still be a while until all parts are in place, but already the results are amazing [7].

It might still be a long time until GTK+ 3.0 gets released. And in any way; GTK+ 3.0 won’t be about adding new features. There are still some mistakes of the past lumbering in GTK+. Exposed private structues, public members that get manipulated directly: things like these have to be fixed before a GTK+ 3.2 can start adding features [8].  But with some of the features, especially a scene-graph, window-independent widget placing and over-rideable paint methods for GTK+ widgets, GTK+ is starting to look very interesting again.

[1] Imendio’s GTK+ 3.0 vision
[2] Gtk+ Hackfest 2008: Day one and a half
[3] GUADEC 5 Notes
[4] New Theme API
[5] Canvas Overview
[6] libgtkhotkey 0.1, Portable Hotkey Integration
Future of GNOME language bindings

[8] GTK+ 3.0: Enabling incrementalism