Posts Tagged ‘vala’

Programming in Vala

January 18th, 2011

As some of you may know, I work for an open source software non-profit called Yorba. Our best known product is Shotwell, a photo management application that’s similar to Picasa or iPhoto, but created for Linux. It’s the default photo app these days in both Ubuntu and Fedora.

What many of our users don’t know is we don’t develop our software in C or C++… we use Vala.

So what the hell is Vala?

The cool thing about Vala is that it’s a fully compiled, statically typed OOP language designed to be built for Gtk applications. The syntax is very similar to Java or C#, but the garbage collection is based entirely on reference counting. In other words, you get the simplicity of a modern language with the speed of a fully compiled program. Vala bindings are already available for Gtk, Gdk, GLib, Gee, and many other libraries. Or you can create your own bindings when needed by creating a Vapi file. There’s a documentation program, Valadoc, which generates pretty HTML documentation for your classes.

The entire Vala package is available under an LGPL license, which is a free software/open source license. You’ll never have to worry about Microsoft or Oracle stepping on your toes.

Here’s the “Hello World” app from the Vala tutorial.

class Demo.HelloWorld : GLib.Object {
    public static int main(string[] args) {
        stdout.printf("Hello, World\n");
        return 0;
    }
}

Save your file as hello.vala. You can compile from the command line with:
valac hello.vala
Now watch closely… the Vala compiler actually just creates a .c file! It’s what’s called a “source compiler” in that it converts source code from one language to source code in a different language.

Next, valac automatically invokes GCC to compile the .c file into an executable binary.

Run your demo code with:
./hello

Simple, huh?

Vala syntax includes the language constructs you’d expect in 2011, including:

  • interfaces
  • single inheritance
  • non-nullable variables
  • foreach loops
  • delegates
  • signals
  • reflection
  • built-in multidimensional arrays
  • type inference

There’s plenty more sample code and tutorials on Gnome’s Vala site.

Documentation for some of the most common library bindings is available at Valadoc.org.

Okay, ready for the bad news? Despite being a relatively feature-complete language, there’s really no perfect IDE for Vala yet. If you’re used to powerful graphical debuggers, class browsers, and jumping around the code like in Eclipse and Visual Studio, you’re out of luck.

The only Vala IDEs at the moment are:

  • MonoDevelop: A great start, but for the features it’s rather heavy.
  • Valide: I was never able to get this one to even compile! But the screenshots look promising.
  • Valencia: This is Yorba’s GEdit plugin, which provides only barebones Vala functionality on top of GEdit, including jump to definition and autocomplete.

So there you go, that’s Vala. It’s still a young language, but it takes away the headaches of developing Gtk apps in C, and it doesn’t have the uncomfortable legacies of C++. Give it a shot!