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GObject Introspection and Grilo: A winner combination

About GObject Introspection

A few days ago Adrian Perez wrote about GObject Introspection (abbreviated GI), explaining why it is gaining so much momentum. While you're really encouraged to visit his blog entry to see the work he did on Lua's GI bindings, I'll take some of his words:

In short, it (GObject Introspection) works like this:

• Library developers add annotations to the documentation comments of functions.
• The GI support tools generate XML and compiled API metadata.
• You have a library to use that metadata at runtime.

The last thing is very interesting, especially the runtime usage of metadata... because it enables dynamic language bindings. This means that developers no longer have to build e.g. the Python bindings for themselves but just annotating the source code!

GObject Introspection in Grilo

As Grilo's primary focus is to allow application developers concentrate on making good user interfaces, without having to deal with the low level stuff done at the framework level, we consider very important providing them with the ability to use their language of choice. At the same time, we'd like to avoid devoting time to write manual bindings, and that's the reason we put so much effort on GObject Introspection support: right now, if not all, most of the API is accessible via GI, and we're working to fix the less binding-friendly parts.

Building Grilo with GObject Introspection enabled

The best way to try Grilo from GI is, in my opinion, using jhbuild. Clone it with

git clone git://git.gnome.org/jhbuild

build and install it, and copy the configuration file provided sample.jhbuildrc to ~/.jhbuilrc. The project page explains everything in detail, from installation details to tweaking the configuration file, but if you don't want to do it, that's fine. You'll probably need to install the build prerequisites, by invoking

$jhbuild bootstrap

To see the dependencies needed to get grilo and grilo plugins installed you can type

$jhbuild list grilo grilo-plugins

But to get the most from Grilo, you'd go for:

$jhbuild build gtk+ pygobject grilo grilo-plugins

That will install grilo core and plugins, pygobject (which includes Python's glue to use GObject Introspection, and has gobject-introspection as a dependency) and Gtk+, needed to run the grilo-test-ui sample done with GI. After a rather long build, you should have an environment with Grilo installed with GI support.

From there, type

$jhbuild shell

to enter the jhbuild environment and go to your Grilo's checkout directory. If everything has worked fine, you should be able to do:

$ python
Python 2.5.2 (r252:60911, Aug  6 2010, 16:46:34)
[GCC 4.4.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from gi.repository import Grl
>>> Grl.init([])
>>>

Under tools/python/ there's a grilo-test-ui.py program, which showcases all the combined potential of GI and Grilo: run it with

$python tools/python/grilo-test-ui.py

and enjoy (And then, start doing you own apps )