Xfce Stopwatch Plugin

2009-08-16 | xfce

I needed an excuse to try Mike's Vala bindings for Xfce, so I created a new little plugin for the panel, the xfce4-stopwatch-plugin.

In the original release announcement on July 28th, I wrote:

This is the first release of the stopwatch panel plugin, which you can use to time yourself on different tasks. It's stable and usable, but quite minimal still.

The functionality is best summarized with this image from the web site:

Vala

From their web site,

Vala is a new programming language that aims to bring modern programming language features to GNOME developers without imposing any additional runtime requirements and without using a different ABI compared to applications and libraries written in C.

Instead of having to write tons of boilerplate code to create new GObjects in C and for other common tasks in developing GTK-based applications, Vala builds these features into the language. The Vala code you write passes through the Vala compiler, which produces GObject-based C code. From there, GCC compiles that to a binary as usual. There is no runtime, so Vala-produced code can run as fast as hand-coded C.

Vala makes it easy to write fast, object-oriented code for GTK-based projects. With Mike's Xfce bindings for Vala, you gain access to Xfce's libraries from Vala, letting you write panel plugins or other Xfce projects in Vala. It's a cool idea and something I definitely wanted to try.

Developing the Stopwatch Plugin

In general, Vala is pretty easy to write if you've worked with GObject before. I did hit a few bugs while developing even this simple plugin, so it's evident that Vala and the Xfce bindings aren't mature yet:

• I filed GNOME Bug 587150, a bug in Vala's POSIX bindings for the time_t type. Vala treats it as a GObject instead of an integer, making it unusable to pass around your program in many ways. This bug hasn't seen any attention yet, but I've worked around it for Stopwatch by not using time_t.

  Update: Evan Nemerson fixed this one.

• I patched a small bug in Xfce's Vala bindings for the XfceHVBox widget. The Vala compiler was producing calls to xfce_hv_box_new() instead of xfce_hvbox_new(), which of course caused a problem when GCC tried to resolve the symbol.
• I also filed GNOME Bug 589930, a bug in Vala's generated code for sscanf. It always added an extra NULL argument at the end of the arguments list. Jürg Billeter fixed this one quickly with this commit, which made it into Vala 0.7.5.

Despite these hurdles, writing the Stopwatch plugin in Vala has been a pleasure. Admittedly the plugin doesn't do much, but the code is very short and straight-forward.

Stopwatch will probably see just one or two more releases before it's feature-complete. I'd also like to port the Places plugin to Vala at some point, but I'm waiting to see how volume management plays out once ThunarVFS is gone.