Gnome libraries and Rust

Currently, the Gtk-rs organization provides the bindings for the following libraries:

• Gtk
• Gdk
• Gdk-pixbuf
• Cairo
• Glib
• Gio
• Pango

The goal is to provide a safe abstraction using Rust paradigms.

Objects

First thing to note (it’s very important!) is that the Gtk-rs objects can be cloned and it costs nothing more than copying a pointer, so basically nothing. The reason is quite simple (and I suppose you already guessed it): it’s simply because Gtk-rs structs only contains a pointer to the corresponding Gnome objects.

Now: why is cloning safe? One thing to note before going any further: it’s not thread safe (and you shouldn’t try to call a Gnome library function inside another thread). Otherwise, when a struct is dropped, it calls internally the g_object_unref function and calls the g_object_ref function when you call clone().

To put it simply: Gnome handles the resources allocation/removal for us.

Trait hierarchy

In Gtk, there is a widget hierarchy. In Rust, it’s implemented through “traits inheritance” and enforced by the compiler at compile-time. So, what does that mean exactly? Let’s take an example:

You have a Button. As says the gnome documentation, a Button inheritance tree (a bit simplified) looks like this:

 GObject
  ╰── GtkWidget
       ╰── GtkContainer
            ╰── GtkBin
                 ╰── GtkButton

Which means that a Button can use methods from any of its parents.

So basically, you just need to import a parent’s trait to be able to use its methods:

// we import Widget's methods.
use gtk::WidgetExt;

// we create a button
let button = gtk::Button::new_with_label("Click me!");

// we use the method from the widget
button.show_all();

As easy as that!

Interfaces

The same goes for interfaces. The gnome documentation also says that a Button implements the following interfaces: GtkBuildable, GtkActionable and GtkActivatable. Just like parents’ methods, import the corresponding interface and then you’ll be able to use the methods.

I think that with this, you’ll be able to write anything you want without too much difficulties. Now it’s time to go deeper into Gtk-rs usage!