Interfacing Raku to Gnome GTK+

A warning: Although you can do marvelous things with the packages already, the documentation here as well as the different packages are far from complete!

What’s this all about

There are already a few interfaces made by other fellow programmers such as GTK::Simple, GTK::Simpler and GTK::Scintilla. Why then, would you ask, build another one? There were several reasons to do this, to sum up a few;

  • Learning to handle Raku native interface to C libraries and having example code with the packages mentioned above.
  • I wanted to follow the Gnome documents as closely as possible. This meant that the subroutine names are kept the same as those in the libs. Later on, I introduced some modifications to shorten these names where possible. See also the design notes
  • I wanted to have classes with methods instead of the subroutines.
  • I wanted the event handling code in separate classes where the information about specific procedures can be stored.
  • I wanted all possible event handlers available for the user, not just the most used ones.
  • I didn’t want to fix signals/events in method calls like click().
  • Later, I decided that I also wanted a more complete set of methods interfaced to GTK+ et al. This happened after I had created a program to skim through the source code of the gtk libraries (.h and .c), because these files are very well documented, and generate a Raku module from it.
  • I wanted to follow the obsolete markings of Gnome. E.g. the GtkHBox and GtkVBox are not supported anymore in favor of GtkGrid (in Raku module Gnome::Gtk3::Grid).


There is already a bit of history for these packages. It started off building the GTK::Glade package which soon became too big. So a part was separated into GTK::V3. After some time working with the library I felt that the class names were a bit too long and that the words gtk and gdk were repeated too many times in the class path. E.g. there was GTK::V3::Gtk::GtkButton and GTK::V3::Gdk::GdkScreen to name a few. So, finally it was split into several other packages named, Gnome::N for the native linkup on behalf of any other Gnome module, Gnome::Glib, Gnome::GObject, Gnome::Gdk3, Gnome::Gtk3 and some others, according to what is shown on the developers page here. The classes in these packages are now renamed into e.g. Gnome::Gtk3::Button, Gnome::Gdk3::Screen, Gnome::GObject::Object and Gnome::Glib::List. As a side effect the package GTK::Glade is also renamed into Gnome::Gtk3::Glade to show that it is from Gnome and that it is based on Gtk version 3.

A later step might be merging some tools from Gnome::Gtk3::Glade back to Gnome::Gtk3 or make other modules. Here, I think for example about moving the testing part of interfaces to Gnome::T (I’ve taken short names like Gnome::N so it will not interfere with eventually new names from Gnome in the future). Gnome::Gtk3::Glade is definitely not extended and will be obsoleted in the near future.

What are the benefits

When the packages mature, the next points are/become available;


  • The defaults of GTK+ are kept. Therefore, e.g, the buttons are in the proper size. The user may decide to set sizes of windows and widgets but the libraries should not impose this.
  • Separation of callbacks from other code by having the callbacks defined in classes. Callbacks can then just read/write the data in the classes attributes. Also, data can be provided with named arguments to the register-signal() method defined in class Gnome::GObject::Object. This method is available to any class inheriting from Gnome::GObject::Object which almost every class does.
  • Building the interface by hand like in the examples and tutorial, is not always necessary. Feeding a saved design from the glade designer program to methods in module Gnome::Gtk3::Builder is preferable when building larger user interfaces.
  • No fancy stuff like tapping into channels to run signal handlers.
  • It is possible to create threads where longer runs can be done without crippling the user interface responses and also show the results from there in the gui.
  • It is possible to make use of actions besides signal processing.
  • It is possible to make use of resource files. This is a different approach than what Raku can do for you. It can be combined however.
  • It is possible to make use of D-Bus. This is one of the things that makes an application able to interact with the system and other processes as well as the desktop manager. (Not yet fully implemented in these libraries though)
  • Drag and drop will help you to drag documents from a filebrowser into your application as well as moving widgets from one place to another in your GUI.
  • Drawing is available with Cairo. The Gnome::Cairo package must be improved however.
  • Text manipulations are supported using Pango. (Not yet implemented in these libraries though)


  • The code base is much larger but I think it gives you greater flexibility.
  • Code is somewhat slower. That is not a big problem when a user interface is mostly set up and drawn once. Compiling the software takes much time when installing the packages.
  • When programs run the first time, it might take some time to compile.


This package, together with a few others is an interface to the great Gnome libraries Gtk, Gdk, Pango, GObject, Gio and Glib. Cairo is an independed project but Gnome makes significant use of that package. Not all libraries are available yet like Pango and not all modules are defined in any of those packages.

Package Travis-CI & Appveyor tests and Notes
Gnome::Gtk3 T A
Version 3 widget toolkit for graphical interfaces.
Gnome::Gdk3 T A
Version 3 low-level abstraction for the windowing system.
Gnome::Gio T A
File and URI handling. Support of resources for applications and D-Bus communication.
Gnome::Cairo T A
2D, vector-based drawing for high-quality graphics.
Gnome::Pango T A
International text rendering with full Unicode support. Not yet available to the public.
Gnome::GObject T A
Data structures and utilities for C programs.
Gnome::Glib T A
C-based object and type system with signals and slots.
Gnome::T T A
GUI test package. Not yet available to the public.
Gnome::N T A
Used to hold any access specs to the libraries and a map of glib types to raku types. Also there is some debugging possible and an exception class defined.
Gnome::Gtk4 T A
Version 4 widget toolkit for graphical interfaces. Yes, of course I will … but not yet. So, not available to the public.
Gnome::Gdk4 T A
Version 4 low-level abstraction for the windowing system. Must be combined with Gnome::Gtk4. Also not yet available to the public.

Site Contents

  • Tutorials: Tutorials about using the modules in all its forms.

  • Examples: A series of examples.

  • Reference: References of all the modules in all packages. All information is contained here so there is no need to go to the other packages for information.

  • Design: Notes on how things are set up.

  • Todo: There’s still a lot to do.


Dependencies on external software

The software in these packages do not install the GTK+ libraries and tools (gtk, glib, cairo, pango, glade, etc), so there is a dependency on several libraries which must be installed before the Raku software can be used.

Before any code can be run we must also install the packages we want to use. It is assumed that Raku (See Raku Site) and the GTK+ libraries (See Gtk Site) are already installed. The program zef is used to install the modules. Enter the following command on the command line to install the modules needed for this tutorial and any other dependencies will be installed too. Run zef install Gnome::Gtk3 to work with GTK+.


GTK+ Documentation derived from

  • Cairo; 1.16.0
  • Gdk Pixbuf; 2.38.2
  • Glib, Gio and Gobject; 2.60.7
  • Gtk and Gdk; 3.24.13


  • Tested against version 2021.10-149-g0851a253a.* with MoarVM.


There are always some problems! If you find one, please help by filing an issue at my github project.


  • The inventors and developers of Raku, formerly known as Perl 6, of course and the writers of the documentation.
  • The builders of the GTK+ library and the documentation.
  • Helpful hands are there when issues are raised, after requesting for help or developers returning ideas tips, etcetera for documentation; Pixlmixr, Hkdtam, JackKuhan, Alain Barbason, Clifton Wood, Rob Ransbottom, Håkon Hægland (some names are Github names).
  • Icons used from, humility icons, Andy Fitzsimon, licensed GPL.
  • Documentation found to use in tutorials and examples
    • Wikibooks For explanations on Gtk+, Pango and Cairo.
    • Zetcode for the several tutorials on Gtk+ and Cairo.
    • Prof Stewart Weiss, web address. On his site are numerous documents under which many about GTK+. I have used parts from these to explain many aspects of the user interface system.
    • Bert Timmerman for his Cairo transformation examples:


  • Raku code and pod documentation: Artistic License 2.0
  • Use of Gnome reference documentation: GNU Free Documentation License Version 1.3
  • Documentation from other external sources used in tutorials: Creative Commons Attribution-ShareAlike 4.0 International Public License