GTK+

GTK+ (GIMP Toolkit) is a cross-platform widget toolkit for creating graphical user interfaces. It is licensed under the terms of the GNU LGPL, allowing both free and proprietary software to use it. It is one of the most popular toolkits for the X Window System, along with Qt.

The name GTK+ originates from GTK; the plus was added to distinguish an enhanced version.^[1] It was originally created for the GNU Image Manipulation Program (GIMP), a free software raster graphics editor, in 1997 by Spencer Kimball and Peter Mattis, members of eXperimental Computing Facility (XCF) at the University of California, Berkeley. It is now maintained by members of the GNOME Foundation.

Design

GTK+ is an object-oriented widget toolkit written in the C programming language; object-orientation is achieved by using the GLib object system. On the X11 display server, GTK+ uses Xlib to draw widgets. Using Xlib provides flexibility and allows GTK+ to be used on platforms where the X Window System is unavailable. While GTK+ is primarily targeted at the X Window System, other platforms are supported, including Microsoft Windows (interfaced with the Windows API), and Mac OS X (interfaced with Quartz). HTML5 and Wayland backends are in development.

GTK+ can be configured to change the look of the widgets drawn; this is done using different display engines. Several display engines exist which try to emulate the look of the native widgets on the platform in use.

Programming language bindings

A library written in one programming language may be used in another programming language if bindings are written; GTK+ has bindings in many languages.^[2]

See the table below:

GUI designers

There were several attempts to create a GUI designer for GTK+. The following projects are active as of July 2011:

• Glade, supports GtkBuilder, which is a GTK+ built-in GUI description format.
• Crow Designer, relies on its own GuiXml format and GuiLoader library.
• Stetic, part of MonoDevelop, oriented towards Gtk#.

History

GTK+ was originally designed and used in the GNU Image Manipulation Program (GIMP) as a replacement of the Motif toolkit; at some point Peter Mattis became disenchanted with Motif and began to write his own GUI toolkit called the GIMP toolkit and had successfully replaced Motif by the 0.60 release of GIMP.^[3] Finally GTK was re-written to be object oriented and was renamed GTK+. This was first used in the 0.99 release of GIMP.

The GTK+ 2.0.0 release series introduced new features which include improved text rendering using Pango, a new theme engine, improved accessibility using the Accessibility Toolkit, complete transition to Unicode using UTF-8 strings, and a more flexible API. Starting with version 2.8, GTK+ 2 depends on the Cairo graphics library for rendering vector graphics in GTK+ 2.

GTK+ version 3.0.0 included revised input device handling, support for themes written with CSS-like syntax, and the ability to receive information about other opened GTK+ applications.

Future developments

Project Ridley is an attempt to consolidate several libraries that are currently external to GTK+, including libgnome, libgnomeui, libgnomeprint22, libgnomeprintui22, libglade, libgnomecanvas, libegg, libeel, gtkglext, and libsexy.^[4]

Developers are also considering new directions for the library, including removing deprecated API components and adding an integrated scene graph system, similar to the Clutter graphics library, effectively integrating GTK+ with OpenGL.^[5][6]

Development and design of the GTK+ 3 release of the toolkit started in February 2009 during the GTK+ Theming Hackfest held in Dublin.^[7] A first draft of the development roadmap has been released on 9 April 2009.^[8]

GTK+ hello world

The following code presents a graphical GTK+ hello-world program in the C programming language. This program has a window with the title "Hello, world!" and a label with similar text.

#include <gtk/gtk.h>
 
int main (int argc, char *argv[])
{
    GtkWidget *window;
    GtkWidget *label;
 
    gtk_init(&argc, &argv);
 
    /* Create the main, top level window */
    window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
 
    /* Give it the title */
    gtk_window_set_title(GTK_WINDOW(window), "Hello, world!");
 
    /*
    ** Map the destroy signal of the window to gtk_main_quit;
    ** When the window is about to be destroyed, we get a notification and
    ** stop the main GTK+ loop by returning 0
    */
    g_signal_connect(window, "destroy", G_CALLBACK(gtk_main_quit), NULL);
 
    /*
    ** Assign the variable "label" to a new GTK label,
    ** with the text "Hello, world!"
    */
    label = gtk_label_new("Hello, world!");
 
    /* Plot the label onto the main window */
    gtk_container_add(GTK_CONTAINER(window), label);
 
    /* Make sure that everything, window and label, are visible */
    gtk_widget_show_all(window);
 
    /*
    ** Start the main loop, and do nothing (block) until
    ** the application is closed
    */
    gtk_main();
 
    return 0;
}

Using GCC and pkg-config in a Unix shell, this code can be compiled with the following command (assume above source has file name "helloworld.c"):

$ gcc -Wall helloworld.c -o helloworld `pkg-config --cflags gtk+-3.0` `pkg-config --libs gtk+-3.0`

GTK+ example using Vala instead of C

To create a "Hello World" program in Vala instead of C, do the following:

Uses

Environments that use GTK+

• GNOME is based on GTK+, meaning that programs native to GNOME use GTK+
• Xfce is based on GTK+
• LXDE (Lightweight X11 Desktop Environment) is based on GTK+
• ROX Desktop is a lightweight desktop, with features from the GUI of RISC OS
• GPE Palmtop Environment
• Access Linux Platform (successor of the Palm OS PDA platform)
• Sugar is a desktop environment oriented on helping children learn, which uses GTK+ and PyGTK
• KDE, though based on Qt, has integration with GTK+-based programs and themes (since version 4.2).

GTK+ programs do not require a desktop environment made with GTK+. If the required libraries are installed, a GTK+ program can run on top of other X11-based desktop environments or window managers; this includes Mac OS X if X11.app is installed (which is the default since the Leopard release). GTK+ can also run under Microsoft Windows, where it is used by some popular cross-platform applications like Pidgin and GIMP. wxWidgets, a cross-platform GUI toolkit, uses GTK+ for Unix-like operating systems.^[9] Other ports include DirectFB (used by the Debian installer, for example) and ncurses.^[10]

Window managers

The following window managers use GTK+

• Aewm
• AfterStep
• Amaterus
• IceWM
• Metacity
• Mutter
• Sawfish
• Wmg
• Xfwm

Applications

Some notable applications that use GTK+ as a widget toolkit include:

• AbiWord – Word processor
• Anjuta – Integrated development environment (IDE)
• Ardour – Digital audio workstation
• Chromium – Secure web browser employing WebKit and developed in large part by Google
• Ekiga (formerly GnomeMeeting) – VoIP and video conferencing application
• Epiphany – Official GNOME web browser
• Evolution – Personal information manager
• GIMP – Raster graphics editor
• Gnumeric – Spreadsheet software
• GRAMPS – Genealogy software
• Inkscape – SVG Vector graphics editor
• LiVES – Video editor
• Midori – Minimalistic web browser
• Pidgin – Instant messenger
• gconfig – Linux kernel source configuration utility

See also

• gtkmm – C++ bindings for GTK+
• FLTK – A light, cross-platform, non-native widget toolkit
• FOX toolkit – A fast, open source, cross-platform widget toolkit
• Microsoft Foundation Class Library (MFC)
• Object Windows Library (OWL)
• Qt
• Ultimate++
• Visual Component Library (VCL)
• wxWidgets - cross platform open source C++ widgets toolkit developed by community
• Widget toolkit
• List of widget toolkits

References

Bibliography

External links

• Official website
• GTK+ Reference Manual
• List of GTK+ applications
• Another list of GTK+ applications