GTK+

From the GTK+ website:

GTK+, or the GIMP Toolkit, is a multi-platform toolkit for creating graphical user interfaces. Offering a complete set of widgets, GTK+ is suitable for projects ranging from small one-off tools to complete application suites.

GTK+, The GIMP Toolkit, was initially made by the GNU Project for the GIMP but is now a very popular toolkit with bindings for many languages.

Configuration programs

These GUI programs allow theme selection and at least customising of a font. They generally overwrite the ~/.gtkrc-2.0 file.

• lxappearance: A configuration tool from the LXDE project, which does not require any other parts of LXDE or other desktop environment. More flexible customisation than the other programs.
• gtk-chtheme
• gtk-theme-switch2
• gtk2_prefs

Example install command:

# pacman -S gtk-theme-switch2

See also Uniform Look for Qt and GTK Applications#Changing styles in each toolkit.

Themes

GTK+ 1.x

Old GTK+ 1 apps (like xmms) often do not look very nice at first. This is because they use ugly themes by default. To change this, you need to:

1. download and install some nice themes
2. change the theme

Some nice themes are in the AUR. To install them, see gtk-smooth-engine^AUR.

To change the theme you can use gtk-theme-switch2. Run it with the 'switch' command.

GTK+ 2.x

Major desktop environments provide tools to configure the GTK+ theme, icons, font and font size. Alternatively, tools such as those mentioned above may be used.

It is recommended to install some GTK+ 2 themes as well. The popular Clearlooks theme is included within the gtk-engines package.

Further themes can be found in the AUR:

• https://aur.archlinux.org/packages.php?O=0&K=gtk2-theme&do_Search=Go
• https://aur.archlinux.org/packages.php?O=0&K=gtk-theme&do_Search=Go

Alternatively, GTK+ settings can be configured manually by editing ~/.gtkrc-2.0. A list of GTK+ settings can be found in the GNOME library. To manually change the GTK+ theme, icons, font and font size, add the following to ~/.gtkrc-2.0:

~/.gtkrc-2.0

gtk-icon-theme-name = "[name-of-icon-theme]"
gtk-theme-name = "[name-of-theme]"
gtk-font-name = "[font-name] [size]"

For example:

~/.gtkrc-2.0

gtk-icon-theme-name = "Tango"
gtk-theme-name = "Murrine-Gray"
gtk-font-name = "DejaVu Sans 8"

Note: The above example requires the packages ttf-dejavu, tangerine-icon-theme, gtk-engine-murrine from the official repositories, and murrine-themes-collection^AUR from the AUR.

GTK+ 3.x

If you use GNOME 3, the theme can be changed with the gnome-tweak-tool.

If you use Xfce 4.8, both GTK+ 3.x and GTK+ 2.x themes can be managed by Appearance tool. Go to Settings-->Appearance. If selected style has both GTK+ 2.x and GTK+ 3.x themes, they will be used. If selected style has only GTK+ 2.x theme, it will be used for GTK+ 2.x applications and (ugly) defaults will be used for GTK+ 3.x applications. If selected style has only GTK+ 3.x theme, it will be used for GTK+ 3.x applications and (ugly) defaults will be used for GTK+ 2.x applications. Thus for uniform UI appearance and best experience one can use style that has both GTK+ 2.x and GTK+ 3.x themes. Search packages and AUR. One example of this is theme clearwaita-gtk-theme^AUR.

If you use a GTK+ 2.x based DE, like Xfce, LXDE, gnome-tweak-tool won't work; see FS#23644. You need to install librsvg, and set your theme manually in $XDG_CONFIG_HOME/gtk-3.0/settings.ini (this is usually ~/.config/gtk-3.0/settings.ini. An example settings.ini file:

$XDG_CONFIG_HOME/gtk-3.0/settings.ini

[Settings]
gtk-application-prefer-dark-theme = false
gtk-theme-name = Zukitwo
gtk-fallback-icon-theme = gnome
gtk-icon-theme-name = [icon theme name]
gtk-font-name = [font name] [font size]

If it still does not change, delete old gtk-3.0 folder in $XDG_CONFIG_HOME and copy gtk-3.0 folder from /path/to/theme to $XDG_CONFIG_HOME. Example:

$ rm -r ~/.config/gtk-3.0/
$ cp -r /usr/share/themes/Zukitwo/gtk-3.0/ ~/.config/  

After this, you need to set the same theme in your DE's appearance configuration tool. There are only a few themes which provide a uniform look for GTK+ 3.x and GTK+ 2.x apps. A few examples:

1. Adwaita for GTK+ 3 and Advaicium for GTK+ 2
2. Newlooks for GKT+ 3 and Clearlooks for GTK+ 2
3. Zukitwo
4. Elegant Brit
5. Atolm
6. Hope

You could find what themes installed on your system have both an GTK+ 2.x and GTK+ 3.x version by using this command (don't work with names containing spaces):

find $(find ~/.themes /usr/share/themes/ -wholename "*/gtk-3.0" | sed -e "s/^\(.*\)\/gtk-3.0$/\1/")\
-wholename "*/gtk-2.0" | sed -e "s/.*\/\(.*\)\/gtk-2.0/\1"/

Note: There probably are other themes. Some of these themes are available in the AUR. Also, some of them are not usable as is for displaying a GTK+ 2.x panel (light text over light background), so you need to use the provided panel background.

GTK+ and Qt

If you have GTK+ and Qt (KDE) applications on your desktop then you know that their looks do not blend well. If you wish to make your GTK+ styles match your Qt styles please read Uniform Look for Qt and GTK Applications.

Configuration file

Note: See the GtkSettings properties in the GTK+ programming reference manual for the full list of GTK configuration options.

The purpose of this section is to collect GTK+ configuration settings which can e.g. be used within ~/.gtkrc-2.0.

Enabling Customizable Keyboard Shortcuts

You can customize your GTK+ applications' keyboard shortcuts (those are called accelerators in GTK+ terminology) by hovering your mouse over a menu item and pressing your desired key combination. However, this feature is disabled by default. To enable it, set

gtk-can-change-accels = 1

Speed up your GNOME menu

This setting controls the delay between you pointing the mouse at a menu and that menu opening in GNOME. Change this to a setting you prefer. I guess the number is in milliseconds, e.g. 250 being a quarter of a second.

gtk-menu-popup-delay = 0

Reduce widget sizes

If you have a small screen or you just do not like big icons and widgets, you can resize things easily. To have icons without text in toolbars, use

gtk-toolbar-style = GTK_TOOLBAR_ICONS

To use smaller icons, use a line like this:

gtk-icon-sizes = "panel-menu=16,16:panel=16,16:gtk-menu=16,16:gtk-large-toolbar=16,16\
:gtk-small-toolbar=16,16:gtk-button=16,16"

Or to remove icons from buttons completely:

gtk-button-images = 0

You can also remove icons from menus:

gtk-menu-images = 0

There is some more tweaking to do in your themes gtkrc like explained here and there's another theme that does it all.

Development

When writing a start-from-scratch GTK+ 3 program with C, it's necessary to add CFLAGS for gcc:

gcc -g -Wall `pkg-config --cflags --libs gtk+-3.0` -o base base.c

-g and -Wall parameters are not necessary since they are only for verbose debugging outputs. You may try out the official Hello World example.

Write a simple message dialog app

You can write your own GTK+ 3 message dialog easily in many programming languages through GObject-Introspection or bindings, or you can simply use bash.

The following examples display a simple "Hello world" in a message dialog.

Bash

• Dependency: zenity

hello_world.sh

#!/bin/bash
zenity --info --title='Hello world!' --text='This is an example dialog.'

Boo

• Dependency: gtk-sharp-git^AUR from AUR (boo)
• Makedependency: boo
• Build with: booc hello_world.boo
• Run with: mono hello_world.exe (or booi hello_world.boo)

hello_world.boo

import Gtk from "gtk-sharp"
Application.Init()
Hello = MessageDialog(null, DialogFlags.Modal, MessageType.Info, ButtonsType.Close, "Hello world!")
Hello.SecondaryText = "This is an example dialog."
Hello.Run()

C

• Dependency: gtk3
• Build with: gcc -o hello_world `pkg-config --cflags --libs gtk+-3.0` hello_world.c

hello_world.c

#include <gtk/gtk.h>
void main (int argc, char *argv[]) {
	gtk_init (&argc, &argv);
        GtkWidget *hello = gtk_message_dialog_new (NULL, GTK_DIALOG_MODAL, GTK_MESSAGE_INFO, GTK_BUTTONS_OK, "Hello world!");
	gtk_message_dialog_format_secondary_text (GTK_MESSAGE_DIALOG (hello), "This is an example dialog.");
        gtk_dialog_run(GTK_DIALOG (hello));
}

C++

• Dependency: gtkmm3
• Build with: g++ -o hello_world `pkg-config --cflags --libs gtkmm-3.0` hello_world.cc

hello_world.cc

#include <gtkmm/main.h>
#include <gtkmm/messagedialog.h>
int main(int argc, char *argv[]) {
	Gtk::Main kit(argc, argv);
	Gtk::MessageDialog Hello("Hello world!", false, Gtk::MESSAGE_INFO, Gtk::BUTTONS_OK);
	Hello.set_secondary_text("This is an example dialog.");
	Hello.run();
}

C#

• Dependency: gtk-sharp-git^AUR from AUR
• Build with: mcs -pkg:gtk-sharp-3.0 hello_world.cs
• Run with: mono hello_world.exe

hello_world.cs

using Gtk;
public class HelloWorld {
	static void Main() {
		Application.Init ();
		MessageDialog Hello = new MessageDialog (null, DialogFlags.Modal, MessageType.Info, ButtonsType.Close, "Hello world!");
		Hello.SecondaryText="This is an example dialog.";
		Hello.Run ();
	}
}

Genie

• Dependency: gtk3
• Makedependency: vala
• Build with: valac --pkg gtk+-3.0 hello_world.gs

hello_world.gs

uses 
	Gtk
init
	Gtk.init (ref args)
	var Hello=new MessageDialog (null, Gtk.DialogFlags.MODAL, Gtk.MessageType.INFO, Gtk.ButtonsType.OK, "Hello world!")
	Hello.format_secondary_text ("This is an example dialog.")
	Hello.run ()

Java

• Dependency: java-gnome^AUR from AUR
• Makedependency: java-environment
• Build with: mkdir HelloWorld && javac -classpath /usr/share/java/gtk.jar -d HelloWorld HelloWorld.java
• Run with: java -classpath /usr/share/java/gtk.jar:HelloWorld HelloWorld

HelloWorld.java

import org.gnome.gtk.Gtk;
import org.gnome.gtk.Dialog;
import org.gnome.gtk.InfoMessageDialog;

public class HelloWorld
{
    public static void main(String[] args) {
        Gtk.init(args);
        Dialog Hello = new InfoMessageDialog(null, "Hello world!", "This is an example dialog.");
        Hello.run();
    }
}

JavaScript

• Dependencies: gtk3, gjs (works also with seed)

hello_world.js

#!/usr/bin/gjs
Gtk = imports.gi.Gtk
Gtk.init(null, null)
Hello = new Gtk.MessageDialog({type: Gtk.MessageType.INFO,
                               buttons: Gtk.ButtonsType.OK,
                               text: "Hello world!",
                               "secondary-text": "This is an example dialog."})
Hello.run()

Perl

• Dependency: perl-gtk3^AUR from AUR

hello_world.pl

#!/usr/bin/perl
use Gtk3 -init;
my $hello = Gtk3::MessageDialog->new (undef, 'modal', 'info', 'ok', "Hello world!");
$hello->set ('secondary-text' => 'This is an example dialog.');
$hello->run;

Python

• Dependencies: gtk3, python-gobject

hello_world.py

#!/usr/bin/python
from gi.repository import Gtk
Gtk.init(None)
Hello=Gtk.MessageDialog(None, Gtk.DialogFlags.MODAL, Gtk.MessageType.INFO, Gtk.ButtonsType.CLOSE, "Hello world!")
Hello.format_secondary_text("This is an example dialog.")
Hello.run()

Vala

• Dependency: gtk3
• Makedependency: vala
• Build with: valac --pkg gtk+-3.0 hello_world.vala

hello_world.vala

using Gtk;
public class HelloWorld {
	static void main (string[] args) {
		Gtk.init (ref args);
		var Hello=new MessageDialog (null, Gtk.DialogFlags.MODAL, Gtk.MessageType.INFO, Gtk.ButtonsType.OK, "Hello world!");
		Hello.format_secondary_text ("This is an example dialog.");
		Hello.run ();
	}
}

Visual Basic .NET

• Dependency: gtk-sharp-git^AUR from AUR
• Makedependency: mono-basic
• Build with: vbnc -r:/usr/lib/mono/gtk-sharp-3.0/gio-sharp.dll -r:/usr/lib/mono/gtk-sharp-3.0/glib-sharp.dll -r:/usr/lib/mono/gtk-sharp-3.0/gtk-sharp.dll hello_world.vb
• Run with: mono hello_world.exe

hello_world.vb

Imports Gtk
Public Class Hello
	Inherits MessageDialog
	Public Sub New
		MyBase.New(Me, DialogFlags.Modal, MessageType.Info, ButtonsType.Close, "Hello world!")
		Me.SecondaryText = "This is an example dialog."
	End Sub
	Public Shared Sub Main
		Application.Init
		Dim Dialog As New Hello
		Dialog.Run
	End Sub
End Class

Resources

• The official GTK+ website
• Wikipedia article about GTK+
• GTK+ 2.0 Tutorial
• GTK+ 3 Reference Manual
• gtkmm Tutorial
• gtkmm Reference Manual