Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License".


Common Lisp bindings for Qt and KDE using Smoke.

Table of Contents

1. Introduction
Supported Platforms
2. Usage
Overload Resolution
Setter Methods
Static Methods
Member variables
Garbage Collection
Saving a Core Image
Clozure CL
3. Qt
Interactive Development
4. KDE
A. GNU Free Documentation License

List of Examples

3.1. Hello World
3.2. Quit
3.3. i18n Hello World
3.4. Repl
3.5. Class Browser
3.6. Origami
4.1. Hello World
4.2. KMandelbrot

Chapter 1. Introduction

CL-Smoke provides CLOS bindings for the Qt and KDE libraries.



  • Ownership transfer to / from C++ of non QObject objects is seldom known to cl-smoke. E.g.: cl-smoke might delete an instance even though it is still needed by C++. (One that is known is QUndoStack::push().)

  • Limited conversions to and from C++. You will get an NO-APPLICABLE-CXX-METHOD error when a Lisp to C++ conversion is missing and a pointer will be returned when there is no C++ to Lisp conversion.

  • 6 seconds startup time[1] (for qt.examples) on a Pentium M 1.7GHz.

  • Needs to be recompiled when the Smoke library is updated.

  • Could be faster


Method calling is near 3000 times slower than native C++. The overhead is mainly in the overload resolution and to/from foreign object translation. Some measurements by :cl-smoke.benchmark are in benchmark.pdf.



  • Smoke2 bindings from svn. [2]

  • Qt (development package)

  • CMake 2.6

  • a C++ compiler (GCC)

Supported Platforms


Not Working


You need to checkout the darcs repositories:

for r in smoke qt.core qt.gui qt.test qt.tests qt.examples qt.uitools qt.webkit qt.phonon; do
	darcs get "$r"


There are also the following repositories: qt.svg qt.dbus kde.core kde.ui kde.tests kde.examples

Build and install the :smoke and :qt.core C wrapper libraries with:

cmake ./ && make && sudo make install

in the smoke/ and qt/ directories.

When you have symlinked the .asd system files, you should be able to load the systems. The system name has a :cl-smoke. prefix. e.g.:

(asdf:oos 'asdf:load-op :cl-smoke.qt.examples) 

[1] Using a core image it is around 1 second. (see the section called “Saving a Core Image”)

[2] The new smokegenerator is needed (developed by Arno Rehn for the GSOC 09).

Chapter 2. Usage


C++ names are converted to Lisp symbols by converting camelCase to camel-case. Underscores #\_ are replaced with #\- and a leading uppercase K or Q is removed.

E.g.: QHelloWorld_foo becomes hello-world-foo.


C++ classes have a corresponding CLOS class. The can be used like any CLOS class; E.g: to make a QObject instance:

(make-instance 'qt:object)

Supply arguments as list to the :args keyword:

(let ((parent (make-instance 'qt:object)))
  (make-instance 'qt:object :args (list parent)))

or use :arg0, :arg1 and :arg2.

(let ((parent (make-instance 'qt:object)))
  (make-instance 'qt:object :arg0 parent))

To extend a C++ class you have to use cxx:class as metaclass:

(defclass my-object (qt:object)
  (:metaclass cxx:class))

(make-instance 'my-object)

The first superclass must be a Smoke class. When you define a class that has several Smoke superclasses, they will be constructed with their default constructor. For the first Smoke superclass you can supply arguments with the :args and :arg0 etc. keywords.

(defclass my-graphics-object (qt:object qt:graphics-item)
  (:metaclass cxx:class))


C++ methods are generic functions in the :cxx package.

The C++ method call: myInstance->frob(1); is in Lisp:

(frob my-instance 1)

Overload Resolution

C++ style overload resolution with conversion sequences is supported. For example this:

(cxx:set-pen (make-instance 'qt:painter) (make-instance 'qt:color :args '("green")))

is equivalent to:

(cxx:set-pen (make-instance 'qt:painter) "green")

In the second case a temporary qt:color instance is implicitly created.

Setter Methods

Instead of calling a setter method that takes no additional arguments,

(cxx:set-object-name (make-instance 'qt:object) "foo")

you can use its setfable getter.

(setf (cxx:object-name (make-instance 'qt:object)) "foo")


You can extend the :cxx generic functions by adding methods. :around, :before, :after and (call-next-method) are supported.

(defclass the-object-does-nothing (qt:object)
  (:metaclass cxx:class))

(defmethod cxx:timer-event ((object the-object-does-nothing) event)
  (declare (ignore object event))

:cxx generic functions can be overload by argument count. Lambda list keywords (e.g.: &rest and &key) are not supported.


Make sure you have the right number of arguments when adding a method; otherwise it will not be called.


The arguments of the method might have dynamic extend; i.e.: they are only valid in the body of the method.


Unwinding of the C++ stack is not supported. This means that you must not invoke a restart that skips any foreign function. You will most likely encounter this problem when an error is signaled in a virtual method you have overwritten. [3]. For this case restarts are provide that allow to return a value for the failed method, call the default C++ implementation instead (something like #'call-next-method) or retry.


Instead of using the various cxx:operator methods you can use their Lisp equivalent in the :cxx package.







Static Methods

The static C++ method QByteArray::number(int n, int base=10) can be called by:

(qt:byte-array.number 37)

which is equivalent to the C++ code QByteArray::number(37);. Or with:

(cxx:number (find-class 'qt:byte-array) 37)


(cxx:number (make-instance 'qt:byte-array) 37)


C++ Class enums available as constants. E.g.: QColor::Rgb is qt:color.+rgb+. See :cxx-support.

Member variables

C++ member variables of an instance can be accessed by using slot-value; e.g.:

(slot-value (make-instance 'qt:object) :static-meta-object)


(slot-value (find-class 'qt:object) :static-meta-object)

Usually they can also be accessed using methods from the :cxx package.

Garbage Collection

You should be able to use C++ Class instances like normal Lisp object.

C++ classes are automatically deleted when their Lisp object gets garbage collected; except when they (QObjects) have a parent and thus the parent is responsible for their deletion. When a qt:object has a parent, a strong reference is kept to prevent the garbage collection removing it until the parent is deleted.


Ownership transfer for non QObject instances is mostly unimplemented.

Saving a Core Image

For near instant startup you can save an image. Since saving C++ instances is not supported, it is best to save the image immediately after loading the packages.


Initializing the Smoke bindings when the image is loaded is implementation dependent. It is implemented for SBCL and Clozure CL.


To save an image in SBCL you can use: sb-ext:save-lisp-and-die


To create a bundle containing an SBCL image and the required C wrappers libraries you can use smoke:save-bundle. The bundle is created using makeself. See in :qt.examples for an example.

Clozure CL

To save an image in CCL ccl:save-application is usually used.


To allow the image to find the C wrapper libraries, they have to be installed with:

sudo make install

run in the smoke/ and qt/ directory.

[3] For example an event handler that is called from the C++ library.

Chapter 3. Qt

Besides the :cl-smoke.qt.gui there are these modules:

  • :cl-smoke.qt.uitools QtUiTools

  • :cl-smoke.qt.test QtTest

  • :cl-smoke.qt.webkit QtWebKit

  • :cl-smoke.qt.phonon Phonon

  • The network classes of Qt.

  • :cl-smoke.qt.core the nogui Qt core.

which provide bindings for their Qt module. The class names of this modules are in the :qt package. (E.g. Phonon::VideoPlayer is ' and QTest is 'qt:test)

Additionally there is the :cl-smoke.qt.tests system, containing the unit tests and :cl-smoke.qt.examples for various examples.


The qt:application object should created with: qt:with-app. In its body the event loop can be started with qt:exec.

Example 3.1. Hello World

;;; Copyright 2009 Tobias Rautenkranz
;;; License: X11 license

(in-package :qt.examples)

(defun hello-world ()
  "Hello world"
  (qt:with-app ()
    (let ((widget (make-instance 'qt:push-button :args '("Hello world"))))
      (cxx:show widget)

Subclasses of qt:paint-device (e.g. qt:widget) can only be used when a qt:application instance exists. When there are, for example, qt:widget instances at the end of qt:with-app, they are deleted by the qt:application destructor.

Custom cxx:paint-event methods can use qt:with-painter to ensure that the qt:painter is deactivated at the end of the method.

Interactive Development

The :cl-smoke.repl allows you to start a qt:application event loop in the background for interactive development in SLIME. To start the event loop use cl-smoke.repl:start-event-loop-in-background (or cl-smoke.repl:start-event-loop-in-repl). [4] As long as you do not kill the thread or unwind over a foreign function, you should be fine.


qt:connect connects a signal to a slot. The signal is either a qt:qsignal created with qt:make-signal or a C++ signal by using qt:get-signal. The slot can be a slot returned by qt:make-slot, a function or a C++ slot a return from qt:get-slot.

Example 3.2. Quit

;;; Copyright 2009 Tobias Rautenkranz
;;; License: X11 license

(in-package :qt.examples)

(defun hello-world-quit ()
  "Quit on push-button click"
  (qt:with-app ()
    (let ((quit (make-instance 'qt:push-button :args '("Quit")))
          (font (make-instance 'qt:font :args (list "Times"
      (cxx:resize quit 75 30)
      (setf (cxx:font quit) font)
      (qt:connect (qt:get-signal quit "pressed()")
      		  #'(lambda ()
                      (format t "About to quit()~%")))
      (qt:connect (qt:get-signal quit "clicked()")
                  (qt:get-slot (qt:app) "quit()"))
      (cxx:show quit)

When the argument types for a slot or signal are not specified they are determined when the first connection is made. Note that when connecting a qt:qsignal to a qt:qslot at least one must have its arguments types specified. Type specifier T allows to pass a Lisp object as is from a Lisp signal to a Lisp slot.

The functionality of the Qt SIGNAL and SLOT macros is provided by qt:qsignal and qt:qslot.


qt:object properties can be accessed with qt:property (setf-able). The name of the property can be either a string in C++ style or a symbol in Lisp style. The predefined Qt properties can be accessed with symbols in the keyword package.

(let ((object (make-instance 'qt:object)))
  (setf (qt:property object :object-name) "Foo")
  (assert (string= "Foo" (qt:property object "objectName"))))


A qt:variant can be constructed with qt:make-variant or to pass a Lisp object with qt:make-lisp-variant. Its value is returned by qt:value.


You can use qt:tr to translate strings.

Example 3.3. i18n Hello World

;;; Copyright 2009 Tobias Rautenkranz
;;; License: X11 license

(in-package :qt.examples)

(defun i18n-hello-world ()
  "i18n hello world"
  (qt:with-app ()
    (qt:with-translator ("hello-world" 
      (let ((widget (make-instance 'qt:label)))
        (setf (cxx:window-title widget) (qt:tr "Lisp Qt Example" "hello-world")
              (cxx:text widget) (format nil (qt:tr "<h1>Hello world</h1>

You are running ~A version ~A on a ~A ~A")
        (cxx:show widget)

;; calling #'software-version from the qt:application event loop
;; segfaults in SBCL. The first call caches the result in
;; sb-sys::*software-version* and we thus prevent the crash in
;; (run-program "/bin/uname" [...]).
(smoke:eval-startup (:load-toplevel)


# This file is distributed under the same license as the PACKAGE package.
# Tobias Rautenkranz <>, 2009.
msgid ""
msgstr ""
"Project-Id-Version: hello-world\n"
"Report-Msgid-Bugs-To: \n"
"POT-Creation-Date: 2009-07-01 01:17+0200\n"
"PO-Revision-Date: 2009-03-21 11:41+0100\n"
"Last-Translator: Tobias Rautenkranz <>\n"
"Language-Team: German <>\n"
"MIME-Version: 1.0\n"
"Content-Type: text/plain; charset=UTF-8\n"
"Content-Transfer-Encoding: 8bit\n"
"X-Generator: Lokalize 0.3\n"
"Plural-Forms: nplurals=2; plural=n != 1;\n"

#: i18n-hello-world.lisp:21
msgctxt "hello-world"
msgid "Lisp Qt Example"
msgstr "Lisp Qt Beispiel"

#: i18n-hello-world.lisp:22
#, lisp-format
msgid ""
"<h1>Hello world</h1>\n"
"You are running ~A version ~A on a ~A ~A"
msgstr ""
"<h1>Hallo Welt</h1>\n"
"Du verwendest, auf ~2@*~A ~A, ~0@*~A version ~A"

Gettext is used to extract the i18n strings and compile the message catalog. See CMakeLists.txt and UseClQti18n.cmake in the src/ directory of :cl-smoke.qt.examples on how to do this.


You can run the examples with:

(asdf:oos 'asdf:load-op :cl-smoke.qt.examples)

Example 3.4. Repl

Use a qt:string-list-model with a qt:list-view to show evaluated lisp expressions.

;;; Copyright 2009 Tobias Rautenkranz
;;; License: X11 license

(in-package :qt.examples)

(defclass repl (qt:widget)
  ((model :reader model
          :initform (make-instance 'qt:string-list-model))
   (output :reader output
           :initform (make-instance 'qt:list-view))
   (input :reader input
          :initform (make-instance 'qt:line-edit)))
  (:metaclass cxx:class))

(defun append-list-model (list-model string)
  "Appends STRING to LIST-MODEL."
  (let ((index (cxx:row-count list-model)))
    (unless (cxx:insert-row list-model index)
      (error "insert-row ~A for ~A failed." index list-model))
    (unless (cxx:set-data list-model (cxx:index list-model index) string)
      (error "set-data failed."))))

(defmethod initialize-instance :after ((repl repl) &rest args)
  (declare (ignore args))
  (setf (cxx:model (output repl)) (model repl))
  (qt:connect (qt:get-signal (input repl) "returnPressed()")
              #'(lambda ()
                  (append-list-model ;; Input
                   (model repl)
                   (format nil "> ~A" (cxx:text (input repl))))
                  (append-list-model ;; return value
                   (model repl)
                    (handler-case (eval (read-from-string
                                         (cxx:text (input repl))))
                      (error (condition) condition))))
                  (cxx:clear (input repl))))
  (let ((layout (make-instance 'qt:vbox-layout)))
    (cxx:add-widget layout (output repl))
    (cxx:add-widget layout (input repl))
    (setf (cxx:layout repl) layout))
  (cxx:set-focus (input repl)))

(defun repl ()
  "Lisp REPL"
  (qt:with-app ()
    (let ((repl (make-instance 'repl)))
      (cxx:show repl)

Example 3.5. Class Browser

Qt Classes browser using :cl-smoke.qt.webkit to display the API doc and a custom qt:list-model for the qt:list-view of the available classes.

;;; Copyright 2009 Tobias Rautenkranz
;;; License: X11 license

(in-package :qt.examples)

(defclass classes-model (qt:abstract-list-model)
  ((items :reader items :initarg :items
          :initform (make-array 0 :adjustable t
                                :fill-pointer t)))
  (:metaclass cxx:class))

(defmethod cxx:row-count ((list classes-model) parent)
  (length (items list)))

(defmethod cxx:data ((list classes-model) index role)
  (if (and (cxx:is-valid index)
           (< (cxx:row index) (length (items list)))
           (= role (value qt:+display-role+)))
      (string-downcase (class-name (aref (items list) (cxx:row index))))

(defun class-at (model-index)
  (aref (items (cxx:model model-index)) (cxx:row model-index)))

(defclass class-browser (qt:splitter)
  ((classes :accessor classes
            :initform (make-instance 'classes-model))
   (classes-list :reader classes-list
                 :initform (make-instance 'qt:list-view))
   (info :reader class-info
         :initform (make-instance 'qt:label))
   (web-view :reader web-view
             :initform (make-instance 'qt:web-view)))
  (:metaclass cxx:class))

(defun setup-class-list (classes)
  (do-external-symbols (symbol :qt)
    (let ((class (find-class symbol nil)))
      (when (and (not (null class))
                 (typep class (find-class 'smoke::smoke-standard-class)))
        (vector-push-extend class
                            (items classes)))))
  (sort (items classes) #'(lambda (class1 class2)
                            (string< (class-name class1)
                                     (class-name class2)))))

(defmethod initialize-instance :after ((browser class-browser) &rest args)
  (declare (ignore args))
  (let* ((w (make-instance 'qt:widget))
         (layout (make-instance 'qt:vbox-layout)))
    (cxx:add-widget layout (classes-list browser))
    (let ((search (make-instance 'qt:line-edit)))
      (cxx:add-widget layout search)
      (qt:connect (qt:get-signal search "textChanged(QString)")
                  #'(lambda (text)
                      ;; FIXME since the class list is sorted we could do better
                      (cxx:keyboard-search (classes-list browser)
    (let ((scroll (make-instance 'qt:scroll-area)))
      (setf (cxx:widget scroll) (class-info browser)
            (cxx:widget-resizable scroll) t)
      (cxx:add-widget layout scroll))
    (setf (cxx:layout w) layout)
    (cxx:add-widget browser w))
  (cxx:add-widget browser (web-view browser))
    (setup-class-list (classes browser))
    (setf (cxx:uniform-item-sizes (classes-list browser)) t
          (cxx:selection-mode (classes-list browser)) qt:abstract-item-view.+single-selection+
          (cxx:model (classes-list browser)) (classes browser)
          (cxx:word-wrap (class-info browser)) t
          (cxx:window-title browser) "CL Qt Classes")
    (qt:connect (qt:get-signal (cxx:selection-model (classes-list browser))
                               "currentChanged(QModelIndex, QModelIndex)")
                #'(lambda (current previous)
                    (declare (ignore previous))
                    (set-info (class-info browser)
                              (web-view browser) current)))))

(defun set-info (info web-view model-index)
  (let* ((class (class-at model-index)))
    (cxx:load web-view (format nil "" 
                               (subseq (qt:q-version) 0 3)
                               (remove #\: (smoke:name class) :count 1)))
    (cxx:set-text info
                  (format nil "<h1>qt:~A</h1>
<h2>Direct Superclasses</h2>
~{ <li>~A</li> ~}
<h2>Direct Subclasses</h2>
~{ <li>~A</li>~}
                          (string-downcase (class-name class))
                          (smoke:name class)
                          (mapcar #'(lambda (c) (string-downcase (class-name c)))
                                  (closer-mop:class-direct-superclasses class))
                          (mapcar #'(lambda (c) (string-downcase (class-name c)))
                                  (closer-mop:class-direct-subclasses class))))))

(defun class-browser ()
  "Qt Class Browser"
  (qt:with-app ()
    (let ((browser (make-instance 'class-browser)))
      (cxx:show browser)


For OpenGL a binding is needed (e.g.: cl-opengl).

Example 3.6. Origami

Origami draws a pleated hyperbolic paraboloid using the method described in (Non)existence of Pleated Folds: How Paper Folds Between Creases


Axiom is needed to generate the lisp source to that calculates the vertices.

[4] Currently START-EVENT-LOOP-IN-BACKGROUND is recommended.

Chapter 4. KDE

Table of Contents


To use the KDE libraries use the :cl-smoke.kde.ui (Depends on :cl-smoke.kde.core).

Besides these packages there is :kde.tests for the unit tests and :kde.examples containing the examples.


The examples can be run with:

(asdf:oos 'asdf:load-op :cl-smoke.kde.examples)

And then running the function of the example; e.g.:


Example 4.1. Hello World

;;; Copyright 2009 Tobias Rautenkranz
;;; License: X11 license

(in-package :cl-smoke.kde.examples)

(defun hello-world ()
  "KDE Hello World"
  (kde:with-kde ("khelloworld" "Hello World" "0.1")
    (let* ((window (make-instance 'kde:push-button :args '("Hello world"))))
      (cxx:show window)

Example 4.2. KMandelbrot

A port of the Qt Mandelbrot example to KDE.

The Mandelbrot example shows how to use a worker thread to perform heavy computations without blocking the main thread's event loop.

The sources can be found in the src/mandelbrot/ directory of the :kde.examples package

Appendix A. GNU Free Documentation License

Version 1.3, 3 November 2008

Copyright © 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.

Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed.


The purpose of this License is to make a manual, textbook, or other functional and useful document “free” in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others.

This License is a kind of “copyleft”, which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software.

We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference.


This License applies to any manual or other work, in any medium, that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. Such a notice grants a world-wide, royalty-free license, unlimited in duration, to use that work under the conditions stated herein. The “Document”, below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as “you”. You accept the license if you copy, modify or distribute the work in a way requiring permission under copyright law.

A “Modified Version” of the Document means any work containing the Document or a portion of it, either copied verbatim, or with modifications and/or translated into another language.

A “Secondary Section” is a named appendix or a front-matter section of the Document that deals exclusively with the relationship of the publishers or authors of the Document to the Document’s overall subject (or to related matters) and contains nothing that could fall directly within that overall subject. (Thus, if the Document is in part a textbook of mathematics, a Secondary Section may not explain any mathematics.) The relationship could be a matter of historical connection with the subject or with related matters, or of legal, commercial, philosophical, ethical or political position regarding them.

The “Invariant Sections” are certain Secondary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that the Document is released under this License. If a section does not fit the above definition of Secondary then it is not allowed to be designated as Invariant. The Document may contain zero Invariant Sections. If the Document does not identify any Invariant Sections then there are none.

The “Cover Texts” are certain short passages of text that are listed, as Front-Cover Texts or Back-Cover Texts, in the notice that says that the Document is released under this License. A Front-Cover Text may be at most 5 words, and a Back-Cover Text may be at most 25 words.

A “Transparent” copy of the Document means a machine-readable copy, represented in a format whose specification is available to the general public, that is suitable for revising the document straightforwardly with generic text editors or (for images composed of pixels) generic paint programs or (for drawings) some widely available drawing editor, and that is suitable for input to text formatters or for automatic translation to a variety of formats suitable for input to text formatters. A copy made in an otherwise Transparent file format whose markup, or absence of markup, has been arranged to thwart or discourage subsequent modification by readers is not Transparent. An image format is not Transparent if used for any substantial amount of text. A copy that is not “Transparent” is called “Opaque”.

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The “Title Page” means, for a printed book, the title page itself, plus such following pages as are needed to hold, legibly, the material this License requires to appear in the title page. For works in formats which do not have any title page as such, “Title Page” means the text near the most prominent appearance of the work’s title, preceding the beginning of the body of the text.

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The Document may include Warranty Disclaimers next to the notice which states that this License applies to the Document. These Warranty Disclaimers are considered to be included by reference in this License, but only as regards disclaiming warranties: any other implication that these Warranty Disclaimers may have is void and has no effect on the meaning of this License.


You may copy and distribute the Document in any medium, either commercially or noncommercially, provided that this License, the copyright notices, and the license notice saying this License applies to the Document are reproduced in all copies, and that you add no other conditions whatsoever to those of this License. You may not use technical measures to obstruct or control the reading or further copying of the copies you make or distribute. However, you may accept compensation in exchange for copies. If you distribute a large enough number of copies you must also follow the conditions in section 3.

You may also lend copies, under the same conditions stated above, and you may publicly display copies.


If you publish printed copies (or copies in media that commonly have printed covers) of the Document, numbering more than 100, and the Document’s license notice requires Cover Texts, you must enclose the copies in covers that carry, clearly and legibly, all these Cover Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on the back cover. Both covers must also clearly and legibly identify you as the publisher of these copies. The front cover must present the full title with all words of the title equally prominent and visible. You may add other material on the covers in addition. Copying with changes limited to the covers, as long as they preserve the title of the Document and satisfy these conditions, can be treated as verbatim copying in other respects.

If the required texts for either cover are too voluminous to fit legibly, you should put the first ones listed (as many as fit reasonably) on the actual cover, and continue the rest onto adjacent pages.

If you publish or distribute Opaque copies of the Document numbering more than 100, you must either include a machine-readable Transparent copy along with each Opaque copy, or state in or with each Opaque copy a computer-network location from which the general network-using public has access to download using public-standard network protocols a complete Transparent copy of the Document, free of added material. If you use the latter option, you must take reasonably prudent steps, when you begin distribution of Opaque copies in quantity, to ensure that this Transparent copy will remain thus accessible at the stated location until at least one year after the last time you distribute an Opaque copy (directly or through your agents or retailers) of that edition to the public.

It is requested, but not required, that you contact the authors of the Document well before redistributing any large number of copies, to give them a chance to provide you with an updated version of the Document.


You may copy and distribute a Modified Version of the Document under the conditions of sections 2 and 3 above, provided that you release the Modified Version under precisely this License, with the Modified Version filling the role of the Document, thus licensing distribution and modification of the Modified Version to whoever possesses a copy of it. In addition, you must do these things in the Modified Version:

  1. Use in the Title Page (and on the covers, if any) a title distinct from that of the Document, and from those of previous versions (which should, if there were any, be listed in the History section of the Document). You may use the same title as a previous version if the original publisher of that version gives permission.
  2. List on the Title Page, as authors, one or more persons or entities responsible for authorship of the modifications in the Modified Version, together with at least five of the principal authors of the Document (all of its principal authors, if it has fewer than five), unless they release you from this requirement.
  3. State on the Title page the name of the publisher of the Modified Version, as the publisher.
  4. Preserve all the copyright notices of the Document.
  5. Add an appropriate copyright notice for your modifications adjacent to the other copyright notices.
  6. Include, immediately after the copyright notices, a license notice giving the public permission to use the Modified Version under the terms of this License, in the form shown in the Addendum below.
  7. Preserve in that license notice the full lists of Invariant Sections and required Cover Texts given in the Document’s license notice.
  8. Include an unaltered copy of this License.
  9. Preserve the section Entitled “History”, Preserve its Title, and add to it an item stating at least the title, year, new authors, and publisher of the Modified Version as given on the Title Page. If there is no section Entitled “History” in the Document, create one stating the title, year, authors, and publisher of the Document as given on its Title Page, then add an item describing the Modified Version as stated in the previous sentence.
  10. Preserve the network location, if any, given in the Document for public access to a Transparent copy of the Document, and likewise the network locations given in the Document for previous versions it was based on. These may be placed in the “History” section. You may omit a network location for a work that was published at least four years before the Document itself, or if the original publisher of the version it refers to gives permission.
  11. For any section Entitled “Acknowledgements” or “Dedications”, Preserve the Title of the section, and preserve in the section all the substance and tone of each of the contributor acknowledgements and/or dedications given therein.
  12. Preserve all the Invariant Sections of the Document, unaltered in their text and in their titles. Section numbers or the equivalent are not considered part of the section titles.
  13. Delete any section Entitled “Endorsements”. Such a section may not be included in the Modified Version.
  14. Do not retitle any existing section to be Entitled “Endorsements” or to conflict in title with any Invariant Section.
  15. Preserve any Warranty Disclaimers.

If the Modified Version includes new front-matter sections or appendices that qualify as Secondary Sections and contain no material copied from the Document, you may at your option designate some or all of these sections as invariant. To do this, add their titles to the list of Invariant Sections in the Modified Version’s license notice. These titles must be distinct from any other section titles.

You may add a section Entitled “Endorsements”, provided it contains nothing but endorsements of your Modified Version by various parties — for example, statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard.

You may add a passage of up to five words as a Front-Cover Text, and a passage of up to 25 words as a Back-Cover Text, to the end of the list of Cover Texts in the Modified Version. Only one passage of Front-Cover Text and one of Back-Cover Text may be added by (or through arrangements made by) any one entity. If the Document already includes a cover text for the same cover, previously added by you or by arrangement made by the same entity you are acting on behalf of, you may not add another; but you may replace the old one, on explicit permission from the previous publisher that added the old one.

The author(s) and publisher(s) of the Document do not by this License give permission to use their names for publicity for or to assert or imply endorsement of any Modified Version.


You may combine the Document with other documents released under this License, under the terms defined in section 4 above for modified versions, provided that you include in the combination all of the Invariant Sections of all of the original documents, unmodified, and list them all as Invariant Sections of your combined work in its license notice, and that you preserve all their Warranty Disclaimers.

The combined work need only contain one copy of this License, and multiple identical Invariant Sections may be replaced with a single copy. If there are multiple Invariant Sections with the same name but different contents, make the title of each such section unique by adding at the end of it, in parentheses, the name of the original author or publisher of that section if known, or else a unique number. Make the same adjustment to the section titles in the list of Invariant Sections in the license notice of the combined work.

In the combination, you must combine any sections Entitled “History” in the various original documents, forming one section Entitled “History”; likewise combine any sections Entitled “Acknowledgements”, and any sections Entitled “Dedications”. You must delete all sections Entitled “Endorsements”.


You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects.

You may extract a single document from such a collection, and distribute it individually under this License, provided you insert a copy of this License into the extracted document, and follow this License in all other respects regarding verbatim copying of that document.


A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, is called an “aggregate” if the copyright resulting from the compilation is not used to limit the legal rights of the compilation’s users beyond what the individual works permit. When the Document is included in an aggregate, this License does not apply to the other works in the aggregate which are not themselves derivative works of the Document.

If the Cover Text requirement of section 3 is applicable to these copies of the Document, then if the Document is less than one half of the entire aggregate, the Document’s Cover Texts may be placed on covers that bracket the Document within the aggregate, or the electronic equivalent of covers if the Document is in electronic form. Otherwise they must appear on printed covers that bracket the whole aggregate.


Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing Invariant Sections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections. You may include a translation of this License, and all the license notices in the Document, and any Warranty Disclaimers, provided that you also include the original English version of this License and the original versions of those notices and disclaimers. In case of a disagreement between the translation and the original version of this License or a notice or disclaimer, the original version will prevail.

If a section in the Document is Entitled “Acknowledgements”, “Dedications”, or “History”, the requirement (section 4) to Preserve its Title (section 1) will typically require changing the actual title.


You may not copy, modify, sublicense, or distribute the Document except as expressly provided under this License. Any attempt otherwise to copy, modify, sublicense, or distribute it is void, and will automatically terminate your rights under this License.

However, if you cease all violation of this License, then your license from a particular copyright holder is reinstated (a) provisionally, unless and until the copyright holder explicitly and finally terminates your license, and (b) permanently, if the copyright holder fails to notify you of the violation by some reasonable means prior to 60 days after the cessation.

Moreover, your license from a particular copyright holder is reinstated permanently if the copyright holder notifies you of the violation by some reasonable means, this is the first time you have received notice of violation of this License (for any work) from that copyright holder, and you cure the violation prior to 30 days after your receipt of the notice.

Termination of your rights under this section does not terminate the licenses of parties who have received copies or rights from you under this License. If your rights have been terminated and not permanently reinstated, receipt of a copy of some or all of the same material does not give you any rights to use it.


The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. See Copyleft.

Each version of the License is given a distinguishing version number. If the Document specifies that a particular numbered version of this License “or any later version” applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that has been published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation. If the Document specifies that a proxy can decide which future versions of this License can be used, that proxy’s public statement of acceptance of a version permanently authorizes you to choose that version for the Document.


“Massive Multiauthor Collaboration Site” (or “MMC Site”) means any World Wide Web server that publishes copyrightable works and also provides prominent facilities for anybody to edit those works. A public wiki that anybody can edit is an example of such a server. A “Massive Multiauthor Collaboration” (or “MMC”) contained in the site means any set of copyrightable works thus published on the MMC site.

“CC-BY-SA” means the Creative Commons Attribution-Share Alike 3.0 license published by Creative Commons Corporation, a not-for-profit corporation with a principal place of business in San Francisco, California, as well as future copyleft versions of that license published by that same organization.

“Incorporate” means to publish or republish a Document, in whole or in part, as part of another Document.

An MMC is “eligible for relicensing” if it is licensed under this License, and if all works that were first published under this License somewhere other than this MMC, and subsequently incorporated in whole or in part into the MMC, (1) had no cover texts or invariant sections, and (2) were thus incorporated prior to November 1, 2008.

The operator of an MMC Site may republish an MMC contained in the site under CC-BY-SA on the same site at any time before August 1, 2009, provided the MMC is eligible for relicensing.

ADDENDUM: How to use this License for your documents

To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page:

Copyright © YEAR YOUR NAME

Permission is granted to copy, distribute and/or modify this document under the
terms of the GNU Free Documentation License, Version 1.3 or any later version
published by the Free Software Foundation; with no Invariant Sections, no
Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in
the section entitled “GNU Free Documentation License”.

If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the “with… Texts.” line with this:

with the Invariant Sections being LIST THEIR TITLES, with the Front-Cover Texts
being LIST, and with the Back-Cover Texts being LIST.

If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation.

If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.