Protesilaos Stavrou

Fontaine (fontaine.el)

Set Emacs font configurations using presets

This manual, written by Protesilaos Stavrou, describes the customization options for fontaine (or fontaine.el), and provides every other piece of information pertinent to it.

The documentation furnished herein corresponds to stable version 2.1.0, released on 2024-09-02. Any reference to a newer feature which does not yet form part of the latest tagged commit, is explicitly marked as such.

Current development target is 2.2.0-dev.

1. COPYING

Copyright (C) 2022-2023 Free Software Foundation, Inc.

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, with the Front-Cover Texts being “A GNU Manual,” and with the Back-Cover Texts as in (a) below. A copy of the license is included in the section entitled “GNU Free Documentation License.”

(a) The FSF’s Back-Cover Text is: “You have the freedom to copy and modify this GNU manual.”

2. Overview

Fontaine lets the user specify presets of font configurations and set them on demand on graphical Emacs frames. The user option fontaine-presets holds all such presets.

Presets consist of a list of properties that govern the family, weight, height, and slant of the faces listed in the value of the variable fontaine-faces.

Each preset is identified by a user-defined symbol as the car of a property list. It looks like this (check the default value of fontaine-presets for how everything is pieced together): 

(regular
 ;; I keep all properties for didactic purposes, but most can be
 ;; omitted.  See the fontaine manual for the technicalities:
 ;; <https://protesilaos.com/emacs/fontaine>.
 :default-family "Monospace"
 :default-weight regular
 :default-slant normal
 :default-width normal
 :default-height 100

 :fixed-pitch-family nil
 :fixed-pitch-weight nil
 :fixed-pitch-slant nil
 :fixed-pitch-width nil
 :fixed-pitch-height 1.0

 :fixed-pitch-serif-family nil
 :fixed-pitch-serif-weight nil
 :fixed-pitch-serif-slant nil
 :fixed-pitch-serif-width nil
 :fixed-pitch-serif-height 1.0

 :variable-pitch-family "Sans"
 :variable-pitch-weight nil
 :variable-pitch-slant nil
 :variable-pitch-width nil
 :variable-pitch-height 1.0

 :mode-line-active-family nil
 :mode-line-active-weight nil
 :mode-line-active-slant nil
 :mode-line-active-width nil
 :mode-line-active-height 1.0

 :mode-line-inactive-family nil
 :mode-line-inactive-weight nil
 :mode-line-inactive-slant nil
 :mode-line-inactive-width nil
 :mode-line-inactive-height 1.0

 :header-line-family nil
 :header-line-weight nil
 :header-line-slant nil
 :header-line-width nil
 :header-line-height 1.0

 :line-number-family nil
 :line-number-weight nil
 :line-number-slant nil
 :line-number-width nil
 :line-number-height 1.0

 :tab-bar-family nil
 :tab-bar-weight nil
 :tab-bar-slant nil
 :tab-bar-width nil
 :tab-bar-height 1.0

 :tab-line-family nil
 :tab-line-weight nil
 :tab-line-slant nil
 :tab-line-width nil
 :tab-line-height 1.0

 :bold-family nil
 :bold-slant nil
 :bold-weight bold
 :bold-width nil
 :bold-height 1.0

 :italic-family nil
 :italic-weight nil
 :italic-slant italic
 :italic-width nil
 :italic-height 1.0

 :line-spacing nil)

Multiple presets form an alist (a list of lists), like this: 

'((regular
   :default-family "Monospace"
   ;; More properties here
   )
  (medium
   :default-family "Iosevka Comfy Wide")
  ;; More presets here
  )

The doc string of fontaine-presets explains all properties in detail and documents some important caveats or information about font settings in Emacs.

Shared and implicit fallback values for presets.

The command fontaine-set-preset applies the desired preset. If called interactively, it produces a minibuffer prompt with completion among the available presets. When called from Lisp, it requires a PRESET argument, such as: 

(fontaine-set-preset 'regular)

The default behaviour of fontaine-set-preset is to change fonts across all graphical frames. The user can, however, limit the changes to a given frame. For interactive use, this is done by invoking the command with a universal prefix argument (C-u by default), which changes fonts only in the current frame. When used in Lisp, the FRAME argument can be a frame object (satisfies framep) or a non-nil value: the former applies the effects to the given object, while the latter means the current frame and thus is the same as interactively supplying the prefix argument.

As a final step, fontaine-set-preset calls the fontaine-set-preset-hook.

The latest value of fontaine-set-preset is stored in a file whose location is defined in fontaine-latest-state-file (normally part of the .emacs.d directory). Saving is done by the function fontaine-store-latest-preset, which should be assigned to a hook (e.g. kill-emacs-hook). To restore that value, the user can call the function fontaine-restore-latest-preset (such as by adding it to their init file).

The command fontaine-toggle-preset can toggle between the last two valid presets, as set by fontaine-set-preset. If it cannot find two different presets, then it prompts using minibuffer completion. As a final step, it calls the fontaine-set-preset-hook.

For users of the no-littering package, fontaine-latest-state-file is not stored in their .emacs.d, but in a standard directory instead: https://github.com/emacscollective/no-littering.

As for the name of this package, it is the French word for “fountain” which, in turn, is what the font or source is. However, I will not blame you if you can only interpret it as a descriptive acronym: FONTs Are Irrelevant in Non-graphical Emacs (because that is actually true).

2.1. Shared and implicit fallback values for presets

Inherit the properties of another named preset.

The user option fontaine-presets may look like this (though check its default value before you make any edits): 

;; NOTE this example does not include all the properties that
;; `fontaine-presets' accepts.
(setq fontaine-presets
      '((regular
         :default-family "Hack"
         :default-weight normal
         :default-height 100
         :fixed-pitch-family "Fira Code"
         :fixed-pitch-weight nil ; falls back to :default-weight
         :fixed-pitch-height 1.0
         :variable-pitch-family "Noto Sans"
         :variable-pitch-weight normal
         :variable-pitch-height 1.0
         :bold-family nil ; use whatever the underlying face has
         :bold-weight bold
         :italic-family "Source Code Pro"
         :italic-slant italic
         :line-spacing 1)
        (large
         :default-family "Iosevka"
         :default-weight normal
         :default-height 150
         :fixed-pitch-family nil ; falls back to :default-family
         :fixed-pitch-weight nil ; falls back to :default-weight
         :fixed-pitch-height 1.0
         :variable-pitch-family "FiraGO"
         :variable-pitch-weight normal
         :variable-pitch-height 1.05
         :bold-family nil ; use whatever the underlying face has
         :bold-weight bold
         :italic-family nil ; use whatever the underlying face has
         :italic-slant italic
         :line-spacing 1)))

Notice that not all properties need to be specified, as they have reasonable fallback values. The above can be written thus (removed lines are left empty for didactic purposes): 

(setq fontaine-presets
      '((regular
         :default-family "Hack"

         :default-height 100
         :fixed-pitch-family "Fira Code"


         :variable-pitch-family "Noto Sans"




         :italic-family "Source Code Pro"

         :line-spacing 1)
        (large
         :default-family "Iosevka"

         :default-height 150



         :variable-pitch-family "FiraGO"






         :line-spacing 1)))

Without the empty lines, we have this, which yields the same results as the first example: 

(setq fontaine-presets
      '((regular
         :default-family "Hack"
         :default-height 100
         :fixed-pitch-family "Fira Code"
         :variable-pitch-family "Noto Sans"
         :italic-family "Source Code Pro"
         :line-spacing 1)
        (large
         :default-family "Iosevka"
         :default-height 150
         :variable-pitch-family "FiraGO"
         :line-spacing 1)))

We call the properties of the removed lines “implicit fallback values”.

This already shows us that the value of fontaine-presets does not need to be extensive. To further improve its conciseness, it accepts a special preset that provides a list of “shared fallback properties”: the t preset. This one is used to define properties that are common to multiple presets, such as the regular and large we have illustrated thus far. Here is how verbose presets can be expressed succinctly: 

;; NOTE this example does not include all the properties that
;; `fontaine-presets' accepts.

;; Notice the duplication of properties and how we will avoid it.
(setq fontaine-presets
      '((regular
         :default-family "Iosevka Comfy"
         :default-weight normal
         :default-height 100
         :fixed-pitch-family nil ; falls back to :default-family
         :fixed-pitch-weight nil ; falls back to :default-weight
         :fixed-pitch-height 1.0
         :variable-pitch-family "FiraGO"
         :variable-pitch-weight normal
         :variable-pitch-height 1.05
         :bold-family nil ; use whatever the underlying face has
         :bold-weight bold
         :italic-family nil
         :italic-slant italic
         :line-spacing nil)
        (medium
         :default-family "Iosevka Comfy"
         :default-weight semilight
         :default-height 140
         :fixed-pitch-family nil ; falls back to :default-family
         :fixed-pitch-weight nil ; falls back to :default-weight
         :fixed-pitch-height 1.0
         :variable-pitch-family "FiraGO"
         :variable-pitch-weight normal
         :variable-pitch-height 1.05
         :bold-family nil ; use whatever the underlying face has
         :bold-weight bold
         :italic-family nil
         :italic-slant italic
         :line-spacing nil)
        (large
         :default-family "Iosevka Comfy"
         :default-weight semilight
         :default-height 180
         :fixed-pitch-family nil ; falls back to :default-family
         :fixed-pitch-weight nil ; falls back to :default-weight
         :fixed-pitch-height 1.0
         :variable-pitch-family "FiraGO"
         :variable-pitch-weight normal
         :variable-pitch-height 1.05
         :bold-family nil ; use whatever the underlying face has
         :bold-weight extrabold
         :italic-family nil
         :italic-slant italic
         :line-spacing nil)))

(setq fontaine-presets
      '((regular
         :default-height 100)
        (medium
         :default-weight semilight
         :default-height 140)
        (large
         :default-weight semilight
         :default-height 180
         :bold-weight extrabold)
        (t ; our shared fallback properties
         :default-family "Iosevka Comfy"
         :default-weight normal
         ;; :default-height 100
         :fixed-pitch-family nil ; falls back to :default-family
         :fixed-pitch-weight nil ; falls back to :default-weight
         :fixed-pitch-height 1.0
         :variable-pitch-family "FiraGO"
         :variable-pitch-weight normal
         :variable-pitch-height 1.05
         :bold-family nil ; use whatever the underlying face has
         :bold-weight bold
         :italic-family nil
         :italic-slant italic
         :line-spacing nil)))

The t preset does not need to explicitly cover all properties. It can rely on the aforementioned “implicit fallback values” to further reduce its verbosity (though the user can always write all properties if they intend to change their values). We then have this transformation: 

;; The verbose form
(setq fontaine-presets
      '((regular
         :default-height 100)
        (medium
         :default-weight semilight
         :default-height 140)
        (large
         :default-weight semilight
         :default-height 180
         :bold-weight extrabold)
        (t ; our shared fallback properties
         :default-family "Iosevka Comfy"
         :default-weight normal
         ;; :default-height 100
         :fixed-pitch-family nil ; falls back to :default-family
         :fixed-pitch-weight nil ; falls back to :default-weight
         :fixed-pitch-height 1.0
         :variable-pitch-family "FiraGO"
         :variable-pitch-weight normal
         :variable-pitch-height 1.05
         :bold-family nil ; use whatever the underlying face has
         :bold-weight bold
         :italic-family nil
         :italic-slant italic
         :line-spacing nil)))

;; The concise one which relies on "implicit fallback values"
(setq fontaine-presets
      '((regular
         :default-height 100)
        (medium
         :default-weight semilight
         :default-height 140)
        (large
         :default-weight semilight
         :default-height 180
         :bold-weight extrabold)
        (t ; our shared fallback properties
         :default-family "Iosevka Comfy"
         :default-weight normal
         :variable-pitch-family "FiraGO"
         :variable-pitch-height 1.05)))

2.2. Inherit the properties of another named preset

Shared and implicit fallback values for presets.

When defining multiple presets, we may need to duplicate properties and then make tweaks to individual values. Suppose we want to have two distinct presets for presentations: one is for coding related demonstrations and the other for prose. Both must have some common styles, but must define distinct font families each of which is suitable for the given task. In this case, we do not want to fall back to the generic t preset (per the default behaviour) and we also do not wish to duplicate properties manually, potentially making mistakes in the process. Fontaine thus provides a method of inheriting a named preset’s properties by using the :inherit property with a value that references the name of another preset (technically, the car of that list). Here is the idea: 

(setq fontaine-presets
      '((regular
         :default-height 100)
        (code-demo
         :default-family "Source Code Pro"
         :default-weight semilight
         :default-height 170
         :variable-pitch-family "Sans"
         :bold-weight extrabold)
        (prose-demo
         :inherit code-demo ; copy the `code-demo' properties
         :default-family "Sans"
         :variable-pitch-family "Serif"
         :default-height 220)
        (t
         :default-family "Monospace"
         ;; more generic fallback properties here...
         )))

In this scenario, the regular preset gets all its properties from the t preset. We omit them here in the interest of brevity (see the default value of fontaine-presets and its documentation for the details). In turn, the code-demo specifies more properties and falls back to t for any property not explicitly referenced therein. Finally, the prose-demo copies everything in code-demo, overrides every property it specifies, and falls back to t for every other property.

In the interest of simplicity, Fontaine does not support recursive inheritance. If there is a compelling need for it, we can add it in future versions.

3. Installation

3.1. GNU ELPA package

The package is available as fontaine. Simply do: 

M-x package-refresh-contents
M-x package-install

And search for it.

GNU ELPA provides the latest stable release. Those who prefer to follow the development process in order to report bugs or suggest changes, can use the version of the package from the GNU-devel ELPA archive. Read: https://protesilaos.com/codelog/2022-05-13-emacs-elpa-devel/.

3.2. Manual installation

Assuming your Emacs files are found in ~/.emacs.d/, execute the following commands in a shell prompt: 

cd ~/.emacs.d

# Create a directory for manually-installed packages
mkdir manual-packages

# Go to the new directory
cd manual-packages

# Clone this repo, naming it "fontaine"
git clone https://github.com/protesilaos/fontaine fontaine

Finally, in your init.el (or equivalent) evaluate this: 

;; Make Elisp files in that directory available to the user.
(add-to-list 'load-path "~/.emacs.d/manual-packages/fontaine")

Everything is in place to set up the package.

4. Sample configuration

Remember to read the relevant doc strings. 

(require 'fontaine)

(setq fontaine-latest-state-file
      (locate-user-emacs-file "fontaine-latest-state.eld"))

;; Iosevka Comfy is my highly customised build of Iosevka with
;; monospaced and duospaced (quasi-proportional) variants as well as
;; support or no support for ligatures:
;; <https://github.com/protesilaos/iosevka-comfy>.
(setq fontaine-presets
      '((small
         :default-family "Iosevka Comfy Motion"
         :default-height 80
         :variable-pitch-family "Iosevka Comfy Duo")
        (regular) ; like this it uses all the fallback values and is named `regular'
        (medium
         :default-weight semilight
         :default-height 115
         :bold-weight extrabold)
        (large
         :inherit medium
         :default-height 150)
        (presentation
         :default-height 180)
        (t
         ;; I keep all properties for didactic purposes, but most can be
         ;; omitted.  See the fontaine manual for the technicalities:
         ;; <https://protesilaos.com/emacs/fontaine>.
         :default-family "Iosevka Comfy"
         :default-weight regular
         :default-height 100

         :fixed-pitch-family nil ; falls back to :default-family
         :fixed-pitch-weight nil ; falls back to :default-weight
         :fixed-pitch-height 1.0

         :fixed-pitch-serif-family nil ; falls back to :default-family
         :fixed-pitch-serif-weight nil ; falls back to :default-weight
         :fixed-pitch-serif-height 1.0

         :variable-pitch-family "Iosevka Comfy Motion Duo"
         :variable-pitch-weight nil
         :variable-pitch-height 1.0

         :mode-line-active-family nil ; falls back to :default-family
         :mode-line-active-weight nil ; falls back to :default-weight
         :mode-line-active-height 0.9

         :mode-line-inactive-family nil ; falls back to :default-family
         :mode-line-inactive-weight nil ; falls back to :default-weight
         :mode-line-inactive-height 0.9

         :header-line-family nil ; falls back to :default-family
         :header-line-weight nil ; falls back to :default-weight
         :header-line-height 0.9

         :line-number-family nil ; falls back to :default-family
         :line-number-weight nil ; falls back to :default-weight
         :line-number-height 0.9

         :tab-bar-family nil ; falls back to :default-family
         :tab-bar-weight nil ; falls back to :default-weight
         :tab-bar-height 1.0

         :tab-line-family nil ; falls back to :default-family
         :tab-line-weight nil ; falls back to :default-weight
         :tab-line-height 1.0

         :bold-family nil ; use whatever the underlying face has
         :bold-weight bold

         :italic-family nil
         :italic-slant italic

         :line-spacing nil)))

;; Set the last preset or fall back to desired style from `fontaine-presets'
;; (the `regular' in this case).
(fontaine-set-preset (or (fontaine-restore-latest-preset) 'regular))

;; Persist the latest font preset when closing/starting Emacs and
;; while switching between themes.
(fontaine-mode 1)

;; fontaine does not define any key bindings.  This is just a sample that
;; respects the key binding conventions.  Evaluate:
;;
;;     (info "(elisp) Key Binding Conventions")
(define-key global-map (kbd "C-c f") #'fontaine-set-preset)

4.1. Persist font configurations on theme switch

[ Since version 2.0.0, there exists the fontaine-mode which does this automatically. ]

Themes re-apply face definitions when they are loaded. This is necessary to render the theme. For certain faces, such as bold and italic, it means that their font family may be reset (depending on the particularities of the theme).

To avoid such a potential problem, we can arrange to restore the current font preset which was applied by fontaine-set-preset. Fontaine provides the command fontaine-apply-current-preset. It can either be called interactively after loading a theme or be assigned to a hook that is ran at the post load-theme phase.

4.2. Theme-agnostic hook for Emacs 29 or higher

[ Since version 2.0.0, there exists the fontaine-mode which does this automatically. ]

Emacs 29 provides the enable-theme-functions, which we can use to persist or restore a font preset thus (Persist font configurations on theme switch): 

(add-hook 'enable-theme-functions #'fontaine-apply-current-preset)

4.3. Theme-agnostic hook before Emacs 29

[ Since version 2.0.0, there exists the fontaine-mode which does this automatically. ]

For versions of Emacs before 29, there is no built-in theme-agnostic solution to persisting or restoring a font preset (Theme-agnostic hook for Emacs 29 or higher).

Themes have to specify a hook that is called by their relevant commands at the post-theme-load phase. This can also be done in a generic way: 

;; Set up the `after-enable-theme-hook'
(defvar after-enable-theme-hook nil
  "Normal hook run after enabling a theme.")

(defun run-after-enable-theme-hook (&rest _args)
  "Run `after-enable-theme-hook'."
  (run-hooks 'after-enable-theme-hook))

(advice-add 'enable-theme :after #'run-after-enable-theme-hook)

And then simply use that hook: 

(add-hook 'after-enable-theme-hook #'fontaine-apply-current-preset)

5. Acknowledgements

Fontaine is meant to be a collective effort. Every bit of help matters.

Author/maintainer
Protesilaos Stavrou.
Contributions to the code or manual
Christopher League, Eli Zaretskii, Florent Teissier, Terry F. Torrey.
Ideas and user feedback
Adam Porter (alphapapa), Ashlin Eldridge, Joe Higton, Ted Reed.

6. GNU Free Documentation License


                GNU Free Documentation License
                 Version 1.3, 3 November 2008


 Copyright (C) 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.

0. PREAMBLE

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.


1. APPLICABILITY AND DEFINITIONS

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".

Examples of suitable formats for Transparent copies include plain
ASCII without markup, Texinfo input format, LaTeX input format, SGML
or XML using a publicly available DTD, and standard-conforming simple
HTML, PostScript or PDF designed for human modification.  Examples of
transparent image formats include PNG, XCF and JPG.  Opaque formats
include proprietary formats that can be read and edited only by
proprietary word processors, SGML or XML for which the DTD and/or
processing tools are not generally available, and the
machine-generated HTML, PostScript or PDF produced by some word
processors for output purposes only.

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.

The "publisher" means any person or entity that distributes copies of
the Document to the public.

A section "Entitled XYZ" means a named subunit of the Document whose
title either is precisely XYZ or contains XYZ in parentheses following
text that translates XYZ in another language.  (Here XYZ stands for a
specific section name mentioned below, such as "Acknowledgements",
"Dedications", "Endorsements", or "History".)  To "Preserve the Title"
of such a section when you modify the Document means that it remains a
section "Entitled XYZ" according to this definition.

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.

2. VERBATIM COPYING

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.


3. COPYING IN QUANTITY

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.


4. MODIFICATIONS

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:

A. 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.
B. 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.
C. State on the Title page the name of the publisher of the
   Modified Version, as the publisher.
D. Preserve all the copyright notices of the Document.
E. Add an appropriate copyright notice for your modifications
   adjacent to the other copyright notices.
F. 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.
G. Preserve in that license notice the full lists of Invariant Sections
   and required Cover Texts given in the Document's license notice.
H. Include an unaltered copy of this License.
I. 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.
J. 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.
K. 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.
L. 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.
M. Delete any section Entitled "Endorsements".  Such a section
   may not be included in the Modified Version.
N. Do not retitle any existing section to be Entitled "Endorsements"
   or to conflict in title with any Invariant Section.
O. 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.


5. COMBINING DOCUMENTS

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".


6. COLLECTIONS OF DOCUMENTS

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.


7. AGGREGATION WITH INDEPENDENT WORKS

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.


8. TRANSLATION

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.


9. TERMINATION

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.


10. FUTURE REVISIONS OF THIS LICENSE

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
https://www.gnu.org/licenses/.

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.

11. RELICENSING

"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 (c)  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.