Minibuffer and Completions in Tandem (mct.el)

Enhancement of the default Emacs minibuffer completion UI

The source code is available on Gitlab, for the time being. A mirror on Github is also on offer. The official manual is right below. If you have no idea what mct is, it is a very thin layer of interactivity on top of the default completion user interface. Watch the video demonstration of its initial release.


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

The documentation furnished herein corresponds to stable version 0.3.0, released on 2021-11-19. 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 0.4.0-dev.

1. COPYING

Copyright (C) 2021 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 of MCT

Minibuffer and Completions in Tandem, also known as “MCT”, “Mct”, mct, or mct.el, is a package that enhances the default minibuffer and *Completions* buffer of Emacs 27 (or higher) so that they work together as part of a unified framework. The idea is to make the presentation and overall functionality be consistent with other popular, vertically aligned completion UIs while leveraging built-in functionality.

The main feature set that unifies the minibuffer and the *Completions* buffer consists of commands that cycle between the two, making it seem like they are part of a contiguous space (Basic usage).

MCT tries to find a middle ground between the frugal defaults and the more opinionated completion UIs. This is most evident in its approach on how to present completion candidates. Instead of showing them outright or only displaying them on demand, MCT implements a minimum input threshold as well as a slight delay before it pops up the *Completions* buffer and starts updating it to respond to user input.

Customisation options control the input threshold (mct-minimum-input) and the delay between live updates (mct-live-update-delay). Similarly, a blocklist and a passlist for commands are on offer:

  • The blocklist (mct-completion-blocklist) disables the live-updating functionality for the functions specified therein.

  • The passlist (mct-completion-passlist) always shows the Completions’ buffer for the designated function without accounting for the minimum input threshold.

The user option mct-live-completion controls the overall behaviour of the Completions’ buffer:

  • When nil, the user has to manually request completions, using the regular activating commands. The Completions’ buffer is never updated live to match user input. Updating has to be handled manually. This is like the out-of-the-box minibuffer completion experience.
  • When set to the value visible, the Completions’ buffer is live updated only if it is visible. The actual display of the completions is still handled manually. For this reason, the visible style does not read the mct-minimum-input, meaning that it will always try to live update the visible completions, regardless of input length.
  • When non-nil (the default), the Completions’ buffer is automatically displayed once the mct-minimum-input is met and is hidden once the input drops below that threshold. While visible, the buffer is updated live to match the user input.
  • Note that every function in the mct-completion-passlist ignores this option altogether. This means that every such command will always show the Completions’ buffer automatically and will always update its contents live. Same principle for every function declared in the mct-completion-blocklist, which will always disable both the automatic display and live updating of the Completions’ buffer.

Other customisations:

  • mct-hide-completion-mode-line to hide the mode line of the *Completions* buffer. This removes the separation between it and the minibuffer, further contributing to the idea of a unified space between the two.

  • mct-remove-shadowed-file-name to clear shadowed file names when file-name-shadow-mode is enabled. This means that in prompts that use file paths (such as find-file) when you start in, say, ~/Git/mct.el and type ~/ the previous file path is removed and only the new one is inserted. Whereas the default is to keep the original file name visible yet “shadowed” by a different colour.

  • mct-show-completion-line-numbers to always display line numbers in the Completions’ buffer. This can be helpful to get a sense of the length of the completion candidates’ list. Though note that line numbers are displayed ephemerally while using the mct-choose-completion-number command, which is bound to M-g M-g in either the minibuffer or the *Completions* buffer.

  • mct-apply-completion-stripes applies alternative background colours in the Completions’ buffer. This is only tested with the modus-themes and will only work nicely if the main background is pure black or white—other themes would need to add support for the faces we define or, at least, users must modify the mct-stripe face.

3. Usage

3.1. Cyclic behaviour

When mct-mode is enabled, some new keymaps are activated which add commands for cycling between the minibuffer and the completions. Suppose the following standard layout:

-----------------
|               |
|               |
|               |
|  Buffer       |
|               |
|               |
|               |
-----------------
-----------------
|               |
|  Completions  |
|               |
-----------------
-----------------
|  Minibuffer   |
-----------------

When inside the minibuffer, pressing C-n (or down arrow) takes you to the top of the completions, while C-p (or up arrow) moves to the bottom. The commands are mct-switch-to-completions-top for the former and mct-switch-to-completions-bottom for the latter. If the *Completions* are not shown, then the buffer pops up automatically and point moves to the given position.

Similarly, while inside the *Completions* buffer, C-p (or up arrow) at the top of the buffer switches to the minibuffer, while C-n (or down arrow) at the bottom of the buffer also goes to the minibuffer. If point is anywhere else inside the buffer, those key bindings perform a regular line motion. The commands are mct-previous-completion-or-mini and mct-next-completion-or-mini. Both accept an optional numeric argument. If the Nth line lies outside the boundaries of the completions’ buffer, they move the point to the minibuffer.

The display of the *Completions* can be toggled at any time from inside the minibuffer with C-l (mnemonic is “[l]ist completions” and the command is mct-list-completions-toggle).

By default, the *Completions* buffer appears in a window at the bottom of the frame. Users can change its placement by configuring the variable mct-display-buffer-action (its doc string explains how and provides sample code).

3.2. Selecting candidates

There are several ways to select a completion candidate.

  1. Suppose that you are typing mod with the intent to select the modus-themes.el buffer. To force complete the first candidate follow up mod with the TAB key (minibuffer-force-complete). This does not exit the minibuffer, meaning that it does not confirm your choice. It just expands your input to the first likely candidate. To confirm your choice, use RET. If done fast enough, no completions will be shown (depending on your minimum input threshold and the live-update delay). If you made a mistake, just use undo. If the candidates meet the completion-cycle-threshold hit TAB again to switch between them.

  2. While cycling through the completions’ buffer, type RET to select and confirm the current candidate (mct-choose-completion-exit). This works for all types of completion prompts.

  3. Similar to the above, but without exiting the minibuffer (i.e. to confirm your choice) is mct-choose-completion-no-exit which is bound to TAB in the completions’ buffer. This is particularly useful for certain contexts where selecting a candidate does not necessarily mean that the process has to be finalised (e.g. when using find-file). In those cases, the event triggered by TAB is followed by the renewal of the list of completions, where relevant (e.g. TAB over a directory in find-file, which then shows the contents of that directory).

    The command can correctly expand completion candidates even when the active style in completion-styles is partial-completion. In other words, if the minibuffer contains input like ~/G/P/m and the point is in the completions’ buffer over Git/Projects/mct/ the minibuffer’ contents will become ~/Git/Projects/mct/ and then show the contents of that directory.

  4. Type M-e (mct-edit-completion) in the completions’ buffer to place the current candidate in the minibuffer, without exiting the session. This allows you to edit the text before confirming it. If point is in the minibuffer before performing this action, the current candidate is either the one at the top of the completions’ buffer or that which is under the last known point in said buffer (the last known position is reset when the window is deleted). Internally, mct-edit-completion uses mct-choose-completion-no-exit to expand the completion candidate, so it retains its behaviour (as explained right above).

  5. Select a candidate by its line number by typing M-g M-g in either the minibuffer or the *Completions* buffer. This calls the command mct-choose-completion-number which internally enables line numbers and always makes the completions’ buffer visible. Selection in this way exits the minibuffer.

    NOTE: This method only works when mct-completions-format is set to its default value of one-column. The other formats show completions in a grid view, which makes navigation based on line numbers imprecise.

  6. In prompts that allow the selection of multiple candidates (internally via the completing-read-multiple function) a [CRM] label is added to the text of the prompt. The user thus knows that pressing M-RET (mct-choose-completion-dwim) in the *Completions* will append the candidate at point to the list of selections and keep the completions available so that another item may be selected. Any of the aforementioned applicable methods can confirm the final selection. If, say, you want to pick a total of three candidates, do M-RET for the first two and RET (mct-choose-completion-exit) for the last one. In contexts that are not CRM-powered, the M-RET has the same effect as TAB (mct-choose-completion-no-exit).

  7. When point is at the minibuffer, select the current candidate in the completions buffer with C-RET (mct-complete-and-exit), which has the same effect as first completing with TAB and then immediately exit the minibuffer with the completed candidate as the selected one.

3.3. Other commands

  • Emacs 28 has the ability to group candidates inside the completions’ buffer under headings. For example, the Consult package makes good use of those (Extensions). MCT provides motions that jump between such headings, placing the point at the first candidate right below the heading’s text. Use M-n (mct-next-completion-group) and M-p (mct-previous-completion-group) to move to the next or previous one, respectively. Both commands accept an optional numeric argument. For the sake of avoiding surprises, these commands do not cycle between the completions and the minibuffer: they stop at the first or last heading.

  • When using completion categories that involve file paths, such as find-file, the backspace key (DEL) goes up a directory if point is right after a path’s directory delimiter (a forward slash). Otherwise it deletes a single character backwards. The command’s symbol is mct-backward-updir.

4. Installation

4.1. Install the package

mct is available on the official GNU ELPA archive for users of Emacs version 27 or higher. One can install the package without any further configuration. The following commands shall suffice:

M-x package-refresh-contents
M-x package-install RET mct

4.2. Manual installation method

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 and name it "mct"
git clone https://gitlab.com/protesilaos/mct.git mct

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/mct")

Everything is in place to set up the package.

5. Sample setup

Minimal setup:

(require 'mct)
(mct-mode 1)

And with more options:

(require 'mct)

(setq mct-remove-shadowed-file-names t) ; works when `file-name-shadow-mode' is enabled
(setq mct-hide-completion-mode-line t)
(setq mct-show-completion-line-numbers nil)
(setq mct-apply-completion-stripes t)
(setq mct-minimum-input 3)
(setq mct-live-update-delay 0.6)
(setq mct-completions-format 'one-column)

;; NOTE: `mct-completion-blocklist' can be used for commands with lots
;; of candidates, depending also on how low `mct-minimum-input' is.
;; With the settings shown here this is not required, otherwise I would
;; use something like this:
;;
;; (setq mct-completion-blocklist
;;       '( describe-symbol describe-function describe-variable
;;          execute-extended-command insert-char))
(setq mct-completion-blocklist nil)

;; This is for commands that should always pop up the completions'
;; buffer.  It circumvents the default method of waiting for some user
;; input (see `mct-minimum-input') before displaying and updating the
;; completions' buffer.
(setq mct-completion-passlist
      '(imenu
        Info-goto-node
        Info-index
        Info-menu
        vc-retrieve-tag))

;; You can place the Completions' buffer wherever you want, by following
;; the syntax of `display-buffer'.  For example, try this:

;; (setq mct-display-buffer-action
;;       (quote ((display-buffer-reuse-window
;;                display-buffer-in-side-window)
;;               (side . left)
;;               (slot . 99)
;;               (window-width . 0.3))))

(mct-mode 1)

Other useful extras from the Emacs source code (read their doc strings):

(setq completion-styles
      '(basic substring initials flex partial-completion))
(setq completion-category-overrides
      '((file (styles . (basic partial-completion initials substring)))))

(setq completion-cycle-threshold 2)
(setq completion-ignore-case t)
(setq completion-show-inline-help nil)

(setq completions-detailed t)

(setq enable-recursive-minibuffers t)
(setq minibuffer-eldef-shorten-default t)

(setq read-buffer-completion-ignore-case t)
(setq read-file-name-completion-ignore-case t)

(setq resize-mini-windows t)
(setq minibuffer-eldef-shorten-default t)

(file-name-shadow-mode 1)
(minibuffer-depth-indicate-mode 1)
(minibuffer-electric-default-mode 1)

;; Do not allow the cursor in the minibuffer prompt
(setq minibuffer-prompt-properties
      '(read-only t cursor-intangible t face minibuffer-prompt))

(add-hook 'minibuffer-setup-hook #'cursor-intangible-mode)

;;; Minibuffer history
(require 'savehist)
(setq savehist-file (locate-user-emacs-file "savehist"))
(setq history-length 10000)
(setq history-delete-duplicates t)
(setq savehist-save-minibuffer-history t)
(add-hook 'after-init-hook #'savehist-mode)

;;; Extensions

;;;; Enable Consult previews in the Completions buffer.
;; Requires the Consult package.
(add-hook 'completion-list-mode-hook #'consult-preview-at-point-mode)

;;;; Setup for Orderless
;; Requires the Orderless package

;; We make the SPC key insert a literal space and the same for the
;; question mark.  Spaces are used to delimit orderless groups, while
;; the quedtion mark is a valid regexp character.
(let ((map minibuffer-local-completion-map))
  (define-key map (kbd "SPC") nil)
  (define-key map (kbd "?") nil))

;; Because SPC works for Orderless and is trivial to activate, I like to
;; put `orderless' at the end of my `completion-styles'.  Like this:
(setq completion-styles
      '(basic substring initials flex partial-completion orderless))
(setq completion-category-overrides
      '((file (styles . (basic partial-completion orderless)))))

6. Keymaps

MCT defines its own keymaps, which extend those that are active in the minibuffer and the *Completions* buffer, respectively:

  • mct-completion-list-mode-map
  • mct-minibuffer-local-completion-map
  • mct-minibuffer-local-filename-completion-map

You can invoke describe-keymap to learn more about them.

If you want to edit any key bindings, do it in these keymaps, not in those they extend and override (the names of the original ones are the same as above, minus the mct- prefix).

7. Extensions

MCT only tweaks the default minibuffer. To get more out of it, consider these exceptionally well-crafted extras:

Consult by Daniel Mendler
Adds several commands that make interacting with the minibuffer more powerful. There also are multiple packages that build on it, such as consult-dir by Karthik Chikmagalur and consult-notmuch by José Antonio Ortega Ruiz.
Embark by Omar Antolín Camarena
Provides configurable contextual actions for completions and many other constructs inside buffers. A genius package!
Marginalia by Daniel and Omar
Displays informative annotations for all known types of completion candidates.
Orderless by Omar
A completion style that matches a variety of patterns (regexp, flex, initialism, etc.) regardless of the order they appear in.

7.1. Enable Consult previews

One of the nice features of the Consult package is the ability to preview the candidate at point. All we need to enable it in the *Completions* buffer is the following snippet:

(add-hook 'completion-list-mode-hook #'consult-preview-at-point-mode)

8. Alternatives

Like MCT, these alternatives provide a thin layer of functionality over the built-in infrastructure. They all make for a natural complement to the standard Emacs experience (also Extensions).

Vertico by Daniel Mendler

this is a more mature and feature-rich package with a large user base and a highly competent maintainer.

Vertico has some performance optimisations on how candidates are sorted and presented, which means that it displays results right away without any noticeable performance penalty. Whereas MCT does not change the underlying behaviour of how candidates are displayed. As such, MCT will be slower in scenaria where there are lots of candidates because core Emacs lacks those optimisations. One such case is with the describe-symbol (C-h o) prompt. If the user asks for the completions’ buffer without inputting any character (so without narrowing the list), there will be a noticeable delay before the buffer is rendered. This is mitigated in MCT by the requirement for mct-minimum-input, though the underlying mechanics remain in tact.

In terms of the interaction model, the main difference between Vertico and MCT is that the former uses the minibuffer by default and shows the completions there. The minibuffer is expanded to show the candidates in a vertical list. Whereas MCT keeps the *Completions* buffer and the minibuffer as separate entities, the way standard Emacs does it.

The presence of a fully fledged buffer means that the user can invoke all relevant commands at their disposal, such as to write the buffer to a file for future review, use Isearch to move around, copy a string or rectangle to a register, and so on. Also, the placement of such a buffer is configurable (as with all buffers—though refer, in particular, to mct-display-buffer-action).

Vertico also supports buffer display, though only for the placement of the buffer. There is an extension for that in the git repository called vertico-buffer.el. Note, however, that the common combination of Vertico and Embark means that users can always place the list of completion candidates in a standalone buffer by means of Embark’s collect/export facilities.

Elmo - Embark Live MOde for Emacs by Karthik Chikmagalur

this package is best described as a sibling of MCT both in terms of its functionality and overall interaction model. In fact, the cyclic motions that are at the core of the MCT experience were first developed as part of my personal Emacs setup to cycle between the minibuffer and Embark’s “live completions” buffer. That was until Emacs28 got some refinements to the presentation of the *Completions* buffer which allowed for a vertical, single-column view.

Elmo can, in principle, have identical functionality with MCT, given that the only substantive difference is that the former uses an Embark buffer to show live-updating completions, while the latter relies on the generic *Completions* buffer.

For users who are on Emacs 27 and who need a single-column view, Elmo is a better choice because MCT can only display such a view on Emacs 28 or higher (though it has been meticulously tested with the grid views of Emacs 27 and should work perfectly fine with them).

Icomplete and fido-mode (built-in, multiple authors)

Icomplete is closer in spirit to Vertico, as it too uses the minibuffer to display completion candidates. By default, it presents the list horizontally, though there exists icomplete-vertical-mode (and fido-vertical-mode).

For our purposes, Icomplete and Fido are the same in terms of the paradigm they follow. The latter is a re-spin of the former, as it adjusts certain variables and binds some commands for the convenience of the end-user. fido-mode and its accoutrements are defined in icomplete.el.

What MCT borrows from Icomplete is the mct-backward-updir command, the tidying of the shadowed file paths, and ideas for the input delay (explained elsewhere in this document). Internally, I also learnt how to extend local keymaps by studying icomplete.el.

I had used Icomplete for several months before moving to what now has become mct.el. I think it is excellent at providing a thin layer over the built-in infrastructure.

9. Acknowledgements

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

Author/maintainer
Protesilaos Stavrou.
Contributions to code or documentation
Daniel Mendler, James Norman Vladimir Cash, José Antonio Ortega Ruiz, Philip Kaludercic.
Ideas and user feedback
Case Duckworth, Jonathan Irving, José Antonio Ortega Ruiz, Kostadin Ninev, Manuel Uberti, Philip Kaludercic, Theodor Thornhill.
Inspiration for certain features
icomplete.el (built-in—multiple authors), Daniel Mendler (vertico), Omar Antolín Camarena (embark, live-completions), Štěpán Němec (stripes.el).

11. GNU Free Documentation License


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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.