= image:{logo}[K,30,30,link="{website}"] Kakoune image:{travis-img}[link="{travis-url}"] image:{irc-img}[link="{irc-url}"]
ifdef::env-github,env-browser[:outfilesuffix: .asciidoc]
:logo: https://rawgit.com/mawww/kakoune/master/doc/kakoune_logo.svg
:website: http://kakoune.org
:travis-img: https://travis-ci.org/mawww/kakoune.svg?branch=master
:travis-url: https://travis-ci.org/mawww/kakoune
:irc-img: https://img.shields.io/badge/IRC-%23kakoune-blue.svg
:irc-url: https://webchat.freenode.net/?channels=kakoune
:icons: font
:toc: right
:pp: ++

TL;DR
-----

{website}

*Modal editor* -- *Faster as in fewer keystrokes* --
*Multiple selections* -- *Orthogonal design*

---------------------------------------------
git clone http://github.com/mawww/kakoune.git
cd kakoune/src
make
./kak
---------------------------------------------

See http://github.com/mawww/golf for kakoune solutions to vimgolf challenges,
regularly beating the best Vim solution.

See the link:doc/design.asciidoc[design document] for more information on
Kakoune philosophy and design.

:numbered:

Introduction
------------

Kakoune is a code editor that implements Vi's "keystrokes as a text editing
language" model. As it's also a modal editor, it is somewhat similar to the
Vim editor (after which Kakoune was originally inspired).

Kakoune can operate in two modes, normal and insertion. In insertion mode,
keys are directly inserted into the current buffer. In normal mode, keys
are used to manipulate the current selection and to enter insertion mode.

Kakoune has a strong focus on interactivity, most commands provide immediate
and incremental results, while still being competitive (as in keystroke count)
with Vim.

Kakoune works on selections, which are oriented, inclusive range of characters,
selections have an anchor and a cursor character. Most commands move both of
them, except when extending selection where the anchor character stays fixed
and the cursor one moves around.

See http://vimeo.com/82711574

Join us on freenode IRC `#Kakoune`

Features
~~~~~~~~

 * Multiple selections as a central way of interacting
 * Powerful selection manipulation primitives
   - Select all regex matches in current selections
   - Keep selections containing/not containing a match for a given regex
   - Split current selections with a regex
   - Text objects (paragraph, sentence, nestable blocks)
 * Powerful text manipulation primitives
   - Align selections
   - Rotate selection contents
   - Case manipulation
   - Indentation
   - Piping each selection to external filter
 * Client-Server architecture
   - Multiple clients on the same editing session
   - Use tmux or your X11 window manager to manage windows
 * Simple interaction with external programs
 * Automatic contextual help
 * Automatic as you type completion
 * Macros
 * Hooks
 * Syntax Highlighting
   - Supports multiple languages in the same buffer
   - Highlight a buffer differently in different windows

Screenshots
~~~~~~~~~~~

[[screenshot-i3]]
.Kakoune in i3
image::doc/screenshot-i3.gif[Kakoune in i3]

[[screenshot-tmux]]
.Kakoune in tmux
image::doc/screenshot-tmux.gif[Kakoune in tmux]

Getting started
---------------

Building
~~~~~~~~

Kakoune dependencies are:

 * A {cpp}14 compliant compiler (GCC >= 5 or clang >= 3.9) along with its
   associated {cpp} standard library (libstdc{pp} or libc{pp})
 * ncurses with wide-characters support (>= 5.3, generally referred to as libncursesw)
 * asciidoc (for the `a2k` tool), to generate man pages

To build, just type *make* in the src directory.
To generate man pages, type *make man* in the src directory.

Kakoune can be built on Linux, MacOS, and Cygwin. Due to Kakoune relying heavily
on being in a Unix-like environment, no native Windows version is planned.

Installing
~~~~~~~~~~

In order to install kak on your system, rather than running it directly from
its source directory, type *make install*, you can specify the `PREFIX` and
`DESTDIR` if needed.

[TIP]
.Homebrew (macOS) or Linuxbrew
====
---------------------------------
brew install kakoune
---------------------------------
====

[TIP]
.Fedora supported versions and Rawhide
====
Use the https://copr.fedoraproject.org/coprs/jkonecny/kakoune/[copr]
repository.

---------------------------------
dnf copr enable jkonecny/kakoune
dnf install kakoune
---------------------------------
====

[TIP]
.Arch Linux
====
Kakoune is found in the https://www.archlinux.org/packages/community/x86_64/kakoune/[repositories].
--------------------------------------------------
pacman -S kakoune
--------------------------------------------------
====

[TIP]
.Gentoo
====
Kakoune is found in portage as
https://packages.gentoo.org/packages/app-editors/kakoune[app-editors/kakoune]
====

[TIP]
.Exherbo
====
--------------------------------
cave resolve -x repository/mawww
cave resolve -x kakoune
--------------------------------
====

[TIP]
.openSUSE
====
kakoune can be found in the
https://build.opensuse.org/package/show/editors/kakoune[editors] devel
project.  Make sure to adjust the link below to point to the repository of
your openSUSE version.

---------------------------------------------------------------------------------------------------
#Example for Tumbleweed:
sudo zypper addrepo http://download.opensuse.org/repositories/editors/openSUSE_Factory/editors.repo
sudo zypper refresh
sudo zypper install kakoune
---------------------------------------------------------------------------------------------------
====

[TIP]
.Ubuntu
====
Building on Ubuntu 16.04.
Make sure you have .local/bin in your path to make the kak binary available from your shell.

----------------------------------------------------------------
sudo apt install libncursesw5-dev asciidoc
git clone https://github.com/mawww/kakoune.git && cd kakoune/src
make
PREFIX=$HOME/.local make install
----------------------------------------------------------------
====

[TIP]
.FreeBSD
====
Kakoune is available in the official ports tree as
https://www.freshports.org/editors/kakoune[editors/kakoune].

A binary package is also available and can be installed with
--------------------------------------------------
pkg install kakoune
--------------------------------------------------
====

[TIP]
.Solus
====
Kakoune is available in the Solus stable repository.

It can be installed with
---------------------
eopkg install kakoune
---------------------
====

Running
~~~~~~~

Just running *kak* launch a new kak session with a client on local terminal.
Run *kak -help* to discover the valid <<doc/kak.1#options,command line flags>>.

Configuration
^^^^^^^^^^^^^

There are two directories containing Kakoune's scripts:

* `runtime`: located in `../share/kak/` relative to the `kak` binary
  contains the system scripts, installed with Kakoune.
* `userconf`: located in `$XDG_CONFIG_HOME/kak/`, which defaults
  to `$HOME/.config/kak/` on most systems, containing the user
  configuration.

Unless `-n` is specified, Kakoune will load its startup script located
at `${runtime}/kakrc` relative to the `kak` binary. This startup script
is responsible for loading the user configuration.

First, Kakoune will search recursively for `.kak` files in the `autoload`
directory. It will first look for an `autoload` directory at
`${userconf}/autoload` and will fallback to `${runtime}/autoload` if
it does not exist.

Once all those files are loaded, Kakoune will try to source
`${runtime}/kakrc.local` which is expected to contain distribution provided
configuration.

And finally, the user configuration will be loaded from `${userconf}/kakrc`.

NOTE: If you create a user `autoload` directory in `${userconf}/autoload`,
the system one at `${runtime}/autoload` will not be loaded anymore. You can
add a symbolic link to it (or to individual scripts) inside
`${userconf}/autoload` to keep loading system scripts.

Basic Interaction
-----------------

Selections
~~~~~~~~~~

The main concept in Kakoune is the selection. A selection is an inclusive,
directed range of character. A selection has two ends, the anchor and the
cursor.

There is always at least one selection, and a selection is always at least
one character (in which case the anchor and cursor of the selections are
on the same character).

Normal Mode
~~~~~~~~~~~

In normal mode, keys are not inserted directly inside the buffer, but are editing
commands. These commands provide ways to manipulate either the selections themselves,
or the selected text.

Insert Mode
~~~~~~~~~~~

When entering insert mode, keys are now directly inserted before each
selection's cursor. Some additional keys are recognised in insert mode:

 * `<esc>`: leave insert mode
 * `<backspace>`: delete characters before cursors
 * `<del>`: delete characters under cursors
 * `<left>, <right>, <up>, <down>`: move the cursors in given direction
 * `<home>`: move cursors to line begin
 * `<end>`: move cursors to end of line

 * `<c-n>`: select next completion candidate
 * `<c-p>`: select previous completion candidate
 * `<c-x>`: explicit insert completion query, followed by:
   - `f`: explicit file completion
   - `w`: explicit word completion
   - `l`: explicit line completion
 * `<c-o>`: disable automatic completion for this insert session

 * `<c-r>`: insert contents of the register given by next key
 * `<c-v>`: insert next keystroke directly into the buffer,
    without interpreting it.

 * `<c-u>`: commit changes up to now as a single undo group.

 * `<a-;>`: escape to normal mode for a single command

Movement
~~~~~~~~

 * `h`: select the character on the left of selection end
 * `j`: select the character below the selection end
 * `k`: select the character above the selection end
 * `l`: select the character on the right of selection end

 * `w`: select the word and following whitespaces  on the right of selection end
 * `b`: select preceding whitespaces and the word on the left of selection end
 * `e`: select preceding whitespaces and the word on the right of selection end
 * `<a-[wbe]>`: same as [wbe] but select WORD instead of word

 * `f`: select to the next occurence of given character
 * `t`: select until the next occurence of given character
 * `<a-[ft]>`: same as [ft] but in the other direction

 * `m`: select to matching character
 * `M`: extend selection to matching character

 * `x`: select line on which selection end lies (or next line when end lies on
        an end-of-line)
 * `X`: similar to `x`, except the current selection is extended
 * `<a-x>`: expand selections to contain full lines (including end-of-lines)
 * `<a-X>`: trim selections to only contain full lines (not including last
            end-of-line)

 * `%`: select whole buffer

 * `<a-h>`: select to line begin
 * `<a-l>`: select to line end

 * `/`: search (select next match)
 * `<a-/>`: search (select previous match)
 * `?`: search (extend to next match)
 * `<a-?>`: search (extend to previous match)
 * `n`: select next match
 * `N`: add a new selection with next match
 * `<a-n>`: select previous match
 * `<a-N>`: add a new selection with previous match

 * `pageup, <c-b>`: scroll one page up
 * `pagedown, <c-f>`: scroll one page down
 * `<c-u>`: scroll half a page up
 * `<c-d>`: scroll half a page down

 * `)`: rotate selections (the main selection becomes the next one)
 * `(`: rotate selections backwards

 * `;`: reduce selections to their cursor
 * `<a-;>`: flip the selections' direction
 * `<a-:>`: ensure selections are in forward direction (cursor after anchor)

 * `<a-.>`: repeat last object or `f`/`t` selection command.

 * `_`: trim selections

A word is a sequence of alphanumeric characters or underscore, a WORD is a
sequence of non whitespace characters.

Appending
~~~~~~~~~

for most selection commands, using shift permits extending current selection
instead of replacing it. for example, `wWW` selects 3 consecutive words

Using Counts
~~~~~~~~~~~~

Most selection commands also support counts, which are entered before the
command itself.

For example, `3W` selects 3 consecutive words and `3w` select the third word on
the right of selection end.

Disabling Hooks
~~~~~~~~~~~~~~~

Any normal mode command can be prefixed with `\` which will disable hook execution
for the duration for the command (including the duration of modes the command could
move to, so `\i` will disable hooks for the whole insert session).

As autoindentation is implemented in terms of hooks, this can be used to disable
it when pasting text.

Changes
~~~~~~~

 * `i`: enter insert mode before current selection
 * `a`: enter insert mode after current selection
 * `d`: yank and delete current selection
 * `c`: yank and delete current selection and enter insert mode
 * `.`: repeat last insert mode change (`i`, `a`, or `c`, including
        the inserted text)

 * `<a-d>`: delete current selection
 * `<a-c>`: delete current selection and enter insert mode

 * `I`: enter insert mode at current selection begin line start
 * `A`: enter insert mode at current selection end line end
 * `o`: enter insert mode in one (or given count) new lines below
        current selection end
 * `O`: enter insert mode in one (or given count)  new lines above
        current selection begin

 * `<a-o>`: add an empty line below cursor
 * `<a-O>`: add an empty line above cursor

 * `y`: yank selections
 * `p`: paste after current selection end
 * `P`: paste before current selection begin
 * `<a-p>`: paste all after current selection end, and
            select each pasted string.
 * `<a-P>`: paste all before current selection begin, and
            select each pasted string.
 * `R`: replace current selection with yanked text
 * `<a-R>`: replace current selection with every yanked text

 * `r`: replace each character with the next entered one

 * `<a-j>`: join selected lines
 * `<a-J>`: join selected lines and select spaces inserted
            in place of line breaks
 * `<a-m>`: merge contiguous selections together (works across lines as well)

 * `<gt> (>)`: indent selected lines
 * `<a-gt>`: indent selected lines, including empty lines
 * `<lt> (<)`: deindent selected lines
 * `<a-lt>`: deindent selected lines, do not remove incomplete
        indent (3 leading spaces when indent is 4)

 * `|`: pipe each selection through the given external filter program
        and replace the selection with it's output.
 * `<a-|>`: pipe each selection through the given external filter program
        and ignore its output

 * `!`: insert command output before selection
 * `<a-!>`: append command output after selection

 * `u`: undo last change
 * `<a-u>`: move backward in history
 * `U`: redo last change
 * `<a-U>`: move forward in history

 * `&`: align selection, align the cursor of selections by inserting
        spaces before the first character of the selection
 * `<a-&>`: copy indent, copy the indentation of the main selection
        (or the count one if a count is given) to all other ones

 * ```: to lower case
 * `~`: to upper case
 * ``<a-`>``: swap case

 * `@`: convert tabs to spaces in current selections, uses the buffer
        tabstop option or the count parameter for tabstop.
 * `<a-@>`: convert spaces to tabs in current selections, uses the buffer
            tabstop option or the count parameter for tabstop.

 * `<a-)>`: rotate selections content, if specified, the count groups
            selections, so `3<a-">` rotate (1, 2, 3) and (3, 4, 6)
            independently.
 * `<a-(>`: rotate selections content backwards

Goto Commands
~~~~~~~~~~~~~

Commands beginning with `g` are used to goto certain position and or buffer.
If a count is given prior to hitting `g`, `g` will jump to the given line.
Using `G` will extend the selection rather than jump.

See <<doc/pages/keys#goto-commands,`:doc keys goto-commands`>>.

View commands
~~~~~~~~~~~~~

Commands beginning with `v` permit to center or scroll the current
view. Using `V` will lock view mode until `<esc>` is hit

See <<doc/pages/keys#view-commands,`:doc keys view-commands`>>.

Marks
~~~~~

Current selections position can be saved in a register and restored later on.

See <<doc/pages/keys#marks,`:doc keys marks`>>.

Jump list
~~~~~~~~~

Some commands, like the goto commands, buffer switch or search commands,
push the previous selections to the client's jump list.

See <<doc/pages/keys#jump-list,`:doc keys jump-list`>>.

Multi Selection
~~~~~~~~~~~~~~~

Kak was designed from the start to handle multiple selections.
One way to get a multiselection is via the `s` key.

For example, to change all occurrences of word 'roger' to word 'marcel'
in a paragraph, here is what can be done:

 * select the paragraph with enough `x`
 * press `s` and enter roger, then enter
 * now paragraph selection was replaced with multiselection of each roger in
the paragraph
 * press `c` and marcel<esc> to replace rogers with marcels

A multiselection can also be obtained with `S`, which splits the current
selection according to the regex entered. To split a comma separated list,
use `S` then ', *'

The regex syntax supported by Kakoune is the based on the ECMAScript script
syntax and is described at <<doc/pages/regex#,`:doc regex`>>.

`s` and `S` share the search pattern with `/`, and hence entering an empty
pattern uses the last one.

As a convenience, `<a-s>` allows you to split the current selections on
line boundaries.

To clear multiple selections, use `space`. To keep only the nth selection
use `n` followed by `space`, in order to remove a selection, use `<a-space>`.

`<a-k>` allows you to enter a regex and keep only the selections that
contains a match for this regex. Using `<a-K>` you can keep the selections
not containing a match.

`C` copies the current selection to the next line (or lines if a count is given)
`<a-C>` does the same to previous lines.

`$` allows you to enter a shell command and pipe each selection to it.
Selections whose shell command returns 0 will be kept, other will be dropped.

Object Selection
~~~~~~~~~~~~~~~~

Objects are specific portions of text, like sentences, paragraphs, numbers…
Kakoune offers many keys allowing you to select various text objects.

See <<doc/pages/keys#object-selection,`:doc keys object-selection`>>.

Commands
--------

When pressing `:` in normal mode, Kakoune will open a prompt to enter a command.

Commands are used for non editing tasks, such as opening a buffer, writing the
current one, quitting, etc.

See <<doc/pages/keys#prompt-commands,`:doc keys prompt-commands`>>.

Basic Commands
~~~~~~~~~~~~~~

Some commands take an exclamation mark (`!`), which can be used to force
the execution of the command (i.e. to quit a modified buffer, the
command `q!` has to be used).

Commands starting with horizontal whitespace (e.g. a space) will not be
saved in the command history.

 * `cd [<directory>]`: change the current directory to `<directory>`, or the home directory if unspecified
 * `doc <topic>`: display documentation about a topic. The completion list
     displays the available topics.
 * `e[dit][!] <filename> [<line> [<column>]]`: open buffer on file, go to given
     line and column. If file is already opened, just switch to this file.
     Use edit! to force reloading.
 * `w[rite][!] [<filename>]`: write buffer to <filename> or use its name if
     filename is not given. If the file is write-protected, its
     permissions are temporarily changed to allow saving the buffer and
     restored afterwards when the write! command is used.
 * `w[rite]a[ll]`: write all buffers that are associated to a file.
 * `q[uit][!] [<exit status>]`: exit Kakoune, use quit! to force quitting even
     if there is some unsaved buffers remaining. If specified, the client exit
     status will be set to <exit status>.
 * `w[a]q[!] [<exit status>]`: write the current buffer (or all buffers when
     `waq` is used) and quit. If specified, the client exit status will be set
     to <exit status>.
 * `kill[!]`: terminate the current session, all the clients as well as the server,
     use kill! to ignore unsaved buffers
 * `b[uffer] <name>`: switch to buffer <name>
 * `b[uffer]n[ext]`: switch to the next buffer
 * `b[uffer]p[rev]`: switch to the previous buffer
 * `d[el]b[uf][!] [<name>]`: delete the buffer <name>
 * `source <filename>`: execute commands in <filename>
 * `colorscheme <name>`: load named colorscheme.
 * `rename-client <name>`: set current client name
 * `rename-buffer <name>`: set current buffer name
 * `rename-session <name>`: set current session name
 * `echo [options] <text>`: show <text> in status line, with the following options:
   ** `-markup`: expand the markup strings in <text>
   ** `-debug`: print the given text to the `\*debug*` buffer
 * `nop`: does nothing, but as with every other commands, arguments may be
     evaluated. So nop can be used for example to execute a shell command
     while being sure that it's output will not be interpreted by kak.
     `:%sh{ echo echo tchou }` will echo tchou in Kakoune, whereas
     `:nop %sh{ echo echo tchou }` will not, but both will execute the
     shell command.
 * `fail <text>`: raise an error, uses <text> as its description

Multiple commands
~~~~~~~~~~~~~~~~~

Multiple commands can be separated either by new lines or by semicolons,
as such a semicolon must be escaped with `\;` to be considered as a literal
semicolon argument.

String syntax and expansions
^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Values, options and shell context can be interpolated in strings.

See <<doc/pages/expansions#,`:doc expansions`>>.

Configuration & Autoloading
---------------------------

Kakrc
~~~~~

If not launched with the `-n` switch, Kakoune will source the
`../share/kak/kakrc` file relative to the `kak` binary, which
will source additional files:

If the `$XDG_CONFIG_HOME/kak/autoload` directory exists, load every
`*.kak` files in it, and load recursively any subdirectory.

If it does not exist, falls back to the site wide autoload directory
in `../share/kak/autoload/`.

After that, if it exists, source the `$XDG_CONFIG_HOME/kak/kakrc` file
which should be used for user configuration.

In order to continue autoloading site-wide files with a local autoload
directory, just add a symbolic link to `../share/kak/autoload/` into
your local autoload directory.

Color Schemes
~~~~~~~~~~~~~

Kakoune ships with some color schemes that are installed to
`../share/kak/colors/`. If `$XDG_CONFIG_HOME/kak/colors/` is present
the builtin command `colorscheme` will offer completion for those
color schemes. If a scheme is duplicated in userspace, it will take
precedence.

Options
-------

Kakoune can store named and typed values that can be used both to
customize the core editor behaviour, and to keep data used by extension
scripts.

See <<doc/pages/options#,`:doc options`>>.


Advanced topics
---------------

Faces
~~~~~

Faces describe how characters are displayed on the screen: color, bold, italic...

See <<doc/pages/faces#,`:doc faces`>>.

Registers
~~~~~~~~~

Registers are named lists of text. They are used for various purposes,
like storing the last yanked text, or the captured groups associated with the selections.

See <<doc/pages/registers#,`:doc registers`>>.

Macros
~~~~~~

Kakoune can record and replay a sequence of key presses.

See <<doc/pages/keys#macros,`:doc keys macros`>>.

Search selection
~~~~~~~~~~~~~~~~

Using the `*` key, you can set the search pattern to the current selection.
See <<doc/pages/keys#searching,`:doc keys searching`>>.

Regex syntax
~~~~~~~~~~~~

Kakoune regex syntax is based on the ECMAScript syntax (ECMA-262 standard).
It always run on Unicode codepoint sequences, not on bytes.

See <<doc/pages/regex#,`:doc regex`>>.

Exec and Eval
~~~~~~~~~~~~~

The `execute-keys` and `evaluate-commands` are useful for scripting
in non interactive contexts.

See <<doc/pages/execeval#,`:doc execeval`>>.

Insert mode completion
~~~~~~~~~~~~~~~~~~~~~~

Kakoune can propose completions while inserting text: filenames, words, lines…

See <<doc/pages/keys#insert-mode-completion,`:doc keys insert-mode-completion`>>.

Escape to normal mode
~~~~~~~~~~~~~~~~~~~~~

From insert mode, pressing `<a-;>` allows you to execute a single normal mode
command. This provides a few advantages:

 * The selections are not modified: when leaving insert mode using `<esc>` the
   selections can change, for example when insert mode was entered with `a` the
   cursor will go back one char. Or if on an end of line the cursor will go back
   left (if possible).

 * The modes are nested: that means the normal mode can enter prompt (with `:`),
   or any other modes (using `:on-key` or `:menu` for example), and these modes
   will get back to the insert mode afterwards.

This feature is tailored for scripting/macros, as it provides a more predictable
behaviour than leaving insert mode with `<esc>`, executing normal mode command
and entering back insert mode (with which binding ?)

See <<doc/pages/modes#,`:doc modes`>>.

Highlighters
~~~~~~~~~~~~

Manipulation of the displayed text, such as syntax coloration and wrapping
is done through highlighters.

See <<doc/pages/highlighters#,`:doc highlighters`>>.

Hooks
~~~~~

Commands can be registered to be executed when certain events arise with hooks.

See <<doc/pages/hooks#,`:doc hooks`>>.

Key Mapping
~~~~~~~~~~~

Custom key shortcuts can be registered through mappings.

See <<doc/pages/mapping#,`:doc mapping`>>.

Defining Commands
~~~~~~~~~~~~~~~~~

New commands can be created using `:define-command`.

See <<doc/pages/commands#declaring-new-commands,`:doc commands declaring-new-commands`>>.

Some helper commands are available to define composite commands.

See <<doc/pages/commands#helpers,`:doc commands helpers`>>.

Aliases
~~~~~~~

With `:alias` commands can be given additional names. Aliases are scoped, so
that an alias can refer to one command for a buffer, and to another for another
buffer. The following command defines `<alias>` as an alias for `<command>`:

--------------------------------
:alias <scope> <alias> <command>
--------------------------------

`<scope>` can be one of `global`, `buffer` or `window`.

-------------------------------------
:unalias <scope> <alias> [<expected>]
-------------------------------------

Will remove the given alias in the given scope. If `<expected>` is specified
the alias will only be removed if its current value is `<expected>`.

FIFO Buffers
~~~~~~~~~~~

FIFO buffers are very useful for running some commands asynchronously while
progressively displaying their result in Kakoune.

See <<doc/pages/buffers#fifo-buffers,`:doc buffers fifo-buffers`>>.

Menus
~~~~~

When a menu is displayed, you can use `j`, `<c-n>` or `<tab>` to select the next
entry, and `k`, `<c-p>` or `<shift-tab>` to select the previous one.

Using the `/` key, you can enter some regex in order to restrict available choices
to the matching ones.
