Test case for filling long paragraph with link

[markdown-mode.git] / README.md

# Emacs Markdown Mode [![MELPA badge][melpa-badge]][melpa-link] [![MELPA stable badge][melpa-stable-badge]][melpa-stable-link] [![Travis CI Build Status][travis-badge]][travis-link]

  [melpa-link]: https://melpa.org/#/markdown-mode
  [melpa-stable-link]: https://stable.melpa.org/#/markdown-mode
  [melpa-badge]: https://melpa.org/packages/markdown-mode-badge.svg
  [melpa-stable-badge]: https://stable.melpa.org/packages/markdown-mode-badge.svg
  [travis-link]: https://travis-ci.org/jrblevin/markdown-mode
  [travis-badge]: https://travis-ci.org/jrblevin/markdown-mode.svg?branch=master

<!-- This file is autogenerated by webpage.sh from the comments at the top of
     markdown-mode.el. Make edits there, not here. -->

markdown-mode is a major mode for editing [Markdown][]-formatted
text. The latest stable version is markdown-mode 2.1, released on
January 9, 2016. See the [release notes][] for details.
markdown-mode is free software, licensed under the GNU GPL.

![Markdown Mode Screenshot](http://jblevins.org/projects/markdown-mode/screenshots/20160108-001.png)

[Markdown]: http://daringfireball.net/projects/markdown/
[release notes]: http://jblevins.org/projects/markdown-mode/rev-2-1

## Installation

The recommended way to install markdown-mode is to install the package
from [MELPA Stable](https://stable.melpa.org/#/markdown-mode)
using `package.el`. First, configure `package.el` and the MELPA Stable
repository by adding the following to your `.emacs`, `init.el`,
or equivalent startup file:

    (require 'package)
    (add-to-list 'package-archives
                 '("melpa-stable" . "https://stable.melpa.org/packages/"))
    (package-initialize)

Then, after restarting Emacs or evaluating the above statements, issue
the following command: <kbd>M-x package-install RET markdown-mode RET</kbd>.
When installed this way, the major modes `markdown-mode` and `gfm-mode`
will be autoloaded and `markdown-mode` will be used for file names
ending in either `.md` or `.markdown`.

Alternatively, if you manage loading packages with [use-package][]
then you can automatically install and configure `markdown-mode` by
adding a declaration such as this one to your init file (as an
example; adjust settings as desired):

    (use-package markdown-mode
      :ensure t
      :commands (markdown-mode gfm-mode)
      :mode (("README\\.md\\'" . gfm-mode)
             ("\\.md\\'" . markdown-mode)
             ("\\.markdown\\'" . markdown-mode))
      :init (setq markdown-command "multimarkdown"))

[MELPA Stable]: http://stable.melpa.org/
[use-package]: https://github.com/jwiegley/use-package

**Direct Download**

Alternatively you can manually download and install markdown-mode.
First, download the [latest stable version][markdown-mode.el] and
save the file where Emacs can find it (i.e., a directory in your
`load-path`). You can then configure `markdown-mode` and `gfm-mode`
to load automatically by adding the following to your init file:

    (autoload 'markdown-mode "markdown-mode"
       "Major mode for editing Markdown files" t)
    (add-to-list 'auto-mode-alist '("\\.markdown\\'" . markdown-mode))
    (add-to-list 'auto-mode-alist '("\\.md\\'" . markdown-mode))

    (autoload 'gfm-mode "markdown-mode"
       "Major mode for editing GitHub Flavored Markdown files" t)
    (add-to-list 'auto-mode-alist '("README\\.md\\'" . gfm-mode))

[markdown-mode.el]: http://jblevins.org/projects/markdown-mode/markdown-mode.el

**Development Version**

To follow or contribute to markdown-mode development, you can
browse or clone the Git repository
[on GitHub](https://github.com/jrblevin/markdown-mode):

    git clone https://github.com/jrblevin/markdown-mode.git

If you prefer to install and use the development version, which may
become unstable at some times, you can either clone the Git
repository as above or install markdown-mode from
[MELPA](https://melpa.org/#/markdown-mode).

If you clone the repository directly, then make sure that Emacs can
find it by adding the following line to your startup file:

    (add-to-list 'load-path "/path/to/markdown-mode/repository")

**Packaged Installation**

markdown-mode is also available in several package managers. You
may want to confirm that the package you install contains the
latest stable version first (and please notify the package
maintainer if not).

   * Debian Linux: [elpa-markdown-mode][] and [emacs-goodies-el][]
   * Ubuntu Linux: [elpa-markdown-mode][elpa-ubuntu] and [emacs-goodies-el][emacs-goodies-el-ubuntu]
   * RedHat and Fedora Linux: [emacs-goodies][]
   * NetBSD: [textproc/markdown-mode][]
   * MacPorts: [markdown-mode.el][macports-package] ([pending][macports-ticket])
   * FreeBSD: [textproc/markdown-mode.el][freebsd-port]

 [elpa-markdown-mode]: https://packages.debian.org/sid/lisp/elpa-markdown-mode
 [elpa-ubuntu]: http://packages.ubuntu.com/search?keywords=elpa-markdown-mode
 [emacs-goodies-el]: http://packages.debian.org/emacs-goodies-el
 [emacs-goodies-el-ubuntu]: http://packages.ubuntu.com/search?keywords=emacs-goodies-el
 [emacs-goodies]: https://apps.fedoraproject.org/packages/emacs-goodies
 [textproc/markdown-mode]: http://pkgsrc.se/textproc/markdown-mode
 [macports-package]: https://trac.macports.org/browser/trunk/dports/editors/markdown-mode.el/Portfile
 [macports-ticket]: http://trac.macports.org/ticket/35716
 [freebsd-port]: http://svnweb.freebsd.org/ports/head/textproc/markdown-mode.el

**Dependencies**

`markdown-mode` depends on `cl-lib`, which has been bundled with
GNU Emacs since 24.3.  Users of GNU Emacs 24.1 and 24.2 can install
`cl-lib` with `package.el`.

## Usage

Keybindings are grouped by prefixes based on their function.  For
example, the commands for inserting links are grouped under `C-c
C-a`, where the <kbd>C-a</kbd> is a mnemonic for the HTML `<a>` tag.  In
other cases, the connection to HTML is not direct.  For example,
commands dealing with headings begin with <kbd>C-c C-t</kbd> (mnemonic:
titling).  The primary commands in each group will are described
below.  You can obtain a list of all keybindings by pressing `C-c
C-h`.  Movement and shifting commands tend to be associated with
paired delimiters such as <kbd>M-{</kbd> and <kbd>M-}</kbd> or <kbd>C-c <</kbd> and <kbd>C-c ></kbd>.
Outline navigation keybindings the same as in `org-mode`.  Finally,
commands for running Markdown or doing maintenance on an open file
are grouped under the <kbd>C-c C-c</kbd> prefix.  The most commonly used
commands are described below.  You can obtain a list of all
keybindings by pressing <kbd>C-c C-h</kbd>.

  * Hyperlinks: <kbd>C-c C-a</kbd>

    In this group, <kbd>C-c C-a l</kbd> inserts an inline link of the form
    `[text](url)`.  The link text is determined as follows.  First,
    if there is an active region (i.e., when transient mark mode is
    on and the mark is active), use it as the link text.  Second,
    if the point is at a word, use that word as the link text.  In
    these two cases, the original text will be replaced with the
    link and point will be left at the position for inserting a
    URL.  Otherwise, insert empty link markup and place the point
    for inserting the link text.

    <kbd>C-c C-a L</kbd> inserts a reference link of the form `[text][label]`
    and, optionally, a corresponding reference label definition.
    The link text is determined in the same way as with an inline
    link (using the region, when active, or the word at the point),
    but instead of inserting empty markup as a last resort, the
    link text will be read from the minibuffer.  The reference
    label will be read from the minibuffer in both cases, with
    completion from the set of currently defined references.  To
    create an implicit reference link, press <kbd>RET</kbd> to accept the
    default, an empty label.  If the entered referenced label is
    not defined, additionally prompt for the URL and (optional)
    title.  If a URL is provided, a reference definition will be
    inserted in accordance with `markdown-reference-location`.
    If a title is given, it will be added to the end of the
    reference definition and will be used to populate the title
    attribute when converted to XHTML.

    <kbd>C-c C-a u</kbd> inserts a bare url, delimited by angle brackets.  When
    there is an active region, the text in the region is used as the
    URL.  If the point is at a URL, that url is used.  Otherwise,
    insert angle brackets and position the point in between them
    for inserting the URL.

    <kbd>C-c C-a f</kbd> inserts a footnote marker at the point, inserts a
    footnote definition below, and positions the point for
    inserting the footnote text.  Note that footnotes are an
    extension to Markdown and are not supported by all processors.

    <kbd>C-c C-a w</kbd> behaves much like the inline link insertion command
    and inserts a wiki link of the form `[[WikiLink]]`.  If there
    is an active region, use the region as the link text.  If the
    point is at a word, use the word as the link text.  If there is
    no active region and the point is not at word, simply insert
    link markup.  Note that wiki links are an extension to Markdown
    and are not supported by all processors.

  * Images: <kbd>C-c C-i</kbd>

    <kbd>C-c C-i i</kbd> inserts markup for an inline image, using the
    active region or the word at point, if any, as the alt text.
    <kbd>C-c C-i I</kbd> behaves similarly and inserts a reference-style
    image.

    Local images associated with image links may be displayed
    inline in the buffer by pressing <kbd>C-c C-i C-t</kbd>
    (`markdown-toggle-inline-images`). This is a toggle command, so
    pressing this once again will remove inline images.

  * Styles: <kbd>C-c C-s</kbd>

    <kbd>C-c C-s e</kbd> inserts markup to make a region or word italic (<kbd>e</kbd>
    for `<em>` or emphasis).  If there is an active region, make
    the region italic.  If the point is at a non-italic word, make
    the word italic.  If the point is at an italic word or phrase,
    remove the italic markup.  Otherwise, simply insert italic
    delimiters and place the cursor in between them.  Similarly,
    use <kbd>C-c C-s s</kbd> for bold (`<strong>`), <kbd>C-c C-s c</kbd> for
    inline code (`<code>`), and <kbd>C-c C-s k</kbd> for inserting `<kbd>`
    tags.

    <kbd>C-c C-s b</kbd> inserts a blockquote using the active region, if any,
    or starts a new blockquote.  <kbd>C-c C-s C-b</kbd> is a variation which
    always operates on the region, regardless of whether it is
    active or not.  The appropriate amount of indentation, if any,
    is calculated automatically given the surrounding context, but
    may be adjusted later using the region indentation commands.

    <kbd>C-c C-s p</kbd> behaves similarly for inserting preformatted code
    blocks, with <kbd>C-c C-s C-p</kbd> being the region-only counterpart.

  * Headings: <kbd>C-c C-t</kbd>

    All heading insertion commands use the text in the active
    region, if any, as the heading text.  Otherwise, if the current
    line is not blank, they use the text on the current line.
    Finally, the setext commands will prompt for heading text if
    there is no active region and the current line is blank.

    <kbd>C-c C-t h</kbd> inserts a heading with automatically chosen type and
    level (both determined by the previous heading).  <kbd>C-c C-t H</kbd>
    behaves similarly, but uses setext (underlined) headings when
    possible, still calculating the level automatically.
    In cases where the automatically-determined level is not what
    you intended, the level can be quickly promoted or demoted
    (as described below).  Alternatively, a <kbd>C-u</kbd> prefix can be
    given to insert a heading promoted by one level or a <kbd>C-u C-u</kbd>
    prefix can be given to insert a heading demoted by one level.

    To insert a heading of a specific level and type, use <kbd>C-c C-t 1</kbd>
    through <kbd>C-c C-t 6</kbd> for atx (hash mark) headings and <kbd>C-c C-t !</kbd> or
    <kbd>C-c C-t @</kbd> for setext headings of level one or two, respectively.
    Note that <kbd>!</kbd> is <kbd>S-1</kbd> and <kbd>@</kbd> is <kbd>S-2</kbd>.

    If the point is at a heading, these commands will replace the
    existing markup in order to update the level and/or type of the
    heading.  To remove the markup of the heading at the point,
    press <kbd>C-c C-k</kbd> to kill the heading and press <kbd>C-y</kbd> to yank the
    heading text back into the buffer.

  * Horizontal Rules: <kbd>C-c -</kbd>

    <kbd>C-c -</kbd> inserts a horizontal rule.  By default, insert the
    first string in the list `markdown-hr-strings` (the most
    prominent rule).  With a <kbd>C-u</kbd> prefix, insert the last string.
    With a numeric prefix <kbd>N</kbd>, insert the string in position <kbd>N</kbd>
    (counting from 1).

  * Markdown and Maintenance Commands: <kbd>C-c C-c</kbd>

    *Compile:* <kbd>C-c C-c m</kbd> will run Markdown on the current buffer
    and show the output in another buffer.  *Preview*: <kbd>C-c C-c p</kbd>
    runs Markdown on the current buffer and previews, stores the
    output in a temporary file, and displays the file in a browser.
    *Export:* <kbd>C-c C-c e</kbd> will run Markdown on the current buffer
    and save the result in the file `basename.html`, where
    `basename` is the name of the Markdown file with the extension
    removed.  *Export and View:* press <kbd>C-c C-c v</kbd> to export the
    file and view it in a browser.  *Open:* <kbd>C-c C-c o</kbd> will open
    the Markdown source file directly using `markdown-open-command`.
    *Live Export*: Press <kbd>C-c C-c l</kbd> to turn on
    `markdown-live-preview-mode` to view the exported output
    side-by-side with the source Markdown. **For all export commands,
    the output file will be overwritten without notice.**
    `markdown-live-preview-window-function` can be customized to open
    in a browser other than `eww`.

    To summarize:

      - <kbd>C-c C-c m</kbd>: `markdown-command` > `*markdown-output*` buffer.
      - <kbd>C-c C-c p</kbd>: `markdown-command` > temporary file > browser.
      - <kbd>C-c C-c e</kbd>: `markdown-command` > `basename.html`.
      - <kbd>C-c C-c v</kbd>: `markdown-command` > `basename.html` > browser.
      - <kbd>C-c C-c w</kbd>: `markdown-command` > kill ring.
      - <kbd>C-c C-c o</kbd>: `markdown-open-command`.
      - <kbd>C-c C-c l</kbd>: `markdown-live-preview-mode` > `*eww*` buffer.

    <kbd>C-c C-c c</kbd> will check for undefined references.  If there are
    any, a small buffer will open with a list of undefined
    references and the line numbers on which they appear.  In Emacs
    22 and greater, selecting a reference from this list and
    pressing <kbd>RET</kbd> will insert an empty reference definition at the
    end of the buffer.  Similarly, selecting the line number will
    jump to the corresponding line.

    <kbd>C-c C-c n</kbd> renumbers any ordered lists in the buffer that are
    out of sequence.

    <kbd>C-c C-c ]</kbd> completes all headings and normalizes all horizontal
    rules in the buffer.

  * Following Links: <kbd>C-c C-o</kbd>

    Press <kbd>C-c C-o</kbd> when the point is on an inline or reference
    link to open the URL in a browser.  When the point is at a
    wiki link, open it in another buffer (in the current window,
    or in the other window with the <kbd>C-u</kbd> prefix).  Use <kbd>M-p</kbd> and
    <kbd>M-n</kbd> to quickly jump to the previous or next link of any type.

  * Jumping: <kbd>C-c C-l</kbd>

    Use <kbd>C-c C-l</kbd> to jump from the object at point to its counterpart
    elsewhere in the text, when possible.  Jumps between reference
    links and definitions; between footnote markers and footnote
    text.  If more than one link uses the same reference name, a
    new buffer will be created containing clickable buttons for jumping
    to each link.  You may press <kbd>TAB</kbd> or <kbd>S-TAB</kbd> to jump between
    buttons in this window.

  * Promotion and Demotion: <kbd>C-c C--</kbd> and <kbd>C-c C-=</kbd>

    Headings, horizontal rules, and list items can be promoted and
    demoted, as well as bold and italic text.  For headings,
    "promotion" means *decreasing* the level (i.e., moving from
    `<h2>` to `<h1>`) while "demotion" means *increasing* the
    level.  For horizontal rules, promotion and demotion means
    moving backward or forward through the list of rule strings in
    `markdown-hr-strings`.  For bold and italic text, promotion and
    demotion means changing the markup from underscores to asterisks.
    Press <kbd>C-c C--</kbd> or <kbd>M-LEFT</kbd> to promote the element at the point
    if possible.

    To remember these commands, note that <kbd>-</kbd> is for decreasing the
    level (promoting), and <kbd>=</kbd> (on the same key as <kbd>+</kbd>) is for
    increasing the level (demoting).  Similarly, the left and right
    arrow keys indicate the direction that the atx heading markup
    is moving in when promoting or demoting.

  * Completion: <kbd>C-c C-]</kbd>

    Complete markup is in normalized form, which means, for
    example, that the underline portion of a setext header is the
    same length as the heading text, or that the number of leading
    and trailing hash marks of an atx header are equal and that
    there is no extra whitespace in the header text.  <kbd>C-c C-]</kbd>
    completes the markup at the point, if it is determined to be
    incomplete.

  * Editing Lists: <kbd>M-RET</kbd>, <kbd>M-UP</kbd>, <kbd>M-DOWN</kbd>, <kbd>M-LEFT</kbd>, and <kbd>M-RIGHT</kbd>

    New list items can be inserted with <kbd>M-RET</kbd> or <kbd>C-c C-j</kbd>.  This
    command determines the appropriate marker (one of the possible
    unordered list markers or the next number in sequence for an
    ordered list) and indentation level by examining nearby list
    items.  If there is no list before or after the point, start a
    new list.  Prefix this command by <kbd>C-u</kbd> to decrease the
    indentation by one level.  Prefix this command by <kbd>C-u C-u</kbd> to
    increase the indentation by one level.

    Existing list items can be moved up or down with <kbd>M-UP</kbd> or
    <kbd>M-DOWN</kbd> and indented or exdented with <kbd>M-RIGHT</kbd> or <kbd>M-LEFT</kbd>.

  * Editing Subtrees: <kbd>M-S-UP</kbd>, <kbd>M-S-DOWN</kbd>, <kbd>M-S-LEFT</kbd>, and <kbd>M-S-RIGHT</kbd>

    Entire subtrees of ATX headings can be promoted and demoted
    with <kbd>M-S-LEFT</kbd> and <kbd>M-S-RIGHT</kbd>, which mirror the bindings
    for promotion and demotion of list items. Similarly, subtrees
    can be moved up and down with <kbd>M-S-UP</kbd> and <kbd>M-S-DOWN</kbd>.

    Please note the following "boundary" behavior for promotion and
    demotion.  Any level-six headings will not be demoted further
    (i.e., they remain at level six, since Markdown and HTML define
    only six levels) and any level-one headings will promoted away
    entirely (i.e., heading markup will be removed, since a
    level-zero heading is not defined).

  * Shifting the Region: <kbd>C-c <</kbd> and <kbd>C-c ></kbd>

    Text in the region can be indented or exdented as a group using
    <kbd>C-c ></kbd> to indent to the next indentation point (calculated in
    the current context), and <kbd>C-c <</kbd> to exdent to the previous
    indentation point.  These keybindings are the same as those for
    similar commands in `python-mode`.

  * Killing Elements: <kbd>C-c C-k</kbd>

    Press <kbd>C-c C-k</kbd> to kill the thing at point and add important
    text, without markup, to the kill ring.  Possible things to
    kill include (roughly in order of precedece): inline code,
    headings, horizonal rules, links (add link text to kill ring),
    images (add alt text to kill ring), angle URIs, email
    addresses, bold, italics, reference definitions (add URI to
    kill ring), footnote markers and text (kill both marker and
    text, add text to kill ring), and list items.

  * Outline Navigation: <kbd>C-c C-n</kbd>, <kbd>C-c C-p</kbd>, <kbd>C-c C-f</kbd>, <kbd>C-c C-b</kbd>, and <kbd>C-c C-u</kbd>

    Navigation between headings is possible using `outline-mode`.
    Use <kbd>C-c C-n</kbd> and <kbd>C-c C-p</kbd> to move between the next and previous
    visible headings.  Similarly, <kbd>C-c C-f</kbd> and <kbd>C-c C-b</kbd> move to the
    next and previous visible headings at the same level as the one
    at the point.  Finally, <kbd>C-c C-u</kbd> will move up to a lower-level
    (higher precedence) visible heading.

  * Movement by Paragraph or Block: <kbd>M-{</kbd> and <kbd>M-}</kbd>

    The definition of a "paragraph" is slightly different in
    markdown-mode than, say, text-mode, because markdown-mode
    supports filling for list items and respects hard line breaks,
    both of which break paragraphs.  So, markdown-mode overrides
    the usual paragraph navigation commands <kbd>M-{</kbd> and <kbd>M-}</kbd> so that
    with a <kbd>C-u</kbd> prefix, these commands jump to the beginning or
    end of an entire block of text, respectively, where "blocks"
    are separated by one or more lines.

  * Movement by Defun: <kbd>C-M-a</kbd>, <kbd>C-M-e</kbd>, and <kbd>C-M-h</kbd>

    The usual Emacs commands can be used to move by defuns
    (top-level major definitions).  In markdown-mode, a defun is a
    section.  As usual, <kbd>C-M-a</kbd> will move the point to the
    beginning of the current or preceding defun, <kbd>C-M-e</kbd> will move
    to the end of the current or following defun, and <kbd>C-M-h</kbd> will
    put the region around the entire defun.

As noted, many of the commands above behave differently depending
on whether Transient Mark mode is enabled or not.  When it makes
sense, if Transient Mark mode is on and the region is active, the
command applies to the text in the region (e.g., <kbd>C-c C-s s</kbd> makes the
region bold).  For users who prefer to work outside of Transient
Mark mode, since Emacs 22 it can be enabled temporarily by pressing
<kbd>C-SPC C-SPC</kbd>.  When this is not the case, many commands then
proceed to look work with the word or line at the point.

When applicable, commands that specifically act on the region even
outside of Transient Mark mode have the same keybinding as their
standard counterpart, but the letter is uppercase.  For example,
`markdown-insert-blockquote` is bound to <kbd>C-c C-s b</kbd> and only acts on
the region in Transient Mark mode while `markdown-blockquote-region`
is bound to <kbd>C-c C-s B</kbd> and always applies to the region (when nonempty).

Note that these region-specific functions are useful in many
cases where it may not be obvious.  For example, yanking text from
the kill ring sets the mark at the beginning of the yanked text
and moves the point to the end.  Therefore, the (inactive) region
contains the yanked text.  So, <kbd>C-y</kbd> followed by <kbd>C-c C-s C-b</kbd> will
yank text and turn it into a blockquote.

markdown-mode attempts to be flexible in how it handles
indentation.  When you press <kbd>TAB</kbd> repeatedly, the point will cycle
through several possible indentation levels corresponding to things
you might have in mind when you press <kbd>RET</kbd> at the end of a line or
<kbd>TAB</kbd>.  For example, you may want to start a new list item,
continue a list item with hanging indentation, indent for a nested
pre block, and so on.  Exdention is handled similarly when backspace
is pressed at the beginning of the non-whitespace portion of a line.

markdown-mode supports outline-minor-mode as well as org-mode-style
visibility cycling for atx- or hash-style headings.  There are two
types of visibility cycling: Pressing <kbd>S-TAB</kbd> cycles globally between
the table of contents view (headings only), outline view (top-level
headings only), and the full document view.  Pressing <kbd>TAB</kbd> while the
point is at a heading will cycle through levels of visibility for the
subtree: completely folded, visible children, and fully visible.
Note that mixing hash and underline style headings will give undesired
results.

## Customization

Although no configuration is *necessary* there are a few things
that can be customized.  The <kbd>M-x customize-mode</kbd> command
provides an interface to all of the possible customizations:

  * `markdown-command` - the command used to run Markdown (default:
    `markdown`).  This variable may be customized to pass
    command-line options to your Markdown processor of choice.

  * `markdown-command-needs-filename` - set to <kbd>t</kbd> if
    `markdown-command` does not accept standard input (default:
    `nil`).  When `nil`, `markdown-mode` will pass the Markdown
    content to `markdown-command` using standard input (`stdin`).
    When set to <kbd>t</kbd>, `markdown-mode` will pass the name of the file
    as the final command-line argument to `markdown-command`.  Note
    that in the latter case, you will only be able to run
    `markdown-command` from buffers which are visiting a file.

  * `markdown-open-command` - the command used for calling a standalone
    Markdown previewer which is capable of opening Markdown source files
    directly (default: `nil`).  This command will be called
    with a single argument, the filename of the current buffer.
    A representative program is the Mac app [Marked 2][], a
    live-updating Markdown previewer which can be [called from a
    simple shell script](http://jblevins.org/log/marked-2-command).

  * `markdown-hr-strings` - list of strings to use when inserting
    horizontal rules.  Different strings will not be distinguished
    when converted to HTML--they will all be converted to
    `<hr/>`--but they may add visual distinction and style to plain
    text documents.  To maintain some notion of promotion and
    demotion, keep these sorted from largest to smallest.

  * `markdown-bold-underscore` - set to a non-nil value to use two
    underscores when inserting bold text instead of two asterisks
    (default: `nil`).

  * `markdown-italic-underscore` - set to a non-nil value to use
    underscores when inserting italic text instead of asterisks
    (default: `nil`).

  * `markdown-asymmetric-header` - set to a non-nil value to use
    asymmetric header styling, placing header characters only on
    the left of headers (default: `nil`).

  * `markdown-header-scaling` - set to a non-nil value to use
    a variable-pitch font for headings where the size corresponds
    to the level of the heading (default: `nil`).

  * `markdown-header-scaling-values` - list of scaling values,
    relative to baseline, for headers of levels one through six,
    used when `markdown-header-scaling` is non-nil
    (default: `(list 1.8 1.4 1.2 1.0 1.0 1.0)`).

  * `markdown-list-indent-width` - depth of indentation for lists
    when inserting, promoting, and demoting list items (default: 4).

  * `markdown-indent-function` - the function to use for automatic
    indentation (default: `markdown-indent-line`).

  * `markdown-indent-on-enter` - set to a non-nil value to
    automatically indent new lines when the enter key is pressed
    (default: <kbd>t</kbd>)

  * `markdown-enable-wiki-links` - syntax highlighting for wiki
    links (default: `nil`).  Set this to a non-nil value to turn on
    wiki link support by default.  Wiki link support can be toggled
    later using the function `markdown-toggle-wiki-links`."

  * `markdown-wiki-link-alias-first` - set to a non-nil value to
    treat aliased wiki links like `[[link text|PageName]]`
    (default: <kbd>t</kbd>).  When set to nil, they will be treated as
    `[[PageName|link text]]`.

  * `markdown-uri-types` - a list of protocol schemes (e.g., "http")
    for URIs that `markdown-mode` should highlight.

  * `markdown-enable-math` - syntax highlighting for LaTeX
    fragments (default: `nil`).  Set this to <kbd>t</kbd> to turn on math
    support by default.  Math support can be enabled, disabled, or
    toggled later using the function `markdown-toggle-math`."

  * `markdown-css-paths` - CSS files to link to in XHTML output
    (default: `nil`).

  * `markdown-content-type` - when set to a nonempty string, an
    `http-equiv` attribute will be included in the XHTML `<head>`
    block (default: `""`).  If needed, the suggested values are
    `application/xhtml+xml` or `text/html`.  See also:
    `markdown-coding-system`.

  * `markdown-coding-system` - used for specifying the character
    set identifier in the `http-equiv` attribute when included
    (default: `nil`).  See `markdown-content-type`, which must
    be set before this variable has any effect.  When set to `nil`,
    `buffer-file-coding-system` will be used to automatically
    determine the coding system string (falling back to
    `iso-8859-1` when unavailable).  Common settings are `utf-8`
    and `iso-latin-1`.

  * `markdown-xhtml-header-content` - additional content to include
    in the XHTML `<head>` block (default: `""`).

  * `markdown-xhtml-standalone-regexp` - a regular expression which
    `markdown-mode` uses to determine whether the output of
    `markdown-command` is a standalone XHTML document or an XHTML
    fragment (default: `"^\\(<\\?xml\\|<!DOCTYPE\\|<html\\)"`).  If
    this regular expression not matched in the first five lines of
    output, `markdown-mode` assumes the output is a fragment and
    adds a header and footer.

  * `markdown-link-space-sub-char` - a character to replace spaces
    when mapping wiki links to filenames (default: `"_"`).
    For example, use an underscore for compatibility with the
    Python Markdown WikiLinks extension.  In `gfm-mode`, this is
    set to `"-"` to conform with GitHub wiki links.

  * `markdown-reference-location` - where to insert reference
    definitions (default: `header`).  The possible locations are
    the end of the document (`end`), after the current block
    (`immediately`), before the next header (`header`).

  * `markdown-footnote-location` - where to insert footnote text
    (default: `end`).  The set of location options is the same as
    for `markdown-reference-location`.

  * `markdown-nested-imenu-heading-index` - Use nested imenu
    heading instead of a flat index (default: `nil`).  A nested
    index may provide more natural browsing from the menu, but a
    flat list may allow for faster keyboard navigation via tab
    completion.

  * `comment-auto-fill-only-comments` - variable is made
    buffer-local and set to `nil` by default.  In programming
    language modes, when this variable is non-nil, only comments
    will be filled by auto-fill-mode.  However, comments in
    Markdown documents are rare and the most users probably intend
    for the actual content of the document to be filled.  Making
    this variable buffer-local allows `markdown-mode` to override
    the default behavior induced when the global variable is non-nil.

  * `markdown-gfm-additional-languages`, - additional languages to
    make available, aside from those predefined in
    `markdown-gfm-recognized-languages`, when inserting GFM code
    blocks (default: `nil`). Language strings must have be trimmed
    of whitespace and not contain any curly braces. They may be of
    arbitrary capitalization, though.

  * `markdown-gfm-use-electric-backquote` - use
    `markdown-electric-backquote` for interactive insertion of GFM
    code blocks when backquote is pressed three times (default: <kbd>t</kbd>).

  * `markdown-make-gfm-checkboxes-buttons` - Whether GitHub
    Flavored Markdown style task lists (checkboxes) should be
    turned into buttons that can be toggled with mouse-1 or RET. If
    non-nil (default), then buttons are enabled.  This works in
    `markdown-mode` as well as `gfm-mode`.

Additionally, the faces used for syntax highlighting can be modified to
your liking by issuing <kbd>M-x customize-group RET markdown-faces</kbd>
or by using the "Markdown Faces" link at the bottom of the mode
customization screen.

[Marked 2]: https://itunes.apple.com/us/app/marked-2/id890031187?mt=12&uo=4&at=11l5Vs&ct=mm

## Extensions

Besides supporting the basic Markdown syntax, Markdown Mode also
includes syntax highlighting for `[[Wiki Links]]`.  This can be
enabled by setting `markdown-enable-wiki-links` to a non-nil value.
Wiki links may be followed by pressing <kbd>C-c C-o</kbd> when the point
is at a wiki link.  Use <kbd>M-p</kbd> and <kbd>M-n</kbd> to quickly jump to the
previous and next links (including links of other types).
Aliased or piped wiki links of the form `[[link text|PageName]]`
are also supported.  Since some wikis reverse these components, set
`markdown-wiki-link-alias-first` to nil to treat them as
`[[PageName|link text]]`.  If `markdown-wiki-link-fontify-missing`
is also non-nil, Markdown Mode will highlight wiki links with
missing target file in a different color.  By default, Markdown
Mode only searches for target files in the current directory.
Sequential parent directory search (as in [Ikiwiki][]) can be
enabled by setting `markdown-wiki-link-search-parent-directories`
to a non-nil value.

[Ikiwiki]: https://ikiwiki.info

[SmartyPants][] support is possible by customizing `markdown-command`.
If you install `SmartyPants.pl` at, say, `/usr/local/bin/smartypants`,
then you can set `markdown-command` to `"markdown | smartypants"`.
You can do this either by using <kbd>M-x customize-group markdown</kbd>
or by placing the following in your `.emacs` file:

    (setq markdown-command "markdown | smartypants")

[SmartyPants]: http://daringfireball.net/projects/smartypants/

Syntax highlighting for mathematical expressions written
in LaTeX (only expressions denoted by `$..$`, `$$..$$`, or `\[..\]`)
can be enabled by setting `markdown-enable-math` to a non-nil value,
either via customize or by placing `(setq markdown-enable-math t)`
in `.emacs`, and then restarting Emacs or calling
`markdown-reload-extensions`.

## GitHub Flavored Markdown (GFM)

A [GitHub Flavored Markdown][GFM] mode, `gfm-mode`, is also
available.  The GitHub implementation differs slightly from
standard Markdown in that it supports things like different
behavior for underscores inside of words, automatic linking of
URLs, strikethrough text, and fenced code blocks with an optional
language keyword.

The GFM-specific features above apply to `README.md` files, wiki
pages, and other Markdown-formatted files in repositories on
GitHub.  GitHub also enables [additional features][GFM comments] for
writing on the site (for issues, pull requests, messages, etc.)
that are further extensions of GFM.  These features include task
lists (checkboxes), newlines corresponding to hard line breaks,
auto-linked references to issues and commits, wiki links, and so
on.  To make matters more confusing, although task lists are not
part of [GFM proper][GFM], [since 2014][] they are rendered (in a
read-only fashion) in all Markdown documents in repositories on the
site.  These additional extensions are supported to varying degrees
by `markdown-mode` and `gfm-mode` as described below.

* **URL autolinking:** Both `markdown-mode` and `gfm-mode` support
  highlighting of URLs without angle brackets.

* **Multiple underscores in words:** You must enable `gfm-mode` to
  toggle support for underscores inside of words. In this mode
  variable names such as `a_test_variable` will not trigger
  emphasis (italics).

* **Fenced code blocks:** Code blocks quoted with backticks, with
  optional programming language keywords, are highlighted in
  both `markdown-mode` and `gfm-mode`.  They can be inserted with
  <kbd>C-c C-s P</kbd>.  If there is an active region, the text in the
  region will be placed inside the code block.  You will be
  prompted for the name of the language, but may press enter to
  continue without naming a language.

* **Strikethrough:** Strikethrough text is only supported in
  `gfm-mode` and can be inserted (and toggled) using <kbd>C-c C-s d</kbd>.
  Following the mnemonics for the other style keybindings, the
  letter <kbd>d</kbd> coincides with the HTML tag `<del>`.

* **Task lists:** GFM task lists will be rendered as checkboxes
  (Emacs buttons) in both `markdown-mode` and `gfm-mode` when
  `markdown-make-gfm-checkboxes-buttons` is set to a non-nil value
  (and it is set to t by default).  These checkboxes can be
  toggled by clicking `mouse-1`, pressing <kbd>RET</kbd> over the button,
  or by pressing <kbd>C-c C-x C-x</kbd> with the point anywhere in the task
  list item.

* **Wiki links:** Generic wiki links are supported in
  `markdown-mode`, but in `gfm-mode` specifically they will be
  treated as they are on GitHub: spaces will be replaced by hyphens
  in filenames and the first letter of the filename will be
  capitalized.  For example, `[[wiki link]]` will map to a file
  named `Wiki-link` with the same extension as the current file.

* **Newlines:** Neither `markdown-mode` nor `gfm-mode` do anything
  specifically with respect to newline behavior.  If you use
  `gfm-mode` mostly to write text for comments or issues on the
  GitHub site--where newlines are significant and correspond to
  hard line breaks--then you may want to enable `visual-line-mode`
  for line wrapping in buffers.  You can do this with a
  `gfm-mode-hook` as follows:

        ;; Use visual-line-mode in gfm-mode
        (defun my-gfm-mode-hook ()
          (visual-line-mode 1))
        (add-hook 'gfm-mode-hook 'my-gfm-mode-hook)

* **Preview:** GFM-specific preview can be powered by setting
  `markdown-command` to use [Docter][].  This may also be
  configured to work with [Marked 2][] for `markdown-open-command`.

[GFM]: http://github.github.com/github-flavored-markdown/
[GFM comments]: https://help.github.com/articles/writing-on-github/
[since 2014]: https://github.com/blog/1825-task-lists-in-all-markdown-documents
[Docter]: https://github.com/alampros/Docter

## Acknowledgments

markdown-mode has benefited greatly from the efforts of the many
volunteers who have sent patches, test cases, bug reports,
suggestions, helped with packaging, etc.  Thank you for your
contributions!  See the [contributors graph][contrib] for details.

 [contrib]: https://github.com/jrblevin/markdown-mode/graphs/contributors

## Bugs

markdown-mode is developed and tested primarily for compatibility
with GNU Emacs 24.3 and later.  If you find any bugs in
markdown-mode, please construct a test case or a patch and open a
ticket on the [GitHub issue tracker][issues].

 [issues]: https://github.com/jrblevin/markdown-mode/issues

## History

markdown-mode was written and is maintained by Jason Blevins.  The
first version was released on May 24, 2007.

  * 2007-05-24: [Version 1.1][]
  * 2007-05-25: [Version 1.2][]
  * 2007-06-05: [Version 1.3][]
  * 2007-06-29: [Version 1.4][]
  * 2007-10-11: [Version 1.5][]
  * 2008-06-04: [Version 1.6][]
  * 2009-10-01: [Version 1.7][]
  * 2011-08-12: [Version 1.8][]
  * 2011-08-15: [Version 1.8.1][]
  * 2013-01-25: [Version 1.9][]
  * 2013-03-24: [Version 2.0][]
  * 2016-01-09: [Version 2.1][]

[Version 1.1]: http://jblevins.org/projects/markdown-mode/rev-1-1
[Version 1.2]: http://jblevins.org/projects/markdown-mode/rev-1-2
[Version 1.3]: http://jblevins.org/projects/markdown-mode/rev-1-3
[Version 1.4]: http://jblevins.org/projects/markdown-mode/rev-1-4
[Version 1.5]: http://jblevins.org/projects/markdown-mode/rev-1-5
[Version 1.6]: http://jblevins.org/projects/markdown-mode/rev-1-6
[Version 1.7]: http://jblevins.org/projects/markdown-mode/rev-1-7
[Version 1.8]: http://jblevins.org/projects/markdown-mode/rev-1-8
[Version 1.8.1]: http://jblevins.org/projects/markdown-mode/rev-1-8-1
[Version 1.9]: http://jblevins.org/projects/markdown-mode/rev-1-9
[Version 2.0]: http://jblevins.org/projects/markdown-mode/rev-2-0
[Version 2.1]: http://jblevins.org/projects/markdown-mode/rev-2-1