`,

    `
`, `
`, `

* Light and dark themes available under Settings.

* [CodeMirror editor](http://codemirror.net/) supports syntax highlighting,
block folding, bracket matching, line numbering, light and dark themes,
[spell checking](https://github.com/edemaine/codemirror-spell-checker),
"regular" keybindings as well as Vim and Emacs keybindings
(especially useful for rectangular selection for e.g. ASCII art),
multiple cursors for simultaneous editing (ctrl-click).

* **Copy/paste** produces text by default. Special handling of Coauthor
URLs produces `coauthor:...` links or embeds images. Special handling of
user URLs produces @mentions. To paste rich text, you can toggle HTML
paste mode via Ctrl-Shift-H.
* @mentioning has automatic completion of all users in group. You can type
any substring of the real name or username (but skipping spaces, like
GitHub), and select by pressing enter, or ignore by pressing space.

* Messages are organized by **groups** (intended to correspond to groups of
people who meet), so it's easy to share material with everyone in the group.
But it's also possible to share part of a group (only certain threads)
with specific users, for visitors or paper merges etc.

* **Sorting** of threads within a group by title, creator, creation date,
last update, number of posts, number of positive emoji responses, or whether
subscribed (by clicking on the corresponding column, once for default sort
order and again for opposite sort order). Intelligent handling of numbers
while sorting, e.g. "9." comes before "10.". Deleted messages always sort
to the very bottom; minimized messages always sort near the bottom;
pinned messages always sort near the top; and
unpublished messages always sort near the very top.

* "**Live Feed**" to watch messages as they get changed/posted. Useful for
projecting the latest activity onto a big screen while a group is gathered
and some are maybe editing.

* "**Catchup on Recent Posts**" to see all messages since a particular date/time
(including relative specifications like "1 week" or "12 hours").
Useful for progress reports since the last meeting.

* **Threaded** message organization, with arbitrary tree structure (root
messages, replies with arbitrary depth). You can **focus** on the subthread
rooted at any message (click on the arrow), or **fold** away the contents of
a subthread to focus on the rest (click on the minus sign).
Folding with the minus/plus sign is a local and temporary change (resets when
reloading the page), while **minimizing** the message makes it start out
folded for all users (e.g., when a discussion/question resolves and is
no longer important, but you want to preserve it for future reference).

* **Move** (reparent) messages by selecting Action / Move, or by dragging
messages around in the table of contents on the right.
(You can also start a drag in the main view from the right-arrow
of a message, but the drag must end at the table of contents.)
Dragging directly onto a message makes the dragged message the last child,
while dragging onto the slot before a message makes the dragged message the
immediately preceding sibling. Dialog confirms move, and allows you to type
another message title/creator/ID, or the name of a group if you want to
make the message into a new thread's root message.

* **Tags**: attach an arbitrary set of strings to a message. Find other
messages with the same tag by clicking on a tag.

* **Emoji** for super-short responses that show appreciation but don't cause
email notifications or take up much space. (Like GitHub and Slack.)
Hover over an emoji to see a list of people who added the emoji; click to
toggle your own status. Emoji are positive (purple) or negative (red).
Positive emoji on root messages are counted on the group page, enabling
a simple voting system for e.g. which problems to work on.

* **Search** across the current group, thread, or across all groups,
for posts by keywords using the search bar at the top.
* Search for a word as a whole `word` (default behavior), or specify
asterisks to search for partial word matches: `prefix*`, `*suffix`,
`*substring*`, or `prefix*suffix`.
* Lower-case letters are case insensitive,
while upper-case letters are case sensitive.
* Restrict search to title or body via `title:...` or `body:...`
(default is to search both).
* Negative match with minus sign
(e.g., `-word` excludes documents with whole `word`).
* Search for a regular expression via `regex:...`.
* Use double quotes (`"..."`) to search for phrases or `regex:"..."`
to search for regular expressions with spaces in them; normally,
spaces act as an AND query.
* Connect words/phrases with `|` to get an OR query instead.
* Use parentheses to mix AND and OR arbitrarily, e.g. `always (this | that)`.
* Escape special characters with backslash:
`\:`, `\"`, `\|`, `\(`, `\)`, `\\`, `\*`.
* `by:username` searches for messages coauthored by a specified username
(which can include `*`s or use regular expressions via `regex:`);
`by:me` is shorthand for searching for your own username.
* `tag:...` does an exact match for a specified tag; it can be negated.
* `emoji:heart`, `emoji:thumbs-up`, `emoji:thumbs*`, `emoji:*` etc. search
for messages with (certain) emoji symbol responses;
`emoji:@username` searches for messages with emoji response by
a specific user (`emoji:@me` finds your own emoji responses);
or you can combine the two with e.g. `emoji:thumbs*@username`.
* `root:id` matches messages in thread with specified root message ID.
* `is:root` matches root messages (tops of threads).
* `is:file` matches file messages (made via Attach).
* `is:deleted`, `is:published`, `is:private`, `is:minimized`, `is:pinned`,
`is:protected` match various states of messages.
* `is:empty` matches empty messages (no title, body, or file).
* `not:...` or `isnt:...` are negated forms of the above `is:...` operators,
equivalent to `-is:...`.

* **User search**:
find posts by a particular user by clicking on their username.
Search for your own posts in a group by clicking the "My Posts" button.

* **Statistics** about user's and all posts within a group, by day, week
(with configurable week start), month, year, or hour within a day.
Your own statistics are available via the Statistics button on the group
page, while other users' stats are available from their user page.

* **Permanent URLs** for all messages, groups, etc., for easy emailing etc.
(but other than group name, not revealing, so only those with permission
can open). Links to other messages via specical `coauthor:xxx` syntax.
Drag messages (via their arrow icon) into other messages to make such links.

* **Files** (another type of message) can be attached to other messages, as
another type of reply. You can click on the Attach button to select a file
to attach, or drag the file from the operating system onto the Attach
button. Similarly, files can be modified by clicking the Replace File
button or dragging a file onto that button.
File messages can have title and body too; title defaults to the filename.
Image/video files (including PNG, JPEG, SVG, MP4) are displayed inline.
Images automatically detect EXIF orientation, and can be further rotated by
multiples of 90 degrees in edit mode.
PDF files are rendered using [pdf.js](https://mozilla.github.io/pdf.js/),
only when visible on screen, and displayed inline with page-turning buttons.

* Messages can start/be marked **Unpublished** (not yet finished) or
**Deleted** (mistake / no longer useful).
In either state, the message is hidden from people who are not coauthors
(as listed in the "by" line and editable at the bottom of the Edit view)
or superusers who click "Become Superuser".
The default published state is initially true (so everyone sees the new
message and live updates immediately), but can vary by user (e.g., if they
are "shy" and only want to post finished thoughts).

* Threads can be marked as allowing **public** replies only (the default, for
maximum collaboration), **private** replies only (useful for solved
problems/puzzles, to prevent accidentally spoiling the fun), or
**public and private** replies (useful for feedback on lectures, for example,
which can have varying relevance to the entire group).
* Private messages have an **access list** of users who can see the message
beyond the coauthors, initially set to include the access list and all
coauthors of the parent message being replied to ("Reply All" behavior for
back-and-forth private conversation).
Unlike coauthors, access users can only see the message
when it is published and not deleted.
You can add or remove users from the access list, but note that permissions
are not synchronized between parent and children, so if you change a
parent's permissions you might also want to change the children's.
* Replies to replies inherit the public/private state of their parent.
* Superusers can see all the messages and change them between public and
private.
* Superusers can also mark messages as **protected**, meaning they can be
edited only by coauthors and superusers. This is useful to prevent someone
from accidentally becoming a coauthor on the root message of a
private-replies thread, thereby gaining access to all subsequent replies.
Protected messages can still be seen normally and gain emoji responses.

* **Email notifications** for subscribed threads, clustering together all
updates since the last email, with a maximum lag of a specified number of
hours or minutes (default 1 hour).
Each user can specify in Settings whether they are, by default, subscribed
to all threads or none, both globally and local to each group.
Either way, the default can be overridden in the group view using the
checkbox on the right (checked means "subscribed").
Users can choose in Settings whether to receive notifications
about their own edits, and whether to receive separate email messages for
each group (e.g. for email folder separation) or bundle them altogether.

* **Time travel**: You can drag through history and see past versions.
Versions of messages where the user explicitly clicked "Stop Editing"
are marked as "finished" versions, and only those are shown by default.
But if you need to see more intermediate versions,
you can click "Show All Versions".
In general, Coauthor aims to automatically track all history
in case it's useful later.

* **Download ZIP**: You can archive an entire group's contents into a ZIP file
of raw HTML/CSS and attached files which requires no JavaScript to run.
This future-proofs your content against software rot, making it suitable for
NSF's Data Archiving Policy. It is also useful for offline viewing of
content, e.g., while traveling.

* **Permissions** can be specified for each user at the group level
(typical case --- user can access the entire group of messages),
at the thread level (user can access only certain threads within group),
or at the global level: just click "Users" in the appropriate view.
Levels of access:

* read: see the group and read the messages (otherwise invisible)
* post: create new messages, replies, etc. in the group
* edit: modify other people's messages
* super: somewhat dangerous "super" operations like history-destroying
superdelete, history-creating import, and the ability to see other users'
deleted messages
* admin: administer over other users, in particular setting permissions

Anonymous access means that everyone, even not-logged-in users, can see the
messages and group. This is generally not recommended as it opens Coauthor
to spam, so it requires global admin privileges to enable.

* **Superuser operations** (only for superusers):
* Import from LaTeX document with figures attached as a ZIP file
* Import from osqa's XML dump, including old edit history
* Superdelete (permanently destroying a message including its history)
* Setting the default sort for a group
* Setting message threads as allowing public and/or private messages

## User Tips

* On Android, the
[Chrome browser](https://play.google.com/store/apps/details?id=com.android.chrome&hl=en)
with [SwiftKey keyboard](https://play.google.com/store/apps/details?id=com.touchtype.swiftkey)
seems to work best for editing messages in Coauthor.
(Firefox and Gboard have cursor positioning issues.)
* LaTeX mode supports LaTeX accents (like `\'e`), but other modes do not.
To easily type Unicode accented characters,
use [WinCompose](https://github.com/samhocevar/wincompose) on Windows,
[set up a compose key on Linux](https://help.ubuntu.com/community/ComposeKey),
or
[press and hold keys on MacOS](https://support.apple.com/guide/mac-help/enter-characters-with-accent-marks-on-mac-mh27474/mac).
* Conversely, if you're on modern MacOS, holding down letter keys will bring
up an accent tool instead of repeating the key. If you'd rather repeat the
key (e.g. for Vim mode),
[follow these instructions](http://www.idownloadblog.com/2015/01/14/how-to-enable-key-repeats-on-your-mac/):
`defaults write NSGlobalDomain ApplePressAndHoldEnabled -bool false`
then restart your web browser.
* [Vimium](https://vimium.github.io/) is incompatible with the Vim editor mode
(specifically, both capture the Escape key), so be sure to disable Vimium if
you want to use Vim keybindings in the message editor.

## [Installation](INSTALL.md)