1 Introduction
══════════════

  `crdt.el' is a real-time collaborative editing environment for Emacs
  using Conflict-free Replicated Data Types.

  Highlights:
  • [CRDT], darling child of collaborative editing researches…
  • Share multiple buffer in one session
  • See other users' cursor and region
  • Synchronize Org mode folding status
  • Org mode integration
  • Comint derivatives integration (experimental)


[CRDT]
<https://en.wikipedia.org/wiki/Conflict-free_replicated_data_type>


2 Usage
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2.1 Installation
────────────────

  `crdt.el' is now on GNU ELPA! Just `M-x package-install crdt'.

  *Caution!!!* Please make sure that you and your peers are on the same
  `crdt.el' version!  It turns out to be one of the most common causes
  of `crdt.el' not working.  Because currently the network protocol is
  not stablized, behavior when using mismatched versions is
  unexpectable.
  • Strictly speaking, it should work when `crdt-protocol-version' are
    defined (added after version `0.2.5') and the same on all peers.
    But why not save some hassle and keep everyone on the latest
    version.
  • To upgrade, just `M-x package-reinstall crdt', then preferably
    restart Emacs. To check your `crdt.el' version, `M-x crdt-version'.


2.2 Start a shared session
──────────────────────────

  A shared session is a place that can contains multiple buffers (or
  files), and multiple users can join to collaboratively edit those
  buffers (or files).  Think about a meeting room with some people
  working together on some papers.

  In some buffer, `M-x crdt-share-buffer'. Then enter session name.
  This add the current buffer to the existing session with that name.
  If no such exists, it creates a new session with the provided session
  name, and initially contains the current buffer as a shared buffer.

  If a new session is to be created, you need to enter port (default to
  6530), optional password and your display name (default to your
  current `(user-full-name)').

  Experimental settings: "Secure Port" specifies TLS port, and "Command
  Functions" specifies user permissions. It's ok to just use the default
  values.


2.3 Join a session
──────────────────

  `M-x crdt-connect', then enter address, port, and your display name.

  If the server has provided the permission (this is the default case),
  connected user may also add their buffers to the session via `M-x
  crdt-share-buffer'.


2.4 Navigate through sessions
─────────────────────────────

  Sessions
        `M-x crdt-list-sessions' lists all sessions.

  Buffers
        `M-x crdt-list-buffers' lists all buffers in current session.
        In the displayed buffer list, press `RET' in the session list to
        see buffers in the selected session.

        You can also use `M-x crdt-switch-to-buffer' to interactively
        switch to another buffer in the current session.

  Users
        In a CRDT shared buffer (either server or client), `M-x
        crdt-list-users' to list active users. In the displayed user
        list, press `RET' on an entry to goto that user's cursor
        position.  Press `f' to follow that user, and press `f' again or
        `M-x crdt-stop-follow' to stop following.

        You can also use `M-x crdt-goto-next-user' and `M-x
        crdt-goto-prev-user' to cycle through users' cursor positions
        from any CRDT shared buffer (don't need to be in the user list
        buffer).


2.5 Stop sharing
────────────────

  `M-x crdt-stop-session' stops a session you've started and disconnect
  all other users from it.  This will ask for your confirmation,
  customize `crdt-confirm-stop-session' if you want to disable it.

  You can also press `k' or `d' in the session list (show it by `M-x
  crdt-list-sessions').

  `M-x crdt-stop-share-buffer' removes current buffer from its CRDT
  session (this operation is only allowed at server side). You can also
  press `k' or `d' in the buffer list.


2.6 Disconnect from a session
─────────────────────────────

  `M-x crdt-disconnect', then choose a session to disconnect from.

  You can also press `k' or `d' in the session list (show it by `M-x
  crdt-list-sessions').

  The server Emacs has the privilege to disconnect a user from a
  session.  To do so, press `k' or `d' on an entry in the user list
  (show it by `M-x crdt-list-users').


2.7 Fancy stuff
───────────────

  Visualizing author of parts of the document
        Turn on `crdt-visualize-author-mode' to color text based on
        which user authored it.

  Synchronizing Org folding status
        Turn on `crdt-org-sync-overlay-mode'. All peers that have this
        enabled have their folding status synchronized. Peers without
        enabling this minor mode are unaffected.

  Comint integration
        Just go ahead and share you comint REPL buffer! Tested: `shell'
        and `cmuscheme'.  By default, when sharing a comint buffer,
        `crdt.el' temporarily reset input history (as in `M-n' `M-p') so
        others don't spy into your `.bash_history' and alike.  You can
        customize this behavior using variable
        `crdt-comint-share-input-history'.


2.8 What if we don't have a public IP?
──────────────────────────────────────

  There're various workaround.

  • You can use [tuntox] to proxy your connection over the [Tox]
    protocol.  `crdt.el' has experimental built-in integration for
    `tuntox'.  To enable it, you need to install `tuntox', set up the
    custom variable `crdt-tuntox-executable' accordingly (the path to
    your `tuntox' binary), and set the custom variable
    `crdt-use-tuntox'.  Setting it to `t' make `crdt.el' always create
    `tuntox' proxy for new server sessions, and setting it to `'confirm'
    make `crdt.el' ask you every time when creating new sessions.  After
    starting a session with `tuntox' proxy, you can `M-x crdt-copy-url'
    to copy a URL recognizable by `M-x crdt-connect' and share it to
    your friends.  Be aware that according to my experience, `tuntox'
    takes significant time to establish a connection (sometimes up to
    half a minute), however it gets much faster after the connection is
    established.

  • You can use Teredo to get a public routable IPv6 address.  One free
    software implementation is Miredo. Get it from your favorite package
    manager or from [their website].  A typical usage is (run as root)
    ┌────
    │ # /usr/local/sbin/miredo
    │ # ifconfig teredo
    └────
    The `ifconfig' command should print the information of your IPv6
    address.  Now your traffic go through IPv6, and once you start a
    `crdt.el' session, your friends should be able to join using the
    IPv6 address.  For more information, see the user guide on the
    Miredo website.

  • You can use SSH port forwarding if you have a VPS with public IP.
    Example usage:
    ┌────
    │ $ ssh -R EXAMPLE.COM:6530:127.0.0.1:6530 EXAMPLE.COM
    └────
    This make your `crdt.el' session on local port `6530' accessible
    from `EXAMPLE.COM:6530'.

    Note that you need to set the following `/etc/ssh/sshd_config'
    option on your VPS
    ┌────
    │ GatewayPorts yes
    └────


[tuntox] <https://gitlab.com/gjedeer/tuntox>

[Tox] <https://tox.chat>

[their website] <https://www.remlab.net/miredo/>
