org-capture-server/server

Servers
=======

Because the Chrome(ium) security model doesn't allow for extensions
spawning processes we can't just exec() the editor process. Instead we
have to implement an "edit server" which listens to XmlHttp requests
on port 9292 (default) and then sends a response when the edit is
complete. We include a couple here:

* pycl.py - Original version, only edit one file at a time
* edit_server.el - An native Emacs Lisp implementation

There is another project called TextAid which does a similar thing to
Edit with Emacs. It's edit server is implemented in perl and be found
at:

* http://opencoder.net/edit-server

As the edit server concept is fairly simple we will try and keep them
compatible with each other.

Customizing the look of Emacs
=============================

By default, Emacs opens up a new frame upon an edit request. All the
UI elements are removed to better mimic a bare text box. You can
customize the default behavior by `M-x customize-group [RET]
edit-server [RET]`. Or you can set the variables' values directly in
your ~/.emacs.


Hooks
=====

edit-server.el provides two hooks for customising behaviour when edit
requests are being made. These are:

* edit-server-start-hook - called when editing starts
* edit-server-done-hook - called when just before the text returned

For an example of what can be achieved please see Roland McGrath's
excellent edit-server-htmlize.el [1] which provides some example
functions which can be added to these hooks to deal with a popular web
based email client which sends HTML even in plain text mode.

[1] https://github.com/frobtech/edit-server-htmlize

How it works
============

The browser sends a request to the edit server of the form:

http://${HOSTNAME}:${HOSTPORT}/${CMD}

HOSTNAME is usually localhost, i.e. 127.0.0.1
HOSTPORT is the server port, in our case defaults to 9292
CMD is the command to the edit server, it may be one of the following:

* edit

The edit command is sent as an HTTP POST request. After the headers
the data is the current contents of the text area.

Once the edit is complete the server sends an HTTP 200 (OK) response
with the data containing the new text area text. Any other response
will result in the text area not being updated.

The extension also sets some headers which may be used by the edit
servers to create more identifiable names for the buffers/temp files
to help the user keep track.

x-url: The URL of the source page
x-id: The unique (on the page) ID of the text area

* status

The status command is sent as an HTTP GET request. The intention is to
use it as a simple test for the status of Edit Server and to be used
as a "Are you there?" test.

The response is basically a text string describing the state of the
edit server.