CDE/cde/lib/tt/demo/CoEd

/* $XConsortium: README /main/2 1996/07/15 14:07:37 drk $ */
This is CoEd, a shared text editor. Building CoEd requires DevGuide,
C++, and ToolTalk (which is part of OpenWindows). CoEd is known to
build with DevGuide 3.0.1, C++ from SPARCompilers 2.0.1, and either
OpenWindows 3.1 or OpenWindows 3.2.

NOTE: The libgolit in DevGuide 3.0.1 was based on the OW3.0.1/3.1 OLIT
libraries, and has some incompatibilites with the OW3.2 OLIT
libraries. A CoEd built with with libgolit 3.0.1 and running under
OW3.2 will crash, e.g., if you press MENU or HELP over the OLIT
textedit widget embedded in CoEd. However, the basic features of
editing, selecting, copy/paste, drag-and-drop, and scrolling seem to
work.

Run it with "CoEd ". (Of course, the ToolTalk dbserver must
be installed on the machine that owns the file. See the ToolTalk
Setup And Administration Guide.)

Basically, it's an editor that uses ToolTalk so that multiple
instances of the editor can edit the same file at the same time,
and have all the changes keep in sync. It has some serious limitations:

- CoEd has no facility for saving the edited file to disk.

- All the CoEd's must come up before any typing occurs. We haven't
implemented the part of the protocol where newcomers can request
the current state of the file. CoEd's can quit at any time without
messing up the others. Here's a sketch for the rest of
the protocol, in case anyone is interested in completely implementing
the dOPT algorithm (cf. C.A. Ellis and S.J. Gibbs,
"Concurrency Control in Groupware Systems", Proc. 1989 ACM SIGMOD,
Int. Conf. on the Mgt. of Data).

* CoEd protocol
* Notices every editor should register for
* Text_File_Changed(
in CoEdTextVersion appliesTo,
in int changeNum,
in int start,
in int end,
in string text )
* Text_File_Poll_Version()
* Used by the moderator to detect quiescence.
* Text_File_Saved()
* Text_File_Reverted()
* Text_File_Renamed(
in string newName )
* Requests every editor should register to handle
* Text_File_New_Moderator()
* Sent by the Moderator when closing the file. Whoever
handles it must register for the Moderator requests and
act as the new Moderator.
* Point-to-point notices the Moderator should be ready for
* Text_File_Version_Vote(
in CoEdTextVersion myVersion )
* When a Text_File_Poll_Version notice is received,
this notice is sent directly to the party that called
for the version vote.
* Requests the moderator should register to handle
* Text_File_Join(
out CoEdSiteIDList coEditors )
* Sent every time an editor opens a file. If the request
fails, then no one is editing the file and the requestor
should become the Moderator -- i.e., register to handle
this request. If the request succeeds, then issue a
Text_File_Poll_Version notice, and wait until each
coEditor responds with a Text_File_Version_Vote.
Then send a Text_File_Update_Me request to catch up on
what you've missed.
* Text_File_Update_Me(
inout CoEdTextVersion version,
out string text )
* Sent by new coEditors after they've received a
Text_File_Version_Vote from each coEditor they learned
about when they did their Text_File_Join. In the
request, is the earliest version of the text
that would not leave the requestor with missing changes
from any of the coEditors. In the reply, is
identical to or later than the requested version, and
corresponds to the in the reply.