rdesktop/doc/seamlessrdp-channel.txt

TODO
----

* Command for executing new programs.

* Commands for changing z order and focus.

* Command for transferring icon.

* Think about protocol version management

* Try to assure that messages aren't repeated or are sent for hidden windows.

Overview
========

The protocol is a line based protocol following this simple syntax:

        OPERATION,SERIAL[,ARG1[,ARG2,[...]]]

Each operation will have an increasing serial number. The initial value is
implementation defined.

The goal is to have a generic protocol that can be used for other display
systems (e.g. VNC) as well.

One line may not exceed 1024 bytes, including newline.

The protocol has no concept of hidden or unmapped windows. A window does not
exist unless it is visible. Note that a minimized window is an exception to
this rule.

The protocol has no way of indicating failure, meaning that all commands are
expected to succeed. If a command fails, the receiving end must send a
corresponding command back, indicating the actual state.

Data types
==========
Window ID are written in hex, like 0x4321. 

Window positions can be negative. This happens when a window is moved
outside the desktop.

All integers fit inside 32 bits.

Strings are sent in UTF-8 and do not contain any characters less than 0x20 or
the character , (comma).

Server to Client Operations
===========================

CREATE
------

Allocate structures for a new window.

Syntax:
        CREATE,<SERIAL>,<ID>,<GRPID>,<PARENT>,<FLAGS>

Indicates that a window has appeared on the server. If PARENT is non-zero then
the new window is a child of that window (it's transient for it). The special
value 0xFFFFFFFF for PARENT means that the window is a popup window without a
parent. It's commonly used for splash screens, tool tips and context menus.

The group id identifies a set of windows that belong together. It is currently
only used for modal windows and DESTROYGRP.

Flags:
        0x0001 : Create a window that's modal with regard to the other windows
                 in the same group.

Note that very little information is included in this message. Things like
title and state will come in subsequent messages. This message should only
be used to allocate data structures for the new window.

DESTROY
-------

Remove a window.

Syntax:
        DESTROY,<SERIAL>,<ID>,<FLAGS>

Remove the window and deallocate all associated structures.

DESTROYGRP
----------

Destroy an entire group of windows.

Syntax:
        DESTROYGRP,<SERIAL>,<GRPID>,<FLAGS>

Every window that belongs to the group GRPID should be destroyed as if they
each got a DESTROY message.

POSITION
--------

Move and/or resize a window.

Syntax:
        POSITION,<SERIAL>,<ID>,<X>,<Y>,<WIDTH>,<HEIGHT>,<FLAGS>

If the window isn't visible yet (because a
STATE hasn't been set or because it's minimized), you must store the position
and size. A new POSITION is not guaranteed to be sent when the window changes
state.

TITLE
-----

Sets a window title.

Syntax:
        TITLE,<SERIAL>,<ID>,<TITLE>,<FLAGS>

The text is guaranteed to be stripped of control characters (< 0x20).

Note that this has the same requirement as POSITION, that the title needs to
be stored for newly created windows until a STATE is sent. It is however not
guaranteed that a TITLE will be sent before the first STATE.


ZCHANGE
-------

The window moved in z order.

Syntax:
        ZCHANGE,<SERIAL>,<ID>,<BEHIND>,<FLAGS>

The window with the id ID is behind the window with the id BEHIND. If
BEHIND is 0, then this window should be brought to the front. 

STATE
-----

Changes the window's state and/or title.

Syntax:
        STATE,<SERIAL>,<ID>,<STATE>,<FLAGS>

State can have one of three values:
 0 : "Normal" window.
 1 : Minimized.
 2 : Maximized.

The initial STATE for a window will always be preceeded by one CREATE and one
POSITION. Optionally, a TITLE may also be sent before the first STATE.

DEBUG
-----

Debug output from the server component.

Syntax:
        DEBUG,<SERIAL>,<STRING>

Used for debugging.

SYNCBEGIN
---------

Indicates that a synchronisation has begun.

Syntax:
        SYNCBEGIN,<SERIAL>,<FLAGS>

Sent when the server starts a synchronisation. The client should flush all
information at this point.

SYNCEND
-------

Indicates that a synchronisation is complete.

Syntac:
        SYNCEND,<SERIAL>,<FLAGS>

Sent when the last message that is part of the synchronisation has been sent.
This may be followed by duplicate messages and/or messages referring invalid
windows that were queued up during the synchronisation.

HELLO
-----

Initial message sent by server.

Syntax:
        HELLO,<SERIAL>,<FLAGS>

The server starts each connection by sending this message. Normally the client
will react by sending a SYNC back to the server. 

Flags:
  0x0001 : This is a reconnect to an existing session.
  0x0002 : The desktop is currently hidden (see HIDE).

ACK
---

Acknowledgement of a request to manipulate a window.

Syntax:
        ACK,<SERIAL>,<ACKSERIAL>

Whenever one of the commands POSITION, ZCHANGE, STATE or FOCUS is executed on
the server, the server will send an ACK back to the client. The purpose of this
is to inform the client of when the operation was actually performed, allowing
high latencies in the channel.

HIDE
----

The desktop has become hidden on the server.

Syntax:
        HIDE,<SERIAL>,<FLAGS>

This message is sent when the desktop on the server is obscured by something
that cannot be tracked. The client should remove all windows and display the
entire desktop, allowing the user to handle whatever is blocking the view.

Note that updates to windows will still be sent as the windows still exist on
the server, they are merely not visible.

UNHIDE
------

The desktop has been restored on the server.

Syntax:
        UNHIDE,<SERIAL>,<FLAGS>

This message is sent some time after a HIDE, indicating that the windowed view
has been restored. If the client has dropped all information about windows then
it can send a SYNC to re-enumerate them.

Client to Server Operations
===========================

SYNC
----

Request a synchronisation of window information.

Syntax:
        SYNC,<SERIAL>,<FLAGS>

For each window, the server will send CREATE, POSITION and STATE, in that
order, just as if the window was created. Note that a TITLE may also,
optionally, be sent before the STATE.

POSITION
--------

Identical to the command sent from server to client.

TITLE
-----

Identical to the command sent from server to client.

ZCHANGE
-------

Identical to the command sent from server to client.

STATE
-----

Identical to the command sent from server to client.

FOCUS
-----

Sets which window has input focus.

Syntax:
        FOCUS,<SERIAL>,<ID>,<FLAGS>

Changes which window that will recieve the keyboard events. Note that this
might cause the window to change z order.
1	TODO
2	----
3
4	* Command for executing new programs.
5
6	* Commands for changing z order and focus.
7
8	* Command for transferring icon.
9
10	* Think about protocol version management
11
12	* Try to assure that messages aren't repeated or are sent for hidden windows.
13
14	Overview
15	========
16
17	The protocol is a line based protocol following this simple syntax:
18
19	OPERATION,SERIAL[,ARG1[,ARG2,[...]]]
20
21	Each operation will have an increasing serial number. The initial value is
22	implementation defined.
23
24	The goal is to have a generic protocol that can be used for other display
25	systems (e.g. VNC) as well.
26
27	One line may not exceed 1024 bytes, including newline.
28
29	The protocol has no concept of hidden or unmapped windows. A window does not
30	exist unless it is visible. Note that a minimized window is an exception to
31	this rule.
32
33	The protocol has no way of indicating failure, meaning that all commands are
34	expected to succeed. If a command fails, the receiving end must send a
35	corresponding command back, indicating the actual state.
36
37	Data types
38	==========
39	Window ID are written in hex, like 0x4321.
40
41	Window positions can be negative. This happens when a window is moved
42	outside the desktop.
43
44	All integers fit inside 32 bits.
45
46	Strings are sent in UTF-8 and do not contain any characters less than 0x20 or
47	the character , (comma).
48
49	Server to Client Operations
50	===========================
51
52	CREATE
53	------
54
55	Allocate structures for a new window.
56
57	Syntax:
58	CREATE,<SERIAL>,<ID>,<GRPID>,<PARENT>,<FLAGS>
59
60	Indicates that a window has appeared on the server. If PARENT is non-zero then
61	the new window is a child of that window (it's transient for it). The special
62	value 0xFFFFFFFF for PARENT means that the window is a popup window without a
63	parent. It's commonly used for splash screens, tool tips and context menus.
64
65	The group id identifies a set of windows that belong together. It is currently
66	only used for modal windows and DESTROYGRP.
67
68	Flags:
69	0x0001 : Create a window that's modal with regard to the other windows
70	in the same group.
71
72	Note that very little information is included in this message. Things like
73	title and state will come in subsequent messages. This message should only
74	be used to allocate data structures for the new window.
75
76	DESTROY
77	-------
78
79	Remove a window.
80
81	Syntax:
82	DESTROY,<SERIAL>,<ID>,<FLAGS>
83
84	Remove the window and deallocate all associated structures.
85
86	DESTROYGRP
87	----------
88
89	Destroy an entire group of windows.
90
91	Syntax:
92	DESTROYGRP,<SERIAL>,<GRPID>,<FLAGS>
93
94	Every window that belongs to the group GRPID should be destroyed as if they
95	each got a DESTROY message.
96
97	POSITION
98	--------
99
100	Move and/or resize a window.
101
102	Syntax:
103	POSITION,<SERIAL>,<ID>,<X>,<Y>,<WIDTH>,<HEIGHT>,<FLAGS>
104
105	If the window isn't visible yet (because a
106	STATE hasn't been set or because it's minimized), you must store the position
107	and size. A new POSITION is not guaranteed to be sent when the window changes
108	state.
109
110	TITLE
111	-----
112
113	Sets a window title.
114
115	Syntax:
116	TITLE,<SERIAL>,<ID>,<TITLE>,<FLAGS>
117
118	The text is guaranteed to be stripped of control characters (< 0x20).
119
120	Note that this has the same requirement as POSITION, that the title needs to
121	be stored for newly created windows until a STATE is sent. It is however not
122	guaranteed that a TITLE will be sent before the first STATE.
123
124
125	ZCHANGE
126	-------
127
128	The window moved in z order.
129
130	Syntax:
131	ZCHANGE,<SERIAL>,<ID>,<BEHIND>,<FLAGS>
132
133	The window with the id ID is behind the window with the id BEHIND. If
134	BEHIND is 0, then this window should be brought to the front.
135
136	STATE
137	-----
138
139	Changes the window's state and/or title.
140
141	Syntax:
142	STATE,<SERIAL>,<ID>,<STATE>,<FLAGS>
143
144	State can have one of three values:
145	0 : "Normal" window.
146	1 : Minimized.
147	2 : Maximized.
148
149	The initial STATE for a window will always be preceeded by one CREATE and one
150	POSITION. Optionally, a TITLE may also be sent before the first STATE.
151
152	DEBUG
153	-----
154
155	Debug output from the server component.
156
157	Syntax:
158	DEBUG,<SERIAL>,<STRING>
159
160	Used for debugging.
161
162	SYNCBEGIN
163	---------
164
165	Indicates that a synchronisation has begun.
166
167	Syntax:
168	SYNCBEGIN,<SERIAL>,<FLAGS>
169
170	Sent when the server starts a synchronisation. The client should flush all
171	information at this point.
172
173	SYNCEND
174	-------
175
176	Indicates that a synchronisation is complete.
177
178	Syntac:
179	SYNCEND,<SERIAL>,<FLAGS>
180
181	Sent when the last message that is part of the synchronisation has been sent.
182	This may be followed by duplicate messages and/or messages referring invalid
183	windows that were queued up during the synchronisation.
184
185	HELLO
186	-----
187
188	Initial message sent by server.
189
190	Syntax:
191	HELLO,<SERIAL>,<FLAGS>
192
193	The server starts each connection by sending this message. Normally the client
194	will react by sending a SYNC back to the server.
195
196	Flags:
197	0x0001 : This is a reconnect to an existing session.
198	0x0002 : The desktop is currently hidden (see HIDE).
199
200	ACK
201	---
202
203	Acknowledgement of a request to manipulate a window.
204
205	Syntax:
206	ACK,<SERIAL>,<ACKSERIAL>
207
208	Whenever one of the commands POSITION, ZCHANGE, STATE or FOCUS is executed on
209	the server, the server will send an ACK back to the client. The purpose of this
210	is to inform the client of when the operation was actually performed, allowing
211	high latencies in the channel.
212
213	HIDE
214	----
215
216	The desktop has become hidden on the server.
217
218	Syntax:
219	HIDE,<SERIAL>,<FLAGS>
220
221	This message is sent when the desktop on the server is obscured by something
222	that cannot be tracked. The client should remove all windows and display the
223	entire desktop, allowing the user to handle whatever is blocking the view.
224
225	Note that updates to windows will still be sent as the windows still exist on
226	the server, they are merely not visible.
227
228	UNHIDE
229	------
230
231	The desktop has been restored on the server.
232
233	Syntax:
234	UNHIDE,<SERIAL>,<FLAGS>
235
236	This message is sent some time after a HIDE, indicating that the windowed view
237	has been restored. If the client has dropped all information about windows then
238	it can send a SYNC to re-enumerate them.
239
240	Client to Server Operations
241	===========================
242
243	SYNC
244	----
245
246	Request a synchronisation of window information.
247
248	Syntax:
249	SYNC,<SERIAL>,<FLAGS>
250
251	For each window, the server will send CREATE, POSITION and STATE, in that
252	order, just as if the window was created. Note that a TITLE may also,
253	optionally, be sent before the STATE.
254
255	POSITION
256	--------
257
258	Identical to the command sent from server to client.
259
260	TITLE
261	-----
262
263	Identical to the command sent from server to client.
264
265	ZCHANGE
266	-------
267
268	Identical to the command sent from server to client.
269
270	STATE
271	-----
272
273	Identical to the command sent from server to client.
274
275	FOCUS
276	-----
277
278	Sets which window has input focus.
279
280	Syntax:
281	FOCUS,<SERIAL>,<ID>,<FLAGS>
282
283	Changes which window that will recieve the keyboard events. Note that this
284	might cause the window to change z order.