[qemu.git] / docs / vnc-ledstate-Pseudo-encoding.txt

VNC LED state Pseudo-encoding
=============================

Introduction
------------

This document describes the Pseudo-encoding of LED state for RFB which
is the protocol used in VNC as reference link below:

http://tigervnc.svn.sourceforge.net/viewvc/tigervnc/rfbproto/rfbproto.rst?content-type=text/plain

When accessing a guest by console through VNC, there might be mismatch
between the lock keys notification LED on the computer running the VNC
client session and the current status of the lock keys on the guest
machine.

To solve this problem it attempts to add LED state Pseudo-encoding
extension to VNC protocol to deal with setting LED state.

Pseudo-encoding
---------------

This Pseudo-encoding requested by client declares to server that it supports
LED state extensions to the protocol.

The Pseudo-encoding number for LED state defined as:

======= ===============================================================
Number  Name
======= ===============================================================
-261    'LED state Pseudo-encoding'
======= ===============================================================

LED state Pseudo-encoding
--------------------------

The LED state Pseudo-encoding describes the encoding of LED state which
consists of 3 bits, from left to right each bit represents the Caps, Num,
and Scroll lock key respectively. '1' indicates that the LED should be
on and '0' should be off.

Some example encodings for it as following:

======= ===============================================================
Code    Description
======= ===============================================================
100     CapsLock is on, NumLock and ScrollLock are off
010     NumLock is on, CapsLock and ScrollLock are off
111     CapsLock, NumLock and ScrollLock are on
======= ===============================================================
Commit	Line	Data
7504ae69 LL	1	VNC LED state Pseudo-encoding
	2	=============================
	3
	4	Introduction
	5	------------
	6
	7	This document describes the Pseudo-encoding of LED state for RFB which
	8	is the protocol used in VNC as reference link below:
	9
	10	http://tigervnc.svn.sourceforge.net/viewvc/tigervnc/rfbproto/rfbproto.rst?content-type=text/plain
	11
	12	When accessing a guest by console through VNC, there might be mismatch
	13	between the lock keys notification LED on the computer running the VNC
	14	client session and the current status of the lock keys on the guest
	15	machine.
	16
	17	To solve this problem it attempts to add LED state Pseudo-encoding
	18	extension to VNC protocol to deal with setting LED state.
	19
	20	Pseudo-encoding
	21	---------------
	22
	23	This Pseudo-encoding requested by client declares to server that it supports
	24	LED state extensions to the protocol.
	25
	26	The Pseudo-encoding number for LED state defined as:
	27
	28	======= ===============================================================
	29	Number Name
	30	======= ===============================================================
	31	-261 'LED state Pseudo-encoding'
	32	======= ===============================================================
	33
	34	LED state Pseudo-encoding
	35	--------------------------
	36
	37	The LED state Pseudo-encoding describes the encoding of LED state which
	38	consists of 3 bits, from left to right each bit represents the Caps, Num,
	39	and Scroll lock key respectively. '1' indicates that the LED should be
	40	on and '0' should be off.
	41
	42	Some example encodings for it as following:
	43
	44	======= ===============================================================
	45	Code Description
	46	======= ===============================================================
	47	100 CapsLock is on, NumLock and ScrollLock are off
	48	010 NumLock is on, CapsLock and ScrollLock are off
	49	111 CapsLock, NumLock and ScrollLock are on
	50	======= ===============================================================