








		X Session Management Library

			Version 1.0

		   X Consortium Standard

		 X Version 11, Release 6.4

			 Ralph Mor
			X Consortium



	   Copyright (C) 1993, 1994 X Consortium







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1.  Overview of Session Management

The purpose of the X Session Management Protocol  (XSMP)  is
to provide a uniform mechanism for users to save and restore
their sessions.  A session is a group of  clients,  each  of
which  has a particular state.	The session is controlled by
a network service called the session manager.	The  session
manager  issues  commands  to  its  clients on behalf of the
user.  These commands may cause clients to save their  state
or  to	terminate.  It is expected that the client will save
its state in such a way that the client can be restarted  at
a  later  time	and  resume its operation as if it had never
been terminated.  A client's state might include information
about  the file currently being edited, the current position
of the insertion point within the file, or the start  of  an
uncommitted  transaction.   The  means	by which clients are
restarted is unspecified by this protocol.

For purposes of this protocol, a client of the session	man-
ager  is  defined as a connection to the session manager.  A
client is typically, though not necessarily, a process	run-
ning an application program connected to an X display.	How-
ever, a client may be connected to more than one  X  display
or not be connected to any X displays at all.

2.  The Session Management Library

The  Session  Management  Library (SMlib) is a low-level "C"
language interface to XSMP.   It  is  expected	that  higher
level toolkits, such as Xt, will hide many of the details of
session management  from  clients.   Higher  level  toolkits
might  also be developed for session managers to use, but no
such effort is currently under way.

SMlib has two parts to it:

o    One set of functions for clients that want to  be	part
     of a session

o    One set of functions for session managers to call

Some applications will use both sets of functions and act as
nested session managers.  That is, they will be both a	ses-
sion manager and a client of another session.  An example is
a mail program that could start a text	editor	for  editing
the  text  of a mail message.  The mail program is part of a
regular session and, at the same time, is also acting  as  a
session manager to the editor.

Clients  initialize by connecting to the session manager and
obtaining a client-ID that uniquely identifies them  in  the
session.  The session manager maintains a list of properties
for each client in the session.  These	properties  describe
the client's environment and, most importantly, describe how



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X Session Management Library		    X11, Release 6.4


the client  can  be  restarted	(via  an  SmRestartCommand).
Clients are expected to save their state in such a way as to
allow multiple instantiations of themselves  to  be  managed
independently.	For example, clients may use their client-ID
as part of a filename in which to store the state for a par-
ticular  instantiation.   The  client-ID  should be saved as
part of the SmRestartCommand so that the client will  retain
the same ID after it is restarted.

Once the client initializes itself with the session manager,
it must be ready to respond to	messages  from	the  session
manager.   For	example, it might be asked to save its state
or to terminate.  In the case of  a  shutdown,	the  session
manager might give each client a chance to interact with the
user and cancel the shutdown.

3.  Understanding SMlib's Dependence on ICE

The X Session Management Protocol is layered on top  of  the
Inter-Client  Exchange	(ICE) Protocol.  The ICE protocol is
designed to multiplex several protocols over a	single	con-
nection.   As a result, working with SMlib requires a little
knowledge of how the ICE library works.

The ICE library  utilizes  callbacks  to  process  messages.
When  a  client detects that there is data to read on an ICE
connection, it should call the IceProcessMessages  function.
IceProcessMessages  will read the message header and look at
the major opcode in order to determine	which  protocol  the
message  was intended for.  The appropriate protocol library
will then be triggered to unpack the message and hand it off
to the client via a callback.

The  main  point to be aware of is that an application using
SMlib must have some code that detects when there is data to
read  on  an  ICE connection.  This can be done via a select
call on the file descriptor for the ICE connection, but more
typically, XtAppAddInput will be used to register a callback
that will invoke IceProcessMessages each time there is	data
to read on the ICE connection.

To further complicate things, knowing which file descriptors
to call select on requires an understanding of how ICE	con-
nections  are  created.   On the client side, a call must be
made to SmcOpenConnection in order to open a connection with
a session manager.  SmcOpenConnection will internally make a
call into IceOpenConnection, which will, in turn,  determine
if  an	ICE connection already exists between the client and
session manager.  Most likely, a connection will not already
exist  and  a  new ICE connection will be created.  The main
point to be aware of is that, on the client side, it is  not
obvious  when  ICE  connections  get  created  or destroyed,
because connections are shared when possible.  To deal	with
this,  the  ICE  library lets the application register watch



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X Session Management Library		    X11, Release 6.4


procedures that will be invoked each time an ICE  connection
is  opened  or closed.	These watch procedures could be used
to add or remove ICE  file  descriptors  from  the  list  of
descriptors to call select on.

On  the session manager side, things work a bit differently.
The session manager has complete control over  the  creation
of  ICE  connections.  The session manager has to first call
IceListenForConnections in order to start listening for con-
nections   from  clients.   Once  a  connection  attempt  is
detected, IceAcceptConnection must be called, and  the	ses-
sion  manager  can simply add the new ICE file descriptor to
the list of descriptors to call select on.

For further information on the library functions related  to
ICE connections, see the Inter-Client Exchange Library stan-
dard.

4.  Header Files and Library Name

Applications (both  session  managers  and  clients)  should
include  the header file <X11/SM/SMlib.h>.  This header file
defines all of the SMlib data structures and function proto-
types.	 SMlib.h  includes  the  header  file <X11/SM/SM.h>,
which defines all of the SMlib constants.

Because SMlib is dependent on ICE, applications should	link
against SMlib and ICElib by using -lSM -lICE.

5.  Session Management Client (Smc) Functions

This section discusses how Session Management clients:

o    Connect to the Session Manager

o    Close the connection

o    Modify callbacks

o    Set, delete, and retrieve Session Manager properties

o    Interact with the user

o    Request a ``Save Yourself''

o    Request a ``Save Yourself Phase 2''

o    Complete a ``Save Yourself''

o    Use Smc informational functions

o    Handle Errors





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X Session Management Library		    X11, Release 6.4


5.1.  Connecting to the Session Manager

To   open   a	connection   with  a  session  manager,  use
SmcOpenConnection.
__
|
SmcConn SmcOpenConnection(network_ids_list, context, xsmp_major_rev, xsmp_minor_rev,
		    mask, callbacks, previous_id, client_id_ret, error_length, error_string_ret)
    char *network_ids_list;
    SmPointer context;
    int xsmp_major_rev;
    int xsmp_minor_rev;
    unsigned long mask;
    SmcCallbacks *callbacks;
    char *previous_id;
    char **client_id_ret;
    int error_length;
    char *error_string_ret;


network_ids_list
	  Specifies the network ID(s) of  the  session	man-
	  ager.

context   A  pointer  to  an opaque object or NULL.  Used to
	  determine if an ICE connection can be shared	(see
	  below).

xsmp_major_rev
	  The highest major version of the XSMP the applica-
	  tion supports.

xsmp_minor_rev
	  The highest minor version of the XSMP the applica-
	  tion	supports (for the specified xsmp_major_rev).

mask	  A mask indicating which callbacks to register.

callbacks The callbacks to register.   These  callbacks  are
	  used	to respond to messages from the session man-
	  ager.

previous_id
	  The client ID from the previous session.

client_id_ret
	  The client ID for the current session is returned.

error_length
	  Length of the error_string_ret argument passed in.

error_string_ret
	  Returns a null-terminated error message,  if	any.
	  The	error_string_ret  argument  points  to	user



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X Session Management Library		    X11, Release 6.4


	  supplied memory.  No more than error_length  bytes
	  are used.
|__

The  network_ids_list  argument  is a null-terminated string
containing a list of network IDs for  the  session  manager,
separated by commas.  If network_ids_list is NULL, the value
of the SESSION_MANAGER environment variable  will  be  used.
Each network ID has the following format:

     tcp/<hostname>:<portnumber>    or
     decnet/<hostname>::<objname>   or
     local/<hostname>:<path>


An  attempt  will  be  made to use the first network ID.  If
that fails, an attempt will be made using the second network
ID, and so on.

After  the connection is established, SmcOpenConnection reg-
isters the client with the session manager.  If  the  client
is  being  restarted  from  a  previous session, previous_id
should contain a null  terminated  string  representing  the
client ID from the previous session.  If the client is first
joining the session, previous_id should be set to NULL.   If
previous_id  is specified but is determined to be invalid by
the session manager, SMlib will re-register the client	with
previous_id set to NULL.

If  SmcOpenConnection succeeds, it returns an opaque connec-
tion pointer of type SmcConn and the client_id_ret  argument
contains  the  client  ID  to be used for this session.  The
client_id_ret should be freed with a call to  free  when  no
longer	needed.  On failure, SmcOpenConnection returns NULL,
and the reason for failure is returned in  error_string_ret.

Note that SMlib uses the ICE protocol to establish a connec-
tion with the session manager.	If an ICE connection already
exists	between  the client and session manager, it might be
possible for the same ICE connection to be used for  session
management.

The  context argument indicates how willing the client is to
share the ICE connection with other protocols.	 If  context
is NULL, then the caller is always willing to share the con-
nection.  If context is not NULL, then	the  caller  is  not
willing to use a previously opened ICE connection that has a
different non-NULL context associated with it.

As previously discussed (section 3, ``Understanding  SMlib's
Dependence  on ICE''), the client will have to keep track of
when ICE connections are created or destroyed (using IceAdd-
ConnectionWatch and IceRemoveConnectionWatch), and will have
to call IceProcessMessages each time  a  select  shows	that



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there  is  data  to  read on an ICE connection.  For further
information, see the Inter-Client Exchange Library standard.

The  callbacks	argument contains a set of callbacks used to
respond to session manager events.  The mask argument speci-
fies  which  callbacks are set.  All of the callbacks speci-
fied in this version of SMlib are mandatory.  The mask argu-
ment is necessary in order to maintain backwards compatibil-
ity in future versions of the library.

The following values may be ORed together to obtain  a	mask
value:


SmcSaveYourselfProcMask
SmcDieProcMask
SmcSaveCompleteProcMask
SmcShutdownCancelledProcMask


For  each  callback,  the  client  can register a pointer to
client data.  When SMlib invokes the callback, it will	pass
the client data pointer.

__
|
typedef struct {

     struct {
	  SmcSaveYourselfProc callback;
	  SmPointer client_data;
     } save_yourself;

     struct {
	  SmcDieProc callback;
	  SmPointer client_data;
     } die;

     struct {
	  SmcSaveCompleteProc callback;
	  SmPointer client_data;
     } save_complete;

     struct {
	  SmcShutdownCancelledProc callback;
	  SmPointer client_data;
     } shutdown_cancelled;

} SmcCallbacks;

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5.1.1.	The Save Yourself Callback

The Save Yourself callback is of type SmcSaveYourselfProc.
__
|
typedef void (*SmcSaveYourselfProc)();

void SaveYourselfProc(smc_conn, client_data, save_type, shutdown, interact_style, fast)
    SmcConn smc_conn;
    SmPointer client_data;
    int save_type;
    Bool shutdown;
    int interact_style;
    Bool fast;


smc_conn  The session management connection object.

client_data
	  Client data specified when the callback was regis-
	  tered.

save_type Specifies the type of information that  should  be
	  saved.

shutdown  Specifies if a shutdown is taking place.

interact_style
	  The type of interaction allowed with the user.

fast	  If  True,  the  client  should  save	its state as
	  quickly as possible.
|__

The session manager sends a ``Save Yourself'' message  to  a
client either to checkpoint it or just before termination so
that it can save its state.  The client responds  with	zero
or  more  calls to SmcSetProperties to update the properties
indicating how to restart the client.  When all the  proper-
ties have been set, the client calls SmcSaveYourselfDone.

If  interact_style  is	SmInteractStyleNone, the client must
not interact with the user while saving  state.   If  inter-
act_style  is SmInteractStyleErrors, the client may interact
with the user only if an error condition arises.  If  inter-
act_style  is SmInteractStyleAny, then the client may inter-
act with the user for any purpose.  Because only one  client
can  interact  with the user at a time, the client must call
SmcInteractRequest and wait for an ``Interact'' message from
the  session  manager.	 When the client is done interacting
with the user, it calls  SmcInteractDone.   The  client  may
only  call  SmcInteractRequest	after  it  receives a ``Save
Yourself'' message and before it calls	SmcSaveYourselfDone.




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If  save_type  is  SmSaveLocal,  the  client must update the
properties to reflect its current state.   Specifically,  it
should	save enough information to restore the state as seen
by the user of this client.  It should not affect the  state
as  seen  by other users.  If save_type is SmSaveGlobal, the
user wants the client to commit all of its  data  to  perma-
nent,	globally   accessible	storage.   If  save_type  is
SmSaveBoth, the client should do both of  these  (it  should
first  commit  the data to permanent storage before updating
its properties).

Some examples are as follows:


o    If a word processor were sent a ``Save Yourself''	with
     a type of SmSaveLocal, it could create a temporary file
     that included the current contents  of  the  file,  the
     location  of  the cursor, and other aspects of the cur-
     rent  editing  session.   It  would  then	update	 its
     SmRestartCommand  property  with  enough information to
     find this temporary file.

o    If a word processor were sent a ``Save Yourself''	with
     a	type  of SmSaveGlobal, it would simply save the cur-
     rently edited file.

o    If a word processor were sent a ``Save Yourself''	with
     a type of SmSaveBoth, it would first save the currently
     edited file.  It would then  create  a  temporary	file
     with  information	such  as the current position of the
     cursor and what file  is  being  edited.	Finally,  it
     would  update its SmRestartCommand property with enough
     information to find the temporary file.

The shutdown argument specifies whether the system is  being
shut  down.   The  interaction	is  different  depending  on
whether or not shutdown is set.  If not shutting  down,  the
client	should	save  its  state  and wait for a ``Save Com-
plete'' message.  If shutting down,  the  client  must	save
state  and then prevent interaction until it receives either
a ``Die'' or a ``Shutdown Cancelled.''

The fast argument specifies that the client should save  its
state  as  quickly as possible.  For example, if the session
manager knows that power is about to fail, it would set fast
to True.

5.1.2.	The Die Callback

The Die callback is of type SmcDieProc.
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typedef void (*SmcDieProc)();

void DieProc(smc_conn, client_data)
    SmcConn smc_conn;
    SmPointer client_data;


smc_conn  The session management connection object.

client_data
	  Client data specified when the callback was regis-
	  tered.
|__

The session manager sends a ``Die'' message to a client when
it  wants  it  to die.	The client should respond by calling
SmcCloseConnection.  A session manager that behaves properly
will  send  a  ``Save  Yourself'' message before the ``Die''
message.

5.1.3.	The Save Complete Callback

The Save Complete callback is of type SmcSaveCompleteProc.
__
|
typedef void (*SmcSaveCompleteProc)();

void SaveCompleteProc(smc_conn, client_data)
    SmcConn smc_conn;
    SmPointer client_data;


smc_conn  The session management connection object.

client_data
	  Client data specified when the callback was regis-
	  tered.
|__

When  the session manager is done with a checkpoint, it will
send each of the clients a ``Save Complete''  message.	 The
client is then free to change its state.

5.1.4.	The Shutdown Cancelled Callback

The    Shutdown    Cancelled	callback    is	  of	type
SmcShutdownCancelledProc.
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typedef void (*SmcShutdownCancelledProc)();

void ShutdownCancelledProc(smc_conn, client_data)
    SmcConn smc_conn;
    SmPointer client_data;


smc_conn  The session management connection object.

client_data
	  Client data specified when the callback was regis-
	  tered.
|__

The  session  manager sends a ``Shutdown Cancelled'' message
when the user cancelled the shutdown during  an  interaction
(see  section  5.5,  ``Interacting  With  the  User'').  The
client can now continue as if the shutdown  had  never	hap-
pened.	 If  the  client  has not called SmcSaveYourselfDone
yet, it can either abort the save and then call SmcSaveYour-
selfDone  with	the success argument set to False, or it can
continue with the save	and  then  call  SmcSaveYourselfDone
with  the success argument set to reflect the outcome of the
save.

5.2.  Closing the Connection

To  close  a  connection  with	a   session   manager,	 use
SmcCloseConnection.

__
|
SmcCloseStatus SmcCloseConnection(smc_conn, count, reason_msgs)
    SmcConn smc_conn;
    int count;
    char **reason_msgs;


smc_conn  The session management connection object.

count	  The number of reason messages.

reason_msgs
	  The reasons for closing the connection.
|__

The  reason_msgs argument will most likely be NULL if resig-
nation is expected by the client.  Otherwise, it contains  a
list  of  null-terminated Compound Text strings representing
the reason for termination.  The session manager should dis-
play these reason messages to the user.

Note that SMlib used the ICE protocol to establish a connec-
tion with the session manager, and various  protocols  other



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X Session Management Library		    X11, Release 6.4


than session management may be active on the ICE connection.
When SmcCloseConnection is called, the ICE  connection	will
be  closed  only  if all protocols have been shutdown on the
connection.  Check the ICElib standard for IceAddConnection-
Watch  and IceRemoveConnectionWatch to learn how to set up a
callback to be invoked each time an ICE connection is opened
or  closed.   Typically  this  callback adds/removes the ICE
file descriptor from the list of active descriptors to	call
select on (or calls XtAppAddInput or XtRemoveInput).

SmcCloseConnection returns one of the following values:

o    SmcClosedNow  -  the  ICE connection was closed at this
     time, the watch procedures were invoked, and  the	con-
     nection was freed.

o    SmcClosedASAP - an IO error had occurred on the connec-
     tion, but SmcCloseConnection is being called  within  a
     nested  IceProcessMessages.   The watch procedures have
     been invoked at this time, but the connection  will  be
     freed  as	soon  as  possible  (when  the nesting level
     reaches zero and IceProcessMessages returns a status of
     IceProcessMessagesConnectionClosed).

o    SmcConnectionInUse  -  the connection was not closed at
     this time, because it is being  used  by  other  active
     protocols.

5.3.  Modifying Callbacks

To   modify  callbacks	set  up  in  SmcOpenConnection,  use
SmcModifyCallbacks.
__
|
void SmcModifyCallbacks(smc_conn, mask, callbacks)
    SmcConn smc_conn;
    unsigned long mask;
    SmcCallbacks *callbacks;


smc_conn  The session management connection object.

mask	  A mask indicating which callbacks to modify.

callbacks The new callbacks.
|__

When specifying a value for the mask argument, the following
values may be ORed together:


SmcSaveYourselfProcMask
SmcDieProcMask
SmcSaveCompleteProcMask



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SmcShutdownCancelledProcMask


5.4.   Setting,  Deleting, and Retrieving Session Management
Properties

To  set  session  management properties for this client, use
SmcSetProperties.
__
|
void SmcSetProperties(smc_conn, num_props, props)
    SmcConn smc_conn;
    int num_props;
    SmProp **props;


smc_conn  The session management connection object.

num_props The number of properties.

props	  The list of properties to set.
|__

The properties are specified as an array of property  point-
ers.   Previously  set	property  values may be over-written
using the SmcSetProperties function.  Note that the  session
manager  is not expected to restore property values when the
session is restarted.  Because of this, clients  should  not
try  to  use  the  session manager as a database for storing
application specific state.

For a description of session management properties  and  the
SmProp	structure, see section 7, ``Session Management Prop-
erties.''


To delete properties  previously  set  by  the	client,  use
SmcDeleteProperties.
__
|
void SmcDeleteProperties(smc_conn, num_props, prop_names)
    SmcConn smc_conn;
    int num_props;
    char **prop_names;


smc_conn  The session management connection object.

num_props The number of properties.

prop_names
	  The list of properties to delete.





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|__


To  get  properties  previously  stored  by  the client, use
SmcGetProperties.
__
|
Status SmcGetProperties(smc_conn, prop_reply_proc, client_data)
    SmcConn smc_conn;
    SmcPropReplyProc prop_reply_proc;
    SmPointer client_data;


smc_conn  The session management connection object.

prop_reply_proc
	  The callback to be  invoked  when  the  properties
	  reply comes back.

client_data
	  This	pointer to client data will be passed to the
	  SmcPropReplyProc callback.
|__

The return value of SmcGetProperties is zero for failure and
a positive value for success.

Note  that  the  library does not block until the properties
reply comes back.  Rather, a  callback	of  type  SmcPropRe-
plyProc is invoked when the data is ready.
__
|
typedef void (*SmcPropReplyProc)();

void PropReplyProc(smc_conn, client_data, num_props, props)
    SmcConn smc_conn;
    SmPointer client_data;
    int num_props;
    SmProp **props;


smc_conn  The session management connection object.

client_data
	  Client data specified when the callback was regis-
	  tered.

num_props The number of properties returned.

props	  The list of properties returned.
|__

To free each property, use SmFreeProperty  (see  section  8,
``Freeing  Data'').   To  free the actual array of pointers,



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use free.

5.5.  Interacting With the User

After receiving a ``Save Yourself'' message with  an  inter-
act_style  of  SmInteractStyleErrors  or SmInteractStyleAny,
the client may choose to interact with	the  user.   Because
only  one  client  can interact with the user at a time, the
client must call SmcInteractRequest and wait for an ``Inter-
act'' message from the session manager.
__
|
Status SmcInteractRequest(smc_conn, dialog_type, interact_proc, client_data)
    SmcConn smc_conn;
    int dialog_type;
    SmcInteractProc interact_proc;
    SmPointer client_data;


smc_conn  The session management connection object.

dialog_type
	  The type of dialog the client wishes to present to
	  the user.

interact_proc
	  The callback to be invoked when  the	``Interact''
	  message arrives from the session manager.

client_data
	  This	pointer to client data will be passed to the
	  SmcInteractProc  callback  when  the	``Interact''
	  message arrives.
|__

The  return  value of SmcInteractRequest is zero for failure
and a positive value for success.

The dialog_type  argument  specifies  either  SmDialogError,
indicating  that  the client wants to start an error dialog,
or SmDialogNormal, meaning that the client wishes to start a
nonerror dialog.

Note  that  if	a shutdown is in progress, the user may have
the option of cancelling the shutdown.	If the	shutdown  is
cancelled, the clients that have not interacted yet with the
user will receive a ``Shutdown Cancelled''  message  instead
of the ``Interact'' message.

The  SmcInteractProc  callback	will  be  invoked  when  the
``Interact'' message arrives from the session manager.
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X Session Management Library		    X11, Release 6.4


typedef void (*SmcInteractProc)();

void InteractProc(smc_conn, client_data)
    SmcConn smc_conn;
    SmPointer client_data;


smc_conn  The session management connection object.

client_data
	  Client data specified when the callback was regis-
	  tered.
|__


After  interacting with the user (in response to an ``Inter-
act'' message), you should call SmcInteractDone.
__
|
void SmcInteractDone(smc_conn, cancel_shutdown)
    SmcConn smc_conn;
    Bool cancel_shutdown;


smc_conn  The session management connection object.

cancel_shutdown
	  If True, indicates that the user requests that the
	  entire shutdown be cancelled.
|__

The  cancel_shutdown argument may only be True if the corre-
sponding ``Save Yourself'' specified True for  shutdown  and
SmInteractStyleErrors  or  SmInteractStyleAny for the inter-
act_style.

5.6.  Requesting a Save Yourself

To request  a  checkpoint  from  the  session  manager,  use
SmcRequestSaveYourself.
__
|
void SmcRequestSaveYourself(smc_conn, save_type, shutdown, interact_style, fast, global)
    SmcConn smc_conn;
    int save_type;
    Bool shutdown;
    int interact_style;
    Bool fast;
    Bool global;


smc_conn  The session management connection object.





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X Session Management Library		    X11, Release 6.4


save_type Specifies  the  type of information that should be
	  saved.

shutdown  Specifies if a shutdown is taking place.

interact_style
	  The type of interaction allowed with the user.

fast	  If True, the	client	should	save  its  state  as
	  quickly as possible.

global	  Controls who gets the ``Save Yourself.''
|__

The  save_type, shutdown, interact_style, and fast arguments
are discussed in more detail in section  5.1.1,  ``The	Save
Yourself Callback.''

If  global  is	set to True, then the resulting ``Save Your-
self'' should be sent to all clients in  the  session.	 For
example,  a  vendor  of a Uninterruptible Power Supply (UPS)
might include a Session Management client that would monitor
the  status  of  the UPS and generate a fast shutdown if the
power is about to be lost.

If global is set to False, then the ``Save Yourself'' should
only be sent to the client that requested it.

5.7.  Requesting a Save Yourself Phase 2

In  response to a ``Save Yourself, the client may request to
be informed when all the other clients are quiescent so that
it    can    save    their    state.	 To   do   so,	 use
SmcRequestSaveYourselfPhase2.
__
|
Status SmcRequestSaveYourselfPhase2(smc_conn, save_yourself_phase2_proc, client_data)
    SmcConn smc_conn;
    SmcSaveYourselfPhase2Proc save_yourself_phase2_proc;
    SmPointer client_data;


smc_conn  The session management connection object.

save_yourself_phase2_proc
	  The callback to be invoked when the  ``Save  Your-
	  self	Phase  2''  message arrives from the session
	  manager.

client_data
	  This pointer to client data will be passed to  the
	  SmcSaveYourselfPhase2Proc callback when the ``Save
	  Yourself Phase 2'' message arrives.




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X Session Management Library		    X11, Release 6.4


|__

The return value of SmcRequestSaveYourselfPhase2 is zero for
failure and a positive value for success.

This  request is needed by clients that manage other clients
(for example, window managers, workspace  managers,  and  so
on).   The  manager  must  make sure that all of the clients
that are being managed are in an idle state  so  that  their
state can be saved.

5.8.  Completing a Save Yourself

After  saving  state in response to a ``Save Yourself'' mes-
sage, you should call SmcSaveYourselfDone.
__
|
void SmcSaveYourselfDone(smc_conn, success)
    SmcConn smc_conn;
    Bool success;


smc_conn  The session management connection object.

success   If True, the ``Save Yourself'' operation was	com-
	  pleted successfully.
|__

Before calling SmcSaveYourselfDone, the client must have set
each required property at least once since the client regis-
tered with the session manager.

5.9.  Using Smc Informational Functions

__
|
int SmcProtocolVersion(smc_conn)
    SmcConn smc_conn;
|__

SmcProtocolVersion  returns the major version of the session
management protocol associated with this session.


__
|
int SmcProtocolRevision(smc_conn)
    SmcConn smc_conn;
|__

SmcProtocolRevision returns the minor version of the session
management protocol associated with this session.





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X Session Management Library		    X11, Release 6.4

__
|
char *SmcVendor(smc_conn)
    SmcConn smc_conn;
|__

SmcVendor returns a string that provides some identification
of the owner of the session manager.  The string  should  be
freed with a call to free.


__
|
char *SmcRelease(smc_conn)
    SmcConn smc_conn;
|__

SmcRelease returns a string that provides the release number
of the session manager.  The string should be freed  with  a
call to free.


__
|
char *SmcClientID(smc_conn)
    SmcConn smc_conn;
|__

SmcClientID  returns a null-terminated string for the client
ID associated with this connection.   This  information  was
also  returned in SmcOpenConnection (it is provided here for
convenience).  Call free on this pointer when the client  ID
is no longer needed.


__
|
IceConn SmcGetIceConnection(smc_conn)
    SmcConn smc_conn;
|__

SmcGetIceConnection  returns the ICE connection object asso-
ciated with this session management connection object.	 The
ICE  connection  object  can  be used to get some additional
information about the connection.  Some of the	more  useful
functions   which   can   be   used   on   the	IceConn  are
IceConnectionNumber,			IceConnectionString,
IceLastSentSequenceNumber,    IceLastReceivedSequenceNumber,
and IcePing.  For further information, see the	Inter-Client
Exchange Library standard.

5.10.  Error Handling

If the client receives an unexpected protocol error from the
session manager, an error handler is invoked  by  SMlib.   A



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default  error	handler  exists that simply prints the error
message to stderr and exits if the severity of the error  is
fatal.	 The client can change this error handler by calling
the SmcSetErrorHandler function.
__
|
SmcErrorHandler SmcSetErrorHandler(handler)
    SmcErrorHandler handler;


handler   The  error  handler.	 You  should  pass  NULL  to
	  restore the default handler.
|__

SmcSetErrorHandler returns the previous error handler.

The SmcErrorHandler has the following type:
__
|
typedef void (*SmcErrorHandler)();

void ErrorHandler(smc_conn, swap, offending_minor_opcode, offending_sequence_num, error_class, severity, values)
    SmcConn smc_conn;
    Bool swap;
    int offending_minor_opcode;
    unsigned long offending_sequence_num;
    int error_class;
    int severity;
    IcePointer values;


smc_conn  The session management connection object.

swap	  A flag that indicates if the specified values need
	  byte swapping.

offending_minor_opcode
	  The minor opcode of the offending message.

offending_sequence_num
	  The sequence number of the offending message.

error_class
	  The error class of the offending message.

severity  IceCanContinue,	IceFatalToProtocol,	  or
	  IceFatalToConnection.

values	  Any  additional error values specific to the minor
	  opcode and class.
|__

Note that this error handler is invoked for protocol related
errors.   To  install an error handler to be invoked when an



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X Session Management Library		    X11, Release 6.4


IO error  occurs,  use	IceSetIOErrorHandler.	For  further
information, see the Inter-Client Exchange Library standard.

6.  Session Management Server (Sms) Functions

This section discusses how Session Management servers:

o    Initialize the library

o    Register the client

o    Send a ``Save Yourself'' message

o    Send a ``Save Yourself Phase 2'' message

o    Send an ``Interact'' message

o    Send a ``Save Complete'' message

o    Send a ``Die'' message

o    Cancel a shutdown

o    Return properties

o    Ping a client

o    Clean up after a client disconnects

o    Use Sms informational functions

o    Handle errors

6.1.  Initializing the Library

SmsInitialize is the first SMlib  function  that  should  be
called	by a session manager.  It provides information about
the session manager and registers a callback  that  will  be
invoked  each time a new client connects to the session man-
ager.
__
|
Status SmsInitialize(vendor, release, new_client_proc, manager_data, host_based_auth_proc,
		    error_length, error_string_ret)
    char *vendor;
    char *release;
    SmsNewClientProc new_client_proc;
    SmPointer manager_data;
    IceHostBasedAuthProc host_based_auth_proc;
    int error_length;
    char *error_string_ret;






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X Session Management Library		    X11, Release 6.4


vendor	  A string specifying the session manager vendor.

release   A string specifying the  session  manager  release
	  number.

new_client_proc
	  Callback to be invoked each time a new client con-
	  nects to the session manager.

manager_data
	  When the  SmsNewClientProc  callback	is  invoked,
	  this pointer to manager data will be passed.

host_based_auth_proc
	  Host based authentication callback.

error_length
	  Length of the error_string_ret argument passed in.

error_string_ret
	  Returns a null-terminated error message,  if	any.
	  The  error_string_ret points to user supplied mem-
	  ory.	No more than error_length bytes are used.
|__

After the SmsInitialize function is called, the session man-
ager  should  call  the  IceListenForConnections function to
listen for new connections.  Afterwards, each time a  client
connects,     the     session	  manager     should	call
IceAcceptConnection.

See section  9,  ``Authentication  of  Clients,''  for	more
details  on authentication (including host based authentica-
tion).	Also see the Inter-Client Exchange Library  standard
for  further details on listening for and accepting ICE con-
nections.

Each time a new client connects to the session manager,  the
SmsNewClientProc  callback  is invoked.  The session manager
obtains a new opaque connection object that  it  should  use
for  all  future interaction with the client.  At this time,
the session manager must also register a set of callbacks to
respond  to  the  different  messages  that the client might
send.
__
|











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X Session Management Library		    X11, Release 6.4


typedef Status (*SmsNewClientProc)();

Status NewClientProc(sms_conn, manager_data, mask_ret, callbacks_ret, failure_reason_ret)
    SmsConn sms_conn;
    SmPointer manager_data;
    unsigned long *mask_ret;
    SmsCallbacks *callbacks_ret;
    char **failure_reason_ret;


sms_conn  A new opaque connection object.

manager_data
	  Manager data specified when the callback was	reg-
	  istered.

mask_ret  On  return,  indicates which callbacks were set by
	  the session manager.

callbacks_ret
	  On return, contains the  callbacks  registered  by
	  the session manager.

failure_reason_ret
	  Failure reason returned.
|__

If  a  failure	occurs, the SmsNewClientProc should return a
zero status as well as allocate and return a failure  reason
string in failure_reason_ret.  SMlib will be responsible for
freeing this memory.

The session manager must register  a  set  of  callbacks  to
respond  to  client events.  The mask_ret argument specifies
which callbacks are set.  All of the callbacks specified  in
this  version of SMlib are mandatory.  The mask_ret argument
is necessary in order to maintain backwards compatibility in
future versions of the library.

The  following	values may be ORed together to obtain a mask
value:


SmsRegisterClientProcMask
SmsInteractRequestProcMask
SmsInteractDoneProcMask
SmsSaveYourselfRequestProcMask
SmsSaveYourselfP2RequestProcMask
SmsSaveYourselfDoneProcMask
SmsCloseConnectionProcMask
SmsSetPropertiesProcMask
SmsDeletePropertiesProcMask
SmsGetPropertiesProcMask




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For each  callback,  the  session  manager  can  register  a
pointer  to  manager  data  specific to that callback.	This
pointer will be passed to the callback when it is invoked by
SMlib.
__
|

typedef struct {
     struct {
	  SmsRegisterClientProc callback;
	  SmPointer manager_data;
     } register_client;

     struct {
	  SmsInteractRequestProc callback;
	  SmPointer manager_data;
     } interact_request;

     struct {
	  SmsInteractDoneProc callback;
	  SmPointer manager_data;
     } interact_done;

     struct {
	  SmsSaveYourselfRequestProc callback;
	  SmPointer manager_data;
     } save_yourself_request;

     struct {
	  SmsSaveYourselfPhase2RequestProc callback;
	  SmPointer manager_data;
     } save_yourself_phase2_request;

     struct {
	  SmsSaveYourselfDoneProc callback;
	  SmPointer manager_data;
     } save_yourself_done;

     struct {
	  SmsCloseConnectionProc callback;
	  SmPointer manager_data;
     } close_connection;

     struct {
	  SmsSetPropertiesProc callback;
	  SmPointer manager_data;
     } set_properties;

     struct {
	  SmsDeletePropertiesProc callback;
	  SmPointer manager_data;
     } delete_properties;

     struct {



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X Session Management Library		    X11, Release 6.4


	  SmsGetPropertiesProc callback;
	  SmPointer manager_data;
     } get_properties;

} SmsCallbacks;

|__


6.1.1.	The Register Client Callback

The Register Client callback is the first callback that will
be invoked after the client connects to the session manager.
Its type is SmsRegisterClientProc.
__
|
typedef Status (*SmsRegisterClientProc();

Status RegisterClientProc(sms_conn, manager_data, previous_id)
    SmsConn sms_conn;
    SmPointer manager_data;
    char *previous_id;


sms_conn  The session management connection object.

manager_data
	  Manager  data specified when the callback was reg-
	  istered.

previous_id
	  The client ID from the previous session.
|__

Before any further interaction takes place with the  client,
the client must be registered with the session manager.

If  the  client  is being restarted from a previous session,
previous_id will contain a null-terminated string represent-
ing  the  client ID from the previous session.	Call free on
the previous_id pointer when it is no longer needed.  If the
client	is  first  joining  the session, previous_id will be
NULL.

If previous_id is invalid, the session	manager  should  not
register  the  client  at  this  time.	This callback should
return a status of zero, which will cause an  error  message
to  be	sent  to  the client.  The client should re-register
with previous_id set to NULL.

Otherwise, the session manager should  register  the  client
with  a unique client ID by calling the SmsRegisterClientRe-
ply function (to be discussed shortly), and the SmsRegister-
ClientProc callback should return a status of one.



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6.1.2.	The Interact Request Callback

The	Interact     Request	callback    is	  of	type
SmsInteractRequestProc.
__
|
typedef void (*SmsInteractRequestProc)();

void InteractRequestProc(sms_conn, manager_data, dialog_type)
    SmsConn sms_conn;
    SmPointer manager_data;
    int dialog_type;


sms_conn  The session management connection object.

manager_data
	  Manager data specified when the callback was	reg-
	  istered.

dialog_type
	  The type of dialog the client wishes to present to
	  the user.
|__

When a client receives a ``Save Yourself'' message  with  an
interact_style	     of       SmInteractStyleErrors	  or
SmInteractStyleAny, the client may choose to  interact	with
the  user.   Because  only  one client can interact with the
user at a time, the client must request to interact with the
user.	The  session  manager  should  keep  a	queue of all
clients wishing to interact.  It should send an ``Interact''
message  to  one client at a time and wait for an ``Interact
Done'' message before continuing with the next client.

The dialog_type  argument  specifies  either  SmDialogError,
indicating  that  the client wants to start an error dialog,
or SmDialogNormal, meaning that the client wishes to start a
nonerror dialog.

If  a  shutdown is in progress, the user may have the option
of cancelling the shutdown.  If the  shutdown  is  cancelled
(specified  in	the  ``Interact Done'' message), the session
manager should send a ``Shutdown Cancelled'' message to each
client that requested to interact.

6.1.3.	The Interact Done Callback

When  the  client  is  done  interacting  with the user, the
SmsInteractDoneProc callback will be invoked.
__
|





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X Session Management Library		    X11, Release 6.4


typedef void (*SmsInteractDoneProc)();

void InteractDoneProc(sms_conn, manager_data, cancel_shutdown)
    SmsConn sms_conn;
    SmPointer manager_data;
    Bool cancel_shutdown;


sms_conn  The session management connection object.

manager_data
	  Manager data specified when the callback was	reg-
	  istered.

cancel_shutdown
	  Specifies  if  the  user  requests that the entire
	  shutdown be cancelled.
|__

Note that the shutdown can be cancelled only if  the  corre-
sponding  ``Save  Yourself'' specified True for shutdown and
SmInteractStyleErrors or SmInteractStyleAny for  the  inter-
act_style.

6.1.4.	The Save Yourself Request Callback

The    Save   Yourself	 Request   callback   is   of	type
SmsSaveYourselfRequestProc.
__
|
typedef void (*SmsSaveYourselfRequestProc)();

void SaveYourselfRequestProc(sms_conn, manager_data, save_type, shutdown, interact_style, fast, global)
    SmsConn sms_conn;
    SmPointer manager_data;
    int save_type;
    Bool shutdown;
    int interact_style;
    Bool fast;
    Bool global;


sms_conn  The session management connection object.

manager_data
	  Manager data specified when the callback was	reg-
	  istered.

save_type Specifies  the  type of information that should be
	  saved.

shutdown  Specifies if a shutdown is taking place.





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X Session Management Library		    X11, Release 6.4


interact_style
	  The type of interaction allowed with the user.

fast	  If True, the	client	should	save  its  state  as
	  quickly as possible.

global	  Controls who gets the ``Save Yourself.''
|__

The  Save  Yourself  Request  prompts the session manager to
initiate a checkpoint or shutdown.  For information  on  the
save_type, shutdown, interact_style, and fast arguments, see
section 6.3, ``Sending a Save Yourself Message.''

If global is set to True, then the  resulting  ``Save  Your-
self'' should be sent to all applications.  If global is set
to False, then the ``Save Yourself'' should only be sent  to
the client that requested it.

6.1.5.	The Save Yourself Phase 2 Request Callback

The Save Yourself  Phase  2  Request  callback	is  of	type
SmsSaveYourselfPhase2RequestProc.
__
|
typedef void (*SmsSaveYourselfPhase2RequestProc)();

void SmsSaveYourselfPhase2RequestProc(sms_conn, manager_data)
    SmsConn sms_conn;
    SmPointer manager_data;


sms_conn  The session management connection object.

manager_data
	  Manager  data specified when the callback was reg-
	  istered.
|__

This request is sent by clients that  manage  other  clients
(for  example,	window	managers, workspace managers, and so
on).  Such managers must make sure that all of	the  clients
that  are  being  managed are in an idle state so that their
state can be saved.

6.1.6.	The Save Yourself Done Callback

When the client is done saving its state in  response  to  a
``Save	Yourself'' message, the SmsSaveYourselfDoneProc will
be invoked.
__
|





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X Session Management Library		    X11, Release 6.4


typedef void (*SmsSaveYourselfDoneProc)();

void SaveYourselfDoneProc(sms_conn, manager_data, success)
    SmsConn sms_conn;
    SmPointer manager_data;
    Bool success;


sms_conn  The session management connection object.

manager_data
	  Manager data specified when the callback was	reg-
	  istered.

success   If True, the Save Yourself operation was completed
	  successfully.
|__

Before the ``Save Yourself Done'' was sent, the client	must
have  set each required property at least once since it reg-
istered with the session manager.

6.1.7.	The Connection Closed Callback

If  the  client  properly  terminates  (that  is,  it  calls
SmcCloseConnection),  the SmsCloseConnectionProc callback is
invoked.
__
|
typedef void (*SmsCloseConnectionProc)();

void CloseConnectionProc(sms_conn, manager_data, count, reason_msgs)
    SmsConn sms_conn;
    SmPointer manager_data;
    int count;
    char **reason_msgs;


sms_conn  The session management connection object.

manager_data
	  Manager data specified when the callback was	reg-
	  istered.

count	  The number of reason messages.

reason_msgs
	  The reasons for closing the connection.
|__

The  reason_msgs  argument  will most likely be NULL and the
count argument zero (0) if resignation is  expected  by  the
user.  Otherwise, it contains a list of null-terminated Com-
pound Text strings representing the reason for	termination.



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X Session Management Library		    X11, Release 6.4


The  session manager should display these reason messages to
the user.

Call SmFreeReasons to free the reason messages.  For further
information, see section 8, ``Freeing Data.''

6.1.8.	The Set Properties Callback

When the client sets session management properties, the Sms-
SetPropertiesProc callback will be invoked.
__
|
typedef void (*SmsSetPropertiesProc)();

void SetPropertiesProc(sms_conn, manager_data, num_props, props)
    SmsConn sms_conn;
    SmPointer manager_data;
    int num_props;
    SmProp **props;


smc_conn  The session management connection object.

manager_data
	  Manager data specified when the callback was	reg-
	  istered.

num_props The number of properties.

props	  The list of properties to set.
|__

The  properties are specified as an array of property point-
ers.  For a description of session management properties and
the  SmProp  structure,  see section 7, ``Session Management
Properties.''

Previously set property values may  be	over-written.	Some
properties  have  predefined semantics.  The session manager
is required to store nonpredefined properties.

To free each  property,  use  SmFreeProperty.	For  further
information,  see  section  8, ``Freeing Data.''  You should
free the actual array of pointers with a call to free.

6.1.9.	The Delete Properties Callback

When the client deletes session management  properties,  the
SmsDeletePropertiesProc callback will be invoked.
__
|






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X Session Management Library		    X11, Release 6.4


typedef void (*SmsDeletePropertiesProc)();

void DeletePropertiesProc(sms_conn, manager_data, num_props, prop_names)
    SmsConn sms_conn;
    SmPointer manager_data;
    int num_props;
    char **prop_names;


smc_conn  The session management connection object.

manager_data
	  Manager  data specified when the callback was reg-
	  istered.

num_props The number of properties.

prop_names
	  The list of properties to delete.
|__

The properties are specified as an array of strings.  For  a
description  of session management properties and the SmProp
structure, see section 7, ``Session Management Properties.''

6.1.10.  The Get Properties Callback

The SmsGetPropertiesProc callback is invoked when the client
wants to retrieve properties it set.
__
|
typedef void (*SmsGetPropertiesProc)();

void GetPropertiesProc(sms_conn, manager_data)
    SmsConn sms_conn;
    SmPointer manager_data;


smc_conn  The session management connection object.

manager_data
	  Manager data specified when the callback was	reg-
	  istered.
|__

The    session	  manager    should   respond	by   calling
SmsReturnProperties.  All of the  properties  set  for	this
client should be returned.

6.2.  Registering the Client

To register a client (in response to a SmsRegisterClientProc





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X Session Management Library		    X11, Release 6.4


callback), use SmsRegisterClientReply.
__
|
Status SmsRegisterClientReply(sms_conn, client_id)
    SmsConn sms_conn;
    char *client_id;


sms_conn  The session management connection object.

client_id A null-terminated  string  representing  a  unique
	  client ID.
|__

The return value of SmsRegisterClientReply is zero for fail-
ure and a positive value for success.  Failure will occur if
SMlib  can  not allocate memory to hold a copy of the client
ID for it's own internal needs.

If a non-NULL previous_id was specified when the client reg-
istered  itself,  client_id  should  be  identical to previ-
ous_id.

Otherwise, client_id should be a unique ID freshly generated
by  the  session  manager.  In addition, the session manager
should send a ``Save Yourself'' message with type  =  Local,
shutdown  =  False,  interact-style = None, and fast = False
immediately after registering the client.

Note that once a client ID has been assigned to the  client,
the  client  keeps  this  ID indefinitely.  If the client is
terminated and restarted, it will be reassigned the same ID.
It  is	desirable  to be able to pass client IDs around from
machine to machine, from user to user, and from session man-
ager to session manager, while retaining the identity of the
client.  This, combined with the indefinite  persistence  of
client	IDs,  means  that  client  IDs	need  to be globally
unique.

You should call the SmsGenerateClientID function to generate
a globally unique client ID.
__
|
char *SmsGenerateClientID(sms_conn)
    SmsConn sms_conn;


sms_conn  The session management connection object.
|__

NULL  will  be	returned  if  the ID could not be generated.
Otherwise, the return value of the function  is  the  client
ID.   It  should be freed with a call to free when no longer
needed.



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6.3.  Sending a Save Yourself Message

To   send   a	``Save	 Yourself''   to   a   client,	 use
SmsSaveYourself.
__
|
void SmsSaveYourself(sms_conn, save_type, shutdown, interact_style, fast)
    SmsConn sms_conn;
    int save_type;
    Bool shutdown;
    int interact_style;
    Bool fast;


sms_conn  The session management connection object.

save_type Specifies  the  type of information that should be
	  saved.

shutdown  Specifies if a shutdown is taking place.

interact_style
	  The type of interaction allowed with the user.

fast	  If True, the	client	should	save  its  state  as
	  quickly as possible.
|__

The  session  manager sends a ``Save Yourself'' message to a
client either to checkpoint it or just before termination so
that  it  can save its state.  The client responds with zero
or more ``Set Properties'' messages to update the properties
indicating  how to restart the client.	When all the proper-
ties have been set,  the  client  sends  a  ``Save  Yourself
Done'' message.

If  interact_style  is	SmInteractStyleNone, the client must
not interact with the user while saving  state.   If  inter-
act_style  is SmInteractStyleErrors, the client may interact
with the user only if an error condition arises.  If  inter-
act_style  is SmInteractStyleAny, then the client may inter-
act with the user for any purpose.  The client must send  an
``Interact  Request''  message	and wait for an ``Interact''
message from the session manager before it can interact with
the  user.   When  the	client	is done interacting with the
user, it should send  an  ``Interact  Done''  message.	 The
``Interact  Request''  message	can be sent any time after a
``Save Yourself'' and before a ``Save Yourself Done.''

If save_type is SmSaveLocal,  the  client  must  update  the
properties  to	reflect its current state.  Specifically, it
should save enough information to restore the state as	seen
by  the user of this client.  It should not affect the state
as seen by other users.  If save_type  is  SmSaveGlobal  the



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X Session Management Library		    X11, Release 6.4


user  wants  the  client to commit all of its data to perma-
nent,  globally  accessible  storage.	 If   save_type   is
SmSaveBoth,  the  client  should do both of these (it should
first commit the data to permanent storage  before  updating
its properties).

The shutdown argument specifies whether the session is being
shut  down.   The  interaction	is  different  depending  on
whether  or not shutdown is set.  If not shutting down, then
the client can save and resume normal operation.   If  shut-
ting down, the client must save and then must prevent inter-
action until it receives either a ``Die''  or  a  ``Shutdown
Cancelled,''  because  anything the user does after the save
will be lost.

The fast argument specifies that the client should save  its
state  as  quickly as possible.  For example, if the session
manager knows that power is about to  fail,  it  should  set
fast to True.

6.4.  Sending a Save Yourself Phase 2 Message

In  order  to  send a ``Save Yourself Phase 2'' message to a
client, use SmsSaveYourselfPhase2.
__
|
void SmsSaveYourselfPhase2(sms_conn)
    SmsConn sms_conn;


sms_conn  The session management connection object.
|__

The session manager sends this message to a client that  has
previously sent a ``Save Yourself Phase 2 Request'' message.
This message informs the client that all other	clients  are
in  a  fixed  state  and  this client can save state that is
associated with other clients.

6.5.  Sending an Interact Message

To  send  an  ``Interact''  message   to   a   client,	 use
SmsInteract.
__
|
void SmsInteract(sms_conn)
    SmsConn sms_conn;


sms_conn  The session management connection object.
|__

The  ``Interact'' message grants the client the privilege of
interacting  with  the	user.	When  the  client  is	done



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X Session Management Library		    X11, Release 6.4


interacting with the user, it must send an ``Interact Done''
message to the session manager.

6.6.  Sending a Save Complete Message

To send  a  ``Save  Complete''	message  to  a	client,  use
SmsSaveComplete.
__
|
void SmsSaveComplete(sms_conn)
    SmsConn sms_conn;


sms_conn  The session management connection object.
|__

The  session manager sends this message when it is done with
a checkpoint.  The client is then free to change its  state.

6.7.  Sending a Die Message

To send a ``Die'' message to a client, use SmsDie.
__
|
void SmsDie(sms_conn)
    SmsConn sms_conn;


sms_conn  The session management connection object.
|__

Before	the session manager terminates, it should wait for a
``Connection Closed'' message from each client that it	sent
a ``Die'' message to, timing out appropriately.

6.8.  Cancelling a Shutdown

To cancel a shutdown, use SmsShutdownCancelled.
__
|
void SmsShutdownCancelled(sms_conn)
    SmsConn sms_conn;


sms_conn  The session management connection object.
|__

The  client  can  now  continue as if the shutdown had never
happened.  If the client has  not  sent  a  ``Save  Yourself
Done''	message yet, it can either abort the save and send a
``Save Yourself Done'' with  the  success  argument  set  to
False,	or  it	can continue with the save and send a ``Save
Yourself Done'' with the success argument set to reflect the
outcome of the save.



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X Session Management Library		    X11, Release 6.4


6.9.  Returning Properties

In  response  to  a  ``Get Properties'' message, the session
manager should call SmsReturnProperties.
__
|
void SmsReturnProperties(sms_conn, num_props, props)
    SmsConn sms_conn;
    int num_props;
    SmProp **props;


sms_conn  The session management connection object.

num_props The number of properties.

props	  The list of properties to return to the client.
|__

The properties are returned as an array of  property  point-
ers.  For a description of session management properties and
the SmProp structure, see section  7,  ``Session  Management
Properties.''

6.10.  Pinging a Client

To  check  that  a client is still alive, you should use the
IcePing function provided by the ICE library.  To do so, the
ICE  connection  must be obtained using the SmsGetIceConnec-
tion (see section  6.12,  ``Using  Sms	Informational  Func-
tions'').

__
|
void IcePing(ice_conn, ping_reply_proc, client_data)
    IceConn ice_conn;
    IcePingReplyProc ping_reply_proc;
    IcePointer client_data;


ice_conn  A valid ICE connection object.

ping_reply_proc
	  The	callback  to  invoke  when  the  Ping  reply
	  arrives.

client_data
	  This pointer will  be  passed  to  the  IcePingRe-
	  plyProc callback.
|__

When the Ping reply is ready (if ever), the IcePingReplyProc
callback will be invoked.  A  session  manager	should	have
some  sort  of	timeout  period,  after which it assumes the



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X Session Management Library		    X11, Release 6.4


client has unexpectedly died.

__
|
typedef void (*IcePingReplyProc)();

void PingReplyProc(ice_conn, client_data)
    IceConn ice_conn;
    IcePointer client_data;


ice_conn  The ICE connection object.

client_data
	  The client data specified in the call to  IcePing.
|__


6.11.  Cleaning Up After a Client Disconnects

When  the  session  manager receives a ``Connection Closed''
message or otherwise detects that  the	client	aborted  the
connection,  it should call the SmsCleanUp function in order
to free up the connection object.
__
|
void SmsCleanUp(sms_conn)
    SmsConn sms_conn;


sms_conn  The session management connection object.
|__


6.12.  Using Sms Informational Functions

__
|
int SmsProtocolVersion(sms_conn)
    SmsConn sms_conn;

|__

SmsProtocolVersion returns the major version of the  session
management protocol associated with this session.


__
|
int SmsProtocolRevision(sms_conn)
    SmsConn sms_conn;






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X Session Management Library		    X11, Release 6.4


|__

SmsProtocolRevision returns the minor version of the session
management protocol associated with this session.


__
|
char *SmsClientID(sms_conn)
    SmsConn sms_conn;

|__

SmsClientID returns a null-terminated string for the  client
ID associated with this connection.  You should call free on
this pointer when the client ID is no longer needed.


To obtain the host name of a client, use  SmsClientHostName.
This host name will be needed to restart the client.
__
|
char *SmsClientHostName(sms_conn)
    SmsConn sms_conn;
|__

The  string returned is of the form protocol/hostname, where
protocol is one of {tcp, decnet, local}.   You	should	call
free on the string returned when it is no longer needed.


__
|
IceConn SmsGetIceConnection(sms_conn)
    SmsConn sms_conn;
|__

SmsGetIceConnection  returns the ICE connection object asso-
ciated with this session management connection object.	 The
ICE  connection  object  can  be used to get some additional
information about the connection.  Some of the	more  useful
functions   which   can   be   used   on   the	IceConn  are
IceConnectionNumber, and IceLastSequenceNumber.  For further
information, see the Inter-Client Exchange Library standard.

6.13.  Error Handling

If the session manager receives an unexpected protocol error
from  a  client,  an  error  handler is invoked by SMlib.  A
default error handler exists which simply prints  the  error
message  (it does not exit).  The session manager can change






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X Session Management Library		    X11, Release 6.4


this error handler by calling SmsSetErrorHandler.
__
|
SmsErrorHandler SmsSetErrorHandler(handler)
    SmsErrorHandler handler;


handler   The  error  handler.	 You  should  pass  NULL  to
	  restore the default handler.
|__

SmsSetErrorHandler  returns the previous error handler.  The
SmsErrorHandler has the following type:
__
|
typedef void (*SmsErrorHandler)();

void ErrorHandler(sms_conn, swap, offending_minor_opcode, offending_sequence_num, error_class, severity, values)
    SmsConn sms_conn;
    Bool swap;
    int offending_minor_opcode;
    unsigned long offending_sequence_num;
    int error_class;
    int severity;
    IcePointer values;


sms_conn  The session management connection object.

swap	  A flag which indicates  if  the  specified  values
	  need byte swapping.

offending_minor_opcode
	  The minor opcode of the offending message.

offending_sequence_num
	  The sequence number of the offending message.

error_class
	  The error class of the offending message.

severity  IceCanContinue,	IceFatalToProtocol,	  or
	  IceFatalToConnection.

values	  Any additional error values specific to the  minor
	  opcode and class.
|__

Note that this error handler is invoked for protocol related
errors.  To install an error handler to be invoked  when  an
IO  error  occurs,  use  IceSetIOErrorHandler.	 For further
information, see the Inter-Client Exchange Library standard.





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X Session Management Library		    X11, Release 6.4


7.  Session Management Properties

Each property is defined by the SmProc structure:


typedef struct {
     char *name;	 /* name of property */
     char *type;	 /* type of property */
     int num_vals;	 /* number of values */
     SmPropValue *vals;  /* the list of values */
} SmProp;

typedef struct {
     int length;	 /* the length of the value */
     SmPointer value;	 /* the value */
} SmPropValue;


The  X	Session Management Protocol defines a list of prede-
fined properties, several of which are required to be set by
the  client.   The  following table specifies the predefined
properties and indicates  which  ones  are  required.	Each
property has a type associated with it.

A  type  of  SmCARD8 indicates that there is a single 1-byte
value.	A type of SmARRAY8 indicates that there is a  single
array  of  bytes.   A  type of SmLISTofARRAY8 indicates that
there is a list of array of bytes.


-------------------------------------------------------------
Name		     Type	   POSIX Type	    Required
-------------------------------------------------------------
SmCloneCommand	     OS-specific   SmLISTofARRAY8     Yes
SmCurrentDirectory   OS-specific   SmARRAY8	       No
SmDiscardCommand     OS-specific   SmLISTofARRAY8     No*
SmEnvironment	     OS-specific   SmLISTofARRAY8      No
SmProcessID	     OS-specific   SmARRAY8	       No
SmProgram	     OS-specific   SmARRAY8	      Yes
SmRestartCommand     OS-specific   SmLISTofARRAY8     Yes
SmResignCommand      OS-specific   SmLISTofARRAY8      No
SmRestartStyleHint   SmCARD8	   SmCARD8	       No
SmShutdownCommand    OS-specific   SmLISTofARRAY8      No
SmUserID	     SmARRAY8	   SmARRAY8	      Yes
-------------------------------------------------------------


* Required if any state is stored in an external  repository
(for example, state file).

o    SmCloneCommand

     This is like the SmRestartCommand, except it restarts a
     copy of the application.  The only difference  is	that



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X Session Management Library		    X11, Release 6.4


     the application does not supply its client ID at regis-
     ter time.	On POSIX systems, this	should	be  of	type
     SmLISTofARRAY8.

o    SmCurrentDirectory

     On POSIX-based systems, this specifies the value of the
     current directory that needs to  be  set  up  prior  to
     starting the SmProgram and should of type SmARRAY8.

o    SmDiscardCommand

     The discard command contains a command that when deliv-
     ered to the host that the client is running on  (deter-
     mined  from  the  connection), will cause it to discard
     any information about the current state.  If this	com-
     mand  is not specified, the Session Manager will assume
     that all of  the  client's  state	is  encoded  in  the
     SmRestartCommand.	On POSIX systems, the type should be
     SmLISTofARRAY8.

o    SmEnvironment

     On POSIX based systems, this will be of  type  SmLISTo-
     fARRAY8,  where  the ARRAY8s alternate between environ-
     ment variable name and environment variable value.

o    SmProcessID

     This specifies an OS-specific identifier for  the	pro-
     cess.  On POSIX systems, this should contain the return
     value of getpid turned into a Latin-1 (decimal) string.

o    SmProgram

     This  is  the  name of the program that is running.  On
     POSIX systems, this should be first parameter passed to
     execve and should be of type SmARRAY8.

o    SmRestartCommand

     The  restart  command  contains  a  command  that, when
     delivered to the host that the  client  is  running  on
     (determined from the connection), will cause the client
     to restart in its current state.  On  POSIX-based	sys-
     tems,  this  is of type SmLISTofARRAY8, and each of the
     elements in the array represents an element in the argv
     array.   This  restart  command  should ensure that the
     client restarts with the specified client-ID.

o    SmResignCommand

     A client that sets the SmRestartStyleHint to  SmRestar-
     tAnway  uses  this  property  to specify a command that



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X Session Management Library		    X11, Release 6.4


     undoes the effect of the client and removes  any  saved
     state.   As  an  example,	consider  a  user  that runs
     xmodmap, which registers with the Session Manager, sets
     SmRestartStyleHint  to SmRestartAnyway, and then termi-
     nates.  To allow the Session  Manager  (at  the  user's
     request)  to  undo this, xmodmap would register a SmRe-
     signCommand that undoes the effects of the xmodmap.

o    SmRestartStyleHint

     If the RestartStyleHint property is  present,  it	will
     contain the style of restarting the client prefers.  If
     this style  is  not  specified,  SmRestartIfRunning  is
     assumed.  The possible values are as follows:

     -----------------------------
     Name		    Value
     -----------------------------
     SmRestartIfRunning       0
     SmRestartAnyway	      1
     SmRestartImmediately     2
     SmRestartNever	      3
     -----------------------------


     The SmRestartIfRunning style is used in the usual case.
     The client should be restarted in the next  session  if
     it was running at the end of the current session.

     The  SmRestartAnyway  style is used to tell the Session
     Manager that the application should be restarted in the
     next  session  even if it exits before the current ses-
     sion is terminated.  It should be noted  that  this  is
     only  a  hint  and  the Session Manager will follow the
     policies specified by its	users  in  determining	what
     applications to restart.

     A	client that uses SmRestartAnyway should also set the
     SmResignCommand  and  SmShutdownCommand  properties  to
     commands  that  undo  the	state of the client after it
     exits.

     The SmRestartImmediately style is like SmRestartAnyway,
     but,  in  addition, the client is meant to run continu-
     ously.  If the client exits, the Session Manager should
     try to restart it in the current session.

     SmRestartNever style specifies that the client does not
     wish to be restarted in the next session.

o    SmShutdownCommand

     This command is executed at shutdown time to  clean  up
     after  a  client that is no longer running but retained



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X Session Management Library		    X11, Release 6.4


     its state by setting  SmRestartStyleHint  to  SmRestar-
     tAnyway.  The client must not remove any saved state as
     the client is still part of the session.  As  an  exam-
     ple,  consider a client that turns on a camera at start
     up time.  This client then exits.	At session shutdown,
     the  user	wants  the  camera  turned off.  This client
     would set the SmRestartStyleHint to SmRestartAnyway and
     would  register a SmShutdownCommand that would turn off
     the camera.

o    SmUserID

     Specifies the user ID.  On  POSIX-based  systems,	this
     will  contain  the  user's  name (the pw_name member of
     struct passwd).

8.  Freeing Data

To free an individual property, use SmFreeProperty.
__
|
void SmFreeProperty(prop)
    SmProp *prop;


prop	  The property to free.
|__


To free the reason strings from  the  SmsCloseConnectionProc
callback, use SmFreeReasons.
__
|
void SmFreeReasons(count, reasons)
    int count;
    char **reasons;


count	  The number of reason strings.

reasons   The list of reason strings to free.
|__


9.  Authentication of Clients

As  stated  earlier, the session management protocol is lay-
ered on top of ICE.  Authentication occurs at two levels  in
the ICE protocol:

o    The first is when an ICE connection is opened.

o    The  second  is  when a Protocol Setup occurs on an ICE
     connection.



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X Session Management Library		    X11, Release 6.4


The authentication methods that are available are  implemen-
tation-dependent  (that  is.,  dependent  on  the ICElib and
SMlib implementations in use).	For further information, see
the Inter-Client Exchange Library standard.

10.  Working in a Multi-Threaded Environment

To  declare  that multiple threads in an application will be
using SMlib (or any other library layered on top of ICElib),
you  should  call  IceInitThreads.  For further information,
see the Inter-Client Exchange Library standard.

11.  Acknowledgements

Thanks to the following people for  their  participation  in
the  X Session Management design: Jordan Brown, Ellis Cohen,
Donna  Converse,  Stephen  Gildea,  Vania  Joloboff,  Stuart
Marks, Bob Scheifler, Ralph Swick, and Mike Wexler.







































			   - 43 -

































































			   - 44 -








		     Table of Contents


1. Overview of Session Management  . . . . . . . . . . .   1
2. The Session Management Library  . . . . . . . . . . .   1
3. Understanding SMlib's Dependence on ICE . . . . . . .   2
4. Header Files and Library Name . . . . . . . . . . . .   3
5. Session Management Client (Smc) Functions . . . . . .   3
5.1. Connecting to the Session Manager . . . . . . . . .   4
5.1.1. The Save Yourself Callback  . . . . . . . . . . .   7
5.1.2. The Die Callback  . . . . . . . . . . . . . . . .   8
5.1.3. The Save Complete Callback  . . . . . . . . . . .   9
5.1.4. The Shutdown Cancelled Callback . . . . . . . . .   9
5.2. Closing the Connection  . . . . . . . . . . . . . .  10
5.3. Modifying Callbacks . . . . . . . . . . . . . . . .  11
5.4. Setting, Deleting, and Retrieving Session Man-
agement Properties . . . . . . . . . . . . . . . . . . .  12
5.5. Interacting With the User . . . . . . . . . . . . .  14
5.6. Requesting a Save Yourself  . . . . . . . . . . . .  15
5.7. Requesting a Save Yourself Phase 2  . . . . . . . .  16
5.8. Completing a Save Yourself  . . . . . . . . . . . .  17
5.9. Using Smc Informational Functions . . . . . . . . .  17
5.10. Error Handling . . . . . . . . . . . . . . . . . .  18
6. Session Management Server (Sms) Functions . . . . . .  20
6.1. Initializing the Library  . . . . . . . . . . . . .  20
6.1.1. The Register Client Callback  . . . . . . . . . .  24
6.1.2. The Interact Request Callback . . . . . . . . . .  25
6.1.3. The Interact Done Callback  . . . . . . . . . . .  25
6.1.4. The Save Yourself Request Callback  . . . . . . .  26
6.1.5. The Save Yourself Phase 2 Request Callback  . . .  27
6.1.6. The Save Yourself Done Callback . . . . . . . . .  27
6.1.7. The Connection Closed Callback  . . . . . . . . .  28
6.1.8. The Set Properties Callback . . . . . . . . . . .  29
6.1.9. The Delete Properties Callback  . . . . . . . . .  29
6.1.10. The Get Properties Callback  . . . . . . . . . .  30
6.2. Registering the Client  . . . . . . . . . . . . . .  30
6.3. Sending a Save Yourself Message . . . . . . . . . .  32
6.4. Sending a Save Yourself Phase 2 Message . . . . . .  33
6.5. Sending an Interact Message . . . . . . . . . . . .  33
6.6. Sending a Save Complete  Message  . . . . . . . . .  34
6.7. Sending a Die Message . . . . . . . . . . . . . . .  34
6.8. Cancelling a Shutdown . . . . . . . . . . . . . . .  34
6.9. Returning Properties  . . . . . . . . . . . . . . .  35
6.10. Pinging a Client . . . . . . . . . . . . . . . . .  35
6.11. Cleaning Up After a Client Disconnects . . . . . .  36
6.12. Using Sms Informational Functions  . . . . . . . .  36
6.13. Error Handling . . . . . . . . . . . . . . . . . .  37
7. Session Management Properties . . . . . . . . . . . .  39
8. Freeing Data  . . . . . . . . . . . . . . . . . . . .  42
9. Authentication of Clients . . . . . . . . . . . . . .  42
10. Working in a Multi-Threaded Environment  . . . . . .  43
11. Acknowledgements . . . . . . . . . . . . . . . . . .  43





			     iii


