X Consortium Standard X Version 11, Release 6.4 RalphMor X Consortium Standard
19931994 X Consortium Version 1.0 X Consortium X Version 11, Release 7
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shall not be used in advertising or otherwise to promote the sale, use or other
dealings in this Software without prior written authorization from the X
Consortium. X Window System is a trademark of The Open Group. 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 manager is defined as a connection to the
session manager. A client is typically, though not necessarily, a process
running an application program connected to an X display. However, a client may
be connected to more than one X display or not be connected to any X displays
at all. 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: One set of functions
for clients that want to be part of a session 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 session 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 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 particular
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. 
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 connection. 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
connections 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 makea 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 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 connections from clients. Once a connection attempt is detected,
IceAcceptConnection must be called, and the session 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 standard. 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 prototypes. 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. This section discusses how Session
Management clients: Connect to the Session Manager Close the connection Modify
callbacks Set, delete, and retrieve Session Manager properties Interact with
the user Request a ?Save Yourself? Request a ?Save Yourself Phase 2? Complete a
?Save Yourself? Use Smc informational functions Handle Errors To open a
connection with a session manager, use SmcOpenConnection SmcConn
SmcOpenConnection 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 manager. 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
application supports. xsmp_minor_rev The highest minor version of the XSMP the
application 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 manager. 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 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 registers 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 connection 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 connection 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 connection. 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
IceAddConnectionWatch and IceRemoveConnectionWatch and will have to call
IceProcessMessages each time a select shows that 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 specifies which callbacks are set.
All of the callbacks specified in this version of SMlib are mandatory. The mask
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: 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; The Save Yourself
callback is of type SmcSaveYourselfProc typedef void (*SaveYourselfProc)
SmcConn smc_conn SmcConn 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 registered. save_type
Specifies the type of information that should be saved. shut_down Specifies if
a shutdown is taking place. interact_style The type of interaction allowed with
the user. fast if True, then 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
properties have been set, the client calls SmcSaveYourselfDone If
interact_style is SmInteractStyleNone the client must not interact with the
user while saving state. If interact_style is SmInteractStyleErrors the client
may interact with the user only if an error condition arises. If interact_style
is SmInteractStyleAny then the client may interact 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 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 permanent, 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: 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 current editing session. It
would then update its SmRestartCommand property with enough information to find
this temporary file. If a word processor were sent a ?Save Yourself? with a
type of SmSaveGlobal it would simply save the currently edited file. 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 Complete? 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. The Die callback
is of type SmcDieProc typedef void (*SmcDieProc) SmcConn smc_conn SmcConn
client_data smc_conn The session management connection object. client_data
Client data specified when the callback was registered. 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. The Save Complete
callback is of type SmcSaveCompleteProc typedef void (*SmcSaveCompleteProc)
SmcConn smc_conn SmPointer client_data smc_conn The session management
connection object. client_data Client data specified when the callback was
registered. The Shutdown Cancelled callback is of type SmcShutdownCancelledProc
typedef void (*SmcShutdownCancelledProc) SmcConn smc_conn SmPointer client_data
smc_conn The session management connection object. client_data Client data
specified when the callback was registered. 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 happened. If the client has not called
SmcSaveYourselfDone yet, it can either abort the save and then call
SmcSaveYourselfDone 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. To close a connection with a session
manager, use SmcCloseConnection SmcCloseStatus SmcCloseConnection SmcConn
smc_conn int count char **reason_msgs smc_conn The session management
connection object. count The number of reasons for closing the connection.
reason_msgs The reasons for closing the connection. The reason_msgs argument
will most likely be NULL if resignation 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 display these reason
messages to the user. Note that SMlib used the ICE protocol to establish a
connection with the session manager, and various protocols other 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 IceAddConnectionWatch
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: SmcClosedNow - the ICE connection was closed at
this time, the watch procedures were invoked, and the connection was freed.
SmcClosedASAP - an IO error had occurred on the connection, 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 SmcConnectionInUse - the
connection was not closed at this time, because it is being used by other
active protocols. To modify callbacks set up in SmcOpenConnection use
SmcModifyCallbacks void SmcModifyCallbacks 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
SmcShutdownCancelledProcMask To set session management properties for this
client, use SmcSetProperties void SmcSetProperties 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 pointers. 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 Properties.? To delete properties previously set
by the client, use SmcDeleteProperties void SmcDeleteProperties 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 set. To get properties previously stored by the client, use
SmcGetProperties Status SmcGetProperties 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 SmcPropReplyProc is invoked when the data is ready. typedef void
(*SmcPropReplyProc) SmcConn smc_conn SmPointer client_data int num_props SmProp
**props smc_conn The session management connection object. client_data This
pointer to client data will be passed to the SmcPropReplyProc callback.
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, use free After receiving 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 call
SmcInteractRequest and wait for an ?Interact? message from the session manager.
Status SmcInteractRequest 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. typedef void (*SmcInteractProc) SmcConn
smc_conn SmPointer client_data smc_conn The session management connection
object. client_data Client data specified when the callback was registered.
After interacting with the user (in response to an ?Interact? message), you
should call SmcInteractDone void SmcInteractDone 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
corresponding ?Save Yourself? specified True for shutdown and
SmInteractStyleErrors or SmInteractStyleAny for the interact_style. To request
a checkpoint from the session manager, use SmcRequestSaveYourself void
SmcRequestSaveYourself SmcConn smc_conn int save_type Bool shutdown int
interact_style Bool fast Bool global smc_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. 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 Yourself? 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. 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 SmcConn smc_conn SmcSaveYourselfPhase2Proc
save_yourself_phase2_proc SmPointer client_data smc_conn The session management
connection object. save_type_phase2_proc The callback to be invoked when the
?Save Yourself 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. 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. After saving state in response to a ?Save
Yourself? message, you should call SmcSaveYourselfDone void SmcSaveYourselfDone
SmcConn smc_conn Bool success smc_conn The session management connection
object. success If True the ?Save Yourself? operation was completed
successfully. Before calling SmcSaveYourselfDone the client must have set each
required property at least once since the client registered with the session
manager. int SmcProtocolVersion SmcConn smc_conn SmcProtocolVersion returns the
major version of the session management protocol associated with this session.
int SmcProtocolRevision SmcConn smc_conn SmcProtocolRevision returns the minor
version of the session management protocol associated with this session. char
*SmcVendor 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 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 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 SmcConn smc_conn
SmcGetIceConnection returns the ICE connection object associated 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. If the client receives an unexpected protocol error from the session
manager, an error handler is invoked by SMlib. A 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 SmcErrorHandler
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) 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
IO error occurs, use IceSetIOErrorHandler For further information, see the
Inter-Client Exchange Library standard. This section discusses how Session
Management servers: Initialize the library Register the client Send a ?Save
Yourself? message Send a ?Save Yourself Phase 2? message Send an ?Interact?
message Send a ?Save Complete? message Send a ?Die? message Cancel a shutdown
Return properties Ping a client Clean up after a client disconnects Use Sms
informational functions Handle errors 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 manager. Status SmsInitialize char *vendor char
*release SmsNewClientProc new_client_proc SmPointer manager_data
IceHostBasedAuthProc host_based_auth_proc int error_length char
*error_string_ret 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 connects 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 memory. No more than error_length
bytes are used. After the SmsInitialize function is called, the session manager
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 authentication). Also see the
Inter-Client Exchange Library standard for further details on listening for and
accepting ICE connections. 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.
typedef Status (*SmsNewClientProc) 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 registered. 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 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 { SmsGetPropertiesProc
callback; SmPointer manager_data; } get_properties; } SmsCallbacks; 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) 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 registered.
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 representing 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 SmsRegisterClientReply
function (to be discussed shortly), and the SmsRegisterClientProc callback
should return a status of one. The Interact Request callback is of type
SmsInteractRequestProc typedef void (*SmsInteractRequestProc) 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
registered. 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. When the client
is done interacting with the user, the SmsInteractDoneProc callback will be
invoked. typedef void (*SmsInteractDoneProc) 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 registered.
cancel_shutdown Specifies if the user requests that the entire shutdown be
cancelled. Note that the shutdown can be cancelled only if the corresponding
?Save Yourself? specified True for shutdown and SmInteractStyleErrors or
SmInteractStyleAny for the interact_style. The Save Yourself Request callback
is of type SmsSaveYourselfRequestProc typedef void (*SaveYourselfRequestProc)
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 registered.
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 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 Yourself? 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. The Save Yourself Phase 2 Request callback is of type
SmsSaveYourselfPhase2RequestProc typedef void
(*SmsSaveYourselfPhase2RequestProc) SmsConn sms_conn SmPointer manager_data
sms_conn The session management connection object. manager_data Manager data
specified when the callback was registered. 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. When the client
is done saving its state in response to a ?Save Yourself? message, the
SmsSaveYourselfDoneProc will be invoked. typedef void (*SaveYourselfDoneProc)
SmsConn sms_conn SmPointer manager_data Bool success sms_conn The session
management connection object. manager_data Manager data specified when the
callback was registered. 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 registered with the
session manager. If the client properly terminates (that is, it calls
SmcCloseConnection, the SmsCloseConnectionProc callback is invoked. typedef
void (*SmsCloseConnectionProc) 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 registered. 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 Compound Text strings representing the reason for termination.
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? When the client sets session management properties, the
SmsSetPropertiesProc callback will be invoked. typedef void
(*SmsSetPropertiesProc) SmsConn sms_conn SmPointer manager_data int num_props
SmProp **props sms_conn The session management connection object. manager_data
Manager data specified when the callback was registered. num_props The number
of properties. props The list of properties to set. The properties are
specified as an array of property pointers. 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 When the client deletes session
management properties, the SmsDeletePropertiesProc callback will be invoked.
typedef void (*SmsDeletePropertiesProc) SmsConn sms_conn SmPointer manager_data
int num_props char **prop_names sms_conn The session management connection
object. manager_data Manager data specified when the callback was registered.
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.? The SmsGetPropertiesProc callback is invoked
when the client wants to retrieve properties it set. typedef void
(*SmsGetPropertiesProc) SmsConn sms_conn SmPointer manager_data sms_conn The
session management connection object. manager_data Manager data specified when
the callback was registered. The session manager should respond by calling
SmsReturnProperties. All of the properties set for this client should be
returned. To register a client (in response to a SmsRegisterClientProc
callback), use SmsRegisterClientReply. Status SmsRegisterClientReply 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 failure 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 registered itself, client_id should be identical to
previous_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 manager 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 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. To send a ?Save
Yourself? to a client, use SmsSaveYourself. void SmsSaveYourself 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 properties 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 interact_style is
SmInteractStyleErrors the client may interact with the user only if an error
condition arises. If interact_style is SmInteractStyleAny then the client may
interact 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
user wants the client to commit all of its data to permanent, 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
shutting down, the client must save and then must prevent interaction 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. In order
to send a ?Save Yourself Phase 2? message to a client, use
SmsSaveYourselfPhase2 void SmsSaveYourselfPhase2 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. To send an
?Interact? message to a client, use SmsInteract. void SmsInteract 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 interacting with the user, it must send an ?Interact Done?
message to the session manager. To send a ?Save Complete? message to a client,
use SmsSaveComplete. void SmsSaveComplete 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. To send a
?Die? message to a client, use SmsDie. void SmsDie 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. To cancel a
shutdown, use SmsShutdownCancelled. void SmsShutdownCancelled 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. In response to a ?Get Properties? message, the
session manager should call SmsReturnProperties. void SmsReturnProperties
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 pointers. For a description of session management properties and the
SmProp structure, see section 7, ?Session Management Properties.? 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
SmsGetIceConnection (see section 6.12, ?Using Sms Informational Functions?).
void IcePing 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 IcePingReplyProc 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 client has
unexpectedly died. typedef void (*IcePingReplyProc) IceConn ice_conn IcePointer
client_data ice_conn A valid ICE connection object. client_data The client data
specified in the call to IcePing 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 SmsConn sms_conn sms_conn The session
management connection object. int SmsProtocolVersion SmsConn sms_conn
SmsProtocolVersion returns the major version of the session management protocol
associated with this session. int SmsProtocolRevision SmsConn sms_conn
SmsProtocolRevision returns the minor version of the session management
protocol associated with this session. char *SmsClientID 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 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 SmsConn sms_conn
SmsGetIceConnection returns the ICE connection object associated 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. 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 this error handler by calling SmsSetErrorHandler.
SmsErrorHandler SmsSetErrorHandler SmsErrorHandler 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) 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. Each
property is defined by the SmProp 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
predefined 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). SmCloneCommand This is like the SmRestartCommand, except
it restarts a copy of the application. The only difference is that the
application does not supply its client ID at register time. On POSIX systems,
this should be of type SmLISTofARRAY8. 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.
SmDiscardCommand The discard command contains a command that when delivered to
the host that the client is running on (determined from the connection), will
cause it to discard any information about the current state. If this command 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. SmEnvironment On POSIX based systems, this will be of type
SmLISTofARRAY8, where the ARRAY8s alternate between environment variable name
and environment variable value. SmProcessID This specifies an OS-specific
identifier for the process. On POSIX systems, this should contain the return
value of getpid turned into a Latin-1 (decimal) string. 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. 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 systems, 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. SmResignCommand A client that sets the
SmRestartStyleHint to SmRestartAnyway uses this property to specify a command
that 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 terminates. To
allow the Session Manager (at the user's request) to undo this, xmodmap would
register a SmResignCommand that undoes the effects of the xmodmap.
SmRestartStyleHint If the SmRestartStyleHint 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 session 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 continuously. 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.
SmShutdownCommand This command is executed at shutdown time to clean up after a
client that is no longer running but retained its state by setting
SmRestartStyleHint to SmRestartAnyway. The client must not remove any saved
state as the client is still part of the session. As an example, 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. SmUserID Specifies the user
ID. On POSIX-based systems, this will contain the user's name (the pw_name
member of struct passwd). To free an individual property, use SmFreeProperty
void SmFreeProperty SmProp *prop prop The property to free. To free the reason
strings from the SmsCloseConnectionProc callback, use SmFreeReasons void
SmFreeReasons int count char **reasons count The number of reason strings.
reasons The list of reason strings to free. As stated earlier, the session
management protocol is layered on top of ICE. Authentication occurs at two
levels in the ICE protocol: The first is when an ICE connection is opened. The
second is when a Protocol Setup occurs on an ICE connection. The authentication
methods that are available are implementation-dependent (that is., dependent on
the ICElib and SMlib implementations in use). For further information, see the
Inter-Client Exchange Library standard. 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. 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.
