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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
Permission is hereby granted, free of charge, to any person
obtaining a copy of this software and associated documenta-
tion files (the ``Software''), to deal in the Software with-
out restriction, including without limitation the rights to
use, copy, modify, merge, publish, distribute, sublicense,
and/or sell copies of the Software, and to permit persons to
whom the Software is furnished to do so, subject to the fol-
lowing conditions:
The above copyright notice and this permission notice shall
be included in all copies or substantial portions of the
Software.
THE SOFTWARE IS PROVIDED ``AS IS'', WITHOUT WARRANTY OF ANY
KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PUR-
POSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE X CONSOR-
TIUM BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE
OR OTHER DEALINGS IN THE SOFTWARE.
Except as contained in this notice, the name of the X Con-
sortium 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 X Consortium, Inc.
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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X Session Management Library X11, Release 6.4
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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X Session Management Library X11, Release 6.4
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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X Session Management Library X11, Release 6.4
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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X Session Management Library X11, Release 6.4
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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X Session Management Library X11, Release 6.4
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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X Session Management Library X11, Release 6.4
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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X Session Management Library X11, Release 6.4
|__
To get properties previously stored by the client, use
SmcGetProperties.
__
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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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X Session Management Library X11, Release 6.4
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.
__
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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.
__
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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.
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|
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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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.
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|
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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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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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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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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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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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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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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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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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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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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6.9. Returning Properties
In response to a ``Get Properties'' message, the session
manager should call SmsReturnProperties.
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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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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
