1mX Session Management Library0m 1mVersion 1.00m 1mX Consortium Standard0m 1mX Version 11, Release 6.40m 4mRalph24m 4mMor0m X Consortium Copyright © 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. 1m1. Overview of Session Management0m The purpose of the X Session Management Protocol (XSMP) is to provide a uniform mechanism for users to save and restore their sessions. A 4msession24m is a group of clients, each of which has a particular state. The session is controlled by a network service called the 4msession24m 4mmanager24m. 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 4mclient24m 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. 1m2. The Session Management Library0m 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 4mnested24m 4msession24m 4mmanagers24m. 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 4mclient-ID24m 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 - 1 - 1mX Session Management Library X11, Release 6.40m the client can be restarted (via an 4mSmRestartCommand24m). 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 4mSmRestartCommand24m 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. 1m3. Understanding SMlib's Dependence on ICE0m 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 4mIceProcessMessages24m function. 4mIceProcessMessages24m 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 4mselect0m call on the file descriptor for the ICE connection, but more typically, 4mXtAppAddInput24m will be used to register a callback that will invoke 4mIceProcessMessages24m each time there is data to read on the ICE connection. To further complicate things, knowing which file descriptors to call 4mselect24m on requires an understanding of how ICE con- nections are created. On the client side, a call must be made to 4mSmcOpenConnection24m in order to open a connection with a session manager. 4mSmcOpenConnection24m will internally make a call into 4mIceOpenConnection24m, 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 - 2 - 1mX Session Management Library X11, Release 6.40m 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 4mselect24m 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 4mIceListenForConnections24m in order to start listening for con- nections from clients. Once a connection attempt is detected, 4mIceAcceptConnection24m must be called, and the ses- sion manager can simply add the new ICE file descriptor to the list of descriptors to call 4mselect24m on. For further information on the library functions related to ICE connections, see the 4mInter-Client24m 4mExchange24m 4mLibrary24m stan- dard. 1m4. Header Files and Library Name0m Applications (both session managers and clients) should include the header file <4mX11/SM/SMlib.h24m>. This header file defines all of the SMlib data structures and function proto- types. 4mSMlib.h24m includes the header file <4mX11/SM/SM.h24m>, which defines all of the SMlib constants. Because SMlib is dependent on ICE, applications should link against SMlib and ICElib by using 4m-lSM24m 4m-lICE24m. 1m5. Session Management Client (Smc) Functions0m 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 - 3 - 1mX Session Management Library X11, Release 6.40m 1m5.1. Connecting to the Session Manager0m To open a connection with a session manager, use 4mSmcOpenCon-0m 4mnection24m. __ | SmcConn SmcOpenConnection(4mnetwork_ids_list24m, 4mcontext24m, 4mxsmp_major_rev24m, 4mxsmp_minor_rev24m, 4mmask24m, 4mcallbacks24m, 4mprevious_id24m, 4mclient_id_ret24m, 4merror_length24m, 4merror_string_ret24m) char *4mnetwork_ids_list24m; SmPointer 4mcontext24m; int 4mxsmp_major_rev24m; int 4mxsmp_minor_rev24m; unsigned long 4mmask24m; SmcCallbacks *4mcallbacks24m; char *4mprevious_id24m; char **4mclient_id_ret24m; int 4merror_length24m; char *4merror_string_ret24m; 4mnetwork_ids_list0m Specifies the network ID(s) of the session man- ager. 4mcontext24m A pointer to an opaque object or NULL. Used to determine if an ICE connection can be shared (see below). 4mxsmp_major_rev0m The highest major version of the XSMP the applica- tion supports. 4mxsmp_minor_rev0m The highest minor version of the XSMP the applica- tion supports (for the specified xsmp_major_rev). 4mmask24m A mask indicating which callbacks to register. 4mcallbacks24m The callbacks to register. These callbacks are used to respond to messages from the session man- ager. 4mprevious_id0m The client ID from the previous session. 4mclient_id_ret0m The client ID for the current session is returned. 4merror_length0m Length of the error_string_ret argument passed in. 4merror_string_ret0m Returns a null-terminated error message, if any. The error_string_ret argument points to user - 4 - 1mX Session Management Library X11, Release 6.40m 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 4mSESSION_MANAGER24m environment variable will be used. Each network ID has the following format: tcp/: or decnet/:: or local/: 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, 4mSmcOpenConnection24m 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 4mSmcOpenConnection24m succeeds, it returns an opaque connec- tion pointer of type 4mSmcConn24m 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 4mfree24m when no longer needed. On failure, 4mSmcOpenConnection24m 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 4mIceAdd-0m 4mConnectionWatch24m and 4mIceRemoveConnectionWatch24m), and will have to call 4mIceProcessMessages24m each time a 4mselect24m shows that - 5 - 1mX Session Management Library X11, Release 6.40m there is data to read on an ICE connection. For further information, see the 4mInter-Client24m 4mExchange24m 4mLibrary24m 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: 4mSmcSaveYourselfProcMask0m 4mSmcDieProcMask0m 4mSmcSaveCompleteProcMask0m 4mSmcShutdownCancelledProcMask0m 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; |__ - 6 - 1mX Session Management Library X11, Release 6.40m 1m5.1.1. The Save Yourself Callback0m The Save Yourself callback is of type 4mSmcSaveYourselfProc24m. __ | typedef void (*SmcSaveYourselfProc)(); void SaveYourselfProc(4msmc_conn24m, 4mclient_data24m, 4msave_type24m, 4mshutdown24m, 4minteract_style24m, 4mfast24m) SmcConn 4msmc_conn24m; SmPointer 4mclient_data24m; int 4msave_type24m; Bool 4mshutdown24m; int 4minteract_style24m; Bool 4mfast24m; 4msmc_conn24m The session management connection object. 4mclient_data0m Client data specified when the callback was regis- tered. 4msave_type24m Specifies the type of information that should be saved. 4mshutdown24m Specifies if a shutdown is taking place. 4minteract_style0m The type of interaction allowed with the user. 4mfast24m If 4mTrue24m, 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 4mSmcSetProperties24m to update the properties indicating how to restart the client. When all the proper- ties have been set, the client calls 4mSmcSaveYourselfDone24m. If interact_style is 4mSmInteractStyleNone24m, the client must not interact with the user while saving state. If inter- act_style is 4mSmInteractStyleErrors24m, the client may interact with the user only if an error condition arises. If inter- act_style is 4mSmInteractStyleAny24m, 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 4mSmcInteractRequest24m and wait for an ``Interact'' message from the session manager. When the client is done interacting with the user, it calls 4mSmcInteractDone24m. The client may only call 4mSmcInteractRequest24m after it receives a ``Save Yourself'' message and before it calls 4mSmcSaveYourselfDone24m. - 7 - 1mX Session Management Library X11, Release 6.40m If save_type is 4mSmSaveLocal24m, 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 4mSmSaveGlobal24m, the user wants the client to commit all of its data to perma- nent, globally accessible storage. If save_type is 4mSmSave-0m 4mBoth24m, 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 4mSmSaveLocal24m, 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. · If a word processor were sent a ``Save Yourself'' with a type of 4mSmSaveGlobal24m, it would simply save the cur- rently edited file. · If a word processor were sent a ``Save Yourself'' with a type of 4mSmSaveBoth24m, 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 4mTrue24m. 1m5.1.2. The Die Callback0m The Die callback is of type 4mSmcDieProc24m. __ | - 8 - 1mX Session Management Library X11, Release 6.40m typedef void (*SmcDieProc)(); void DieProc(4msmc_conn24m, 4mclient_data24m) SmcConn 4msmc_conn24m; SmPointer 4mclient_data24m; 4msmc_conn24m The session management connection object. 4mclient_data0m 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 4mSmcCloseConnection24m. A session manager that behaves properly will send a ``Save Yourself'' message before the ``Die'' message. 1m5.1.3. The Save Complete Callback0m The Save Complete callback is of type 4mSmcSaveCompleteProc24m. __ | typedef void (*SmcSaveCompleteProc)(); void SaveCompleteProc(4msmc_conn24m, 4mclient_data24m) SmcConn 4msmc_conn24m; SmPointer 4mclient_data24m; 4msmc_conn24m The session management connection object. 4mclient_data0m 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. 1m5.1.4. The Shutdown Cancelled Callback0m The Shutdown Cancelled callback is of type 4mSmcShutdownCan-0m 4mcelledProc24m. __ | - 9 - 1mX Session Management Library X11, Release 6.40m typedef void (*SmcShutdownCancelledProc)(); void ShutdownCancelledProc(4msmc_conn24m, 4mclient_data24m) SmcConn 4msmc_conn24m; SmPointer 4mclient_data24m; 4msmc_conn24m The session management connection object. 4mclient_data0m 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 4mSmcSaveYourselfDone0m yet, it can either abort the save and then call 4mSmcSaveYour-0m 4mselfDone24m with the success argument set to 4mFalse24m, or it can continue with the save and then call 4mSmcSaveYourselfDone0m with the success argument set to reflect the outcome of the save. 1m5.2. Closing the Connection0m To close a connection with a session manager, use 4mSmcCloseC-0m 4monnection24m. __ | SmcCloseStatus SmcCloseConnection(4msmc_conn24m, 4mcount24m, 4mreason_msgs24m) SmcConn 4msmc_conn24m; int 4mcount24m; char **4mreason_msgs24m; 4msmc_conn24m The session management connection object. 4mcount24m The number of reason messages. 4mreason_msgs0m 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 - 10 - 1mX Session Management Library X11, Release 6.40m than session management may be active on the ICE connection. When 4mSmcCloseConnection24m is called, the ICE connection will be closed only if all protocols have been shutdown on the connection. Check the ICElib standard for 4mIceAddConnection-0m 4mWatch24m and 4mIceRemoveConnectionWatch24m 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 4mselect24m on (or calls 4mXtAppAddInput24m or 4mXtRemoveInput24m). 4mSmcCloseConnection24m returns one of the following values: · 4mSmcClosedNow24m - the ICE connection was closed at this time, the watch procedures were invoked, and the con- nection was freed. · 4mSmcClosedASAP24m - an IO error had occurred on the connec- tion, but 4mSmcCloseConnection24m is being called within a nested 4mIceProcessMessages24m. 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 4mIceProcessMessages24m returns a status of 4mIceProcessMessagesConnectionClosed24m). · 4mSmcConnectionInUse24m - the connection was not closed at this time, because it is being used by other active protocols. 1m5.3. Modifying Callbacks0m To modify callbacks set up in 4mSmcOpenConnection24m, use 4mSmcMod-0m 4mifyCallbacks24m. __ | void SmcModifyCallbacks(4msmc_conn24m, 4mmask24m, 4mcallbacks24m) SmcConn 4msmc_conn24m; unsigned long 4mmask24m; SmcCallbacks *4mcallbacks24m; 4msmc_conn24m The session management connection object. 4mmask24m A mask indicating which callbacks to modify. 4mcallbacks24m The new callbacks. |__ When specifying a value for the mask argument, the following values may be ORed together: 4mSmcSaveYourselfProcMask0m 4mSmcDieProcMask0m 4mSmcSaveCompleteProcMask0m - 11 - 1mX Session Management Library X11, Release 6.40m 4mSmcShutdownCancelledProcMask0m 1m5.4. Setting, Deleting, and Retrieving Session Management0m 1mProperties0m To set session management properties for this client, use 4mSmcSetProperties24m. __ | void SmcSetProperties(4msmc_conn24m, 4mnum_props24m, 4mprops24m) SmcConn 4msmc_conn24m; int 4mnum_props24m; SmProp **4mprops24m; 4msmc_conn24m The session management connection object. 4mnum_props24m The number of properties. 4mprops24m 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 4mSmcSetProperties24m 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 4mSmProp24m structure, see section 7, ``Session Management Prop- erties.'' To delete properties previously set by the client, use 4mSmcDeleteProperties24m. __ | void SmcDeleteProperties(4msmc_conn24m, 4mnum_props24m, 4mprop_names24m) SmcConn 4msmc_conn24m; int 4mnum_props24m; char **4mprop_names24m; 4msmc_conn24m The session management connection object. 4mnum_props24m The number of properties. 4mprop_names0m The list of properties to delete. - 12 - 1mX Session Management Library X11, Release 6.40m |__ To get properties previously stored by the client, use 4mSmcGetProperties24m. __ | Status SmcGetProperties(4msmc_conn24m, 4mprop_reply_proc24m, 4mclient_data24m) SmcConn 4msmc_conn24m; SmcPropReplyProc 4mprop_reply_proc24m; SmPointer 4mclient_data24m; 4msmc_conn24m The session management connection object. 4mprop_reply_proc0m The callback to be invoked when the properties reply comes back. 4mclient_data0m This pointer to client data will be passed to the 4mSmcPropReplyProc24m callback. |__ The return value of 4mSmcGetProperties24m 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 4mSmcPropRe-0m 4mplyProc24m is invoked when the data is ready. __ | typedef void (*SmcPropReplyProc)(); void PropReplyProc(4msmc_conn24m, 4mclient_data24m, 4mnum_props24m, 4mprops24m) SmcConn 4msmc_conn24m; SmPointer 4mclient_data24m; int 4mnum_props24m; SmProp **4mprops24m; 4msmc_conn24m The session management connection object. 4mclient_data0m Client data specified when the callback was regis- tered. 4mnum_props24m The number of properties returned. 4mprops24m The list of properties returned. |__ To free each property, use 4mSmFreeProperty24m (see section 8, ``Freeing Data''). To free the actual array of pointers, - 13 - 1mX Session Management Library X11, Release 6.40m use 4mfree24m. 1m5.5. Interacting With the User0m After receiving a ``Save Yourself'' message with an inter- act_style of 4mSmInteractStyleErrors24m or 4mSmInteractStyleAny24m, 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 4mSmcInteractRequest24m and wait for an ``Inter- act'' message from the session manager. __ | Status SmcInteractRequest(4msmc_conn24m, 4mdialog_type24m, 4minteract_proc24m, 4mclient_data24m) SmcConn 4msmc_conn24m; int 4mdialog_type24m; SmcInteractProc 4minteract_proc24m; SmPointer 4mclient_data24m; 4msmc_conn24m The session management connection object. 4mdialog_type0m The type of dialog the client wishes to present to the user. 4minteract_proc0m The callback to be invoked when the ``Interact'' message arrives from the session manager. 4mclient_data0m This pointer to client data will be passed to the 4mSmcInteractProc24m callback when the ``Interact'' message arrives. |__ The return value of 4mSmcInteractRequest24m is zero for failure and a positive value for success. The dialog_type argument specifies either 4mSmDialogError24m, indicating that the client wants to start an error dialog, or 4mSmDialogNormal24m, 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 4mSmcInteractProc24m callback will be invoked when the ``Interact'' message arrives from the session manager. __ | - 14 - 1mX Session Management Library X11, Release 6.40m typedef void (*SmcInteractProc)(); void InteractProc(4msmc_conn24m, 4mclient_data24m) SmcConn 4msmc_conn24m; SmPointer 4mclient_data24m; 4msmc_conn24m The session management connection object. 4mclient_data0m Client data specified when the callback was regis- tered. |__ After interacting with the user (in response to an ``Inter- act'' message), you should call 4mSmcInteractDone24m. __ | void SmcInteractDone(4msmc_conn24m, 4mcancel_shutdown24m) SmcConn 4msmc_conn24m; Bool 4mcancel_shutdown24m; 4msmc_conn24m The session management connection object. 4mcancel_shutdown0m If 4mTrue24m, indicates that the user requests that the entire shutdown be cancelled. |__ The cancel_shutdown argument may only be 4mTrue24m if the corre- sponding ``Save Yourself'' specified 4mTrue24m for shutdown and 4mSmInteractStyleErrors24m or 4mSmInteractStyleAny24m for the inter- act_style. 1m5.6. Requesting a Save Yourself0m To request a checkpoint from the session manager, use 4mSmcRe-0m 4mquestSaveYourself24m. __ | void SmcRequestSaveYourself(4msmc_conn24m, 4msave_type24m, 4mshutdown24m, 4minteract_style24m, 4mfast24m, 4mglobal24m) SmcConn 4msmc_conn24m; int 4msave_type24m; Bool 4mshutdown24m; int 4minteract_style24m; Bool 4mfast24m; Bool 4mglobal24m; 4msmc_conn24m The session management connection object. - 15 - 1mX Session Management Library X11, Release 6.40m 4msave_type24m Specifies the type of information that should be saved. 4mshutdown24m Specifies if a shutdown is taking place. 4minteract_style0m The type of interaction allowed with the user. 4mfast24m If 4mTrue24m, the client should save its state as quickly as possible. 4mglobal24m 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 4mTrue24m, 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 4mFalse24m, then the ``Save Yourself'' should only be sent to the client that requested it. 1m5.7. Requesting a Save Yourself Phase 20m 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 4mSmcRequestSaveYour-0m 4mselfPhase224m. __ | Status SmcRequestSaveYourselfPhase2(4msmc_conn24m, 4msave_yourself_phase2_proc24m, 4mclient_data24m) SmcConn 4msmc_conn24m; SmcSaveYourselfPhase2Proc 4msave_yourself_phase2_proc24m; SmPointer 4mclient_data24m; 4msmc_conn24m The session management connection object. 4msave_yourself_phase2_proc0m The callback to be invoked when the ``Save Your- self Phase 2'' message arrives from the session manager. 4mclient_data0m This pointer to client data will be passed to the 4mSmcSaveYourselfPhase2Proc24m callback when the ``Save Yourself Phase 2'' message arrives. - 16 - 1mX Session Management Library X11, Release 6.40m |__ The return value of 4mSmcRequestSaveYourselfPhase224m 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. 1m5.8. Completing a Save Yourself0m After saving state in response to a ``Save Yourself'' mes- sage, you should call 4mSmcSaveYourselfDone24m. __ | void SmcSaveYourselfDone(4msmc_conn24m, 4msuccess24m) SmcConn 4msmc_conn24m; Bool 4msuccess24m; 4msmc_conn24m The session management connection object. 4msuccess24m If 4mTrue24m, the ``Save Yourself'' operation was com- pleted successfully. |__ Before calling 4mSmcSaveYourselfDone24m, the client must have set each required property at least once since the client regis- tered with the session manager. 1m5.9. Using Smc Informational Functions0m __ | int SmcProtocolVersion(4msmc_conn24m) SmcConn 4msmc_conn24m; |__ 4mSmcProtocolVersion24m returns the major version of the session management protocol associated with this session. __ | int SmcProtocolRevision(4msmc_conn24m) SmcConn 4msmc_conn24m; |__ 4mSmcProtocolRevision24m returns the minor version of the session management protocol associated with this session. - 17 - 1mX Session Management Library X11, Release 6.40m __ | char *SmcVendor(4msmc_conn24m) SmcConn 4msmc_conn24m; |__ 4mSmcVendor24m returns a string that provides some identification of the owner of the session manager. The string should be freed with a call to 4mfree24m. __ | char *SmcRelease(4msmc_conn24m) SmcConn 4msmc_conn24m; |__ 4mSmcRelease24m returns a string that provides the release number of the session manager. The string should be freed with a call to 4mfree24m. __ | char *SmcClientID(4msmc_conn24m) SmcConn 4msmc_conn24m; |__ 4mSmcClientID24m returns a null-terminated string for the client ID associated with this connection. This information was also returned in 4mSmcOpenConnection24m (it is provided here for convenience). Call 4mfree24m on this pointer when the client ID is no longer needed. __ | IceConn SmcGetIceConnection(4msmc_conn24m) SmcConn 4msmc_conn24m; |__ 4mSmcGetIceConnection24m 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 4mIceConnec-0m 4mtionNumber24m, 4mIceConnectionString24m, 4mIceLastSentSequenceNumber24m, 4mIceLastReceivedSequenceNumber24m, and 4mIcePing24m. For further information, see the 4mInter-Client24m 4mExchange24m 4mLibrary24m standard. 1m5.10. Error Handling0m 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 - 18 - 1mX Session Management Library X11, Release 6.40m message to 4mstderr24m and exits if the severity of the error is fatal. The client can change this error handler by calling the 4mSmcSetErrorHandler24m function. __ | SmcErrorHandler SmcSetErrorHandler(4mhandler24m) SmcErrorHandler 4mhandler24m; 4mhandler24m The error handler. You should pass NULL to restore the default handler. |__ 4mSmcSetErrorHandler24m returns the previous error handler. The 4mSmcErrorHandler24m has the following type: __ | typedef void (*SmcErrorHandler)(); void ErrorHandler(4msmc_conn24m, 4mswap24m, 4moffending_minor_opcode24m, 4moffending_sequence_num24m, 4merror_class24m, 4mseverity24m, 4mvalues24m) SmcConn 4msmc_conn24m; Bool 4mswap24m; int 4moffending_minor_opcode24m; unsigned long 4moffending_sequence_num24m; int 4merror_class24m; int 4mseverity24m; IcePointer 4mvalues24m; 4msmc_conn24m The session management connection object. 4mswap24m A flag that indicates if the specified values need byte swapping. 4moffending_minor_opcode0m The minor opcode of the offending message. 4moffending_sequence_num0m The sequence number of the offending message. 4merror_class0m The error class of the offending message. 4mseverity24m 4mIceCanContinue24m, 4mIceFatalToProtocol24m, or 4mIceFatalTo-0m 4mConnection24m. 4mvalues24m 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 4mIceSetIOErrorHandler24m. For further - 19 - 1mX Session Management Library X11, Release 6.40m information, see the 4mInter-Client24m 4mExchange24m 4mLibrary24m standard. 1m6. Session Management Server (Sms) Functions0m 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 1m6.1. Initializing the Library0m 4mSmsInitialize24m 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(4mvendor24m, 4mrelease24m, 4mnew_client_proc24m, 4mmanager_data24m, 4mhost_based_auth_proc24m, 4merror_length24m, 4merror_string_ret24m) char *4mvendor24m; char *4mrelease24m; SmsNewClientProc 4mnew_client_proc24m; SmPointer 4mmanager_data24m; IceHostBasedAuthProc 4mhost_based_auth_proc24m; int 4merror_length24m; char *4merror_string_ret24m; 4mvendor24m A string specifying the session manager vendor. - 20 - 1mX Session Management Library X11, Release 6.40m 4mrelease24m A string specifying the session manager release number. 4mnew_client_proc0m Callback to be invoked each time a new client con- nects to the session manager. 4mmanager_data0m When the 4mSmsNewClientProc24m callback is invoked, this pointer to manager data will be passed. 4mhost_based_auth_proc0m Host based authentication callback. 4merror_length0m Length of the error_string_ret argument passed in. 4merror_string_ret0m 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 4mSmsInitialize24m function is called, the session man- ager should call the 4mIceListenForConnections24m function to listen for new connections. Afterwards, each time a client connects, the session manager should call 4mIceAcceptConnec-0m 4mtion24m. See section 9, ``Authentication of Clients,'' for more details on authentication (including host based authentica- tion). Also see the 4mInter-Client24m 4mExchange24m 4mLibrary24m standard for further details on listening for and accepting ICE con- nections. Each time a new client connects to the session manager, the 4mSmsNewClientProc24m 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)(); Status NewClientProc(4msms_conn24m, 4mmanager_data24m, 4mmask_ret24m, 4mcallbacks_ret24m, 4mfailure_reason_ret24m) SmsConn 4msms_conn24m; SmPointer 4mmanager_data24m; unsigned long *4mmask_ret24m; SmsCallbacks *4mcallbacks_ret24m; char **4mfailure_reason_ret24m; - 21 - 1mX Session Management Library X11, Release 6.40m 4msms_conn24m A new opaque connection object. 4mmanager_data0m Manager data specified when the callback was reg- istered. 4mmask_ret24m On return, indicates which callbacks were set by the session manager. 4mcallbacks_ret0m On return, contains the callbacks registered by the session manager. 4mfailure_reason_ret0m Failure reason returned. |__ If a failure occurs, the 4mSmsNewClientProc24m 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: 4mSmsRegisterClientProcMask0m 4mSmsInteractRequestProcMask0m 4mSmsInteractDoneProcMask0m 4mSmsSaveYourselfRequestProcMask0m 4mSmsSaveYourselfP2RequestProcMask0m 4mSmsSaveYourselfDoneProcMask0m 4mSmsCloseConnectionProcMask0m 4mSmsSetPropertiesProcMask0m 4mSmsDeletePropertiesProcMask0m 4mSmsGetPropertiesProcMask0m 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 { - 22 - 1mX Session Management Library X11, Release 6.40m 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; |__ - 23 - 1mX Session Management Library X11, Release 6.40m 1m6.1.1. The Register Client Callback0m The Register Client callback is the first callback that will be invoked after the client connects to the session manager. Its type is 4mSmsRegisterClientProc24m. __ | typedef Status (*SmsRegisterClientProc(); Status RegisterClientProc(4msms_conn24m, 4mmanager_data24m, 4mprevious_id24m) SmsConn 4msms_conn24m; SmPointer 4mmanager_data24m; char *4mprevious_id24m; 4msms_conn24m The session management connection object. 4mmanager_data0m Manager data specified when the callback was reg- istered. 4mprevious_id0m 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 4mfree24m 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 4mSmsRegisterClientRe-0m 4mply24m function (to be discussed shortly), and the 4mSmsRegister-0m 4mClientProc24m callback should return a status of one. 1m6.1.2. The Interact Request Callback0m The Interact Request callback is of type 4mSmsInteractRequest-0m 4mProc24m. __ | - 24 - 1mX Session Management Library X11, Release 6.40m typedef void (*SmsInteractRequestProc)(); void InteractRequestProc(4msms_conn24m, 4mmanager_data24m, 4mdialog_type24m) SmsConn 4msms_conn24m; SmPointer 4mmanager_data24m; int 4mdialog_type24m; 4msms_conn24m The session management connection object. 4mmanager_data0m Manager data specified when the callback was reg- istered. 4mdialog_type0m 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 4mSmInteractStyleErrors24m or 4mSmInteract-0m 4mStyleAny24m, 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 wish- ing to interact. It should send an ``Interact'' message to one client at a time and wait for an ``Interact Done'' mes- sage before continuing with the next client. The dialog_type argument specifies either 4mSmDialogError24m, indicating that the client wants to start an error dialog, or 4mSmDialogNormal24m, 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. 1m6.1.3. The Interact Done Callback0m When the client is done interacting with the user, the 4mSmsInteractDoneProc24m callback will be invoked. __ | typedef void (*SmsInteractDoneProc)(); void InteractDoneProc(4msms_conn24m, 4mmanager_data24m, 4mcancel_shutdown24m) SmsConn 4msms_conn24m; SmPointer 4mmanager_data24m; Bool 4mcancel_shutdown24m; - 25 - 1mX Session Management Library X11, Release 6.40m 4msms_conn24m The session management connection object. 4mmanager_data0m Manager data specified when the callback was reg- istered. 4mcancel_shutdown0m 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 4mTrue24m for shutdown and 4mSmInteractStyleErrors24m or 4mSmInteractStyleAny24m for the inter- act_style. 1m6.1.4. The Save Yourself Request Callback0m The Save Yourself Request callback is of type 4mSmsSaveYour-0m 4mselfRequestProc24m. __ | typedef void (*SmsSaveYourselfRequestProc)(); void SaveYourselfRequestProc(4msms_conn24m, 4mmanager_data24m, 4msave_type24m, 4mshutdown24m, 4minteract_style24m, 4mfast24m, 4mglobal24m) SmsConn 4msms_conn24m; SmPointer 4mmanager_data24m; int 4msave_type24m; Bool 4mshutdown24m; int 4minteract_style24m; Bool 4mfast24m; Bool 4mglobal24m; 4msms_conn24m The session management connection object. 4mmanager_data0m Manager data specified when the callback was reg- istered. 4msave_type24m Specifies the type of information that should be saved. 4mshutdown24m Specifies if a shutdown is taking place. 4minteract_style0m The type of interaction allowed with the user. 4mfast24m If 4mTrue24m, the client should save its state as quickly as possible. 4mglobal24m Controls who gets the ``Save Yourself.'' - 26 - 1mX Session Management Library X11, Release 6.40m |__ 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 4mTrue24m, then the resulting ``Save Your- self'' should be sent to all applications. If global is set to 4mFalse24m, then the ``Save Yourself'' should only be sent to the client that requested it. 1m6.1.5. The Save Yourself Phase 2 Request Callback0m The Save Yourself Phase 2 Request callback is of type 4mSmsSaveYourselfPhase2RequestProc24m. __ | typedef void (*SmsSaveYourselfPhase2RequestProc)(); void SmsSaveYourselfPhase2RequestProc(4msms_conn24m, 4mmanager_data24m) SmsConn 4msms_conn24m; SmPointer 4mmanager_data24m; 4msms_conn24m The session management connection object. 4mmanager_data0m 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. 1m6.1.6. The Save Yourself Done Callback0m When the client is done saving its state in response to a ``Save Yourself'' message, the 4mSmsSaveYourselfDoneProc24m will be invoked. __ | typedef void (*SmsSaveYourselfDoneProc)(); void SaveYourselfDoneProc(4msms_conn24m, 4mmanager_data24m, 4msuccess24m) SmsConn 4msms_conn24m; SmPointer 4mmanager_data24m; Bool 4msuccess24m; - 27 - 1mX Session Management Library X11, Release 6.40m 4msms_conn24m The session management connection object. 4mmanager_data0m Manager data specified when the callback was reg- istered. 4msuccess24m If 4mTrue24m, 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. 1m6.1.7. The Connection Closed Callback0m If the client properly terminates (that is, it calls 4mSmc-0m 4mCloseConnection24m), the 4mSmsCloseConnectionProc24m callback is invoked. __ | typedef void (*SmsCloseConnectionProc)(); void CloseConnectionProc(4msms_conn24m, 4mmanager_data24m, 4mcount24m, 4mreason_msgs24m) SmsConn 4msms_conn24m; SmPointer 4mmanager_data24m; int 4mcount24m; char **4mreason_msgs24m; 4msms_conn24m The session management connection object. 4mmanager_data0m Manager data specified when the callback was reg- istered. 4mcount24m The number of reason messages. 4mreason_msgs0m 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. The session manager should display these reason messages to the user. Call 4mSmFreeReasons24m to free the reason messages. For further information, see section 8, ``Freeing Data.'' - 28 - 1mX Session Management Library X11, Release 6.40m 1m6.1.8. The Set Properties Callback0m When the client sets session management properties, the 4mSms-0m 4mSetPropertiesProc24m callback will be invoked. __ | typedef void (*SmsSetPropertiesProc)(); void SetPropertiesProc(4msms_conn24m, 4mmanager_data24m, 4mnum_props24m, 4mprops24m) SmsConn 4msms_conn24m; SmPointer 4mmanager_data24m; int 4mnum_props24m; SmProp **4mprops24m; 4msmc_conn24m The session management connection object. 4mmanager_data0m Manager data specified when the callback was reg- istered. 4mnum_props24m The number of properties. 4mprops24m 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 4mSmProp24m 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 4mSmFreeProperty24m. For further information, see section 8, ``Freeing Data.'' You should free the actual array of pointers with a call to 4mfree24m. 1m6.1.9. The Delete Properties Callback0m When the client deletes session management properties, the 4mSmsDeletePropertiesProc24m callback will be invoked. __ | typedef void (*SmsDeletePropertiesProc)(); void DeletePropertiesProc(4msms_conn24m, 4mmanager_data24m, 4mnum_props24m, 4mprop_names24m) SmsConn 4msms_conn24m; SmPointer 4mmanager_data24m; int 4mnum_props24m; char **4mprop_names24m; - 29 - 1mX Session Management Library X11, Release 6.40m 4msmc_conn24m The session management connection object. 4mmanager_data0m Manager data specified when the callback was reg- istered. 4mnum_props24m The number of properties. 4mprop_names0m The list of properties to delete. |__ The properties are specified as an array of strings. For a description of session management properties and the 4mSmProp0m structure, see section 7, ``Session Management Properties.'' 1m6.1.10. The Get Properties Callback0m The 4mSmsGetPropertiesProc24m callback is invoked when the client wants to retrieve properties it set. __ | typedef void (*SmsGetPropertiesProc)(); void GetPropertiesProc(4msms_conn24m, 4mmanager_data24m) SmsConn 4msms_conn24m; SmPointer 4mmanager_data24m; 4msmc_conn24m The session management connection object. 4mmanager_data0m Manager data specified when the callback was reg- istered. |__ The session manager should respond by calling 4mSmsReturnProp-0m 4merties24m. All of the properties set for this client should be returned. 1m6.2. Registering the Client0m To register a client (in response to a 4mSmsRegisterClientProc0m callback), use 4mSmsRegisterClientReply24m. __ | Status SmsRegisterClientReply(4msms_conn24m, 4mclient_id24m) SmsConn 4msms_conn24m; char *4mclient_id24m; 4msms_conn24m The session management connection object. - 30 - 1mX Session Management Library X11, Release 6.40m 4mclient_id24m A null-terminated string representing a unique client ID. |__ The return value of 4mSmsRegisterClientReply24m 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 4mSmsGenerateClientID24m function to generate a globally unique client ID. __ | char *SmsGenerateClientID(4msms_conn24m) SmsConn 4msms_conn24m; 4msms_conn24m 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 4mfree24m when no longer needed. 1m6.3. Sending a Save Yourself Message0m To send a ``Save Yourself'' to a client, use 4mSmsSaveYour-0m 4mself24m. __ | - 31 - 1mX Session Management Library X11, Release 6.40m void SmsSaveYourself(4msms_conn24m, 4msave_type24m, 4mshutdown24m, 4minteract_style24m, 4mfast24m) SmsConn 4msms_conn24m; int 4msave_type24m; Bool 4mshutdown24m; int 4minteract_style24m; Bool 4mfast24m; 4msms_conn24m The session management connection object. 4msave_type24m Specifies the type of information that should be saved. 4mshutdown24m Specifies if a shutdown is taking place. 4minteract_style0m The type of interaction allowed with the user. 4mfast24m If 4mTrue24m, 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 4mSmInteractStyleNone24m, the client must not interact with the user while saving state. If inter- act_style is 4mSmInteractStyleErrors24m, the client may interact with the user only if an error condition arises. If inter- act_style is 4mSmInteractStyleAny24m, 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 4mSmSaveLocal24m, 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 4mSmSaveGlobal24m the user wants the client to commit all of its data to perma- nent, globally accessible storage. If save_type is 4mSmSave-0m 4mBoth24m, the client should do both of these (it should first commit the data to permanent storage before updating its properties). - 32 - 1mX Session Management Library X11, Release 6.40m 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 4mTrue24m. 1m6.4. Sending a Save Yourself Phase 2 Message0m In order to send a ``Save Yourself Phase 2'' message to a client, use 4mSmsSaveYourselfPhase224m. __ | void SmsSaveYourselfPhase2(4msms_conn24m) SmsConn 4msms_conn24m; 4msms_conn24m 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. 1m6.5. Sending an Interact Message0m To send an ``Interact'' message to a client, use 4mSmsInter-0m 4mact24m. __ | void SmsInteract(4msms_conn24m) SmsConn 4msms_conn24m; 4msms_conn24m The session management connection object. |__ The ``Interact'' message grants the client the privilege of interacting with the user. When the client is done inter- acting with the user, it must send an ``Interact Done'' mes- sage to the session manager. - 33 - 1mX Session Management Library X11, Release 6.40m 1m6.6. Sending a Save Complete Message0m To send a ``Save Complete'' message to a client, use 4mSmsSaveComplete24m. __ | void SmsSaveComplete(4msms_conn24m) SmsConn 4msms_conn24m; 4msms_conn24m 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. 1m6.7. Sending a Die Message0m To send a ``Die'' message to a client, use 4mSmsDie24m. __ | void SmsDie(4msms_conn24m) SmsConn 4msms_conn24m; 4msms_conn24m 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. 1m6.8. Cancelling a Shutdown0m To cancel a shutdown, use 4mSmsShutdownCancelled24m. __ | void SmsShutdownCancelled(4msms_conn24m) SmsConn 4msms_conn24m; 4msms_conn24m 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 4mFalse24m, 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. - 34 - 1mX Session Management Library X11, Release 6.40m 1m6.9. Returning Properties0m In response to a ``Get Properties'' message, the session manager should call 4mSmsReturnProperties24m. __ | void SmsReturnProperties(4msms_conn24m, 4mnum_props24m, 4mprops24m) SmsConn 4msms_conn24m; int 4mnum_props24m; SmProp **4mprops24m; 4msms_conn24m The session management connection object. 4mnum_props24m The number of properties. 4mprops24m 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 4mSmProp24m structure, see section 7, ``Session Management Properties.'' 1m6.10. Pinging a Client0m To check that a client is still alive, you should use the 4mIcePing24m function provided by the ICE library. To do so, the ICE connection must be obtained using the 4mSmsGetIceConnec-0m 4mtion24m (see section 6.12, ``Using Sms Informational Func- tions''). __ | void IcePing(4mice_conn24m, 4mping_reply_proc24m, 4mclient_data24m) IceConn 4mice_conn24m; IcePingReplyProc 4mping_reply_proc24m; IcePointer 4mclient_data24m; 4mice_conn24m A valid ICE connection object. 4mping_reply_proc0m The callback to invoke when the Ping reply arrives. 4mclient_data0m This pointer will be passed to the 4mIcePingRe-0m 4mplyProc24m callback. |__ When the Ping reply is ready (if ever), the 4mIcePingReplyProc0m callback will be invoked. A session manager should have some sort of timeout period, after which it assumes the - 35 - 1mX Session Management Library X11, Release 6.40m client has unexpectedly died. __ | typedef void (*IcePingReplyProc)(); void PingReplyProc(4mice_conn24m, 4mclient_data24m) IceConn 4mice_conn24m; IcePointer 4mclient_data24m; 4mice_conn24m The ICE connection object. 4mclient_data0m The client data specified in the call to 4mIcePing24m. |__ 1m6.11. Cleaning Up After a Client Disconnects0m When the session manager receives a ``Connection Closed'' message or otherwise detects that the client aborted the connection, it should call the 4mSmsCleanUp24m function in order to free up the connection object. __ | void SmsCleanUp(4msms_conn24m) SmsConn 4msms_conn24m; 4msms_conn24m The session management connection object. |__ 1m6.12. Using Sms Informational Functions0m __ | int SmsProtocolVersion(4msms_conn24m) SmsConn 4msms_conn24m; |__ 4mSmsProtocolVersion24m returns the major version of the session management protocol associated with this session. __ | int SmsProtocolRevision(4msms_conn24m) SmsConn 4msms_conn24m; - 36 - 1mX Session Management Library X11, Release 6.40m |__ 4mSmsProtocolRevision24m returns the minor version of the session management protocol associated with this session. __ | char *SmsClientID(4msms_conn24m) SmsConn 4msms_conn24m; |__ 4mSmsClientID24m returns a null-terminated string for the client ID associated with this connection. You should call 4mfree24m on this pointer when the client ID is no longer needed. To obtain the host name of a client, use 4mSmsClientHostName24m. This host name will be needed to restart the client. __ | char *SmsClientHostName(4msms_conn24m) SmsConn 4msms_conn24m; |__ The string returned is of the form 4mprotocol24m/4mhostname24m, where 4mprotocol24m is one of {tcp, decnet, local}. You should call 4mfree24m on the string returned when it is no longer needed. __ | IceConn SmsGetIceConnection(4msms_conn24m) SmsConn 4msms_conn24m; |__ 4mSmsGetIceConnection24m 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 4mIceConnec-0m 4mtionNumber24m, and 4mIceLastSequenceNumber24m. For further informa- tion, see the 4mInter-Client24m 4mExchange24m 4mLibrary24m standard. 1m6.13. Error Handling0m 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 - 37 - 1mX Session Management Library X11, Release 6.40m this error handler by calling 4mSmsSetErrorHandler24m. __ | SmsErrorHandler SmsSetErrorHandler(4mhandler24m) SmsErrorHandler 4mhandler24m; 4mhandler24m The error handler. You should pass NULL to restore the default handler. |__ 4mSmsSetErrorHandler24m returns the previous error handler. The 4mSmsErrorHandler24m has the following type: __ | typedef void (*SmsErrorHandler)(); void ErrorHandler(4msms_conn24m, 4mswap24m, 4moffending_minor_opcode24m, 4moffending_sequence_num24m, 4merror_class24m, 4mseverity24m, 4mvalues24m) SmsConn 4msms_conn24m; Bool 4mswap24m; int 4moffending_minor_opcode24m; unsigned long 4moffending_sequence_num24m; int 4merror_class24m; int 4mseverity24m; IcePointer 4mvalues24m; 4msms_conn24m The session management connection object. 4mswap24m A flag which indicates if the specified values need byte swapping. 4moffending_minor_opcode0m The minor opcode of the offending message. 4moffending_sequence_num0m The sequence number of the offending message. 4merror_class0m The error class of the offending message. 4mseverity24m 4mIceCanContinue24m, 4mIceFatalToProtocol24m, or 4mIceFatalTo-0m 4mConnection24m. 4mvalues24m 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 4mIceSetIOErrorHandler24m. For further information, see the 4mInter-Client24m 4mExchange24m 4mLibrary24m standard. - 38 - 1mX Session Management Library X11, Release 6.40m 1m7. Session Management Properties0m Each property is defined by the 4mSmProc24m 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. ------------------------------------------------------------- 1mName Type POSIX Type Required0m ------------------------------------------------------------- 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 - 39 - 1mX Session Management Library X11, Release 6.40m the application does not supply its client ID at regis- ter 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 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. · 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. · SmProcessID This specifies an OS-specific identifier for the process. On POSIX systems, this should contain the return value of 4mgetpid24m 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 4mexecve24m 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 sys- tems, this is of type SmLISTofARRAY8, and each of the elements in the array represents an element in the 4margv0m array. This restart command should ensure that the client restarts with the specified client-ID. · SmResignCommand - 40 - 1mX Session Management Library X11, Release 6.40m A client that sets the SmRestartStyleHint to SmRestar- tAnway 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 4mxmodmap24m, 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, 4mxmodmap24m would register a SmRe- signCommand that undoes the effects of the 4mxmodmap24m. · 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: ----------------------------- 1mName Value0m ----------------------------- 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. · SmShutdownCommand - 41 - 1mX Session Management Library X11, Release 6.40m 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 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. · SmUserID Specifies the user ID. On POSIX-based systems, this will contain the user's name (the pw_name member of struct 4mpasswd24m). 1m8. Freeing Data0m To free an individual property, use 4mSmFreeProperty24m. __ | void SmFreeProperty(4mprop24m) SmProp *4mprop24m; 4mprop24m The property to free. |__ To free the reason strings from the 4mSmsCloseConnectionProc0m callback, use 4mSmFreeReasons24m. __ | void SmFreeReasons(4mcount24m, 4mreasons24m) int 4mcount24m; char **4mreasons24m; 4mcount24m The number of reason strings. 4mreasons24m The list of reason strings to free. |__ 1m9. Authentication of Clients0m As stated earlier, the session management protocol is lay- ered on top of ICE. Authentication occurs at two levels in the ICE protocol: · The first is when an ICE connection is opened. - 42 - 1mX Session Management Library X11, Release 6.40m · The second is when a Protocol Setup occurs on an ICE connection. 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 4mInter-Client24m 4mExchange24m 4mLibrary24m standard. 1m10. Working in a Multi-Threaded Environment0m To declare that multiple threads in an application will be using SMlib (or any other library layered on top of ICElib), you should call 4mIceInitThreads24m. For further information, see the 4mInter-Client24m 4mExchange24m 4mLibrary24m standard. 1m11. Acknowledgements0m 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 - 1mTable of Contents0m 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 . . . . . . . . . . 24 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 . . . . . . . . . . 31 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