[1mX Session Management Library[0m [1mVersion 1.0[0m [1mX Consortium Standard[0m [1mX Version 11, Release 6.4[0m [4mRalph[24m [4mMor[0m 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. [1m1. Overview of Session Management[0m The purpose of the X Session Management Protocol (XSMP) is to provide a uniform mechanism for users to save and restore their sessions. A [4msession[24m is a group of clients, each of which has a particular state. The session is controlled by a network service called the [4msession[24m [4mmanager[24m. 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 [4mclient[24m 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 Library[0m 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 [4mnested[24m [4msession[24m [4mmanagers[24m. 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-ID[24m 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 6.4[0m the client can be restarted (via an Clients are expected to save their state in such a way as to allow multiple instan- tiations of themselves to be managed independently. For example, clients may use their client-ID as part of a file- name in which to store the state for a particular instantia- tion. The client-ID should be saved as part of the 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 ICE[0m 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 function. will read the mes- sage header and look at the major opcode in order to deter- mine 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 call- back. 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 call on the file descriptor for the ICE connection, but more typi- cally, will be used to register a callback that will invoke each time there is data to read on the ICE connection. To further complicate things, knowing which file descriptors to call on requires an understanding of how ICE connections are created. On the client side, a call must be made to in order to open a connection with a session manager. will internally make a call into which will, in turn, determine if an ICE connection already exists between the client and session manager. Most likely, a connection will not already exist and a new ICE connection will be created. The main point to be aware of is that, on the client side, it is not obvious when ICE connections get created or destroyed, because connections are shared when possible. To deal with this, the ICE library lets the application register watch procedures that will be invoked each time an ICE connection is opened or closed. These watch procedures could be used to add or remove ICE file descriptors from the list of - 2 - [1mX Session Management Library X11, Release 6.4[0m descriptors to call 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 in order to start listening for connections from clients. Once a connection attempt is detected, must be called, and the session manager can simply add the new ICE file descrip- tor to the list of descriptors to call on. For further information on the library functions related to ICE connections, see the [4mInter-Client[24m [4mExchange[24m [4mLibrary[24m stan- dard. [1m4. Header Files and Library Name[0m Applications (both session managers and clients) should include the header file This header file defines all of the SMlib data structures and function prototypes. includes the header file which defines all of the SMlib constants. Because SMlib is dependent on ICE, applications should link against SMlib and ICElib by using [1m5. Session Management Client (Smc) Functions[0m 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 [1m5.1. Connecting to the Session Manager[0m To open a connection with a session manager, use __ || SmcConn SmcOpenConnection([4mnetwork_ids_list[24m, [4mcontext[24m, [4mxsmp_major_rev[24m, [4mxsmp_minor_rev[24m, - 3 - [1mX Session Management Library X11, Release 6.4[0m [4mmask[24m, [4mcallbacks[24m, [4mprevious_id[24m, [4mclient_id_ret[24m, [4merror_length[24m, [4merror_string_ret[24m) char *[4mnetwork_ids_list[24m; SmPointer [4mcontext[24m; int [4mxsmp_major_rev[24m; int [4mxsmp_minor_rev[24m; unsigned long [4mmask[24m; SmcCallbacks *[4mcallbacks[24m; char *[4mprevious_id[24m; char **[4mclient_id_ret[24m; int [4merror_length[24m; char *[4merror_string_ret[24m; [4mnetwork_ids_list[0m Specifies the network ID(s) of the session man- ager. [4mcontext[24m A pointer to an opaque object or NULL. Used to determine if an ICE connection can be shared (see below). [4mxsmp_major_rev[0m The highest major version of the XSMP the applica- tion supports. [4mxsmp_minor_rev[0m The highest minor version of the XSMP the applica- tion supports (for the specified xsmp_major_rev). [4mmask[24m A mask indicating which callbacks to register. [4mcallbacks[24m The callbacks to register. These callbacks are used to respond to messages from the session man- ager. [4mprevious_id[0m The client ID from the previous session. [4mclient_id_ret[0m The client ID for the current session is returned. [4merror_length[0m Length of the error_string_ret argument passed in. [4merror_string_ret[0m Returns a null-terminated error message, if any. The error_string_ret argument points to user sup- plied 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 - 4 - [1mX Session Management Library X11, Release 6.4[0m of the environment variable will be used. Each network ID has the following format: lw(0.25i) lw(2.5i) lw(1i). tcp/<hostname>:<portnum- ber> 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, registers the client with the session manager. If the client is being restarted from a previous session, previous_id should contain a null terminated string representing the client ID from the previ- ous session. If the client is first joining the session, previous_id should be set to NULL. If previous_id is speci- fied but is determined to be invalid by the session manager, SMlib will re-register the client with previous_id set to NULL. If succeeds, it returns an opaque connection pointer of type 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 when no longer needed. On failure, 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 and and will have to call each time a shows that there is data to read on an ICE connection. For further information, see the [4mInter-Client[24m [4mExchange[24m [4mLibrary[24m 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 - 5 - [1mX Session Management Library X11, Release 6.4[0m compatibility in future versions of the library. The following values may be ORed together to obtain a mask value: 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; ||__ [1m5.1.1. The Save Yourself Callback[0m The Save Yourself callback is of type __ || typedef void (*SmcSaveYourselfProc)(); void SaveYourselfProc([4msmc_conn[24m, [4mclient_data[24m, [4msave_type[24m, [4mshutdown[24m, [4minteract_style[24m, [4mfast[24m) SmcConn [4msmc_conn[24m; SmPointer [4mclient_data[24m; int [4msave_type[24m; Bool [4mshutdown[24m; int [4minteract_style[24m; Bool [4mfast[24m; [4msmc_conn[24m The session management connection object. [4mclient_data[0m Client data specified when the callback was regis- tered. [4msave_type[24m Specifies the type of information that should be saved. - 6 - [1mX Session Management Library X11, Release 6.4[0m [4mshutdown[24m Specifies if a shutdown is taking place. [4minteract_style[0m The type of interaction allowed with the user. [4mfast[24m If 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 to update the properties indicating how to restart the client. When all the properties have been set, the client calls If interact_style is the client must not interact with the user while saving state. If interact_style is the client may interact with the user only if an error condition arises. If interact_style is then the client may interact with the user for any purpose. Because only one client can interact with the user at a time, the client must call and wait for an ``Interact'' message from the session manager. When the client is done interacting with the user, it calls The client may only call after it receives a ``Save Your- self'' message and before it calls If save_type is 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 the user wants the client to commit all of its data to permanent, globally accessible storage. If save_type is 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 it could create a temporary file that included the current contents of the file, the location of the cursor, and other aspects of the current editing session. It would then update its SmRestartCommand property with enough information to find this temporary file. +o If a word processor were sent a ``Save Yourself'' with a type of it would simply save the currently edited file. +o If a word processor were sent a ``Save Yourself'' with a type of it would first save the currently edited - 7 - [1mX Session Management Library X11, Release 6.4[0m 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 infor- mation 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 [1m5.1.2. The Die Callback[0m The Die callback is of type __ || typedef void (*SmcDieProc)(); void DieProc([4msmc_conn[24m, [4mclient_data[24m) SmcConn [4msmc_conn[24m; SmPointer [4mclient_data[24m; [4msmc_conn[24m The session management connection object. [4mclient_data[0m 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 A session manager that behaves properly will send a ``Save Yourself'' message before the ``Die'' message. [1m5.1.3. The Save Complete Callback[0m The Save Complete callback is of type __ || typedef void (*SmcSaveCompleteProc)(); void SaveCompleteProc([4msmc_conn[24m, [4mclient_data[24m) SmcConn [4msmc_conn[24m; SmPointer [4mclient_data[24m; [4msmc_conn[24m The session management connection object. - 8 - [1mX Session Management Library X11, Release 6.4[0m [4mclient_data[0m 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 Callback[0m The Shutdown Cancelled callback is of type __ || typedef void (*SmcShutdownCancelledProc)(); void ShutdownCancelledProc([4msmc_conn[24m, [4mclient_data[24m) SmcConn [4msmc_conn[24m; SmPointer [4mclient_data[24m; [4msmc_conn[24m The session management connection object. [4mclient_data[0m 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 yet, it can either abort the save and then call with the success argument set to or it can continue with the save and then call with the success argument set to reflect the outcome of the save. [1m5.2. Closing the Connection[0m To close a connection with a session manager, use __ || SmcCloseStatus SmcCloseConnection([4msmc_conn[24m, [4mcount[24m, [4mrea-[0m [4mson_msgs[24m) SmcConn [4msmc_conn[24m; int [4mcount[24m; char **[4mreason_msgs[24m; [4msmc_conn[24m The session management connection object. [4mcount[24m The number of reason messages. [4mreason_msgs[0m The reasons for closing the connection. - 9 - [1mX Session Management Library X11, Release 6.4[0m ||__ 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 than session management may be active on the ICE connection. When is called, the ICE connection will be closed only if all protocols have been shutdown on the connection. Check the ICElib standard for and to learn how to set up a call- back 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 on (or calls or returns one of the following values: +o - the ICE connection was closed at this time, the watch procedures were invoked, and the connection was freed. +o - an IO error had occurred on the connection, but is being called within a nested 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 returns a status of +o - the connection was not closed at this time, because it is being used by other active protocols. [1m5.3. Modifying Callbacks[0m To modify callbacks set up in use __ || void SmcModifyCallbacks([4msmc_conn[24m, [4mmask[24m, [4mcallbacks[24m) SmcConn [4msmc_conn[24m; unsigned long [4mmask[24m; SmcCallbacks *[4mcallbacks[24m; [4msmc_conn[24m The session management connection object. [4mmask[24m A mask indicating which callbacks to modify. [4mcallbacks[24m The new callbacks. ||__ When specifying a value for the mask argument, the following values may be ORed together: - 10 - [1mX Session Management Library X11, Release 6.4[0m [1m5.4. Setting, Deleting, and Retrieving Session Management[0m [1mProperties[0m To set session management properties for this client, use __ || void SmcSetProperties([4msmc_conn[24m, [4mnum_props[24m, [4mprops[24m) SmcConn [4msmc_conn[24m; int [4mnum_props[24m; SmProp **[4mprops[24m; [4msmc_conn[24m The session management connection object. [4mnum_props[24m The number of properties. [4mprops[24m 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 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 structure, see section 7, ``Session Management Properties.'' To delete properties previously set by the client, use __ || void SmcDeleteProperties([4msmc_conn[24m, [4mnum_props[24m, [4mprop_names[24m) SmcConn [4msmc_conn[24m; int [4mnum_props[24m; char **[4mprop_names[24m; [4msmc_conn[24m The session management connection object. [4mnum_props[24m The number of properties. [4mprop_names[0m The list of properties to delete. ||__ To get properties previously stored by the client, use __ || Status SmcGetProperties([4msmc_conn[24m, [4mprop_reply_proc[24m, [4mclient_data[24m) SmcConn [4msmc_conn[24m; SmcPropReplyProc [4mprop_reply_proc[24m; SmPointer [4mclient_data[24m; - 11 - [1mX Session Management Library X11, Release 6.4[0m [4msmc_conn[24m The session management connection object. [4mprop_reply_proc[0m The callback to be invoked when the properties reply comes back. [4mclient_data[0m This pointer to client data will be passed to the callback. ||__ The return value of 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 is invoked when the data is ready. __ || typedef void (*SmcPropReplyProc)(); void PropReplyProc([4msmc_conn[24m, [4mclient_data[24m, [4mnum_props[24m, [4mprops[24m) SmcConn [4msmc_conn[24m; SmPointer [4mclient_data[24m; int [4mnum_props[24m; SmProp **[4mprops[24m; [4msmc_conn[24m The session management connection object. [4mclient_data[0m Client data specified when the callback was regis- tered. [4mnum_props[24m The number of properties returned. [4mprops[24m The list of properties returned. ||__ To free each property, use (see section 8, ``Freeing Data''). To free the actual array of pointers, use [1m5.5. Interacting With the User[0m After receiving a ``Save Yourself'' message with an inter- act_style of or 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 and wait for an ``Interact'' message from the session manager. __ || Status SmcInteractRequest([4msmc_conn[24m, [4mdialog_type[24m, [4minter-[0m [4mact_proc[24m, [4mclient_data[24m) SmcConn [4msmc_conn[24m; int [4mdialog_type[24m; SmcInteractProc [4minteract_proc[24m; SmPointer [4mclient_data[24m; - 12 - [1mX Session Management Library X11, Release 6.4[0m [4msmc_conn[24m The session management connection object. [4mdialog_type[0m The type of dialog the client wishes to present to the user. [4minteract_proc[0m The callback to be invoked when the ``Interact'' message arrives from the session manager. [4mclient_data[0m This pointer to client data will be passed to the callback when the ``Interact'' message arrives. ||__ The return value of is zero for failure and a positive value for success. The dialog_type argument specifies either indicating that the client wants to start an error dialog, or 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 callback will be invoked when the ``Interact'' message arrives from the session manager. __ || typedef void (*SmcInteractProc)(); void InteractProc([4msmc_conn[24m, [4mclient_data[24m) SmcConn [4msmc_conn[24m; SmPointer [4mclient_data[24m; [4msmc_conn[24m The session management connection object. [4mclient_data[0m Client data specified when the callback was regis- tered. ||__ After interacting with the user (in response to an ``Inter- act'' message), you should call __ || void SmcInteractDone([4msmc_conn[24m, [4mcancel_shutdown[24m) SmcConn [4msmc_conn[24m; Bool [4mcancel_shutdown[24m; [4msmc_conn[24m The session management connection object. - 13 - [1mX Session Management Library X11, Release 6.4[0m [4mcancel_shutdown[0m If indicates that the user requests that the entire shutdown be cancelled. ||__ The cancel_shutdown argument may only be if the correspond- ing ``Save Yourself'' specified for shutdown and or for the interact_style. [1m5.6. Requesting a Save Yourself[0m To request a checkpoint from the session manager, use __ || void SmcRequestSaveYourself([4msmc_conn[24m, [4msave_type[24m, [4mshutdown[24m, [4minteract_style[24m, [4mfast[24m, [4mglobal[24m) SmcConn [4msmc_conn[24m; int [4msave_type[24m; Bool [4mshutdown[24m; int [4minteract_style[24m; Bool [4mfast[24m; Bool [4mglobal[24m; [4msmc_conn[24m The session management connection object. [4msave_type[24m Specifies the type of information that should be saved. [4mshutdown[24m Specifies if a shutdown is taking place. [4minteract_style[0m The type of interaction allowed with the user. [4mfast[24m If the client should save its state as quickly as possible. [4mglobal[24m 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 then the resulting ``Save Yourself'' should be sent to all clients in the session. For example, a vendor of a Uninterruptible Power Supply (UPS) might include a Session Management client that would monitor the status of the UPS and generate a fast shutdown if the power is about to be lost. If global is set to then the ``Save Yourself'' should only be sent to the client that requested it. - 14 - [1mX Session Management Library X11, Release 6.4[0m [1m5.7. Requesting a Save Yourself Phase 2[0m 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 __ || Status SmcRequestSaveYourselfPhase2([4msmc_conn[24m, [4msave_your-[0m [4mself_phase2_proc[24m, [4mclient_data[24m) SmcConn [4msmc_conn[24m; SmcSaveYourselfPhase2Proc [4msave_yourself_phase2_proc[24m; SmPointer [4mclient_data[24m; [4msmc_conn[24m The session management connection object. [4msave_yourself_phase2_proc[0m The callback to be invoked when the ``Save Your- self Phase 2'' message arrives from the session manager. [4mclient_data[0m This pointer to client data will be passed to the callback when the ``Save Yourself Phase 2'' mes- sage arrives. ||__ The return value of 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 Yourself[0m After saving state in response to a ``Save Yourself'' mes- sage, you should call __ || void SmcSaveYourselfDone([4msmc_conn[24m, [4msuccess[24m) SmcConn [4msmc_conn[24m; Bool [4msuccess[24m; [4msmc_conn[24m The session management connection object. [4msuccess[24m If the ``Save Yourself'' operation was completed successfully. ||__ Before calling the client must have set each required prop- erty at least once since the client registered with the ses- sion manager. - 15 - [1mX Session Management Library X11, Release 6.4[0m [1m5.9. Using Smc Informational Functions[0m __ || int SmcProtocolVersion([4msmc_conn[24m) ||__ SmcConn [4msmc_conn[24m; returns the major version of the session management protocol associated with this session. __ || int SmcProtocolRevision([4msmc_conn[24m) ||__ SmcConn [4msmc_conn[24m; returns the minor version of the session management protocol associated with this session. __ || char *SmcVendor([4msmc_conn[24m) ||__ SmcConn [4msmc_conn[24m; returns a string that provides some identification of the owner of the session manager. The string should be freed with a call to __ || char *SmcRelease([4msmc_conn[24m) ||__ SmcConn [4msmc_conn[24m; returns a string that provides the release number of the session manager. The string should be freed with a call to __ || char *SmcClientID([4msmc_conn[24m) ||__ SmcConn [4msmc_conn[24m; returns a null-terminated string for the client ID associ- ated with this connection. This information was also returned in (it is provided here for convenience). Call on this pointer when the client ID is no longer needed. __ || IceConn SmcGetIceConnection([4msmc_conn[24m) ||__ SmcConn [4msmc_conn[24m; returns the ICE connection object associated with this ses- sion 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 and For further information, see - 16 - [1mX Session Management Library X11, Release 6.4[0m the [4mInter-Client[24m [4mExchange[24m [4mLibrary[24m standard. [1m5.10. Error Handling[0m If the client receives an unexpected protocol error from the session manager, an error handler is invoked by SMlib. A default error handler exists that simply prints the error message to and exits if the severity of the error is fatal. The client can change this error handler by calling the function. __ || SmcErrorHandler SmcSetErrorHandler([4mhandler[24m) SmcErrorHandler [4mhandler[24m; [4mhandler[24m The error handler. You should pass NULL to restore the default handler. ||__ returns the previous error handler. The has the following type: __ || typedef void (*SmcErrorHandler)(); void ErrorHandler([4msmc_conn[24m, [4mswap[24m, [4moffending_minor_opcode[24m, [4moffending_sequence_num[24m, [4merror_class[24m, [4mseverity[24m, [4mvalues[24m) SmcConn [4msmc_conn[24m; Bool [4mswap[24m; int [4moffending_minor_opcode[24m; unsigned long [4moffending_sequence_num[24m; int [4merror_class[24m; int [4mseverity[24m; IcePointer [4mvalues[24m; [4msmc_conn[24m The session management connection object. [4mswap[24m A flag that indicates if the specified values need byte swapping. [4moffending_minor_opcode[0m The minor opcode of the offending message. [4moffending_sequence_num[0m The sequence number of the offending message. [4merror_class[0m The error class of the offending message. [4mseverity[24m or [4mvalues[24m Any additional error values specific to the minor opcode and class. - 17 - [1mX Session Management Library X11, Release 6.4[0m ||__ 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 For further information, see the [4mInter-[0m [4mClient[24m [4mExchange[24m [4mLibrary[24m standard. [1m6. Session Management Server (Sms) Functions[0m 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 [1m6.1. Initializing the Library[0m is the first SMlib function that should be called by a ses- sion manager. It provides information about the session manager and registers a callback that will be invoked each time a new client connects to the session manager. __ || Status SmsInitialize([4mvendor[24m, [4mrelease[24m, [4mnew_client_proc[24m, [4mman-[0m [4mager_data[24m, [4mhost_based_auth_proc[24m, [4merror_length[24m, [4merror_string_ret[24m) char *[4mvendor[24m; char *[4mrelease[24m; SmsNewClientProc [4mnew_client_proc[24m; SmPointer [4mmanager_data[24m; IceHostBasedAuthProc [4mhost_based_auth_proc[24m; int [4merror_length[24m; char *[4merror_string_ret[24m; - 18 - [1mX Session Management Library X11, Release 6.4[0m [4mvendor[24m A string specifying the session manager vendor. [4mrelease[24m A string specifying the session manager release number. [4mnew_client_proc[0m Callback to be invoked each time a new client con- nects to the session manager. [4mmanager_data[0m When the callback is invoked, this pointer to man- ager data will be passed. [4mhost_based_auth_proc[0m Host based authentication callback. [4merror_length[0m Length of the error_string_ret argument passed in. [4merror_string_ret[0m 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 function is called, the session manager should call the function to listen for new connections. After- wards, each time a client connects, the session manager should call See section 9, ``Authentication of Clients,'' for more details on authentication (including host based authentica- tion). Also see the [4mInter-Client[24m [4mExchange[24m [4mLibrary[24m standard for further details on listening for and accepting ICE con- nections. Each time a new client connects to the session manager, the 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 man- ager must also register a set of callbacks to respond to the different messages that the client might send. __ || typedef Status (*SmsNewClientProc)(); Status NewClientProc([4msms_conn[24m, [4mmanager_data[24m, [4mmask_ret[24m, [4mcall-[0m [4mbacks_ret[24m, [4mfailure_reason_ret[24m) SmsConn [4msms_conn[24m; SmPointer [4mmanager_data[24m; unsigned long *[4mmask_ret[24m; SmsCallbacks *[4mcallbacks_ret[24m; char **[4mfailure_reason_ret[24m; - 19 - [1mX Session Management Library X11, Release 6.4[0m [4msms_conn[24m A new opaque connection object. [4mmanager_data[0m Manager data specified when the callback was reg- istered. [4mmask_ret[24m On return, indicates which callbacks were set by the session manager. [4mcallbacks_ret[0m On return, contains the callbacks registered by the session manager. [4mfailure_reason_ret[0m Failure reason returned. ||__ If a failure occurs, the should return a zero status as well as allocate and return a failure reason string in fail- ure_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: 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 { SmsRegisterClient- Proc callback; SmPointer manager_data; } reg- ister_client; struct { SmsInteractRequestProc callback; SmPointer manager_data; } interact_request; struct { SmsInteractDoneProc callback; SmPointer manager_data; } interact_done; struct { SmsSaveYourselfRequestProc callback; SmPointer manager_data; } save_your- self_request; struct { SmsSaveYourselfPhase2RequestProc - 20 - [1mX Session Management Library X11, Release 6.4[0m 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; ||__ [1m6.1.1. The Register Client Callback[0m The Register Client callback is the first callback that will be invoked after the client connects to the session manager. Its type is __ || typedef Status (*SmsRegisterClientProc(); Status RegisterClientProc([4msms_conn[24m, [4mmanager_data[24m, [4mprevi-[0m [4mous_id[24m) SmsConn [4msms_conn[24m; SmPointer [4mmanager_data[24m; char *[4mprevious_id[24m; [4msms_conn[24m The session management connection object. [4mmanager_data[0m Manager data specified when the callback was reg- istered. [4mprevious_id[0m 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 on the previous_id pointer when it is no longer needed. If the client is first joining the session, previous_id will be - 21 - [1mX Session Management Library X11, Release 6.4[0m 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 function (to be dis- cussed shortly), and the callback should return a status of one. [1m6.1.2. The Interact Request Callback[0m The Interact Request callback is of type __ || typedef void (*SmsInteractRequestProc)(); void InteractRequestProc([4msms_conn[24m, [4mmanager_data[24m, [4mdia-[0m [4mlog_type[24m) SmsConn [4msms_conn[24m; SmPointer [4mmanager_data[24m; int [4mdialog_type[24m; [4msms_conn[24m The session management connection object. [4mmanager_data[0m Manager data specified when the callback was reg- istered. [4mdialog_type[0m 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 or 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 indicating that the client wants to start an error dialog, or 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. - 22 - [1mX Session Management Library X11, Release 6.4[0m [1m6.1.3. The Interact Done Callback[0m When the client is done interacting with the user, the call- back will be invoked. __ || typedef void (*SmsInteractDoneProc)(); void InteractDoneProc([4msms_conn[24m, [4mmanager_data[24m, [4mcancel_shut-[0m [4mdown[24m) SmsConn [4msms_conn[24m; SmPointer [4mmanager_data[24m; Bool [4mcancel_shutdown[24m; [4msms_conn[24m The session management connection object. [4mmanager_data[0m Manager data specified when the callback was reg- istered. [4mcancel_shutdown[0m 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 for shutdown and or for the interact_style. [1m6.1.4. The Save Yourself Request Callback[0m The Save Yourself Request callback is of type __ || typedef void (*SmsSaveYourselfRequestProc)(); void SaveYourselfRequestProc([4msms_conn[24m, [4mmanager_data[24m, [4msave_type[24m, [4mshutdown[24m, [4minteract_style[24m, [4mfast[24m, [4mglobal[24m) SmsConn [4msms_conn[24m; SmPointer [4mmanager_data[24m; int [4msave_type[24m; Bool [4mshutdown[24m; int [4minteract_style[24m; Bool [4mfast[24m; Bool [4mglobal[24m; [4msms_conn[24m The session management connection object. [4mmanager_data[0m Manager data specified when the callback was reg- istered. [4msave_type[24m Specifies the type of information that should be saved. - 23 - [1mX Session Management Library X11, Release 6.4[0m [4mshutdown[24m Specifies if a shutdown is taking place. [4minteract_style[0m The type of interaction allowed with the user. [4mfast[24m If the client should save its state as quickly as possible. [4mglobal[24m 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 then the resulting ``Save Yourself'' should be sent to all applications. If global is set to then the ``Save Yourself'' should only be sent to the client that requested it. [1m6.1.5. The Save Yourself Phase 2 Request Callback[0m The Save Yourself Phase 2 Request callback is of type __ || typedef void (*SmsSaveYourselfPhase2RequestProc)(); void SmsSaveYourselfPhase2RequestProc([4msms_conn[24m, [4mman-[0m [4mager_data[24m) SmsConn [4msms_conn[24m; SmPointer [4mmanager_data[24m; [4msms_conn[24m The session management connection object. [4mmanager_data[0m 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 Callback[0m When the client is done saving its state in response to a ``Save Yourself'' message, the will be invoked. __ || typedef void (*SmsSaveYourselfDoneProc)(); void SaveYourselfDoneProc([4msms_conn[24m, [4mmanager_data[24m, [4msuccess[24m) SmsConn [4msms_conn[24m; - 24 - [1mX Session Management Library X11, Release 6.4[0m SmPointer [4mmanager_data[24m; Bool [4msuccess[24m; [4msms_conn[24m The session management connection object. [4mmanager_data[0m Manager data specified when the callback was reg- istered. [4msuccess[24m If the Save Yourself operation was completed suc- cessfully. ||__ 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 Callback[0m If the client properly terminates (that is, it calls the callback is invoked. __ || typedef void (*SmsCloseConnectionProc)(); void CloseConnectionProc([4msms_conn[24m, [4mmanager_data[24m, [4mcount[24m, [4mrea-[0m [4mson_msgs[24m) SmsConn [4msms_conn[24m; SmPointer [4mmanager_data[24m; int [4mcount[24m; char **[4mreason_msgs[24m; [4msms_conn[24m The session management connection object. [4mmanager_data[0m Manager data specified when the callback was reg- istered. [4mcount[24m The number of reason messages. [4mreason_msgs[0m 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 to free the reason messages. For further information, see section 8, ``Freeing Data.'' - 25 - [1mX Session Management Library X11, Release 6.4[0m [1m6.1.8. The Set Properties Callback[0m When the client sets session management properties, the callback will be invoked. __ || typedef void (*SmsSetPropertiesProc)(); void SetPropertiesProc([4msms_conn[24m, [4mmanager_data[24m, [4mnum_props[24m, [4mprops[24m) SmsConn [4msms_conn[24m; SmPointer [4mmanager_data[24m; int [4mnum_props[24m; SmProp **[4mprops[24m; [4msmc_conn[24m The session management connection object. [4mmanager_data[0m Manager data specified when the callback was reg- istered. [4mnum_props[24m The number of properties. [4mprops[24m 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 structure, see section 7, ``Session Management Proper- ties.'' 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 For further information, see sec- tion 8, ``Freeing Data.'' You should free the actual array of pointers with a call to [1m6.1.9. The Delete Properties Callback[0m When the client deletes session management properties, the callback will be invoked. __ || typedef void (*SmsDeletePropertiesProc)(); void DeletePropertiesProc([4msms_conn[24m, [4mmanager_data[24m, [4mnum_props[24m, [4mprop_names[24m) SmsConn [4msms_conn[24m; SmPointer [4mmanager_data[24m; int [4mnum_props[24m; char **[4mprop_names[24m; [4msmc_conn[24m The session management connection object. - 26 - [1mX Session Management Library X11, Release 6.4[0m [4mmanager_data[0m Manager data specified when the callback was reg- istered. [4mnum_props[24m The number of properties. [4mprop_names[0m The list of properties to delete. ||__ The properties are specified as an array of strings. For a description of session management properties and the struc- ture, see section 7, ``Session Management Properties.'' [1m6.1.10. The Get Properties Callback[0m The callback is invoked when the client wants to retrieve properties it set. __ || typedef void (*SmsGetPropertiesProc)(); void GetPropertiesProc([4msms_conn[24m, [4mmanager_data[24m) SmsConn [4msms_conn[24m; SmPointer [4mmanager_data[24m; [4msmc_conn[24m The session management connection object. [4mmanager_data[0m Manager data specified when the callback was reg- istered. ||__ The session manager should respond by calling All of the properties set for this client should be returned. [1m6.2. Registering the Client[0m To register a client (in response to a callback), use __ || Status SmsRegisterClientReply([4msms_conn[24m, [4mclient_id[24m) SmsConn [4msms_conn[24m; char *[4mclient_id[24m; [4msms_conn[24m The session management connection object. [4mclient_id[24m A null-terminated string representing a unique client ID. ||__ The return value of is zero for failure and a positive value for success. Failure will occur if SMlib can not allocate memory to hold a copy of the client ID for it's own internal needs. - 27 - [1mX Session Management Library X11, Release 6.4[0m 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 function to generate a globally unique client ID. __ || char *SmsGenerateClientID([4msms_conn[24m) SmsConn [4msms_conn[24m; [4msms_conn[24m 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 when no longer needed. [1m6.3. Sending a Save Yourself Message[0m To send a ``Save Yourself'' to a client, use __ || void SmsSaveYourself([4msms_conn[24m, [4msave_type[24m, [4mshutdown[24m, [4minter-[0m [4mact_style[24m, [4mfast[24m) SmsConn [4msms_conn[24m; int [4msave_type[24m; Bool [4mshutdown[24m; int [4minteract_style[24m; Bool [4mfast[24m; [4msms_conn[24m The session management connection object. [4msave_type[24m Specifies the type of information that should be saved. [4mshutdown[24m Specifies if a shutdown is taking place. - 28 - [1mX Session Management Library X11, Release 6.4[0m [4minteract_style[0m The type of interaction allowed with the user. [4mfast[24m If 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 the client must not interact with the user while saving state. If interact_style is the client may interact with the user only if an error condition arises. If interact_style is then the client may interact with the user for any purpose. The client must send an ``Interact Request'' message and wait for an ``Interact'' message from the session manager before it can interact with the user. When the client is done interacting with the user, it should send an ``Interact Done'' message. The ``Interact Request'' message can be sent any time after a ``Save Yourself'' and before a ``Save Yourself Done.'' If save_type is 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 the user wants the client to commit all of its data to permanent, globally accessible storage. If save_type is 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 - 29 - [1mX Session Management Library X11, Release 6.4[0m [1m6.4. Sending a Save Yourself Phase 2 Message[0m In order to send a ``Save Yourself Phase 2'' message to a client, use __ || void SmsSaveYourselfPhase2([4msms_conn[24m) SmsConn [4msms_conn[24m; [4msms_conn[24m 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 Message[0m To send an ``Interact'' message to a client, use __ || void SmsInteract([4msms_conn[24m) SmsConn [4msms_conn[24m; [4msms_conn[24m 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. [1m6.6. Sending a Save Complete Message[0m To send a ``Save Complete'' message to a client, use __ || void SmsSaveComplete([4msms_conn[24m) SmsConn [4msms_conn[24m; [4msms_conn[24m 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 Message[0m To send a ``Die'' message to a client, use __ || void SmsDie([4msms_conn[24m) SmsConn [4msms_conn[24m; [4msms_conn[24m The session management connection object. - 30 - [1mX Session Management Library X11, Release 6.4[0m ||__ 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 Shutdown[0m To cancel a shutdown, use __ || void SmsShutdownCancelled([4msms_conn[24m) SmsConn [4msms_conn[24m; [4msms_conn[24m 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 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. [1m6.9. Returning Properties[0m In response to a ``Get Properties'' message, the session manager should call __ || void SmsReturnProperties([4msms_conn[24m, [4mnum_props[24m, [4mprops[24m) SmsConn [4msms_conn[24m; int [4mnum_props[24m; SmProp **[4mprops[24m; [4msms_conn[24m The session management connection object. [4mnum_props[24m The number of properties. [4mprops[24m 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 structure, see section 7, ``Session Management Proper- ties.'' [1m6.10. Pinging a Client[0m To check that a client is still alive, you should use the function provided by the ICE library. To do so, the ICE connection must be obtained using the (see section 6.12, ``Using Sms Informational Functions''). - 31 - [1mX Session Management Library X11, Release 6.4[0m __ || void IcePing([4mice_conn[24m, [4mping_reply_proc[24m, [4mclient_data[24m) IceConn [4mice_conn[24m; IcePingReplyProc [4mping_reply_proc[24m; IcePointer [4mclient_data[24m; [4mice_conn[24m A valid ICE connection object. [4mping_reply_proc[0m The callback to invoke when the Ping reply arrives. [4mclient_data[0m This pointer will be passed to the callback. ||__ When the Ping reply is ready (if ever), the callback will be invoked. A session manager should have some sort of timeout period, after which it assumes the client has unexpectedly died. __ || typedef void (*IcePingReplyProc)(); void PingReplyProc([4mice_conn[24m, [4mclient_data[24m) IceConn [4mice_conn[24m; IcePointer [4mclient_data[24m; [4mice_conn[24m The ICE connection object. [4mclient_data[0m The client data specified in the call to ||__ [1m6.11. Cleaning Up After a Client Disconnects[0m When the session manager receives a ``Connection Closed'' message or otherwise detects that the client aborted the connection, it should call the function in order to free up the connection object. __ || void SmsCleanUp([4msms_conn[24m) SmsConn [4msms_conn[24m; [4msms_conn[24m The session management connection object. ||__ [1m6.12. Using Sms Informational Functions[0m __ || int SmsProtocolVersion([4msms_conn[24m) SmsConn [4msms_conn[24m; - 32 - [1mX Session Management Library X11, Release 6.4[0m ||__ returns the major version of the session management protocol associated with this session. __ || int SmsProtocolRevision([4msms_conn[24m) SmsConn [4msms_conn[24m; ||__ returns the minor version of the session management protocol associated with this session. __ || char *SmsClientID([4msms_conn[24m) SmsConn [4msms_conn[24m; ||__ returns a null-terminated string for the client ID associ- ated with this connection. You should call on this pointer when the client ID is no longer needed. To obtain the host name of a client, use This host name will be needed to restart the client. __ || char *SmsClientHostName([4msms_conn[24m) ||__ SmsConn [4msms_conn[24m; The string returned is of the form [4mprotocol[24m/[4mhostname[24m, where [4mprotocol[24m is one of {tcp, decnet, local}. You should call on the string returned when it is no longer needed. __ || IceConn SmsGetIceConnection([4msms_conn[24m) ||__ SmsConn [4msms_conn[24m; returns the ICE connection object associated with this ses- sion 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 and For further information, see the [4mInter-Client[24m [4mExchange[24m [4mLibrary[24m standard. [1m6.13. Error Handling[0m 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 - 33 - [1mX Session Management Library X11, Release 6.4[0m this error handler by calling __ || SmsErrorHandler SmsSetErrorHandler([4mhandler[24m) SmsErrorHandler [4mhandler[24m; [4mhandler[24m The error handler. You should pass NULL to restore the default handler. ||__ returns the previous error handler. The has the following type: __ || typedef void (*SmsErrorHandler)(); void ErrorHandler([4msms_conn[24m, [4mswap[24m, [4moffending_minor_opcode[24m, [4moffending_sequence_num[24m, [4merror_class[24m, [4mseverity[24m, [4mvalues[24m) SmsConn [4msms_conn[24m; Bool [4mswap[24m; int [4moffending_minor_opcode[24m; unsigned long [4moffending_sequence_num[24m; int [4merror_class[24m; int [4mseverity[24m; IcePointer [4mvalues[24m; [4msms_conn[24m The session management connection object. [4mswap[24m A flag which indicates if the specified values need byte swapping. [4moffending_minor_opcode[0m The minor opcode of the offending message. [4moffending_sequence_num[0m The sequence number of the offending message. [4merror_class[0m The error class of the offending message. [4mseverity[24m or [4mvalues[24m 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 For further information, see the [4mInter-[0m [4mClient[24m [4mExchange[24m [4mLibrary[24m standard. [1m7. Session Management Properties[0m Each property is defined by the structure: - 34 - [1mX Session Management Library X11, Release 6.4[0m typedef struct { char *name; /* name of prop- erty */ 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. l l l c . _ [1mName Type POSIX Type Required[0m _ SmCloneCommand OS-specific SmLISTofARRAY8 Yes SmCurrent- Directory OS-specific SmARRAY8 No SmDiscardCom- mand OS-specific SmLISTofARRAY8 No* SmEnvironment OS- specific SmLISTofARRAY8 No SmProcessID OS-spe- cific SmARRAY8 No SmProgram OS-specific SmARRAY8 Yes SmRestartCommand OS-specific SmLISTofARRAY8 Yes SmRe- signCommand OS-specific SmLISTofARRAY8 No SmRestart- StyleHint SmCARD8 SmCARD8 No SmShutdownCommand OS- specific SmLISTofARRAY8 No SmUserID SmARRAY8 SmAR- RAY8 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 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. - 35 - [1mX Session Management Library X11, Release 6.4[0m +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 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 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 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 undoes the effect of the client and removes any saved state. As an example, consider a user that runs which registers with the Session Manager, sets SmRestart- StyleHint to SmRestartAnyway, and then terminates. To allow the Session Manager (at the user's request) to undo this, would register a SmResignCommand that undoes the effects of the +o SmRestartStyleHint - 36 - [1mX Session Management Library X11, Release 6.4[0m 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: l n. _ [1mName Value[0m [1m_[0m SmRestartIfRunning 0 SmRestartAnyway 1 SmRestar- tImmediately 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 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 - 37 - [1mX Session Management Library X11, Release 6.4[0m Specifies the user ID. On POSIX-based systems, this will contain the user's name (the pw_name member of struct [1m8. Freeing Data[0m To free an individual property, use __ || void SmFreeProperty([4mprop[24m) SmProp *[4mprop[24m; [4mprop[24m The property to free. ||__ To free the reason strings from the callback, use __ || void SmFreeReasons([4mcount[24m, [4mreasons[24m) int [4mcount[24m; char **[4mreasons[24m; [4mcount[24m The number of reason strings. [4mreasons[24m The list of reason strings to free. ||__ [1m9. Authentication of Clients[0m 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. 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-Client[24m [4mExchange[24m [4mLibrary[24m standard. [1m10. Working in a Multi-Threaded Environment[0m To declare that multiple threads in an application will be using SMlib (or any other library layered on top of ICElib), you should call For further information, see the [4mInter-[0m [4mClient[24m [4mExchange[24m [4mLibrary[24m standard. [1m11. Acknowledgements[0m Thanks to the following people for their participation in the X Session Management design: Jordan Brown, Ellis Cohen, - 38 - [1mX Session Management Library X11, Release 6.4[0m Donna Converse, Stephen Gildea, Vania Joloboff, Stuart Marks, Bob Scheifler, Ralph Swick, and Mike Wexler. - 39 -