This is the LASH Audio Session Handler Reference Manual, Edition 0.5.1, March 2006 for LASH version 0.5.1.

Copyright © 2002, 2003 Robert Ham (rah@bash.sh) Copyright © 2005, 2006 Dave Robillard (drobilla@connect.carleton.ca)

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled ``GNU Free Documentation License''.

This is the LASH Audio Session Handler Reference Manual, edition 0.5.1, March 2006 for LASH version 0.5.1.

http://www.nongnu.org/lash

Introduction
************

LASH stands for LASH Audio Session Handler.  It is a session management system for audio applications on GNU/Linux.  It understands the JACK low latency audio API and the ALSA MIDI sequencer interface. The system is comprised of a server program, lashd, an application library, liblash, and a control program - either the command-line lash_control or the GTK lash_panel.  The server and clients communicate over TCP sockets.  There are three kinds of clients: normal clients (audio applications), user interfaces for the server, and connection patchbays.

Nomenclature
============

In order to describe the system, we should introduce some terminology. First of all, the server is the lashd server program, an omni-present marshaller and database for storing arbitrary application data.  The library is the liblash shared library. It contains all the functions that an application uses to communicate with the server and take part in the system.  Such an application is called a client.

The server deals with things in terms of collections of clients, called projects.  A project has a unique string name, a current directory and a list of clients that are in that project.  The server can have one client that is a server interface that allows the user to control the server.  There are two server interface included with the system, the lash_control command-line interface, and the lash_panel GTK interface.

Copying LASH
************

LASH is distributed under the GNU General Public License.  A copy of the license text is provided in the file COPYING along with the software source code, or you can get a copy by writing to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

In plain english, the GPL basically restricts you from restricting other people's use of the LASH source code (ie, all of LASH), and any additions you make to the code, including linking with the LASH library.  If you use code from this software, your software must be relased under the GPL. If you modify this software and release it, your modifications must be released under the GPL. If you release software linked against the LASH library, your software must be released under the GPL.

Note that this in no way restricts those people who want to release non-free LASH clients.  LASH operates using a well defined protocol over TCP sockets.  The high-level protocol is described within this document and the lower-level bit-wise protocol can be garnered from the source itself.

Installation
************

This chapter describes how to get LASH installed on your system.

Dependencies
============

LASH depends on the ALSA library, the JACK library, a unique ID library called libuuid and the XML library libxml2.  You need these installed before attempting to install LASH.

ALSA is available from http://www.alsa-project.org/.

JACK is available from http://jackit.sf.net/.

The libuuid library is included with the ubiquitous e2fsprogs package, but if this is not installed on your system, it is available from http://e2fsprogs.sf.net/.  The libxml2 library is available from http://www.xmlsoft.org/.

The LASH Control client depends on the GNU Readline library, available from ftp://ftp.gnu.org/pub/gnu/readline/.

The LASH GTK Test Client, LASH Save Button, and LASH Panel all depend on the GTK+ 2 toolkit, available from ftp://ftp.gtk.org/pub/gtk/v2.0/. The LASH Synth client has an optional GUI which also uses the GTK+ 2 toolkit.

Installation
============

First off, you need to download the package.  It is available from the LASH webpage, http://www.nongnu.org/lash.  After you have downloaded it, unpack the tarball into a directory using tar -xzf /where/ever/you/put/lash-0.5.1.tar.gz and change into the source directory with cd lash-0.5.1.

The package uses the GNU autotools for configuration and makefile creation.  In order to install the package, you must complete three steps: configuration; building; and installing.

Configuration
-------------

To configure the package, there is a shell script named configure in the top source directory.  It is a standard GNU autoconf configure script, and so accepts the standard GNU configuration options (such as --prefix, --datadir, etc.)  To run it type ./configure and add any options. The non-standard options that the script recognises are described below. Running the script with the --help option will also provide a quick summary of the recognised options.

Configure script options
........................

--disable-gtk2 Prevents the configure script from
     checking for the presence of the GTK+ 2 toolkit and disables the building of any code that relies on it.

--enable-debug Causes the library, server and clients to be built
     with debugging output.  This is not very useful and only recommended for developers working on the LASH code itself.

--with-default-dir=DIR Specifies the default directory, relative
     to \$HOME under which the server will create new project directories. Without this option, the value defaults to audio-projects.

--disable-serv-inst The LASH server and library look up port
     addresses for the LASH service using standard system calls that refer to the /etc/services database.  If /etc/services does not contain a valid entry, an error will result.  By default, the installation routine will install a service entry if one does not exist. This flag disables that action.

Building
--------

To build the package, simply type make in the top source directory.  This will build the server, the library and the clients that are compatible with the resources found by the configure script.

Installing
----------

To install the package, type make install in the top source directory.  By default the package installation prefix is /usr/local but the --prefix option to the configure script will change this.  The lashd server and the clients that were built are installed in PREFIX/bin. The liblash client library is installed in PREFIX/lib. The C header files for the client library are installed under PREFIX/include.  This manual is installed under PREFIX/info.

With make install, the package is installed with debugging symbols in the object files.  To save space, you can install with make install-strip to install the object files without debugging symbols.

Server
******

The LASH server is called lashd.

Server interface
****************

For a command line interface, run the command lashd_control. There is a help command.

For a graphical interface, run the command lash_panel. It should be relatively self-explanatory.

Client reference
****************

This chapter provides a programming guide and library reference for programmers of LASH clients.

Operational overview
====================

In this section we give an overview of how the LASH system operates, describing the server and client objects and operations that make it work.  The lashd server must be running in order for clients to participate in the system; clients cannot interoperate soley between themselves.  The server maintains a list of connected clients and a list of projects with which these clients are associated.

The server and clients exchange events and configs over their connections. There is one, and only one, bi-directional connection between a client and the server.  The transport for this connection is currently TCP.

An event is a very simple object having two relevant properties: a type and an optional arbitrary character string.  The type defines what the event means to the recipient, and the string allows additional information to be included with it.  For example, if a client wishes the server to save the current project, it sends a LASH_Save event to the server.  While saving the project, the server may wish to tell a client to save its data in a certain directory.  To so, it sends a LASH_Save_File event to the client with a string containing the name of a directory into which the client should save its data files.

Clients can save data on the server if they wish.  To do this, the client declares that it wants to save data on the server when it initialises the server connection and then later sends one or more configs to the server.  A config is also a very simple object. It has a client-unique character string key, and a value of arbitrary size and type (well, almost arbitrary; its size must be able to be described by a uint32_t integer due to byte-order conversions done when sending data over the network.)

Session example
---------------

In this section we will examine a typical session in some detail, describing the server and client operations that take place.  In the session, the server is started, a number of clients connect, the session is saved and then restored.

Starting up the server
......................

Before all else, the user starts the server.  It starts up and begins listening for connections from clients.  It doesn't do much else.

To keep track of what is happening with LASH, the user can run the lash_panel program (though this is not necessary, and it can be started later at any time).

The environment variable LASH_START_SERVER can be set to have any LASH client automatically start the server if one isn't already running. Doing this you can simply put lash_panel (or any other LASH client) in your applications menu and have LASH automatically work without having to remember to start the server manually.

If you're using a Bourne compatible shell like bash (if you don't know, you probably are) you can enable auto-start with the following command:

export LASH_START_SERVER=1

If you would like to always have the server started, put that command in the file ~/.bashrc (or in /etc/profile if you are root and want it set system wide) to have it run whenever a new shell is started.

A client connection
...................

The user then starts a JACK client program.  It opens a connection to the server and provides it with all information that the server will need to run the application again.  This information includes: the current directory that the user was in when they ran the program, the command line that started the application and the class of the client (a character string that the client application provides the initialisation routine that will never change over all initialisations.)

With this information is included a set of flags that describe the client to the server.  This particular client saves data to files and wants the server to tell it where to save files when the project is saved, so it has the LASH_Config_File flag set.

The client library starts two threads for communication with the server, one for sending data and the other for recieving.  It also sends, along with the client supplied data, a number of parameters that were extracted from the client's command line options before it checked them. This optionally includes the name of the project that the client should initially be associated with and a 128-bit, world-unique identifier for this particular client instance (the LASH ID.)

Server-side, the server wakes up to the fact that a new connection has arrived and immediately adds it to a list of open connections and then goes back to waiting.  When the client sends the requisite information, the server looks at it and decides what to do with the client. This client has not requested a specific project to which it should be connected.  However, there are no existing projects so the server creates a new project with the name project-1 in the directory /home/USER/audio-projects/project-1 (assuming the user didn't specify a different default directory when running configure.) It also generates a new LASH ID for the client.  It then adds the client to the new project and goes back to listening.

If the user has the lash_panel client running, the new project will appear as a tab with the title project-1, and the new client will appear in the client list for that project.

The client then connects up to the JACK server and, after having done this, sends a LASH_Jack_Client_Name event to the server with the name that it registered to JACK with as the string.  This notifies the server that it is a JACK client and needs its JACK port connections saved and restored.  The server will now pay attention to any activity regarding the client (ie, port creation and destruction and port connection and disconnection.)

Another client
..............

The user then starts a second client that uses the ALSA sequencer interface and wishes to save data on the server.  It connects to the server with a different class to the JACK client and with the LASH_Config_Data_Set flag set.

The server sees that this client also didn't specify a project, and so adds it to the first available project; the same one as the previous project, project-1.  It also sees that the client wants to store data on the server, and so it creates a directory within the project directory for this data to be stored in and creates a database-style object to manage the client's data.

If the user has the lash_panel client running, both clients will now be visible in the clients list for project-1.

The client then connects to the ALSA sequencer and sends its client ID to the server in the first character of the string of a LASH_Alsa_Client_Name event.  The server regards this similarly to the other client's JACK client name.

Saving the project
..................

After the user has done some work in the two clients, they want to save their work.  They click the Save button in lash_panel (or use the save command in lash_control), and a LASH_Save event is sent to the server.  The server recieves this and then iterates through each client in the project and checks its flags. The JACK client saves data by itself (it has the LASH_Config_File flag set,) so the server creates a directory under the project directory for it to save in and then sends a LASH_Save_File event to the client with a string containing the name of the directory it made. The client recieves the event and saves its data into the specified directory.

Next, the server examines the ALSA client.  It wishes to save data on the server, so the server sends a LASH_Save_Data_Set to the client. With all of the clients iterated through, it now saves all the information it needs to be able to restore them; their working directory, command line options, etc.  In order to do this, it asks the JACK server to find the connections for the JACK client, and asks the ALSA sequencer to find the connections for the ALSA client.  It uses the client name and ID that both clients sent to the server after opening their connections to the respective systems.  All of this information is stored in a file under the project's directory.  When this is done, the server goes back to listening for events and configs.

The client, meanwhile, has recieved the LASH_Save_Data_Set event and sends back a number of configs to the server.  When it has sent all the data it wishes to be saved, it sends back a LASH_Save_Data_Set event.  The server passes all of the configs to the object managing the data store for the ALSA client.  When the server recieves the LASH_Save_Data_Set event from the client, it tells the data store to write the data to disk.  The save is now complete.

Client resumption
.................

Unfortunately for the user, the ALSA client crashes.  The server detects that the client has disconnected, and puts the client on a list of lost clients for the project.  The user then starts another copy of the client, which connects to the server in the same way it did before.  This time, however, the server checks through the list of lost clients and finds that the class of the new client matches the class of the lost client and so it resumes the lost client using the new one.  It gives it the 128-bit ID of the lost client, adds it to the project, and then sends a LASH_Restore_Data_Set event to the client.  The client then cleans itself up, ready to recieve the data set.  The server sends the client the configs, and then another LASH_Restore_Data_Set event. The client recieves this data and its state has been restored that of the client that crashed.

The user can stop this behaviour by specifying the --lash-no-autoresume option on the client's command line.

Restoring the project
.....................

The user has to go off and do other things, and so they close down the clients and the server.  Some time later, the user comes back and wants to start working again so first, as always, they start up the server. They then start the lash_panel program.  Using the File->Open menu item, the user selects the directory (not file!) where they saved the project (by default ~/audio-projects/project-1, but you can save to a more descriptive name).  The lash_panel client sends a LASH_Restore event to the server with the specified directory as the string.  The server opens the file that it saved before, and reads in all the information about the project and its clients.  It creates a new project with this information.  The clients are created as lost clients, however.

The server then iterates through each client and starts a new copy of it using the information provided when the original client connected. It also adds some command line options that are extracted by the client library.  These specify the LASH ID of the client, the project name that it should be connecting to and the server's hostname and port. It then goes back to waiting.

The new JACK client then connects to the server as normal.  When the server recieves it connection, it checks the client against the project's list of lost clients.  This time, however, it has its ID specified, so the server will only resume a client with a matching ID.  Lo and behold, such a client exists.  The server resumes the old JACK client, telling it to load its state from the files in the project directory that the client previously stored.  It does so with a LASH_Restore_File event with the string as the directory name.  The ALSA client does exactly the same, except having its data restored through LASH_Restore_Data_Set as described above.

Only one thing remains for the clients to be fully restored: the JACK and ALSA sequencer connections.  This happens when the clients send their LASH_Jack_Client_Name and LASH_Alsa_Client_ID events. The connections are stored with the LASH ID rather than the JACK client name or ALSA client ID.  When the client registers its name or ID, the connections are converted from the LASH ID to the JACK client name or ALSA client ID, and the connections are restored.  It also pays attention to connections to other clients within the same project, converting between JACK client names, ALSA client IDs and LASH IDs as appropriate.

Types and functions
===================

Server interaction
------------------

 -- Function: lash_client_t * lash_init (lash_args_t * ARGS, const char * CLIENT_CLASS, int CLIENT_FLAGS, lash_protocol_t PROTOCOL)
     Open a connection to the server.  Returns NULL on failure.

     The ARGS argument must be obtained using lash_extract_args.

     The CLIENT_CLASS argument must be a string that will never change over invocations of the program.  If using GNU automake, the best way to do this is to use the PACKAGE_NAME macro that is automatically defined.

     The CLIENT_FLAGS argument should be 0 or bitwise-OR'd values from this list:

     LASH_Config_Data_Set
          The client wishes to save its data use the LASH config system.  See Configs and Event protocol.

     LASH_Config_File
          The client saves its data to a file.  See Event protocol.

     LASH_Server_Interface
          The client is a server interface.  See Server interfaces.

     LASH_No_Autoresume
          This flag is set by the --lash-no-autoresume command line option and should not normally be set by clients themselves.

     LASH_Terminal
          The client is dependant on being run in a terminal.

     The PROTOCOL argument should be the version of the high-level protocol that the client implements See Protocol versioning for information on how to contruct a lash_protocol_t variable.

 -- Function: lash_args_t * lash_extract_args (int * ARGC, char *** ARGV)
     Extract LASH-specific arguments from argc/argv for use in lash_init.  This should be done before the client checks the arguments, obviously.

 -- Function: const char * lash_get_server_name (lash_client_t * CLIENT)
     Get the hostname of the server.

 -- Function: unsigned int lash_get_pending_event_count (lash_client_t * CLIENT)
     Get the number of pending events.

 -- Function: lash_event_t * lash_get_event (lash_client_t * CLIENT)
     Retrieve an event. The event must be freed using lash_event_destroy. Returns NULL if there are no events pending.

 -- Function: unsigned int lash_get_pending_config_count (lash_client_t * CLIENT)
     Get the number of pending configs.

 -- Function: lash_config_t * lash_get_config (lash_client_t * CLIENT)
     Retrieve a config. The config must be freed using lash_config_destroy. Returns NULL if there are no configs pending.

 -- Function: void lash_send_event (lash_client_t * CLIENT, lash_event_t * EVENT)
     Send an event to the server.  The event must be created using lash_event_new or lash_event_new_with_type.  The library takes over ownership of the memory and it should not be freed by the client.

 -- Function: void lash_send_config (lash_client_t * CLIENT, lash_config_t * CONFIG)
     Send some configuration data to the server.  The config must be created using lash_config_new, lash_config_new_with_key or lash_config_dup.  The library takes over ownership of the memory (including the key, etc) and it should not be freed by the client.

 -- Macro: lash_enabled (client)
     Check whether the lash_client_t pointer CLIENT is not NULL, and if it isn't, that the server is still connected.

 -- Function: int lash_server_connected (lash_client_t * CLIENT)
     Check whether the server is connected.  Returns 1 if the server is still connected or 0 if it isn't

 -- Function: void lash_jack_client_name (lash_client_t * CLIENT, const char * NAME)
     Tell the server the client's JACK client name.  This is a convenience function that just sends a LASH_Jack_Client_Name event to the server.  See Normal LASH_Jack_Client_Name.

 -- Function: void lash_alsa_client_id (lash_client_t * CLIENT, unsigned char ID);
     Tell the server the client's ALSA client ID.  This just is a convenience function that just sends a LASH_Alsa_Client_ID event to the server.  See Normal LASH_Alsa_Client_ID.

Protocol versioning
-------------------

The event protocol (see Event protocol,) is versioned with a major and minor component. The lash_protocol_t type represents a version number in a 32-bit unsigned integer split 16:16.  A protocol is comptible with the server's protocol if the major numbers are the same and the minor number is less than, or equal to, the server's minor number (ie, 1.0 is compatible with a server using 1.0, 1.1 is compatible with a server using 1.3, but neither 2.0 or 1.6 are compatible with a server using 1.4.  The minor component may be dropped in the future.

 -- Macro: LASH_PROTOCOL (major, minor)
     Contruct a protocol version with a major component MAJOR and a minor component MINOR.

 -- Macro: LASH_PROTOCOL_GET_MAJOR (protocol)
     Obtain the major component of a lash_protocol_t protocol version.

 -- Macro: LASH_PROTOCOL_GET_MINOR (protocol)
     Obtain the minor component of a lash_protocol_t protocol version.

 -- Function: const char * lash_protocol_string (lash_protocol_t PROTOCOL)
     Obtain a string representation of the protocol version PROTOCOL. String representations are of the form ``MAJOR.MINOR''.

Events
------

 -- Function: lash_event_t * lash_event_new (VOID)

 -- Function: lash_event_t * lash_event_new_with_type (enum LASH_Event_Type TYPE)

 -- Function: void lash_event_destroy (lash_event_t * EVENT)

 -- Function: enum LASH_Event_Type lash_event_get_type (const lash_event_t * EVENT)

 -- Function: const char * lash_event_get_string (const lash_event_t * EVENT)

 -- Function: void lash_event_set_type (lash_event_t * EVENT, enum LASH_Event_Type TYPE)

 -- Function: void lash_event_set_string (lash_event_t * EVENT, const char * STRING);

Server interface events
.......................

All events have a LASH ID and project name property.  They are only relevant to server interfaces, however, which need to refer to clients other than themselves and to projects (server interfaces are never assigned to a project.)

 -- Function: void lash_event_get_client_id (const lash_event_t * EVENT, uuid_t ID)
     The event's client ID property will be copied into ID.

 -- Function: const char * lash_event_get_string (const lash_event_t * EVENT)

 -- Function: void lash_event_set_client_id (lash_event_t * EVENT, enum uuid_t ID)

 -- Function: const char * lash_event_get_project (const lash_event_t * EVENT)

 -- Function: void lash_event_set_project (lash_event_t * EVENT, const char * PROJECT_NAME);

Configs
-------

 -- Function: lash_config_t * lash_config_new (VOID)

 -- Function: lash_config_t * lash_config_dup (const lash_config_t * CONFIG)

 -- Function: lash_config_t * lash_config_new_with_key (const char * KEY)

 -- Function: void lash_config_destroy (lash_config_t * CONFIG)

 -- Function: const char * lash_config_get_key (const lash_config_t * CONFIG)

 -- Function: const void * lash_config_get_value (const lash_config_t * CONFIG)

 -- Function: size_t lash_config_get_value_size (const lash_config_t * CONFIG)

 -- Function: void lash_config_set_key (lash_config_t * CONFIG, const char * KEY)

 -- Function: void lash_config_set_value (lash_config_t * CONFIG, const void * VALUE, size_t VALUE_SIZE)

Semi-typed configs
..................

With these functions, no type checking is done; you can do lash_config_get_value_int on a config that was set with lash_config_set_value_float.  The integer values are converted to and from network byte order as appropriate.

 -- Function: uint32_t lash_config_get_value_int (const lash_config_t * CONFIG)

 -- Function: float lash_config_get_value_float (const lash_config_t * CONFIG)

 -- Function: double lash_config_get_value_double (const lash_config_t * CONFIG)

 -- Function: const char * lash_config_get_value_string (const lash_config_t * CONFIG)

 -- Function: void lash_config_set_value_int (lash_config_t * CONFIG, uint32_t VALUE)

 -- Function: void lash_config_set_value_float (lash_config_t * CONFIG, float VALUE)

 -- Function: void lash_config_set_value_double (lash_config_t * CONFIG, double VALUE)

 -- Function: void lash_config_set_value_string (lash_config_t * CONFIG, const char * VALUE)

Event protocol
==============

This section describes version 2.0 of the event protocol.

Normal clients
--------------

This section deals with normal clients (as opposed to Server interfaces.)

LASH_Client_Name

     To server, non-NULL string
          Set the client's user-visible name.

     To server, NULL string
          Request the client's user-visible name.

     From server
          This will only be sent in response to a LASH_Client_Name with a NULL string.  The string will be NULL if the client has not set a user-visible name, and the name itself if it has.

LASH_Jack_Client_Name

     To server, non-NULL string
          Tell the server what name the client is connected to JACK with. Clients should only ever send one non-NULL LASH_Jack_Client_Name event.  Note that you must send this event after calling jack_activate(); otherwise, the server will not be able to connect the client's ports.

     To server, NULL string
          Request the client name that the server thinks the client is connected to JACK with.

     From server
          This will only be sent in response to a LASH_Jack_Client_Name with a NULL string.  The string will be NULL if the client has not set a JACK client name, and the client name itself if it has.

LASH_Alsa_Client_ID
     To communicate ALSA client IDs within events, use the first character of a two character string of the form { ID, '\0' } as the event string.  A convenience function, lash_alsa_client_id, exists to do this for you (see lash_alsa_client_id.)

     To server, non-NULL string
          Tell the server what ID the client is connected to ALSA with. Clients should only ever send one non-NULL LASH_Alsa_Client_ID event.

     To server, NULL string
          Request the client ID that the server thinks the client is connected to ALSA with.

     From server
          This will only be sent in response to a LASH_Alsa_Client_ID with a NULL string.  The string will be NULL if the client has not set an ALSA client ID, and a string containing the ALSA client ID as described above if it has.

LASH_Save_File

     From server
          Tell the client to save all its data to files within a specific directory. The event string will never be NULL and will contain the name of the directory in which the client should save its data.  Clients must always send a LASH_Save_File event back to the server when they have finished saving their data.  The client should not rely on the directory existing after it has sent its LASH_Save_File event back.  It is valid behaviour for a client to save no files within the directory.  Files should always be overwritten (ie, using the "w" flag with fopen(),) preferably without user confirmation if you care for their sanity.

     From client
          Tell the server that the client has finished saving its data within the directory it was told to.  The string is ignored.

LASH_Restore_File

     From server
          Tell the client to load all its data from files within a specific directory. The event string will never be NULL and will contain the name of the directory from which the client should load its data.  Clients must always send a LASH_Restore_File event back to the server when they have finished restoring their data.  The client should not rely on the directory existing after it has sent its LASH_Restore_File event back.

     From client
          Tell the server that the client has finished restoring its data from within the directory it was told to.  The string is ignored.

LASH_Save_Data_Set

     From server
          Tell the client to send all its configuration data to the server with a number of configs.  The client must always send a LASH_Save_Data_Set event back to the server when it has finished sending its configs.  The event string will always be NULL.

     From client
          Tell the server that the client has finished sending its configs to the server.  The event string is ignored.

LASH_Restore_Data_Set

     From server
          Tell the client to immediately expect a stream of configs from the server. This event will only be sent if there are one or more configs to be sent. The event string will always be NULL.  The client must always send a LASH_Restore_Data_Set back to the server when it has recieved all of its configs.

     From client
          Tell the server that the client has finished recieving its configs from the server.  The event string is ignored.

LASH_Save

     From client
          Tell the server to save the project that the client is attached to.

     From server
          Never occurs.

LASH_Quit

     From client
          Tell the server to close all clients in the project that the client is attached to.

     From server
          The client should immediately quit without saving.  No more events will be sent by the server and the client's connection will be terminated.

Server interfaces
-----------------

Server interfaces are treated very differently to normal interfaces.  Events from and to server interfaces are, for the most part, in order to describe and manipulate existing projects and clients.  For this reason, the lash_event_t type has project and client_id properties which facilitate this.  See Server interface events.  The project property contains the name of the project.

A server interface should start up with the default assumption that there are no projects.  Upon connection, the server will send appropriate events (LASH_Project_Add, LASH_Client_Add, LASH_Client_Name, etc) that describe the current state of the system.  From then on, events will be sent to keep the interface up to date with the server's state.

LASH_Project_Add

     From interface
          Restore a project from an existing directory.  The event string should contain the directory's name.

          project
               Ignored.

          client_id
               Ignored.

     From server
          A new project has been added.  The event string will contain the project's name.

          project
               NULL

          client_id
               Undefined.

LASH_Project_Remove

     From interface
          Close an open project.  All of the project's clients will be told to quit and the project will be removed from the server's project list.

          project
               The project to remove.

          client_id
               Ignored.

     From server
          A project has been removed.

          project
               The project that has been removed.

          client_id
               Undefined.

LASH_Project_Dir

     From interface, non-NULL string
          Move a project to a different directory.  The directory name should be contained in the event's string.

          project
               The project to move.

          client_id
               Undefined.

     From interface, NULL string
          Request a project's directory.

          project
               The project whose directory is being requested.

          client_id
               Undefined.

     From server
          A declaration of the project's directory; either because it has been requested or because the project has been moved.  The directory name is contained in the event's string.

          project
               The project whose directory is being declared.

          client ID
               Undefined.

LASH_Project_Name

     From interface
          Change a project's name.  The new project name should be contained in the event's string.

          project
               The project name to change.

          client_id
               Undefined.

     From server
          A project's name has changed.  The new project name is contained in the event's string.

          project
               The project name that has changed.

          client ID
               Undefined.

LASH_Client_Add

     From interface
          Should not occur

     From server
          A new client has been added.

          project
               The project that the new client has been added to.

          client ID
               The new client's ID.

LASH_Client_Name

     From interface, non-NULL string
          Should not occur.

     From interface, NULL string
          Request a client's name.

          project
               The client's project.

          client ID
               The client's ID.

     From server
          A declaration of a client's name; either because it has been requested or because the client set the name.  The name is contained in the event's string.

          project
               The client's project.

          client ID
               The client's ID.

LASH_Jack_Client_Name

     From interface, non-NULL string
          Should not occur.

     From interface, NULL string
          Request a client's JACK client name.

          project
               The client's project.

          client ID
               The client's ID.

     From server
          A declaration of a client's JACK client name; either because it has been requested or because the client set the name.  The client name is contained in the event's string.

          project
               The client's project.

          client ID
               The client's ID.

LASH_Alsa_Client_ID

     From interface, non-NULL string
          Should not occur.

     From interface, NULL string
          Request a client's ALSA client ID.

          project
               The client's project.

          client ID
               The client's LASH ID.

     From server
          A declaration of a client's ALSA client ID; either because it has been requested or because the client set the ID.  The ALSA client ID is contained in the event's string, as desribed in Normal LASH_Alsa_Client_ID.

          project
               The client's project.

          client ID
               The client's LASH ID.

LASH_Percentage
     This event exists to provide user feedback on the status of save operations and perhaps other operations in future.  The server will first send a percentage of 0, then successive percentages up to and including 100.  When the operation is complete, the server will send a percentage of 0 again.

     From interface
          Should not occur.

     From server
          The percentage of completion of the current operation.  The percentage is sent as a string, derived from sprintfing an int.

          project
               The project whose operation is being described.

          client ID
               Undefined.

Copying restrictions
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     [file fdl.texi not included]