diff options
Diffstat (limited to 'lv2/lv2plug.in/ns/ext/state')
| -rw-r--r-- | lv2/lv2plug.in/ns/ext/state/lv2-state.doap.ttl | 66 | ||||
| -rw-r--r-- | lv2/lv2plug.in/ns/ext/state/manifest.ttl | 8 | ||||
| -rw-r--r-- | lv2/lv2plug.in/ns/ext/state/state.h | 363 | ||||
| -rw-r--r-- | lv2/lv2plug.in/ns/ext/state/state.ttl | 382 |
4 files changed, 0 insertions, 819 deletions
diff --git a/lv2/lv2plug.in/ns/ext/state/lv2-state.doap.ttl b/lv2/lv2plug.in/ns/ext/state/lv2-state.doap.ttl deleted file mode 100644 index fd87a13..0000000 --- a/lv2/lv2plug.in/ns/ext/state/lv2-state.doap.ttl +++ /dev/null @@ -1,66 +0,0 @@ -@prefix dcs: <http://ontologi.es/doap-changeset#> . -@prefix doap: <http://usefulinc.com/ns/doap#> . -@prefix foaf: <http://xmlns.com/foaf/0.1/> . -@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> . - -<http://lv2plug.in/ns/ext/state> - a doap:Project ; - doap:created "2010-11-09" ; - doap:name "LV2 State" ; - doap:shortdesc "An interface for LV2 plugins to save and restore state." ; - doap:license <http://opensource.org/licenses/isc> ; - doap:developer <http://lv2plug.in/ns/meta#paniq> , - <http://drobilla.net/drobilla#me> ; - doap:maintainer <http://drobilla.net/drobilla#me> ; - doap:release [ - doap:revision "2.3" ; - doap:created "2016-10-19" ; - dcs:blame <http://drobilla.net/drobilla#me> ; - dcs:changeset [ - dcs:item [ - rdfs:label "Add state:StateChanged for notification events." - ] - ] - ] , [ - doap:revision "2.2" ; - doap:created "2016-07-31" ; - doap:file-release <http://lv2plug.in/spec/lv2-1.14.0.tar.bz2> ; - dcs:blame <http://drobilla.net/drobilla#me> ; - dcs:changeset [ - dcs:item [ - rdfs:label "Add LV2_STATE_ERR_NO_SPACE status flag." - ] , [ - rdfs:label "Add state:threadSafeRestore feature for dropout-free state restoration." - ] - ] - ] , [ - doap:revision "2.0" ; - doap:created "2013-01-16" ; - doap:file-release <http://lv2plug.in/spec/lv2-1.4.0.tar.bz2> ; - dcs:blame <http://drobilla.net/drobilla#me> ; - dcs:changeset [ - dcs:item [ - rdfs:label "Add state:loadDefaultState feature so plugins can have their default state loaded without hard-coding default state as a special case." - ] - ] - ] , [ - doap:revision "1.2" ; - doap:created "2012-10-14" ; - doap:file-release <http://lv2plug.in/spec/lv2-1.2.0.tar.bz2> ; - dcs:blame <http://drobilla.net/drobilla#me> ; - dcs:changeset [ - dcs:item [ - rdfs:label "Use consistent label style." - ] - ] - ] , [ - doap:revision "1.0" ; - doap:created "2012-04-17" ; - doap:file-release <http://lv2plug.in/spec/lv2-1.0.0.tar.bz2> ; - dcs:blame <http://drobilla.net/drobilla#me> ; - dcs:changeset [ - dcs:item [ - rdfs:label "Initial release." - ] - ] - ] . diff --git a/lv2/lv2plug.in/ns/ext/state/manifest.ttl b/lv2/lv2plug.in/ns/ext/state/manifest.ttl deleted file mode 100644 index 2a54874..0000000 --- a/lv2/lv2plug.in/ns/ext/state/manifest.ttl +++ /dev/null @@ -1,8 +0,0 @@ -@prefix lv2: <http://lv2plug.in/ns/lv2core#> . -@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> . - -<http://lv2plug.in/ns/ext/state> - a lv2:Specification ; - lv2:minorVersion 2 ; - lv2:microVersion 3 ; - rdfs:seeAlso <state.ttl> . diff --git a/lv2/lv2plug.in/ns/ext/state/state.h b/lv2/lv2plug.in/ns/ext/state/state.h deleted file mode 100644 index f2a4afa..0000000 --- a/lv2/lv2plug.in/ns/ext/state/state.h +++ /dev/null @@ -1,363 +0,0 @@ -/* - Copyright 2010-2016 David Robillard <http://drobilla.net> - Copyright 2010 Leonard Ritter <paniq@paniq.org> - - Permission to use, copy, modify, and/or distribute this software for any - purpose with or without fee is hereby granted, provided that the above - copyright notice and this permission notice appear in all copies. - - THIS SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES - WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF - MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR - ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES - WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN - ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF - OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. -*/ - -/** - @defgroup state State - - An interface for LV2 plugins to save and restore state, see - <http://lv2plug.in/ns/ext/state> for details. - - @{ -*/ - -#ifndef LV2_STATE_H -#define LV2_STATE_H - -#include <stddef.h> -#include <stdint.h> - -#include "lv2/lv2plug.in/ns/lv2core/lv2.h" - -#define LV2_STATE_URI "http://lv2plug.in/ns/ext/state" ///< http://lv2plug.in/ns/ext/state -#define LV2_STATE_PREFIX LV2_STATE_URI "#" ///< http://lv2plug.in/ns/ext/state# - -#define LV2_STATE__State LV2_STATE_PREFIX "State" ///< http://lv2plug.in/ns/ext/state#State -#define LV2_STATE__interface LV2_STATE_PREFIX "interface" ///< http://lv2plug.in/ns/ext/state#interface -#define LV2_STATE__loadDefaultState LV2_STATE_PREFIX "loadDefaultState" ///< http://lv2plug.in/ns/ext/state#loadDefaultState -#define LV2_STATE__makePath LV2_STATE_PREFIX "makePath" ///< http://lv2plug.in/ns/ext/state#makePath -#define LV2_STATE__mapPath LV2_STATE_PREFIX "mapPath" ///< http://lv2plug.in/ns/ext/state#mapPath -#define LV2_STATE__state LV2_STATE_PREFIX "state" ///< http://lv2plug.in/ns/ext/state#state -#define LV2_STATE__threadSafeRestore LV2_STATE_PREFIX "threadSafeRestore" ///< http://lv2plug.in/ns/ext/state#threadSafeRestore -#define LV2_STATE__StateChanged LV2_STATE_PREFIX "StateChanged" ///< http://lv2plug.in/ns/ext/state#StateChanged - -#ifdef __cplusplus -extern "C" { -#else -# include <stdbool.h> -#endif - -typedef void* LV2_State_Handle; ///< Opaque handle for state save/restore -typedef void* LV2_State_Map_Path_Handle; ///< Opaque handle for state:mapPath feature -typedef void* LV2_State_Make_Path_Handle; ///< Opaque handle for state:makePath feature - -/** - Flags describing value characteristics. - - These flags are used along with the value's type URI to determine how to - (de-)serialise the value data, or whether it is even possible to do so. -*/ -typedef enum { - /** - Plain Old Data. - - Values with this flag contain no pointers or references to other areas - of memory. It is safe to copy POD values with a simple memcpy and store - them for the duration of the process. A POD value is not necessarily - safe to trasmit between processes or machines (e.g. filenames are POD), - see LV2_STATE_IS_PORTABLE for details. - - Implementations MUST NOT attempt to copy or serialise a non-POD value if - they do not understand its type (and thus know how to correctly do so). - */ - LV2_STATE_IS_POD = 1, - - /** - Portable (architecture independent) data. - - Values with this flag are in a format that is usable on any - architecture. A portable value saved on one machine can be restored on - another machine regardless of architecture. The format of portable - values MUST NOT depend on architecture-specific properties like - endianness or alignment. Portable values MUST NOT contain filenames. - */ - LV2_STATE_IS_PORTABLE = 1 << 1, - - /** - Native data. - - This flag is used by the host to indicate that the saved data is only - going to be used locally in the currently running process (e.g. for - instance duplication or snapshots), so the plugin should use the most - efficient representation possible and not worry about serialisation - and portability. - */ - LV2_STATE_IS_NATIVE = 1 << 2 -} LV2_State_Flags; - -/** A status code for state functions. */ -typedef enum { - LV2_STATE_SUCCESS = 0, /**< Completed successfully. */ - LV2_STATE_ERR_UNKNOWN = 1, /**< Unknown error. */ - LV2_STATE_ERR_BAD_TYPE = 2, /**< Failed due to unsupported type. */ - LV2_STATE_ERR_BAD_FLAGS = 3, /**< Failed due to unsupported flags. */ - LV2_STATE_ERR_NO_FEATURE = 4, /**< Failed due to missing features. */ - LV2_STATE_ERR_NO_PROPERTY = 5, /**< Failed due to missing property. */ - LV2_STATE_ERR_NO_SPACE = 6 /**< Failed due to insufficient space. */ -} LV2_State_Status; - -/** - A host-provided function to store a property. - @param handle Must be the handle passed to LV2_State_Interface.save(). - @param key The key to store `value` under (URID). - @param value Pointer to the value to be stored. - @param size The size of `value` in bytes. - @param type The type of `value` (URID). - @param flags LV2_State_Flags for `value`. - @return 0 on success, otherwise a non-zero error code. - - The host passes a callback of this type to LV2_State_Interface.save(). This - callback is called repeatedly by the plugin to store all the properties that - describe its current state. - - DO NOT INVENT NONSENSE URI SCHEMES FOR THE KEY. Best is to use keys from - existing vocabularies. If nothing appropriate is available, use http URIs - that point to somewhere you can host documents so documentation can be made - resolvable (e.g. a child of the plugin or project URI). If this is not - possible, invent a URN scheme, e.g. urn:myproj:whatever. The plugin MUST - NOT pass an invalid URI key. - - The host MAY fail to store a property for whatever reason, but SHOULD - store any property that is LV2_STATE_IS_POD and LV2_STATE_IS_PORTABLE. - Implementations SHOULD use the types from the LV2 Atom extension - (http://lv2plug.in/ns/ext/atom) wherever possible. The plugin SHOULD - attempt to fall-back and avoid the error if possible. - - Note that `size` MUST be > 0, and `value` MUST point to a valid region of - memory `size` bytes long (this is required to make restore unambiguous). - - The plugin MUST NOT attempt to use this function outside of the - LV2_State_Interface.restore() context. -*/ -typedef LV2_State_Status (*LV2_State_Store_Function)( - LV2_State_Handle handle, - uint32_t key, - const void* value, - size_t size, - uint32_t type, - uint32_t flags); - -/** - A host-provided function to retrieve a property. - @param handle Must be the handle passed to LV2_State_Interface.restore(). - @param key The key of the property to retrieve (URID). - @param size (Output) If non-NULL, set to the size of the restored value. - @param type (Output) If non-NULL, set to the type of the restored value. - @param flags (Output) If non-NULL, set to the flags for the restored value. - @return A pointer to the restored value (object), or NULL if no value - has been stored under `key`. - - A callback of this type is passed by the host to - LV2_State_Interface.restore(). This callback is called repeatedly by the - plugin to retrieve any properties it requires to restore its state. - - The returned value MUST remain valid until LV2_State_Interface.restore() - returns. The plugin MUST NOT attempt to use this function, or any value - returned from it, outside of the LV2_State_Interface.restore() context. -*/ -typedef const void* (*LV2_State_Retrieve_Function)( - LV2_State_Handle handle, - uint32_t key, - size_t* size, - uint32_t* type, - uint32_t* flags); - -/** - LV2 Plugin State Interface. - - When the plugin's extension_data is called with argument - LV2_STATE__interface, the plugin MUST return an LV2_State_Interface - structure, which remains valid for the lifetime of the plugin. - - The host can use the contained function pointers to save and restore the - state of a plugin instance at any time, provided the threading restrictions - of the functions are met. - - Stored data is only guaranteed to be compatible between instances of plugins - with the same URI (i.e. if a change to a plugin would cause a fatal error - when restoring state saved by a previous version of that plugin, the plugin - URI MUST change just as it must when ports change incompatibly). Plugin - authors should consider this possibility, and always store sensible data - with meaningful types to avoid such problems in the future. -*/ -typedef struct _LV2_State_Interface { - /** - Save plugin state using a host-provided `store` callback. - - @param instance The instance handle of the plugin. - @param store The host-provided store callback. - @param handle An opaque pointer to host data which MUST be passed as the - handle parameter to `store` if it is called. - @param flags Flags describing desired properties of this save. These - flags may be used to determine the most appropriate values to store. - @param features Extensible parameter for passing any additional - features to be used for this save. - - The plugin is expected to store everything necessary to completely - restore its state later. Plugins SHOULD store simple POD data whenever - possible, and consider the possibility of state being restored much - later on a different machine. - - The `handle` pointer and `store` function MUST NOT be used - beyond the scope of save(). - - This function has its own special threading class: it may not be called - concurrently with any "Instantiation" function, but it may be called - concurrently with functions in any other class, unless the definition of - that class prohibits it (e.g. it may not be called concurrently with a - "Discovery" function, but it may be called concurrently with an "Audio" - function. The plugin is responsible for any locking or lock-free - techniques necessary to make this possible. - - Note that in the simple case where state is only modified by restore(), - there are no synchronization issues since save() is never called - concurrently with restore() (though run() may read it during a save). - - Plugins that dynamically modify state while running, however, must take - care to do so in such a way that a concurrent call to save() will save a - consistent representation of plugin state for a single instant in time. - */ - LV2_State_Status (*save)(LV2_Handle instance, - LV2_State_Store_Function store, - LV2_State_Handle handle, - uint32_t flags, - const LV2_Feature *const * features); - - /** - Restore plugin state using a host-provided `retrieve` callback. - - @param instance The instance handle of the plugin. - @param retrieve The host-provided retrieve callback. - @param handle An opaque pointer to host data which MUST be passed as the - handle parameter to `retrieve` if it is called. - @param flags Currently unused. - @param features Extensible parameter for passing any additional - features to be used for this restore. - - The plugin MAY assume a restored value was set by a previous call to - LV2_State_Interface.save() by a plugin with the same URI. - - The plugin MUST gracefully fall back to a default value when a value can - not be retrieved. This allows the host to reset the plugin state with - an empty map. - - The `handle` pointer and `store` function MUST NOT be used - beyond the scope of restore(). - - This function is in the "Instantiation" threading class as defined by - LV2. This means it MUST NOT be called concurrently with any other - function on the same plugin instance. - */ - LV2_State_Status (*restore)(LV2_Handle instance, - LV2_State_Retrieve_Function retrieve, - LV2_State_Handle handle, - uint32_t flags, - const LV2_Feature *const * features); -} LV2_State_Interface; - -/** - Feature data for state:mapPath (@ref LV2_STATE__mapPath). -*/ -typedef struct { - /** - Opaque host data. - */ - LV2_State_Map_Path_Handle handle; - - /** - Map an absolute path to an abstract path for use in plugin state. - @param handle MUST be the `handle` member of this struct. - @param absolute_path The absolute path of a file. - @return An abstract path suitable for use in plugin state. - - The plugin MUST use this function to map any paths that will be stored - in plugin state. The returned value is an abstract path which MAY not - be an actual file system path; absolute_path() MUST be used to map - it to an actual path in order to use the file. - - Plugins MUST NOT make any assumptions about abstract paths except that - they can be mapped back to the absolute path of the "same" file (though - not necessarily the same original path) using absolute_path(). - - This function may only be called within the context of - LV2_State_Interface methods. The caller is responsible for freeing the - returned value with free(). - */ - char* (*abstract_path)(LV2_State_Map_Path_Handle handle, - const char* absolute_path); - - /** - Map an abstract path from plugin state to an absolute path. - @param handle MUST be the `handle` member of this struct. - @param abstract_path An abstract path (e.g. a path from plugin state). - @return An absolute file system path. - - The plugin MUST use this function in order to actually open or otherwise - use any paths loaded from plugin state. - - This function may only be called within the context of - LV2_State_Interface methods. The caller is responsible for freeing the - returned value with free(). - */ - char* (*absolute_path)(LV2_State_Map_Path_Handle handle, - const char* abstract_path); -} LV2_State_Map_Path; - -/** - Feature data for state:makePath (@ref LV2_STATE__makePath). -*/ -typedef struct { - /** - Opaque host data. - */ - LV2_State_Make_Path_Handle handle; - - /** - Return a path the plugin may use to create a new file. - @param handle MUST be the `handle` member of this struct. - @param path The path of the new file within a namespace unique to this - plugin instance. - @return The absolute path to use for the new file. - - This function can be used by plugins to create files and directories, - either at state saving time (if this feature is passed to - LV2_State_Interface.save()) or any time (if this feature is passed to - LV2_Descriptor.instantiate()). - - The host MUST do whatever is necessary for the plugin to be able to - create a file at the returned path (e.g. using fopen), including - creating any leading directories. - - If this function is passed to LV2_Descriptor.instantiate(), it may be - called from any non-realtime context. If it is passed to - LV2_State_Interface.save(), it may only be called within the dynamic - scope of that function call. - - The caller is responsible for freeing the returned value with free(). - */ - char* (*path)(LV2_State_Make_Path_Handle handle, - const char* path); -} LV2_State_Make_Path; - -#ifdef __cplusplus -} /* extern "C" */ -#endif - -#endif /* LV2_STATE_H */ - -/** - @} -*/ diff --git a/lv2/lv2plug.in/ns/ext/state/state.ttl b/lv2/lv2plug.in/ns/ext/state/state.ttl deleted file mode 100644 index c86fea7..0000000 --- a/lv2/lv2plug.in/ns/ext/state/state.ttl +++ /dev/null @@ -1,382 +0,0 @@ -@prefix lv2: <http://lv2plug.in/ns/lv2core#> . -@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> . -@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> . -@prefix state: <http://lv2plug.in/ns/ext/state#> . - -<http://lv2plug.in/ns/ext/state> - a lv2:Specification ; - rdfs:seeAlso <state.h> , - <lv2-state.doap.ttl> ; - lv2:documentation """ -<p>This extension defines a simple mechanism which allows hosts to save and -restore a plugin instance's state. The goal is for an instance's state to be -<em>completely</em> described by port values (as with all LV2 plugins) and a -simple dictionary.</p> - -<p>The <q>state</q> defined here is conceptually a key:value dictionary, with -URI keys and values of any type. For performance reasons the key and value -type are actually a <q>URID</q>, a URI mapped to an integer. A single -key:value pair is called a <q>property</q>.</p> - -<p>This state model is simple yet has many benefits:</p> -<ul> - <li>Both fast and extensible thanks to URID keys.</li> - <li>No limitations on possible value types.</li> - <li>Easy to serialise in almost any format.</li> - <li>Easy to store in a typical <q>map</q> or <q>dictionary</q> data - structure.</li> - <li>Elegantly described in Turtle, so state can be described in LV2 data - files (including presets).</li> - <li>Does not impose any file formats, data structures, or file system - requirements.</li> - <li>Suitable for portable persistent state as well as fast in-memory - snapshots.</li> - <li>Keys <em>may</em> be well-defined and used meaningfully across several - implementations.</li> - <li>State <em>may</em> be dynamic, but plugins are not required to have a - dynamic dictionary data structure available.</li> -</ul> - -<p>To implement state, the plugin provides a state:interface to the host. To -save or restore, the host calls LV2_State_Interface::save() or -LV2_State_Interface::restore(), passing a callback to be used for handling a -single property. The host is free to implement property storage and retrieval -in any way.</p> - -<p>Since value types are defined by URI, any type is possible. However, a set -of standard types is defined by the <a href="../atom/atom.html">LV2 Atom</a> -extension. Use of these types is recommended. Hosts MUST implement at least -<a href="../atom/atom.html#String">atom:String</a>, which is simply a C -string.</p> - -<h3>Referring to Files</h3> - -<p>Plugins may need to refer to existing files (e.g. loaded samples) in their -state. This is done by storing the file's path as a property just like any -other value. However, there are some rules which MUST be followed when storing -paths, see state:mapPath for details. Plugins MUST use the type <a -href="../atom/atom.html#Path">atom:Path</a> for all paths in their state.</p> - -<p>Plugins are strongly encouraged to avoid creating files, instead storing all -state as properties. However, occasionally the ability to create files is -necessary. To make this possible, the host can provide the feature -state:makePath which allocates paths for plugin-created files. Plugins MUST -NOT create files in any other locations.</p> - -<h3>Plugin Code Example</h3> - -<pre class="c-code"> - -/* Namespace for this plugin's keys. This SHOULD be something that could be - published as a document, even if that document does not exist right now. -*/ -#define NS_MY "http://example.org/myplugin/schema#" - -#define DEFAULT_GREETING "Hello" - -LV2_Handle -my_instantiate(...) -{ - MyPlugin* plugin = ...; - plugin->uris.atom_String = map_uri(LV2_ATOM__String); - plugin->uris.my_greeting = map_uri(NS_MY "greeting"); - plugin->state.greeting = strdup(DEFAULT_GREETING); - return plugin; -} - -LV2_State_Status -my_save(LV2_Handle instance, - LV2_State_Store_Function store, - LV2_State_Handle handle, - uint32_t flags, - const LV2_Feature *const * features) -{ - MyPlugin* plugin = (MyPlugin*)instance; - const char* greeting = plugin->state.greeting; - - store(handle, - plugin->uris.my_greeting, - greeting, - strlen(greeting) + 1, // Careful! Need space for terminator - plugin->uris.atom_String, - LV2_STATE_IS_POD | LV2_STATE_IS_PORTABLE); - - return LV2_STATE_SUCCESS; -} - -LV2_State_Status -my_restore(LV2_Handle instance, - LV2_State_Retrieve_Function retrieve, - LV2_State_Handle handle, - uint32_t flags, - const LV2_Feature *const * features) -{ - MyPlugin* plugin = (MyPlugin*)instance; - - size_t size; - uint32_t type; - uint32_t flags; - const char* greeting = retrieve( - handle, plugin->uris.my_greeting, &size, &type, &flags); - - if (greeting) { - free(plugin->state->greeting); - plugin->state->greeting = strdup(greeting); - } else { - plugin->state->greeting = strdup(DEFAULT_GREETING); - } - - return LV2_STATE_SUCCESS; -} - -const void* -my_extension_data(const char* uri) -{ - static const LV2_State_Interface state_iface = { my_save, my_restore }; - if (!strcmp(uri, LV2_STATE__interface)) { - return &state_iface; - } -} -</pre> - -<h3>Host Code Example</h3> - -<pre class="c-code"> -LV2_State_Status -store_callback(LV2_State_Handle handle, - uint32_t key, - const void* value, - size_t size, - uint32_t type, - uint32_t flags) -{ - if ((flags & LV2_STATE_IS_POD)) { - /* We only care about POD since we're keeping state in memory only. - For disk or network use, LV2_STATE_IS_PORTABLE must also be checked. - */ - Map* state_map = (Map*)handle; - state_map->insert(key, Value(copy(value), size, type)); - return 0; - } else { - return 1; /* Non-POD events are unsupported. */ - } -} - -Map -get_plugin_state(LV2_Handle instance) -{ - LV2_State* state = instance.extension_data(LV2_STATE__interface); - Map state_map; - /** Request a fast/native/POD save, since we're just copying in memory */ - state.save(instance, store_callback, &state_map, - LV2_STATE_IS_POD|LV2_STATE_IS_NATIVE); - return state_map; -} -</pre> - -<h3>Extensions to this Specification</h3> - -<p>It is likely that other interfaces for working with plugin state will be -developed as needed. This is encouraged, however everything SHOULD work within -the state <em>model</em> defined here. That is, <strong>do not complicate the -state model</strong>. Implementations can assume the following:</p> - -<ul> -<li>The current port values and state dictionary completely describe a plugin -instance, at least well enough that saving and restoring will yield an -<q>identical</q> instance from the user's perspective.</li> -<li>Hosts are not expected to save and/or restore any other attributes of a -plugin instance.</li> -</ul> - -<h3>The <q>Property Principle</q></h3> - -<p>The main benefit of this meaningful state model is that it can double as a -plugin control/query mechanism. For plugins that require more advanced control -than simple control ports, instead of defining a set of commands, define -properties whose values can be set appropriately. This provides both a way to -control and save that state <q>for free</q>, since there is no need to define -commands <em>and</em> a set of properties for storing their effects. In -particular, this is a good way for UIs to achieve more advanced control of -plugins.</p> - -<p>This <q>property principle</q> is summed up in the phrase: -<q>Don't stop; set playing to false</q>.</p> - -<p>This extension does not define a dynamic mechanism for state access and -manipulation. The <a href="../patch/patch.html">LV2 Patch</a> extension -defines a generic set of messages which can be used to access or manipulate -properties, and the <a href="../atom/atom.html">LV2 Atom</a> extension defines -a port type and data container capable of transmitting those messages.</p> -""" . - -state:interface - a lv2:ExtensionData ; - lv2:documentation """ -<p>A structure (LV2_State_Interface) which contains functions to be called by -the host to save and restore state. In order to support this extension, the -plugin must return a valid LV2_State_Interface from -LV2_Descriptor::extension_data() when it is called with URI -LV2_STATE__interface.</p> - -<p>The plugin data file should describe this like so:</p> -<pre class="turtle-code"> -@prefix state: <http://lv2plug.in/ns/ext/state#> . - -<plugin> - a lv2:Plugin ; - lv2:extensionData state:interface . -</pre> -""" . - -state:State - a rdfs:Class ; - rdfs:label "State" ; - lv2:documentation """ -<p>A state dictionary. This type should be used wherever instance state is -described. The properties of a resource with this type correspond directly to -the properties of the state dictionary (except the property that states it has -this type).</p> -""" . - -state:loadDefaultState - a lv2:Feature ; - lv2:documentation """ -<p>This feature indicates that the plugin has default state listed with the -state:state property which should be loaded by the host before running the -plugin. Requiring this feature allows plugins to implement a single state -loading mechanism which works for initialisation as well as restoration, -without having to hard-code default state.</p> - -<p>To support this feature, the host MUST <q>restore</q> the default state -after instantiating the plugin but before calling run().</p> -""" . - -state:state - a rdf:Property ; - rdfs:label "state" ; - rdfs:range state:State ; - lv2:documentation """ -<p>The state of this instance. This property may be used anywhere a state -needs to be described, for example:</p> - -<pre class="turtle-code"> -@prefix eg: <http://example.org/> . - -<plugin-instance> - state:state [ - eg:somekey "some value" ; - eg:someotherkey "some other value" ; - eg:favourite-number 2 - ] . -</pre> -""" . - -state:mapPath - a lv2:Feature ; - rdfs:label "map file paths" ; - lv2:documentation """ -<p>This feature maps absolute paths to/from <q>abstract paths</q> which are -stored in state. To support this feature a host must pass an LV2_Feature with -URI LV2_STATE__mapPath and data pointed to an LV2_State_Map_Path to the -plugin's LV2_State_Interface methods.</p> - -<p>The plugin MUST map <em>all</em> paths stored in its state (including those -inside any files in its state). This is necessary to enable host to handle -file system references correctly, e.g. for distribution or archival.</p> - -<p>For example, a plugin may write a path to a state file like so:</p> - -<pre class="c-code"> -void write_path(LV2_State_Map_Path* map_path, FILE* myfile, const char* path) -{ - char* abstract_path = map_path->abstract_path(map_path->handle, path); - fprintf(myfile, "%s", abstract_path); - free(abstract_path); -} -</pre> - -<p>Then, later reload the path like so:</p> - -<pre class="c-code"> -char* read_path(LV2_State_Map_Path* map_path, FILE* myfile) -{ - /* Obviously this is not production quality code! */ - char abstract_path[1024]; - fscanf(myfile, "%s", abstract_path); - return map_path->absolute_path(map_path->handle, abstract_path); -} -</pre> -""" . - -state:makePath - a lv2:Feature ; - rdfs:label "create new file paths" ; - lv2:documentation """ -<p>This feature allows plugins to create new files and/or directories. To -support this feature the host passes an LV2_Feature with URI -LV2_STATE__makePath and data pointed to an LV2_State_Make_Path to the plugin. -The host may make this feature available only during save by passing it to -LV2_State_Interface::save(), or available any time by passing it to -LV2_Descriptor::instantiate(). If passed to LV2_State_Interface::save(), the -feature MUST NOT be used beyond the scope of that call.</p> - -<p>The plugin is guaranteed a hierarchical namespace unique to that plugin -instance, and may expect the returned path to have the requested path as a -suffix. There is <em>one</em> such namespace, even if the feature is passed to -both LV2_Descriptor::instantiate() <em>and</em> LV2_State_Interface::save(). -Beyond this, the plugin MUST NOT make any assumptions about the returned -paths.</p> - -<p>Like any other paths, the plugin MUST map these paths using state:mapPath -before storing them in state. The plugin MUST NOT assume these paths will be -available across a save/restore otherwise, i.e. only mapped paths saved to -state are persistent, any other created paths are temporary.</p> - -<p>For example, a plugin may create a file in a subdirectory like so:</p> - -<pre class="c-code"> -char* save_myfile(LV2_State_Make_Path* make_path) -{ - char* path = make_path->path(make_path->handle, "foo/bar/myfile.txt"); - FILE* myfile = fopen(path, 'w'); - fprintf(myfile, "I am some data"); - fclose(myfile); - return path; -} -</pre> -""" . - -state:threadSafeRestore - a lv2:Feature ; - rdfs:label "thread-safe restore" ; - lv2:documentation """ -<p>If a plugin supports this feature, its LV2_State_Interface::restore method -is thread-safe and may be called concurrently with audio class functions.</p> - -<p>To support this feature, the host MUST pass a <a -href="../worker/worker.html#schedule">work:schedule</a> feature to the restore -method, which will be used to complete the state restoration. The usual -mechanics of the worker apply: the host will call the plugin's work method, -which emits a response which is later applied in the audio thread.</p> - -<p>The host is not required to block run() while restore() and work() load the -state, so this feature allows state to be restored without dropouts.</p> -""" . - -state:Changed - a rdfs:Class ; - rdfs:label "State changed" ; - lv2:documentation """ -<p>A notification that the internal state of the plugin has been changed in a -way that the host can not otherwise know about.</p> - -<p>This is a one-way notification, intended to be used as the type of an <a -href="../atom/atom.html#Object">Object</a> sent from plugins when -necessary.</p> - -<p>Plugins SHOULD emit such an event whenever a change has occurred that would -result in a different state being saved, but not when the host explicity makes -a change which it knows is likely to have that effect, such as changing a -parameter.</p> -""" . |