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-@prefix dcs: <http://ontologi.es/doap-changeset#> .
-@prefix doap: <http://usefulinc.com/ns/doap#> .
-@prefix foaf: <http://xmlns.com/foaf/0.1/> .
-@prefix lv2: <http://lv2plug.in/ns/lv2core#> .
-@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 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 "2.10" ;
- doap:created "2022-05-26" ;
- doap:file-release <http://lv2plug.in/spec/lv2-1.18.4.tar.bz2> ;
- dcs:blame <http://drobilla.net/drobilla#me> ;
- dcs:changeset [
- dcs:item [
- rdfs:label "Fix spelling errors."
- ]
- ]
- ] , [
- doap:revision "2.8" ;
- doap:created "2021-01-07" ;
- doap:file-release <http://lv2plug.in/spec/lv2-1.18.2.tar.bz2> ;
- dcs:blame <http://drobilla.net/drobilla#me> ;
- dcs:changeset [
- dcs:item [
- rdfs:label "Fix state:StateChanged URI in metadata and documentation."
- ]
- ]
- ] , [
- doap:revision "2.6" ;
- doap:created "2020-04-26" ;
- doap:file-release <http://lv2plug.in/spec/lv2-1.18.0.tar.bz2> ;
- dcs:blame <http://drobilla.net/drobilla#me> ;
- dcs:changeset [
- dcs:item [
- rdfs:label "Add state:freePath feature."
- ]
- ]
- ] , [
- doap:revision "2.4" ;
- doap:created "2019-02-03" ;
- doap:file-release <http://lv2plug.in/spec/lv2-1.16.0.tar.bz2> ;
- 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."
- ]
- ]
- ] ;
- lv2:documentation """
-
-This extension defines a simple mechanism that allows hosts to save and restore
-a plugin instance's state. The goal is for an instance's state to be
-completely described by port values and a simple dictionary.
-
-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 "URID", a URI mapped to an integer. A single key:value pair is
-called a "property".
-
-This state model is simple yet has many benefits:
-
- * Both fast and extensible thanks to URID keys.
-
- * No limitations on possible value types.
-
- * Easy to serialise in almost any format.
-
- * Easy to store in a typical "map" or "dictionary" data structure.
-
- * Elegantly described in Turtle, so state can be described in LV2 data files
- (including presets).
-
- * Does not impose any file formats, data structures, or file system
- requirements.
-
- * Suitable for portable persistent state as well as fast in-memory snapshots.
-
- * Keys _may_ be well-defined and used meaningfully across several
- implementations.
-
- * State _may_ be dynamic, but plugins are not required to have a dynamic
- dictionary data structure available.
-
-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.
-
-Since value types are defined by URI, any type is possible. However, a set of
-standard types is defined by the [LV2 Atom](atom.html) extension. Use of these
-types is recommended. Hosts MUST implement at least
-[atom:String](atom.html#String), which is simply a C string.
-
-### Referring to Files
-
-Plugins may need to refer to existing files (such as 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
-[atom:Path](atom.html#Path) for all paths in their state.
-
-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.
-
-### Plugin Code Example
-
- :::c
-
- /* 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;
- }
- }
-
-### Host Code Example
-
- :::c
- 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.
- // Disk or network use would also require LV2_STATE_IS_PORTABLE.
- Map* state_map = (Map*)handle;
- state_map->insert(key, Value(copy(value), size, type));
- return LV2_STATE_SUCCESS;;
- } else {
- return LV2_STATE_ERR_BAD_FLAGS; // Non-POD events are unsupported
- }
- }
-
- Map
- get_plugin_state(LV2_Handle instance)
- {
- LV2_State* state = instance.extension_data(LV2_STATE__interface);
-
- // Request a fast/native/POD save, since we're just copying in memory
- Map state_map;
- state.save(instance, store_callback, &state_map,
- LV2_STATE_IS_POD|LV2_STATE_IS_NATIVE);
-
- return state_map;
- }
-
-### Extensions to this Specification
-
-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 _model_ defined here. That is, **do not complicate the state
-model**. Implementations can assume the following:
-
- * The current port values and state dictionary completely describe a plugin
- instance, at least well enough that saving and restoring will yield an
- "identical" instance from the user's perspective.
-
- * Hosts are not expected to save and/or restore any other attributes of a
- plugin instance.
-
-### The "Property Principle"
-
-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 "for free", since there is no need to define
-commands _and_ a set of properties for storing their effects. In particular,
-this is a good way for UIs to achieve more advanced control of plugins.
-
-This "property principle" is summed up in the phrase: "Don't stop; set playing
-to false".
-
-This extension does not define a dynamic mechanism for state access and
-manipulation. The [LV2 Patch](patch.html) extension defines a generic set of
-messages which can be used to access or manipulate properties, and the [LV2
-Atom](atom.html) extension defines a port type and data container capable of
-transmitting those messages.
-
-"""^^lv2:Markdown .
-
-state:interface
- lv2:documentation """
-
-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.
-
-The plugin data file should describe this like so:
-
- :::turtle
- @prefix state: <http://lv2plug.in/ns/ext/state#> .
-
- <plugin>
- a lv2:Plugin ;
- lv2:extensionData state:interface .
-
-"""^^lv2:Markdown .
-
-state:State
- lv2:documentation """
-
-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).
-
-"""^^lv2:Markdown .
-
-state:loadDefaultState
- lv2:documentation """
-
-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.
-
-To support this feature, the host MUST restore the default state after
-instantiating the plugin but before calling run().
-
-"""^^lv2:Markdown .
-
-state:state
- lv2:documentation """
-
-This property may be used anywhere a state needs to be described, for example:
-
- :::turtle
- @prefix eg: <http://example.org/> .
-
- <plugin-instance>
- state:state [
- eg:somekey "some value" ;
- eg:someotherkey "some other value" ;
- eg:favourite-number 2
- ] .
-
-"""^^lv2:Markdown .
-
-state:mapPath
- lv2:documentation """
-
-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.
-
-The plugin MUST map _all_ paths stored in its state (including those inside any
-files). This is necessary so that hosts can handle file system references
-correctly, for example to share common files, or bundle state for distribution
-or archival.
-
-For example, a plugin may write a path to a state file like so:
-
- :::c
- 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);
- }
-
-Then, later reload the path like so:
-
- :::c
- 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);
- }
-
-"""^^lv2:Markdown .
-
-state:makePath
- lv2:documentation """
-
-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.
-
-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 one such namespace, even if the feature is passed to both
-LV2_Descriptor::instantiate() and LV2_State_Interface::save(). Beyond this,
-the plugin MUST NOT make any assumptions about the returned paths.
-
-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, that is, only mapped paths saved to
-state are persistent, any other created paths are temporary.
-
-For example, a plugin may create a file in a subdirectory like so:
-
- :::c
- 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;
- }
-
-"""^^lv2:Markdown .
-
-state:threadSafeRestore
- lv2:documentation """
-
-If a plugin supports this feature, its LV2_State_Interface::restore method is
-thread-safe and may be called concurrently with audio class functions.
-
-To support this feature, the host MUST pass a
-[work:schedule](worker.html#schedule) 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.
-
-The host is not required to block audio processing while restore() and work()
-load the state, so this feature allows state to be restored without dropouts.
-
-"""^^lv2:Markdown .
-
-state:freePath
- lv2:documentation """
-
-This feature provides a function that can be used by plugins to free paths that
-were allocated by the host via other state features (state:mapPath and
-state:makePath).
-
-"""^^lv2:Markdown .
-
-state:StateChanged
- lv2:documentation """
-
-A notification that the internal state of the plugin has been changed in a way
-that the host can not otherwise know about.
-
-This is a one-way notification, intended to be used as the type of an
-[Object](atom.html#Object) sent from plugins when necessary.
-
-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 explicitly makes
-a change which it knows is likely to have that effect, such as changing a
-parameter.
-
-"""^^lv2:Markdown .
-
generated by cgit v1.2.1 (git 2.18.0) at 2024-09-30 07:01:01 +0000