From 430284545345539c9ffb31df889debac1d3888b5 Mon Sep 17 00:00:00 2001
From: David Robillard <d@drobilla.net>
Date: Sun, 22 Mar 2020 16:36:44 +0100
Subject: Move documentation to metadata files and convert it to Markdown
---
lv2/state/state.meta.ttl | 381 ++++++++++++++++++++++++++++++++++++++++++++++-
lv2/state/state.ttl | 370 +++------------------------------------------
2 files changed, 398 insertions(+), 353 deletions(-)
(limited to 'lv2/state')
diff --git a/lv2/state/state.meta.ttl b/lv2/state/state.meta.ttl
index 784946d..ac3f2d6 100644
--- a/lv2/state/state.meta.ttl
+++ b/lv2/state/state.meta.ttl
@@ -1,7 +1,9 @@
@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 ;
@@ -73,5 +75,382 @@
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 (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
+[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:Changed
+ 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 explicity makes
+a change which it knows is likely to have that effect, such as changing a
+parameter.
+
+"""^^lv2:Markdown .
diff --git a/lv2/state/state.ttl b/lv2/state/state.ttl
index 2140309..de6d18b 100644
--- a/lv2/state/state.ttl
+++ b/lv2/state/state.ttl
@@ -5,388 +5,54 @@
<http://lv2plug.in/ns/ext/state>
a lv2:Specification ;
+ rdfs:label "LV2 State" ;
+ rdfs:comment "An interface for LV2 plugins to save and restore state." ;
rdfs:seeAlso <state.h> ,
- <state.meta.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.html">LV2 Atom</a>
-extension. Use of these types is recommended. Hosts MUST implement at least
-<a href="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.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.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.html">LV2 Atom</a> extension defines
-a port type and data container capable of transmitting those messages.</p>
-""" .
+ <state.meta.ttl> .
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>
-""" .
+ rdfs:label "interface" ;
+ rdfs:comment "A plugin interface for saving and restoring state." .
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>
-""" .
+ rdfs:comment "LV2 plugin state." .
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>
-""" .
+ rdfs:label "load default state" ;
+ rdfs:comment "A feature indicating that the plugin has default state." .
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>
-""" .
+ rdfs:comment "The state of an LV2 plugin instance." .
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>
-""" .
+ rdfs:label "map path" ;
+ rdfs:comment "A feature for mapping between absolute and abstract file paths." .
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>
-""" .
+ rdfs:label "make path" ;
+ rdfs:comment "A feature for creating new files and directories." .
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.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>
-""" .
+ rdfs:comment "A feature indicating support for thread-safe state restoration." .
state:freePath
a lv2:Feature ;
- rdfs:label "free a file path" ;
- lv2:documentation """
-<p>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).</p>
-""" .
+ rdfs:label "free path" ;
+ rdfs:comment "A feature for freeing paths allocated by the host." .
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.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>
-""" .
+ rdfs:label "Changed" ;
+ rdfs:comment "A notification that the internal state of the plugin has changed." .
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