# LV2 String Port Extension.
# Draft Revision 3
# Copyright (C) 2008 Krzysztof Foltman
#
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@prefix sp:   <http://lv2plug.in/ns/ext/string-port#> .
@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 xsd:  <http://www.w3.org/2001/XMLSchema> .
@prefix doap: <http://usefulinc.com/ns/doap#> .
@prefix foaf: <http://xmlns.com/foaf/0.1/> .

<http://lv2plug.in/ns/ext/string-port> a lv2:Specification ;
	doap:license <http://usefulinc.com/doap/licenses/mit> ;
	doap:name    "LV2 String Ports" ;
	doap:maintainer [
		a foaf:Person ;
		foaf:name "Krzysztof Foltman" ;
	] ;
	lv2:documentation """
Defines ports which contain string data.

<h4>UI issues</h4>
When using port_event / write_port (and possible other communication
mechanisms), the format parameter should contain the numeric value of URI
LV2_STRING_PORT_URI (mapped with http://lv2plug.in/ns/extensions/ui specified
as map URI).

It's probably possible to use ports belonging to message context
&lt;http://lv2plug.in/ns/ext/contexts#MessageContext&gt; for transfer. However,
contexts mechanism does not offer any way to notify the message recipient
about which ports have been changed. To remedy that, this extension defines
a flag LV2_STRING_DATA_CHANGED_FLAG that carries that information inside a
port value structure.

<h4>Storage</h4>
The value of string port are assumed to be "persistent": if a host saves
and restores a state of a plugin (e.g. control port values), the values
of input string ports should also be assumed to belong to that state. This
also applies to message context: if a session is being restored, the host
MUST resend the last value that was sent to the port before session has been
saved. In other words, string port values "stick" to message ports.
""" .

sp:StringTransfer a lv2:Feature ;
   rdfs:label "String data transfer via LV2_String_Data" .

sp:StringPort a lv2:Port ;
   rdfs:label "String port" ;
   lv2:documentation """
Indicates that the port data points to a LV2_String_Data structure
as defined in accompanying header file.

<h4>Input Port Semantics</h4>
If the port does not have a context specified (it runs in the default,
realtime audio processing context), the values in the structure and the actual
string data MUST remain unchanged for the time a run() function of a plugin
is executed. However, if the port belongs to a different context, the same
data MUST remain unchanged only for the time a run() or message_process()
function of a given context is executed.

<h4>Output Port Semantics</h4>
The plugin may only change the string or length in a run() function (if
the port belongs to default context) or in context-defined counterparts
(if the port belongs to another context). Because of that, using default
context output string ports is contraindicated for longer strings.
""" .

sp:default a rdf:Property ;
   rdfs:label "Default value" ;
   rdfs:domain sp:StringPort ;
   rdfs:range xsd:string ;
   rdfs:comment """
Gives a default value for a string port.
""" .

sp:requiredSpace a rdf:Property ;
   rdfs:label "Required storage space in bytes" ;
   rdfs:domain sp:StringPort ;
   rdfs:range xsd:nonNegativeInteger ;
   rdfs:comment """
Specifies required buffer space for output string ports and those of
input string ports that are meant to be GUI-controlled. The host MUST
allocate a buffer of at least required size to accommodate for all values
that can be produced by the plugin.
""" .