ui
type: Ontology
type: Specification
imports: lv2core
documentation: This extension is used to create User Interfaces (UIs) for LV2 plugins. UIs are implemented as an LV2UI_Descriptor loaded via lv2ui_descriptor() in a shared library, and are distributed in bundles just like plugins. UIs are associated with plugins in data: @prefix ui: <http://lv2plug.in/ns/extensions/ui#> . <http://my.plugin> ui:ui <http://my.pluginui> . <http://my.pluginui> a ui:GtkUI ; ui:binary <myui.so> . where <http://my.plugin> is the URI of the plugin, <http://my.pluginui> is the URI of the plugin UI and <myui.so> is the relative URI to the shared object file. While it is possible to have the plugin UI and the plugin in the same shared object file it is probably a good idea to keep them separate so that hosts that don't want UIs don't have to load the UI code. A UI MUST specify its class in the RDF data (ui:GtkUI in the above example). The class defines what type the UI is, e.g. what graphics toolkit it uses. Any type of UI class can be defined separately from this extension. It is possible to have multiple UIs for the same plugin, or to have the UI for a plugin in a different bundle from the actual plugin - this way people other than the plugin author can write plugin UIs independently without editing the original plugin bundle. Note that the process that loads the shared object file containing the UI code and the process that loads the shared object file containing the actual plugin implementation are not necessarily the same process (and not even necessarily on the same machine). This means that plugin and UI code MUST NOT use singletons and global variables and expect them to refer to the same objects in the UI and the actual plugin. The function callback interface defined in this header is the only method of communication between UIs and plugin instances (extensions may define more, though this is discouraged unless absolutely necessary since the significant benefits of network transparency and serialisability are lost). UI functionality may be extended …

User Interface
type: Class
comment: A UI for an LV2 plugin

GTK2 UI
type: Class
subclass of: User Interface
comment: A UI where the LV2_Widget is a pointer to a Gtk+ 2.0 compatible GtkWidget, and the host guarantees that the Gtk+ library has been initialised and the Glib main loop is running before the UI is instantiated. Note that this UI type is not suitable for binary distribution since multiple versions of Gtk can not be used in the same process.

GTK3 UI
type: Class
subclass of: User Interface
comment: A UI where the LV2_Widget is a pointer to a Gtk+ 3.0 compatible GtkWidget, and the host guarantees that the Gtk+ library has been initialised and the Glib main loop is running before the UI is instantiated. Note that this UI type is not suitable for binary distribution since multiple versions of Gtk can not be used in the same process.

Qt4 UI
type: Class
subclass of: User Interface
comment: A UI where the LV2_Widget is a pointer to a Qt4 compatible QWidget, and the host guarantees that the Qt4 library has been initialised and the Qt4 main loop is running before the UI is instantiated. Note that this UI type is not suitable for binary distribution since multiple versions of Qt can not be used in the same process.

Qt5 UI
type: Class
subclass of: User Interface
comment: A UI where the LV2_Widget is a pointer to a Qt5 compatible QWidget, and the host guarantees that the Qt5 library has been initialised and the Qt5 main loop is running before the UI is instantiated. Note that this UI type is not suitable for binary distribution since multiple versions of Qt can not be used in the same process.

X11 UI
type: Class
subclass of: User Interface
comment: A UI where the LV2_Widget is an X11 window ID. Note this is actually an integer, i.e. the LV2_Widget is not a pointer to an X11 window ID, but should be itself taken as an integer value. This is the native UI type on most POSIX systems.

Windows UI
type: Class
subclass of: User Interface
comment: A UI where the LV2_Widget is a Windows HWND window ID. Note this is actually an unsigned 32-bit integer, i.e. the LV2_Widget is not a pointer to a HWND but should be interpreted as an HWND itself. This is the native UI type on Microsoft Windows.

Cocoa UI
type: Class
subclass of: User Interface
comment: A UI where the LV2_Widget is a pointer to a NSView, the basic view type for the Cocoa API (formerly OpenStep). This is the native UI type on Mac OS X.

user interface
type: Property
domain: Plugin
range: User Interface
comment: Relates a plugin to a UI that applies to it.

binary
type: Property
deprecated: true
comment: The shared library a UI resides in. This property is redundant, new UIs SHOULD use lv2:binary, however hosts MUST still support ui:binary at this time.

makeSONameResident
type: Feature
deprecated: true
documentation: DEPRECATED This feature was intended to support UIs that link against toolkit libraries which may not be unloaded during the lifetime of the host. This is better achieved by using the appropriate flags when linking the UI, e.g. gcc -Wl,-z,nodelete.

noUserResize
type: Feature
documentation: If a UI requires this feature it indicates that it does not make sense to let the user resize the main widget, and the host should prevent that. This feature may not make sense for all UI types. The data pointer for the LV2_Feature for this feature should always be set to NULL.

fixedSize
type: Feature
documentation: If a UI requires this feature it indicates the same thing as ui:noUserResize, and additionally it means that the UI will not resize the main widget on its own - it will always remain the same size (e.g. a pixmap based GUI). This feature may not make sense for all UI types. The data pointer for the LV2_Feature for this feature should always be set to NULL.

UI scale factor
type: Property
type: DatatypeProperty
type: Option
range: float
documentation: HiDPI (High Dots Per Inch) displays have a high resolution on a relatively small form factor. Many systems use a scale factor to compensate for this, so for example, a scale factor of 2 means things are drawn twice as large as normal. Hosts can pass this as an option to UIs to communicate this information, so that the UI can draw at an appropriate scale.

Background color
type: Property
type: DatatypeProperty
type: Option
documentation: The background color of the host's UI. The host can pass this as an option so that UIs can integrate nicely with the host window around it. Hosts should pass this as an option to UIs with an integer RGBA32 color value. If the value is a 32-bit integer, it is guaranteed to be in RGBA32 format, but the UI must check the value type and not assume this, to allow for other types of color in the future.

Foreground color
type: Property
type: DatatypeProperty
type: Option
documentation: The foreground color of the host's UI. The host can pass this as an option so that UIs can integrate nicely with the host window around it. Hosts should pass this as an option to UIs with an integer RGBA32 color value. If the value is a 32-bit integer, it is guaranteed to be in RGBA32 format, but the UI must check the value type and not assume this, to allow for other types of color in the future.

parent
type: Feature
documentation: The parent for the UI. This feature can be used to pass a parent (e.g. a widget, container, canvas, etc.) the UI should be a child of. The format of data pointer of this feature is determined by the UI type, and is generally the same type as the LV2_Widget the UI would return (e.g. for a GtkUI the data would be a pointer to a GtkWidget which is a GtkContainer). This is particularly useful for cross-toolkit embedding, where the parent often must be known at construction time for embedding to work correctly. UIs should not require this feature unless it is absolutely necessary for them to work at all.

Port Notification
type: Class
subclass of: Restriction
  on property: plugin
  cardinality: 1
  comment: A PortNotification MUST have exactly one ui:plugin.
documentation: A port notification. This describes which ports the host must send notifications to the UI about. The port can be specific by index, using the ui:portIndex property, or symbol, using the lv2:symbol property. Since port indices are not guaranteed to be stable between different revisions (or even instantiations) of a plugin, symbol is recommended, and index may only be used by UIs shipped in the same bundle as the plugin. A ui:PortNotification MUST have either a ui:portIndex or a lv2:symbol to indicate which port it refers to.

port notification
type: Property
type: ObjectProperty
domain: User Interface
range: Port Notification
documentation: Indicates that a UI should receive notification (via LV2UI_Descriptor::port_event()) when a particular port's value changes. For example: eg:ui a ui:GtkUI ; ui:portNotification [ ui:plugin eg:plugin ; lv2:symbol "gain" ; ui:protocol ui:floatProtocol ] .

plugin
type: Property
type: ObjectProperty
domain: Port Notification
range: Plugin
comment: The plugin a portNotification applies to.

port index
type: Property
type: DatatypeProperty
domain: Port Notification
range: decimal
comment: The index of the port a portNotification applies to.

notify type
type: Property
domain: Port Notification
documentation: Indicates a particular type that the UI should be notified of. In the case of ports where several types of data can be present (e.g. event ports), this can be used to indicate that only a particular type of data should cause notification. This is useful where port traffic is very dense, but only a certain small number of events are actually of interest to the UI.

resize
type: Feature
type: ExtensionData
documentation: A feature that allows the UI to notify the host about its current size, or request a size change. This feature corresponds to the LV2UI_Resize struct, which should be passed with the URI LV2_UI__resize. This struct may also be provided by the UI as extension data using the same URI, in which case it is used by the host to request that the UI change its size.

portMap
type: Feature
documentation: A feature for accessing the index of a port by symbol. This makes it possible to implement and distribute UIs separately from the plugin binaries they control. This feature corresponds to the LV2UI_Port_Index struct, which should be passed with the URI LV2_UI__portIndex.

portSubscribe
type: Feature
documentation: A feature for dynamically subscribing to updates from a port. This makes it possible for a UI to explicitly request a particular style of update from a port at run-time, in a more flexible and powerful way than listing subscriptions statically allows. This feature corresponds to the LV2UI_Port_Subscribe struct, which should be passed with the URI LV2_UI__portSubscribe.

touch
type: Feature
documentation: A feature to notify the host that the user has grabbed a particular port control. This is useful for automation, so the host can allow the user to take control of a port, even if that port would otherwise be automated (much like grabbing a physical morotised fader). It can also be used for MIDI learn or in any other situation where the host needs to do something with a particular control and it would be convenient for the user to select it directly from the plugin UI. This feature corresponds to the LV2UI_Touch struct, which should be passed with the URI LV2_UI__touch.

requestValue
type: Feature
documentation: A feature to request a parameter value from the user via the host. This allows a plugin UI to request a new parameter value using the host's UI, for example by showing a dialog or integrating with the host's built-in content browser. This should only be used for complex parameter types where the plugin UI is not capable of showing the expected native platform or host interface to choose a value, such as file path parameters. This feature corresponds to the LV2UI_Request_Value struct, which should be passed with the URI LV2_UI__requestValue.

idleInterface
type: Feature
type: ExtensionData
documentation: A feature that provides a callback for the host to call rapidly to drive the UI. To support this feature, the UI should list it as a lv2:optionalFeature or lv2:requiredFeature in its data, and also as lv2:extensionData. When the UI's extension_data() is called with this URI (LV2_UI__idleInterface), it should return a pointer to an LV2UI_Idle_Interface. To indicate support, the host should pass a feature to instantiate() with this URI, with NULL for data.

showInterface
type: ExtensionData
documentation: An interface for showing and hiding a window for a UI. This allows UIs to gracefully degrade to separate windows when the host is unable to embed the UI widget for whatever reason. When the UI's extension_data() is called with this URI (LV2_UI__showInterface), it should return a pointer to an LV2UI_Show_Interface.

window title
type: Property
range: string
comment: The title for the window shown by LV2UI_Show_Interface.

update rate
type: Property
range: float
comment: The target rate, in Hz, to send updates to the UI.

protocol
type: Property
domain: Port Notification
range: Port Protocol
comment: The protocol to be used for this notification.

Port Protocol
type: Class
subclass of: Feature
documentation: A PortProtocol defines a method to communicate port data between a UI and plugin. Any PortProtocol MUST define: Port Type Which plugin port types the buffer type is valid for. Feature Data What data (if any) should be passed in the LV2_Feature. Any PortProtocol for an output port MUST define: Update Frequency When the host should call port_event(). Update Format The format of the data in the buffer passed to port_event(). Options The format of the options passed to subscribe() and unsubscribe(). Any PortProtocol for an input port MUST define: Write Format The format of the data in the buffer passed to write_port(). Write Effect What happens when the UI calls write_port(). For an example, see ui:floatProtocol or ui:peakProtocol. PortProtocol is a subclass of lv2:Feature, so UIs use lv2:optionalFeature and lv2:requiredFeature to specify which PortProtocols they want to use.

floating point value
type: Port Protocol
documentation: A protocol for transferring single floating point values. The rules for this protocol are: Port Type lv2:ControlPort Feature Data None. Update Frequency The host SHOULD call port_event() as soon as possible when the port value has changed, but there are no timing guarantees. Update Format A single float. Options None. Write Format A single float. Write Effect The host SHOULD set the port to the received value as soon as possible, but there is no guarantee that run() actually sees this value.

peak measurement for a period of audio
type: Port Protocol
documentation: This port protocol defines a way for the host to send continuous peak measurements of the audio signal at a certain port to the UI. The intended use is visualisation, e.g. an animated meter widget that shows the level of the audio input or output. A contiguous sequence of audio samples for which a peak value has been computed is called a measurement period. The rules for this protocol are: Port Type lv2:AudioPort Feature Data None. Update Frequency The host SHOULD call port_event() at regular intervals. The measurement periods used for calls to port_event() for the same port SHOULD be contiguous (i.e. the measurement period for one call should begin right after the end of the measurement period for the previous call ends) unless the UI has removed and re-added the port subscription between those calls. However, UIs MUST NOT depend on either the regularity of the calls or the contiguity of the measurement periods; hosts may change the call rate or skip calls for performance or other reasons. Measurement periods for different calls to port_event() for the same port MUST NOT overlap. Update Format A single LV2UI_Peak_Data object. Options None. Write Format None. Write Effect None.