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authorDavid Robillard <d@drobilla.net>2007-12-15 21:20:06 +0000
committerDavid Robillard <d@drobilla.net>2007-12-15 21:20:06 +0000
commitd11a21b66f75f2e7f5605573565e2bd776c3afcc (patch)
tree1122081159e2282bbe073375b9a73858a8705af5 /slv2/lv2_gui.h
parent3bbd32c902be036d07b911cb0011e8c1d20c0c1c (diff)
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Updated LV2 GUI extension.
git-svn-id: http://svn.drobilla.net/lad/slv2@974 a436a847-0d15-0410-975c-d299462d15a1
Diffstat (limited to 'slv2/lv2_gui.h')
-rw-r--r--slv2/lv2_gui.h634
1 files changed, 288 insertions, 346 deletions
diff --git a/slv2/lv2_gui.h b/slv2/lv2_gui.h
index 7b108b3..1fa643c 100644
--- a/slv2/lv2_gui.h
+++ b/slv2/lv2_gui.h
@@ -1,346 +1,288 @@
-/************************************************************************
- *
- * In-process UI extension for LV2
- *
- * Copyright (C) 2006-2007 Lars Luthman <lars.luthman@gmail.com>
- *
- * Based on lv2.h, which is:
- *
- * Copyright (C) 2000-2002 Richard W.E. Furse, Paul Barton-Davis,
- * Stefan Westerfeld
- * Copyright (C) 2006 Steve Harris, Dave Robillard.
- *
- * This header is free software; you can redistribute it and/or modify it
- * under the terms of the GNU Lesser General Public License as published
- * by the Free Software Foundation; either version 2.1 of the License,
- * or (at your option) any later version.
- *
- * This header is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- * Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public
- * License along with this library; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
- * USA.
- *
- ***********************************************************************/
-
-/** @file
- This extension defines an interface that can be used in LV2 plugins and
- hosts to create GUIs for plugins. The GUIs are plugins that reside in
- shared object files in an LV2 bundle and be referenced in the RDF file
- using the triples (Turtle shown)
-<pre>
- @prefix guiext: <http://ll-plugins.nongnu.org/lv2/ext/ipgui/1#> .
- <http://my.plugin> guiext:gui <http://my.plugingui> .
- <http://my.plugingui> guiext:binary <mygui.so> .
-</pre>
- where <http://my.plugin> is the URI of the plugin, <http://my.plugingui> is
- the URI of the plugin GUI and <mygui.so> is the relative URI to the shared
- object file. While it is possible to have the plugin GUI 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 GUIs don't have to load the GUI code.
-
- (Note: the prefix above is used throughout this file for the same URI)
-
- It's entirely possible to have multiple GUIs for the same plugin, or to have
- the GUI for a plugin in a different bundle from the actual plugin - this
- way people other than the plugin author can write plugin GUIs independently
- without editing the original plugin bundle. If a GUI is in a separate bundle
- the first triple above should be in that bundle's manifest.ttl file so that
- hosts can find the GUI when scanning the manifests.
-
- Note that the process that loads the shared object file containing the GUI
- code and the process that loads the shared object file containing the
- actual plugin implementation does not have to be the same. There are many
- valid reasons for having the plugin and the GUI in different processes, or
- even on different machines. This means that you can _not_ use singletons
- and global variables and expect them to refer to the same objects in the
- GUI and the actual plugin. The function callback interface defined in this
- header is all you can expect to work.
-
- Since the LV2 specification itself allows for extensions that may add
- new types of data and configuration parameters that plugin authors may
- want to control with a GUI, this extension allows for meta-extensions that
- can extend the interface between the GUI and the host. See the
- instantiate() and extension_data() callback pointers for more details.
-
- Note that this extension is NOT a Host Feature. There is no way for a plugin
- to know whether the host that loads it supports GUIs or not, and the plugin
- must ALWAYS work without the GUI (although it may be rather useless unless
- it has been configured using the GUI in a previous session).
-
- GUIs written to this specification do not need to be threadsafe - the
- functions defined below may only be called in the same thread as the UI
- main loop is running in.
-*/
-
-#ifndef LV2_GUI_H
-#define LV2_GUI_H
-
-#include "lv2.h"
-
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-
-/** A pointer to some widget.
- * The actual type of the widget is defined by the type URI of the GUI.
- * e.g. if "<http://example.org/somegui> a guiext:GtkGUI", this is a pointer
- * to a GtkWidget. All the functionality provided by this extension is
- * toolkit independent, the host only needs to pass the necessary callbacks
- * and display the widget, if possible. Plugins may have several GUIs,
- * in various toolkits.
- */
-typedef void* LV2UI_Widget;
-
-
-/** This handle indicates a particular instance of a GUI.
- It is valid to compare this to NULL (0 for C++) but otherwise the
- host MUST not attempt to interpret it. The GUI plugin may use it to
- reference internal instance data. */
-typedef void* LV2UI_Handle;
-
-
-/** This handle indicates a particular plugin instance, provided by the host.
- It is valid to compare this to NULL (0 for C++) but otherwise the
- GUI plugin MUST not attempt to interpret it. The host may use it to
- reference internal instance data. */
-typedef void* LV2UI_Controller;
-
-
-/** This is the type of the host-provided function that the GUI can use to
- send data to a plugin's input ports. The @c buffer parameter must point
- to a block of data, @c buffer_size bytes large. The contents of this buffer
- will depend on the class of the port it's being sent to. For ports of the
- class lv2:ControlPort, buffer_size should be sizeof(float) and the buffer
- contents should be a float value. For ports of the class llext:MidiPort the
- buffer should contain the data bytes of a single MIDI event, and buffer_size
- should be the number of bytes in the event. No other port classes are
- allowed, unless the format and the meaning of the buffer passed to this
- function is defined in the extension that specifies that class or in a
- separate GUI host feature extension that is required by this GUI.
-
- The GUI is responsible for allocating the buffer and deallocating it after
- the call. There are no timing guarantees at all for this function, although
- the faster the host can get the data to the plugin port the better. A
- function pointer of this type will be provided to the GUI by the host in
- the instantiate() function. */
-typedef void (*LV2UI_Write_Function)(LV2UI_Controller controller,
- uint32_t port_index,
- uint32_t buffer_size,
- const void* buffer);
-
-/** This is the type of the host-provided function that the GUI can use to
- send arbitrary commands to the plugin. The parameters after the first one
- should be const char* variables, terminated by a NULL pointer, and will be
- interpreted as a command with arguments. A function of this type will be
- provided to the GUI by the host in the instantiate() function. */
-typedef void (*LV2UI_Command_Function)(LV2UI_Controller controller,
- uint32_t argc,
- const char* const* argv);
-
-/** This is the type of the host-provided function that the GUI can use to
- request a program change in the host. A function of this type will be
- provided to the GUI by the host in the instantiate() function. Calling
- this function does not guarantee that the program will change, it is just
- a request. If the program does change, the GUI's current_program_changed()
- callback will be called, either before or after this function returns
- depending on whether the GUI host <-> plugin instance communication is
- synchronous or asynchronous. */
-typedef void (*LV2UI_Program_Change_Function)(LV2UI_Controller controller,
- unsigned char program);
-
-/** This is the type of the host-provided function that the GUI can use to
- request that the current state of the plugin is saved to a program.
- A function of this type will be provided to the GUI by the host in the
- instantiate function. Calling this function does not guarantee that the
- state will be saved, it is just a request. If the state is saved, the
- GUI's program_added() callback will be called, either before or after
- this function returns depending on whether the GUI host <-> plugin
- instance communication is synchronous or asynchronous. */
-typedef void (*LV2UI_Program_Save_Function)(LV2UI_Controller controller,
- unsigned char program,
- const char* name);
-
-
-/** */
-typedef struct _LV2UI_Descriptor {
-
- /** The URI for this GUI (not for the plugin it controls). */
- const char* URI;
-
- /** Create a new GUI object and return a handle to it. This function works
- similarly to the instantiate() member in LV2_Descriptor, with the
- additions that the URI for the plugin that this GUI is for is passed
- as a parameter, a function pointer and a controller handle are passed to
- allow the plugin to write to input ports in the plugin (write_function
- and controller) and a pointer to a LV2_Widget is passed, which the GUI
- plugin should set to point to a newly created widget which will be the
- GUI for the plugin. This widget may only be destroyed by cleanup().
-
- The features array works like the one in the instantiate() member
- in LV2_Descriptor, except that the URIs should be denoted with the triples
- <pre>
- <http://my.plugingui> guiext:optionalFeature <http://my.guifeature>
- </pre>
- or
- <pre>
- <http://my.plugingui> guiext:requiredFeature <http://my.guifeature>
- </pre>
- in the RDF file, instead of the lv2:optionalFeature or lv2:requiredFeature
- that is used by host features. These features are associated with the GUI,
- not with the plugin - they are not actually LV2 Host Features, they just
- use the same data structure.
-
- The same rules apply for these features as for normal host features -
- if a feature is listed as required in the RDF file and the host does not
- support it, it must not load the GUI.
- */
- LV2UI_Handle (*instantiate)(const struct _LV2UI_Descriptor* descriptor,
- const char* plugin_uri,
- const char* bundle_path,
- LV2UI_Write_Function write_function,
- LV2UI_Command_Function command_function,
- LV2UI_Program_Change_Function program_function,
- LV2UI_Program_Save_Function save_function,
- LV2UI_Controller controller,
- LV2UI_Widget* widget,
- const LV2_Feature* const* features);
-
-
- /** Destroy the GUI object and the associated widget.
- */
- void (*cleanup)(LV2UI_Handle gui);
-
- /** Tell the GUI that something interesting has happened at a plugin port.
- For control ports this would be when the value in the buffer has changed,
- for message-based port classes like MIDI or OSC it would be when a
- message has arrived in the buffer. For other port classes it is not
- defined when this function is called, unless it is specified in the
- definition of that port class extension. For control ports the default
- setting is to call this function whenever an input control port value
- has changed but not when any output control port value has changed, for
- all other port classes the default setting is to never call this function.
-
- However, the default setting can be modified by using the following
- URIs:
- <pre>
- guiext:portNotification
- guiext:noPortNotification
- guiext:plugin
- guiext:portIndex
- </pre>
- For example, if you want the GUI with uri
- <code><http://my.plugingui></code> for the plugin with URI
- <code><http://my.plugin></code> to get notified when the value of the
- output control port with index 4 changes, you would use the following
- in the RDF for your GUI:
- <pre>
- <http://my.plugingui> guiext:portNotification [ guiext:plugin <http://my.plugin> ;
- guiext:portIndex 4 ] .
- </pre>
- and similarly with <code>guiext:noPortNotification</code> if you wanted to
- prevent notifications for a port for which it would be on by default
- otherwise.
-
- The @c buffer is only valid during the time of this function call, so if
- the GUI wants to keep it for later use it has to copy the contents to an
- internal buffer.
-
- The buffer is subject to the same rules as the ones for the
- LV2_Write_Function type. This means that a plugin GUI may not request a
- portNotification for a port that has a class other than lv2:ControlPort
- or llext:MidiPort unless the buffer format and meaning is specified in
- the extension that defines that port class, or in a separate GUI host
- feature extension that is required by the GUI. Any GUI that does that
- should be considered broken and the host should not use it.
-
- This member may be set to NULL if the GUI is not interested in any
- port events.
- */
- void (*port_event)(LV2UI_Handle gui,
- uint32_t port,
- uint32_t buffer_size,
- const void* buffer);
-
- /** This function is called when the plugin instance wants to send feedback
- to the GUI. It may be called in response to a command function call,
- either before or after the command function has returned (depending on
- whether the GUI host <-> plugin instance communication is synchronous or
- asynchronous). */
- void (*feedback)(LV2UI_Handle gui,
- uint32_t argc,
- const char* const* argv);
-
- /** This function is called when the host adds a new program to its program
- list, or changes the name of an old one. It may be set to NULL if the
- GUI isn't interested in displaying program information. */
- void (*program_added)(LV2UI_Handle gui,
- unsigned char number,
- const char* name);
-
- /** This function is called when the host removes a program from its program
- list. It may be set to NULL if the GUI isn't interested in displaying
- program information. */
- void (*program_removed)(LV2UI_Handle gui,
- unsigned char number);
-
- /** This function is called when the host clears its program list. It may be
- set to NULL if the GUI isn't interested in displaying program
- information. */
- void (*programs_cleared)(LV2UI_Handle gui);
-
- /** This function is called when the host changes the current program. It may
- be set to NULL if the GUI isn't interested in displaying program
- information. */
- void (*current_program_changed)(LV2UI_Handle gui,
- unsigned char number);
-
- /** Returns a data structure associated with an extension URI, for example
- a struct containing additional function pointers. Avoid returning
- function pointers directly since standard C++ has no valid way of
- casting a void* to a function pointer. This member may be set to NULL
- if the GUI is not interested in supporting any extensions. This is similar
- to the extension_data() member in LV2_Descriptor.
- */
- void* (*extension_data)(LV2UI_Handle gui,
- const char* uri);
-
-} LV2UI_Descriptor;
-
-
-
-/** A plugin programmer must include a function called "lv2ui_descriptor"
- with the following function prototype within the shared object
- file. This function will have C-style linkage (if you are using
- C++ this is taken care of by the 'extern "C"' clause at the top of
- the file). This function will be accessed by the GUI host using the
- @c dlsym() function and called to get a LV2UI_UIDescriptor for the
- wanted plugin.
-
- Just like lv2_descriptor(), this function takes an index parameter. The
- index should only be used for enumeration and not as any sort of ID number -
- the host should just iterate from 0 and upwards until the function returns
- NULL, or a descriptor with an URI matching the one the host is looking for
- is returned.
-*/
-const LV2UI_Descriptor* lv2ui_descriptor(uint32_t index);
-
-
-/** This is the type of the lv2ui_descriptor() function. */
-typedef const LV2UI_Descriptor* (*LV2UI_DescriptorFunction)(uint32_t index);
-
-
-
-#ifdef __cplusplus
-}
-#endif
-
-
-#endif /* LV2_GUI_H */
-
+/************************************************************************
+ *
+ * In-process UI extension for LV2
+ *
+ * Copyright (C) 2006-2007 Lars Luthman <lars.luthman@gmail.com>
+ *
+ * Based on lv2.h, which was
+ *
+ * Copyright (C) 2000-2002 Richard W.E. Furse, Paul Barton-Davis,
+ * Stefan Westerfeld
+ * Copyright (C) 2006 Steve Harris, Dave Robillard.
+ *
+ * This header is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation; either version 2.1 of the License,
+ * or (at your option) any later version.
+ *
+ * This header is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
+ * USA.
+ *
+ ***********************************************************************/
+
+/** @file
+ This extension defines an interface that can be used in LV2 plugins and
+ hosts to create GUIs for plugins. The GUIs are plugins that reside in
+ shared object files in an LV2 bundle and are referenced in the RDF data
+ using the triples (Turtle shown)
+<pre>
+ @@prefix guiext: <http://ll-plugins.nongnu.org/lv2/ext/gui#> .
+ <http://my.plugin> guiext:gui <http://my.plugingui> .
+ <http://my.plugin> a guiext:GtkGUI .
+ <http://my.plugingui> guiext:binary <mygui.so> .
+</pre>
+ where <http://my.plugin> is the URI of the plugin, <http://my.plugingui> is
+ the URI of the plugin GUI and <mygui.so> is the relative URI to the shared
+ object file. While it is possible to have the plugin GUI 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 GUIs don't have to load the GUI code.
+ A GUI MUST specify its class in the RDF data. In this case the class is
+ guiext:GtkGUI, which is the only class defined by this extension.
+
+ (Note: the prefix above is used throughout this file for the same URI)
+
+ It's entirely possible to have multiple GUIs for the same plugin, or to have
+ the GUI for a plugin in a different bundle from the actual plugin - this
+ way people other than the plugin author can write plugin GUIs independently
+ without editing the original plugin bundle.
+
+ Note that the process that loads the shared object file containing the GUI
+ code and the process that loads the shared object file containing the
+ actual plugin implementation does not have to be the same. There are many
+ valid reasons for having the plugin and the GUI in different processes, or
+ even on different machines. This means that you can _not_ use singletons
+ and global variables and expect them to refer to the same objects in the
+ GUI and the actual plugin. The function callback interface defined in this
+ header is all you can expect to work.
+
+ Since the LV2 specification itself allows for extensions that may add
+ new types of data and configuration parameters that plugin authors may
+ want to control with a GUI, this extension allows for meta-extensions that
+ can extend the interface between the GUI and the host. These extensions
+ mirror the extensions used for plugins - there are required and optional
+ "features" that you declare in the RDF data for the GUI as
+<pre>
+ <http://my.plugingui> guiext:requiredFeature <http://my.feature> .
+ <http://my.plugingui> guiext:optionalFeature <http://my.feature> .
+</pre>
+ These predicates have the same semantics as lv2:requiredFeature and
+ lv2:optionalFeature - if a GUI is declaring a feature as required, the
+ host is NOT allowed to load it unless it supports that feature, and if it
+ does support a feature (required or optional) it MUST pass that feature's
+ URI and any additional data (specified by the meta-extension that defines
+ the feature) to the GUI's instantiate() function.
+
+ These features may be used to specify how to pass data between the GUI
+ and the plugin port buffers - see LV2UI_Write_Function for details.
+
+ GUIs written to this specification do not need to be threadsafe - the
+ functions defined below may only be called in the same thread as the UI
+ main loop is running in.
+
+ Note that this GUI extension is NOT a lv2:Feature. There is no way for a
+ plugin to know whether the host that loads it supports GUIs or not, and
+ the plugin must ALWAYS work without the GUI (although it may be rather
+ useless unless it has been configured using the GUI in a previous session).
+
+*/
+
+#ifndef LV2_IPGUI_H
+#define LV2_IPGUI_H
+
+#include "lv2.h"
+
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+/** A pointer to some widget.
+ The actual type of the widget is defined by the type URI of the GUI.
+ e.g. if "<http://example.org/somegui> a guiext:GtkGUI", this is a pointer
+ to a GtkWidget compatible with GTK+ 2.0 and the GUI can expect the GTK+
+ main loop to be running during the entire lifetime of all instances of that
+ GUI. All the functionality provided by this extension is toolkit
+ independent, the host only needs to pass the necessary callbacks and
+ display the widget, if possible. Plugins may have several GUIs, in various
+ toolkits, but guiext:GtkGUI is the only type that is defined in this
+ extension. */
+typedef void* LV2UI_Widget;
+
+
+/** This handle indicates a particular instance of a GUI.
+ It is valid to compare this to NULL (0 for C++) but otherwise the
+ host MUST not attempt to interpret it. The GUI plugin may use it to
+ reference internal instance data. */
+typedef void* LV2UI_Handle;
+
+
+/** This handle indicates a particular plugin instance, provided by the host.
+ It is valid to compare this to NULL (0 for C++) but otherwise the
+ GUI plugin MUST not attempt to interpret it. The host may use it to
+ reference internal plugin instance data. */
+typedef void* LV2UI_Controller;
+
+
+/** This is the type of the host-provided function that the GUI can use to
+ send data to a plugin's input ports. The @c buffer parameter must point
+ to a block of data, @c buffer_size bytes large. The contents of this buffer
+ will depend on the class of the port it's being sent to, and the transfer
+ mechanism specified for that port class.
+
+ Transfer mechanisms are Features and may be defined in meta-extensions.
+ They specify how to translate the data buffers passed to this function
+ to input data for the plugin ports. If a GUI wishes to write data to an
+ input port, it must list a transfer mechanism Feature for that port's
+ class as an optional or required feature (depending on whether the GUI
+ will work without being able to write to that port or not). The only
+ exception is ports of the class lv2:ControlPort, for which @c buffer_size
+ should always be 4 and the buffer should always contain a single IEEE-754
+ float.
+
+ The GUI MUST NOT try to write to a port for which there is no specified
+ transfer mechanism, or to an output port. The GUI is responsible for
+ allocating the buffer and deallocating it after the call. A function
+ pointer of this type will be provided to the GUI by the host in the
+ instantiate() function. */
+typedef void (*LV2UI_Write_Function)(LV2UI_Controller controller,
+ uint32_t port_index,
+ uint32_t buffer_size,
+ const void* buffer);
+
+
+/** */
+typedef struct _LV2UI_Descriptor {
+
+ /** The URI for this GUI (not for the plugin it controls). */
+ const char* URI;
+
+ /** Create a new GUI object and return a handle to it. This function works
+ similarly to the instantiate() member in LV2_Descriptor.
+
+ @param descriptor The descriptor for the GUI that you want to instantiate.
+ @param plugin_uri The URI of the plugin that this GUI will control.
+ @param bundle_path The path to the bundle containing the RDF data file
+ that references this shared object file, including the
+ trailing '/'.
+ @param write_function A function provided by the host that the GUI can
+ use to send data to the plugin's input ports.
+ @param controller A handle for the plugin instance that should be passed
+ as the first parameter of @c write_function.
+ @param widget A pointer to an LV2UI_Widget. The GUI will write a
+ widget pointer to this location (what type of widget
+ depends on the RDF class of the GUI) that will be the
+ main GUI widget.
+ @param features An array of LV2_Feature pointers. The host must pass
+ all feature URIs that it and the plugin supports and any
+ additional data, just like in the LV2 plugin
+ instantiate() function.
+ */
+ LV2UI_Handle (*instantiate)(const struct _LV2UI_Descriptor* descriptor,
+ const char* plugin_uri,
+ const char* bundle_path,
+ LV2UI_Write_Function write_function,
+ LV2UI_Controller controller,
+ LV2UI_Widget* widget,
+ const LV2_Feature* const* features);
+
+
+ /** Destroy the GUI object and the associated widget. The host must not try
+ to access the widget after calling this function.
+ */
+ void (*cleanup)(LV2UI_Handle gui);
+
+ /** Tell the GUI that something interesting has happened at a plugin port.
+ What is interesting and how it is written to the buffer passed to this
+ function is defined by the specified transfer mechanism for that port
+ class (see LV2UI_Write_Function). The only exception is ports of the
+ class lv2:ControlPort, for which this function should be called
+ when the port value changes (it must not be called for every single
+ change if the host's GUI thread has problems keeping up with the thread
+ the plugin is running in), @c buffer_size should be 4 and the buffer
+ should contain a single IEEE-754 float.
+
+ By default, the host should only call this function for input ports of
+ the lv2:ControlPort class. However, the default setting can be modified
+ by using the following URIs in the GUI's RDF data:
+ <pre>
+ guiext:portNotification
+ guiext:noPortNotification
+ guiext:plugin
+ guiext:portIndex
+ </pre>
+ For example, if you want the GUI with uri
+ <code><http://my.plugingui></code> for the plugin with URI
+ <code><http://my.plugin></code> to get notified when the value of the
+ output control port with index 4 changes, you would use the following
+ in the RDF for your GUI:
+ <pre>
+ <http://my.plugingui> guiext:portNotification [ guiext:plugin <http://my.plugin> ;
+ guiext:portIndex 4 ] .
+ </pre>
+ and similarly with <code>guiext:noPortNotification</code> if you wanted
+ to prevent notifications for a port for which it would be on by default
+ otherwise. The GUI is not allowed to request notifications for ports
+ for which no transfer mechanism is specified, if it does it should be
+ considered broken and the host should not load it.
+
+ The @c buffer is only valid during the time of this function call, so if
+ the GUI wants to keep it for later use it has to copy the contents to an
+ internal buffer.
+
+ This member may be set to NULL if the GUI is not interested in any
+ port events.
+ */
+ void (*port_event)(LV2UI_Handle gui,
+ uint32_t port,
+ uint32_t buffer_size,
+ const void* buffer);
+
+ /** Returns a data structure associated with an extension URI, for example
+ a struct containing additional function pointers. Avoid returning
+ function pointers directly since standard C++ has no valid way of
+ casting a void* to a function pointer. This member may be set to NULL
+ if the GUI is not interested in supporting any extensions. This is similar
+ to the extension_data() member in LV2_Descriptor.
+ */
+ const void* (*extension_data)(const char* uri);
+
+} LV2UI_Descriptor;
+
+
+
+/** A plugin GUI programmer must include a function called "lv2ui_descriptor"
+ with the following function prototype within the shared object
+ file. This function will have C-style linkage (if you are using
+ C++ this is taken care of by the 'extern "C"' clause at the top of
+ the file). This function will be accessed by the GUI host using the
+ @c dlsym() function and called to get a LV2UI_UIDescriptor for the
+ wanted plugin.
+
+ Just like lv2_descriptor(), this function takes an index parameter. The
+ index should only be used for enumeration and not as any sort of ID number -
+ the host should just iterate from 0 and upwards until the function returns
+ NULL, or a descriptor with an URI matching the one the host is looking for
+ is returned.
+*/
+const LV2UI_Descriptor* lv2ui_descriptor(uint32_t index);
+
+
+/** This is the type of the lv2ui_descriptor() function. */
+typedef const LV2UI_Descriptor* (*LV2UI_DescriptorFunction)(uint32_t index);
+
+
+
+#ifdef __cplusplus
+}
+#endif
+
+
+#endif