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audacity/lib-src/slv2/slv2/lv2_ui.h

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/************************************************************************
*
* In-process UI extension for LV2
*
* Copyright (C) 2006-2008 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 UIs for plugins. The UIs 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 uiext: <http://lv2plug.in/ns/extensions/ui#> .
<http://my.plugin> uiext:ui <http://my.pluginui> .
<http://my.plugin> a uiext:GtkUI .
<http://my.pluginui> uiext:binary <myui.so> .
</pre>
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, in this case uiext:GtkUI. The
class defines what type the UI is, e.g. what graphics toolkit it uses.
There are no UI classes defined in this extension, those are specified
separately (and anyone can define their own).
(Note: the prefix above is used throughout this file for the same URI)
It's entirely 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 does not have to be the same. There are many
valid reasons for having the plugin and the UI 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
UI 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 UI, this extension allows for meta-extensions that
can extend the interface between the UI 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 UI as
<pre>
<http://my.pluginui> uiext:requiredFeature <http://my.feature> .
<http://my.pluginui> uiext:optionalFeature <http://my.feature> .
</pre>
These predicates have the same semantics as lv2:requiredFeature and
lv2:optionalFeature - if a UI 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) in a LV2_Feature struct (as defined in lv2.h) to the UI's
instantiate() function.
These features may be used to specify how to pass data between the UI
and the plugin port buffers - see LV2UI_Write_Function for details.
There are four features defined in this extension that hosts may want to
implement:
<pre>
uiext:makeResident
</pre>
If this feature is required by a UI the host MUST NEVER unload the shared
library containing the UI implementation during the lifetime of the host
process (e.g. never calling dlclose() on Linux). This feature may be
needed by e.g. a Gtk UI that registers its own Glib types using
g_type_register_static() - if it gets unloaded and then loaded again the
type registration will break, since there is no way to unregister the
types when the library is unloaded. The data pointer in the LV2_Feature
for this feature should always be set to NULL.
<pre>
uiext:makeSONameResident
</pre>
This feature is ELF specific - it should only be used by UIs that
use the ELF file format for the UI shared object files (e.g. on Linux).
If it is required by an UI the UI should also list a number of SO names
(shared object names) for libraries that the UI shared object
depends on and that may not be unloaded during the lifetime of the host
process, using the predicate @c uiext:residentSONames, like this:
<pre>
<http://my.pluginui> uiext:residentSONames "libgtkmm-2.4.so.1", "libfoo.so.0"
</pre>
The host MUST then make sure that the shared libraries with the given ELF
SO names are not unloaded when the plugin UI is, but stay loaded during
the entire lifetime of the host process. On Linux this can be accomplished
by calling dlopen() on the shared library file with that SO name and never
calling a matching dlclose(). However, if a plugin UI requires the
@c uiext:makeSONameResident feature, it MUST ALWAYS be safe for the host to
just never unload the shared object containing the UI implementation, i.e.
act as if the UI required the @c uiext:makeResident feature instead. Thus
the host only needs to find the shared library files corresponding to the
given SO names if it wants to save RAM by unloading the UI shared object
file when it is no longer needed. The data pointer for the LV2_Feature for
this feature should always be set to NULL.
<pre>
uiext:noUserResize
</pre>
If an 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.
<pre>
uiext:fixedSize
</pre>
If an UI requires this feature it indicates the same thing as
uiext: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.
UIs 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 UI extension is NOT a lv2:Feature. There is no way for a
plugin to know whether the host that loads it supports UIs or not, and
the plugin must ALWAYS work without the UI (although it may be rather
useless unless it has been configured using the UI in a previous session).
A UI does not have to be a graphical widget, it could just as well be a
server listening for OSC input or an interface to some sort of hardware
device, depending on the RDF class of the UI.
*/
#ifndef LV2_UI_H
#define LV2_UI_H
#include <slv2/lv2.h>
#define LV2_UI_URI "http://lv2plug.in/ns/extensions/ui"
#ifdef __cplusplus
extern "C" {
#endif
/** A pointer to some widget or other type of UI handle.
The actual type is defined by the type URI of the UI.
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 UIs, in various
toolkits. */
typedef void* LV2UI_Widget;
/** This handle indicates a particular instance of a UI.
It is valid to compare this to NULL (0 for C++) but otherwise the
host MUST not attempt to interpret it. The UI 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
UI 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 UI 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
and what the host should do with it depends on the value of the @c format
parameter.
The @c format parameter should either be 0 or a numeric ID for a "Transfer
mechanism". 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 UI 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 UI will work without being able to write to that port or not).
The only exception is when the UI wants to write single float values to
input ports of the class lv2:ControlPort, in which case @c buffer_size
should always be 4, the buffer should always contain a single IEEE-754
float, and @c format should be 0.
The numeric IDs for the transfer mechanisms are provided by a
URI-to-integer mapping function provided by the host, using the URI Map
feature <http://lv2plug.in/ns/ext/uri-map> with the map URI
"http://lv2plug.in/ns/extensions/ui". Thus a UI that requires transfer
mechanism features also requires the URI Map feature, but this is
implicit - the UI does not have to list the URI map feature as a required
or optional feature in it's RDF data.
An UI MUST NOT pass a @c format parameter value (except 0) that has not
been returned by the host-provided URI mapping function for a
host-supported transfer mechanism feature URI.
The UI MUST NOT try to write to a port for which there is no specified
transfer mechanism, or to an output port. The UI is responsible for
allocating the buffer and deallocating it after the call.
*/
typedef void (*LV2UI_Write_Function)(LV2UI_Controller controller,
uint32_t port_index,
uint32_t buffer_size,
uint32_t format,
const void* buffer);
/** This struct contains the implementation of an UI. A pointer to an
object of this type is returned by the lv2ui_descriptor() function.
*/
typedef struct _LV2UI_Descriptor {
/** The URI for this UI (not for the plugin it controls). */
const char* URI;
/** Create a new UI object and return a handle to it. This function works
similarly to the instantiate() member in LV2_Descriptor.
@param descriptor The descriptor for the UI that you want to instantiate.
@param plugin_uri The URI of the plugin that this UI 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 UI 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 UI will write a
widget pointer to this location (what type of widget
depends on the RDF class of the UI) that will be the
main UI widget.
@param features An array of LV2_Feature pointers. The host must pass
all feature URIs that it and the UI supports and any
additional data, just like in the LV2 plugin
instantiate() function. Note that UI features and plugin
features are NOT necessarily the same, they just share
the same data structure - this will probably not be the
same array as the one the plugin host passes to a
plugin.
*/
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 UI object and the associated widget. The host must not try
to access the widget after calling this function.
*/
void (*cleanup)(LV2UI_Handle ui);
/** Tell the UI 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 @c format parameter, which has the same
meaning as in 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 does not have to be called for every
single change if the host's UI 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. In this case the @c format
parameter should be 0.
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 UI's RDF data:
<pre>
uiext:portNotification
uiext:noPortNotification
uiext:plugin
uiext:portIndex
</pre>
For example, if you want the UI with uri
<code><http://my.pluginui></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 UI:
<pre>
<http://my.pluginui> uiext:portNotification [ uiext:plugin <http://my.plugin> ;
uiext:portIndex 4 ] .
</pre>
and similarly with <code>uiext:noPortNotification</code> if you wanted
to prevent notifications for a port for which it would be on by default
otherwise. The UI is not allowed to request notifications for ports of
types 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 UI 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 UI is not interested in any
port events.
*/
void (*port_event)(LV2UI_Handle ui,
uint32_t port_index,
uint32_t buffer_size,
uint32_t format,
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 UI 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 UI 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 UI 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.
*/
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
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