/************************************************************************ * * In-process UI extension for LV2 * * Copyright (C) 2006-2007 Lars Luthman * * 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) 
    
    @@prefix guiext:  .
        guiext:gui     .
        a             guiext:GtkGUI .
     guiext:binary  .
where is the URI of the plugin, is the URI of the plugin GUI and 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 
    
     guiext:requiredFeature  .
     guiext:optionalFeature  .
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 " 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: 
      guiext:portNotification
      guiext:noPortNotification
      guiext:plugin
      guiext:portIndex
For example, if you want the GUI with uri for the plugin with URI 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: 
       guiext:portNotification [ guiext:plugin  ;
                                                      guiext:portIndex 4 ] .
and similarly with guiext:noPortNotification 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