audacity/include/tenacity/ModuleInterface.h

/**********************************************************************

   Audacity: A Digital Audio Editor

   ModuleInterface.h

   Leland Lucius

   Copyright (c) 2014, Audacity Team
   All rights reserved.

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   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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**********************************************************************/

#ifndef __AUDACITY_MODULEINTERFACE_H__
#define __AUDACITY_MODULEINTERFACE_H__

#include <functional>
#include <memory>
#include "Identifier.h"
#include "tenacity/ComponentInterface.h"
#include "tenacity/PluginInterface.h"

// ============================================================================
//
// Don't even think about adding module types, like effect, importer, etc. in
// here.  The module interface should not have to change when new types of
// plugins are added to Audacity.
//
// In addition a single module may want to provide multiple plugin types.
// ============================================================================

// ============================================================================
///
/// ModuleInterface is a generic dll or so interface for Audacity, that is
/// used for plug ins.  Classes derived from it can handle more specific plug
/// in types.
///
// ============================================================================

class ModuleInterface  /* not final */ : public ComponentInterface
{
public:
   virtual ~ModuleInterface() {};

   // Called immediately after creation to give the instance a chance to
   // initialize.  Return "true" if initialziation was successful.
   virtual bool Initialize() = 0;

   // Called just prior to deletion to allow releasing any resources.
   virtual void Terminate() = 0;

   // A symbol identifying the family of plugin provided by this module;
   // if it is not empty, then the family as a whole can be enabled or
   // disabled by the user in Preferences
   virtual EffectFamilySymbol GetOptionalFamilySymbol() = 0;

   // "Paths" returned by FindPluginPaths() and passed back to
   // DiscoverPluginsAtPath() have module-specific meaning.
   // They are not necessarily file system paths to existent files that
   // could be placed in any folder and queried for
   // plugin information.
   // This function returns nonempty only when that is the case, and lists
   // the possible extensions of such files (an empty string in a nonempty
   // array means any file is a candidate).
   virtual const FileExtensions &GetFileExtensions() = 0;

   // Returns empty, or else, where to copy a plug-in file or bundle.
   // Drag-and-drop is supported only if GetFileExtensions() returns nonempty and
   // this function returns nonempty.
   virtual FilePath InstallPath() = 0;

   // Modules providing a single or static set of plugins may use
   // AutoRegisterPlugins() to register those plugins.
   virtual bool AutoRegisterPlugins(PluginManagerInterface & pluginManager) = 0;

   // For modules providing an interface to other dynamically loaded plugins,
   // the module returns a list of path names that will be presented to the
   // user as "New" for enablement.
   virtual PluginPaths FindPluginPaths(PluginManagerInterface & pluginManager) = 0;

   // Once the user selects desired paths from FindPluginPaths(),
   // a call to DiscoverPluginsAtPath()
   // will be made to request registration of one or more plugins.  If the module must create
   // an instance of the plugin to register it, then the instance should be deleted
   // after registration.
   // May discover more than one plug-in at the path, and
   // may call-back with paths not equal to path (perhaps appending
   // other information to it).
   // Error message does not need to mention the path and may be nonempty
   // even if some plugins are also discovered successfully.
   // Return value is the number of plugins found.
   using RegistrationCallback =
      std::function<
         const PluginID &(ModuleInterface *, ComponentInterface *) >;
   virtual unsigned DiscoverPluginsAtPath(
      const PluginPath & path, TranslatableString &errMsg,
      const RegistrationCallback &callback )
         = 0;

   // For modules providing an interface to other dynamically loaded plugins,
   // the module returns true if the plugin is still valid, otherwise false.
   virtual bool IsPluginValid(const PluginPath & path, bool bFast) = 0;

   // When appropriate, CreateInstance() will be called to instantiate the plugin.
   virtual std::unique_ptr<ComponentInterface>
      CreateInstance(const PluginPath & path) = 0;
};

// ----------------------------------------------------------------------------
// Since there may be multiple embedded modules, the module entry function will
// be declared static so as not to interfere with other modules during link.
// ----------------------------------------------------------------------------
#define DECLARE_MODULE_ENTRY(name)                    \
static ModuleInterface * name()

// ----------------------------------------------------------------------------
// This will create a class and instance that will register the module entry
// point during Audacity startup.  At the appropriate time, the entry point
// will be called to create the module instance.
// ----------------------------------------------------------------------------

// ----------------------------------------------------------------------------
// Provides the base for embedded module registration.  If used, a Register()
// method must be supplied explicitly.
// ----------------------------------------------------------------------------

#define DECLARE_BUILTIN_MODULE_BASE(name)             \
class name                                            \
{                                                     \
public:                                               \
   name() {Register();}                               \
   ~name() {Unregister();}                            \
   void Register();                                   \
   void Unregister();                                 \
};                                                    \
static name name ## _instance;

// ----------------------------------------------------------------------------
// Provides the full embedded module registration process.  Nothing further is
// required (other than supplying the module entry point function).
// ----------------------------------------------------------------------------
#define DECLARE_BUILTIN_MODULE(name)                  \
DECLARE_BUILTIN_MODULE_BASE(name)                     \
void name::Register()                                 \
{                                                     \
   RegisterProvider(AudacityModule);                  \
}                                                     \
void name::Unregister()                               \
{                                                     \
   UnregisterProvider(AudacityModule);                \
}

#endif // __AUDACITY_MODULEINTERFACE_H__