xref: /haiku/docs/user/translation/TranslatorRoster.dox (revision 70dc2e27e998e93c980065c0b92956a5dce3e83c)

/*
 * Copyright 2014-2015 Markus Himmel. All rights reserved.
 * Distributed under the terms of the MIT License.
 *
 * Authors:
 *		Markus Himmel, markus@himmel-villmar.de
 *
 * Corresponds to:
 *		headers/os/translation/TranslatorRoster.h	hrev48588
 *		src/kits/translation/TranslatorRoster.cpp	hrev48588
 */

/*!
	\file TranslatorRoster.h
	\ingroup translation
	\ingroup libtranslation
	\brief BTranslatorRoster class definition
*/

/*!
	\class BTranslatorRoster
	\ingroup translation
	\ingroup libtranslation
	\brief Class that serves as an interface between applications and
		translators.

	BTranslatorRoster gives applications access to the translation kit.
	Applications can request translations and BTranslatorRoster will
	automatically search for a matching translator and have it perfrom the
	translation.

	\warning BTranslatorRoster does not perform chaining of any sort. Only
		translations that can be made by invoking a single translator are
		supported.

	\note BTranslationUtils provides some helper methods that perform the
		interaction with BTranslatorRoster for you.

	BTranslationRoster acts as a container. While in most cases the default
	roster is used, it is possible to create a roster that interacts with a
	custom set of translators.
*/

/*!
	\name Constructors and Destructor
*/

//! @{

/*!
	\fn BTranslatorRoster::BTranslatorRoster()
	\brief Constructs an empty BTranslatorRoster.

	\warning Only call the contructor if you want to use a custom collection of
		translators. Use Default() if you don't.
*/

/*!
	\fn BTranslatorRoster::BTranslatorRoster(BMessage* model);
	\brief Constructs a BTranslatorRoster and fills it.

	\param model A message that contains information about a
		BTranslatorRoster.

	After initialization, \a model is searched for strings with the name
	\c "be:translator_path". The translators that are located at each path
	are added to the roster. If multiple paths point to translators with the
	same name, the translator at the path with the lowest index within the
	message will be kept.

	\warning Use Instantiate() instead of this constructor if \a model was
		created using Archive().
*/

/*!
	\fn BTranslatorRoster::~BTranslatorRoster();
	\brief Deletes this BTranslatorRoster.

	If the BTranslatorRoster that is deleted is the default roster, a new
	default roster will be created when BTranslatorRoster::Default() is called
	for the next time.

	Release() is called on all translators in the roster.
*/

/*!
	\fn static BTranslatorRoster* BTranslatorRoster::Default();
	\brief Gets the default BTranslatorRoster.

	There is only one default translator. It is created when it is first
	requested. It is poplated according to the following rules:

	If the environment variable \c TRANSLATORS is set, it will be populated
	with all translators that are present in the directories denoted by
	\c TRANSLATORS. The paths are separated by a colon (<tt>:</tt>). If
	multiple paths contain a translator with the same name, the translator
	that is located in the path that appears earliest in \c TRANSLATORS will
	be kept.

	If \c TRANSLATORS is unset, the user non-packaged add-ons directory, the
	user add-ons directory, the system non-packaged add-ons directory and the
	system add-ons directory will be used. If those directories do not contain
	a subdirectory \c Translators, it will be created. The subdirectories are
	then added in the above order. If multiple directories contain a translator
	with the same name, the translator that is located in the path that appears
	earliest in the above list will be kept.
*/

//! @}

/*!
	\name Archiving
*/

//! @{

/*!
	\fn virtual status_t BTranslatorRoster::Archive(BMessage* into, bool deep\
		= true) const;
	\brief Archive this BTranslatorRoster into a BMessage.

	\param into Where the BTranslatorRoster will be stored.
	\param deep Unused.

	\retval B_OK The operation was successful.
	\retval B_BAD_VALUE \a into was NULL.
	\retval B_ERROR The operation failed.
*/

/*!
	\fn static BArchivable* BTranslatorRoster::Instantiate(BMessage* from);
	\brief Creates a new BTranslatorRoster from a message.

	\param from The message that contains information about a
		BTranslatorRoster.

	\returns \c NULL if \a from was \c NULL, contained invalid archive data or
		archive data of a class that is not BTranslatorRoster. A pointer to a
		new BTranslatorRoster containing the information from \a from
		otherwise.
*/

//! @}

/*!
	\name Roster Management
*/

//! @{

/*!
	\fn status_t BTranslatorRoster::AddTranslators(const char* loadPath =\
		NULL);
	\brief Adds translators from a directory to the roster.

	\param loadPath A colon-separated list of directories to search for
		translators in.

	The following method is used to determine which translators to add:

	If \a loadPath is not \c NULL, the roster will be populated with all
	translators that are present in the directores denoted by \a loadPath. The
	paths are separated by a colon (<tt>:</tt>). If multiple paths contain a
	translator with the same name, the translator that is located in the path
	that appears earliest in \a loadPath will be kept.

	If \a loadPath is \c NULL and the environment variable \c TRANSLATORS is
	set, it will be populated with all translators that are present in the
	directories denoted by \c TRANSLATORS. The paths are separated by a colon
	(<tt>:</tt>). If multiple paths contain a translator with the same name,
	the translator that is located in the path that appears earliest in
	\c TRANSLATORS will be kept.

	If \a loadPath is \c NULL and \c TRANSLATORS is unset, the user
	non-packaged add-ons directory, the user add-ons directory, the system
	non-packaged add-ons directory and the system add-ons directory will be
	used. If those directories do not contain a subdirectory \c Translators, it
	will be created. The subdirectories are then added in the above order. If
	multiple directories contain a translator with the same name, the
	translator that is located in the path that appears earliest in the above
	list will be kept.

	\returns \c B_OK if everything went well, an error code specific to the
		operation that failed otherwise.
*/

/*!
	\fn status_t BTranslatorRoster::AddTranslator(BTranslator* translator);
	\brief Adds a single BTranslator to the roster.

	\param translator The translator that should be added.

	\remark AddTranslator() calls Acquire() on the translator, so it is safe
		to release it if you had acquired it before.

	\retval B_OK The translator was successfully added to the roster.
	\retval B_NO_MEMORY There was no memory to enlarge the roster.
	\retval B_BAD_VALUE \a translator was \c NULL.
*/

//! @}

/*!
	\name Translator Access
*/

//! @{

/*!
	\fn virtual status_t BTranslatorRoster::GetTranslators(BPositionIO*\
		source, BMessage* ioExtension, translator_info** _info, int32*\
		_numInfo, uint32 hintType = 0, const char* hintMIME = NULL, uint32\
		wantType = 0);
	\brief Collects information about all translators that are able to perform
		a certain conversion in an array.

	\param source Read and seek interface to the data to be examinded.
	\param ioExtension A message containing configuration information for the
		translators.
	\param _info Where the resulting array will be stored.
	\param _numInfo Where the number of elements in the resulting array will
		be stored.
	\param hintType A hint about the data format in \a source. \c 0 represents
		an unknown type.
	\param hintMIME A hint about the MIME type of \a source. \c NULL represents
		an unknown type.
	\param wantType The format that \a source needs to be translated into. \c 0
		permits any output type.

	If this function returns \c B_OK the caller has to call \c delete[] when
	they are done using \a _info.

	\retval B_OK \a _info and \a _numInfo were successfully populated.
	\retval B_NO_TRANSLATOR No suitable translator was found.
	\retval B_BAD_VALUE \a source, \a _info or \a _numInfo was \c NULL.
	\retval B_IO_ERROR There was an error interacting with \a source.
	\retval B_NO_MEMORY Could not allocate enough memory for the array.
*/

/*!
	\fn virtual status_t BTranslatorRoster::GetAllTranslators(translator_id**\
		_list, int32* _count);
	\brief Collects the IDs of all translators in the roster in an array.

	\param _list Where the resulting array will be stored.
	\param _count Where the number of elements in the resulting array will be
		stored.

	If this function returns \c B_OK the caller has to call \c delete[] when
	they are done using \a _info.

	\retval B_OK \a _list and \a _count were populated successfully.
	\retval B_NO_MEMORY Could not allocate the memory for the array.
*/

/*!
	\fn virtual status_t BTranslatorRoster::GetTranslatorInfo(translator_id\
		translatorID, const char** _name, const char** _info, int32* _version);
	\brief Looks up general information of the translator with a given ID.

	\param translatorID The ID of the translator whose information is
		requested.
	\param _name Where the name of the translator will be stored.
	\param _info Where the description of the translator will be stored.
	\param _version Where the version of the translator will be stored.

	Do not free any returned data. If any of \a _name, \a _info and \a _version
	are \c NULL, the non-null pointers will still be written to.

	\retval B_OK All non-null pointers were written to successfully.
	\retval B_BAD_VALUE All three pointers were \c NULL.
	\retval B_NO_TRANSLATOR The roster does not contain any translator with the
		ID \a translatorID.
*/

/*!
	\fn virtual status_t BTranslatorRoster::GetInputFormats(translator_id\
		translatorID, const translation_format** _formats, int32* _numFormats);
	\brief Looks up the input formats of the translator with a given ID.

	\param translatorID The ID of the translator whose input formats are
		requested.
	\param _formats Where the array of input formats will be stored.
	\param _numFormats Where the number of elements in the array of input
		formats will be stored.

	Do not free any of the returned data.

	\retval B_OK \a _formats and \a _numFormats were successfully set.
	\retval B_BAD_VALUE \a _formats or \a _numFormats was \c NULL.
	\retval B_NO_TRANSLATOR The roster does not contain any translator with the
		ID \a translatorID.
*/

/*!
	\fn virtual status_t BTranslatorRoster::GetOutputFormats(translator_id\
		translatorID, const translation_format** _formats, int32* _numFormats);
	\brief Looks up the output formats of the translator with a given ID.

	\param translatorID The ID of the translator whose output formats are
		requested.
	\param _formats Where the array of output formats will be stored.
	\param _numFormats Where the number of elements in the array of output
		formats will be stored.

	Do not free any of the returned data.

	\retval B_OK \a _formats and \a _numFormats were successfully set.
	\retval B_BAD_VALUE \a _formats or \a _numFormats was \c NULL.
	\retval B_NO_TRANSLATOR The roster does not contain any translator with the
		ID \a translatorID.
*/

/*!
	\fn virtual status_t BTranslatorRoster::MakeConfigurationView(\
		translator_id translatorID, BMessage* ioExtension, BView** _view,\
		BRect* _extent);
	\brief Creates the configuration view of a specified translator from the
		roster.

	\param translatorID The ID of the translator whose configuration view
		should be created.
	\param ioExtension A message containing configuration information for the
		translator.
	\param _view Where a pointer to the newly created configuration view will
		be stored.
	\param _extent Where the size of of the newly created configuration view
		will be stored.

	\retval B_OK Everything went well.
	\retval B_BAD_VALUE \a _view or \a _extent were \c NULL or \a ioExtension
		was \c NULL or contained bad data.
	\retval B_NO_TRANSLATOR The roster does not contain any translator with the
		ID \a translatorID.
	\retval B_ERROR An error occurred or the translator chose not to supply
		a configuration view.
*/

/*!
	\fn virtual status_t BTranslatorRoster::GetConfigurationMessage(\
		translator_id translatorID, BMessage* ioExtension)
	\brief Populates a BMessage with the settings of the specified translator.

	\param translatorID The ID of the translator whose settings \a ioExtension
		should be populated with.
	\param ioExtension The message that should be populated.

	\retval B_OK \a ioExtension was populated successfully.
	\retval B_NO_TRANSLATOR The roster does not contain any translator with the
		ID \a translatorID.
	\retval B_BAD_VALUE \a ioExtension was \c NULL.
	\retval B_ERROR An error occurred or the translator chose not to provide
		this functionality.
*/

/*!
	\fn status_t BTranslatorRoster::GetRefFor(translator_id translatorID,\
		entry_ref* ref);
	\brief Returns the entry_ref of the specified translator.

	\param translatorID The ID of the translator whose entry_ref is to be
		found.
	\param ref Where the entry_ref will be written.

	\retval B_OK Everything went well.
	\retval B_BAD_VALUE \a ref was \c NULL.
	\retval B_NO_TRANSLATOR The roster does not contain any translator with the
		ID \a translatorID.
	\retval B_ERROR An error occurred.
*/

//! @}

/*!
	\name Core Methods
*/

//! @{

/*!
	\fn virtual status_t BTranslatorRoster::Identify(BPositionIO* source,\
		BMessage* ioExtension, translator_info* _info, uint32 hintType = 0,\
		const char* hintMIME = NULL, uint32 wantType = 0);
	\brief Determines the best translator in the roster to perform a certain
		conversion.

	\param source Read and seek interface to the data to be examined.
	\param ioExtension A message containing configuration infortmation for the
		translators.
	\param _info Where information about the best translator will be written.
	\param hintType A hint about the data format in \a source. \c 0 represents
		an unknown type.
	\param hintMIME A hint about the MIME type of \a source. \c NULL represents
		an unknown type.
	\param wantType The format that \a source needs to be translated into. \c 0
		permits any output type.

	To determine the best translator, for all translators that report that
	they are able to perform the translation, the values they return for
	quality and capability are multiplied. The translator with the highest
	value gets returned. Note that quality and capability for the output
	format are not taken into consideration.

	\retval B_OK Identification was successful. Information about the chosen
		translator was written to \a _info.
	\retval B_NO_TRANSLATOR No suitable translator was found.
	\retval B_BAD_VALUE \a source or \a _info was \c NULL.
	\retval B_IO_ERROR There was an error interacting with \a source.
*/

/*!
	\fn virtual status_t BTranslatorRoster::Translate(BPositionIO* source,\
		const translator_info* info, BMessage* ioExtension, BPositionIO*\
		destination, uint32 wantOutType, uint32 hintType = 0, const char*\
		hintMIME = NULL);
	\brief Finds and invokes the best translator for a conversion.

	\param source Read and seek interface to the input data.
	\param info Information about wich translator should be used. If
		\a info is \c NULL, Identify() will be used to find a suitable
		translator.
	\param ioExtension A message containing configuration information for the
		translator.
	\param destination Write interface to the output location.
	\param wantOutType The desired output format. If this is \c 0, any type
		is permitted.
	\param hintType A hint about the type of the data in \a source.
	\param hintMIME A hint about the MIME type of the data in \a source.

	\retval B_OK The translated data was successfully written to
		\a destination.
	\retval B_NO_TRANSLATOR \a info was non-null but did not match to any
		translator in the roster.
	\retval B_NO_TRANSLATOR \a info was \c NULL and no suitable translator was
		found.
	\retval B_ERROR An error occurred.
	\retval B_BAD_VALUE \a source or \a destination was \c NULL or
		\a ioExtension was \c NULL or contained bad data.
	\retval B_IO_ERROR An error occurred accessing \a source or \a destination.
*/

/*!
	\fn virtual status_t BTranslatorRoster::Translate(translator_id\
		translatorID, BPositionIO* source, BMessage* ioExtension, BPositionIO*\
		destination, uint32 wantOutType);
	\brief Uses a specified translator from the roster to perform a conversion.

	\param translatorID The ID of the translator that should be used.
	\param source Read and seek interface to the input data.
	\param ioExtension A message containing configuration information for the
		translator.
	\param destination Write interface to the output location.
	\param wantOutType The desired output format. If this is \c 0, any type is
		permitted.

	\retval B_OK The translated data was successfully written to
		\a destination.
	\retval B_NO_TRANSLATOR The specified translator cannot handle the data in
		\a source.
	\retval B_ERROR An error occurred.
	\retval B_BAD_VALUE \a source or \a destination was \c NULL or
		\a ioExtension was \c NULL or contained bad data.
	\retval B_IO_ERROR An error occurred accessing \a source or \a destination.
*/

//! @}

/*!
	\name Miscellaneous
*/

//! @{

/*!
	\fn bool BTranslatorRoster::IsTranslator(entry_ref* ref);
	\brief Determines whether the specified add-on contains at least one
		translator.

	\param ref The entry_ref to be tested.

	\retval true The add-on exposes translators.
	\retval false The add-on exposes no translators or an error occurred.
*/

//! @}

/*!
	\name Notifications
*/

//! @{

/*!
	\fn status_t BTranslatorRoster::StartWatching(BMessenger target);
	\brief Register a messenger to be notified when the roster changes.

	\param target The BMessenger to be registered.

	Whenever a translator is added to or removed from the roster, all
	messengers that were registered through this method are sent a message.
	\c message->what will be \c B_TRANSLATOR_ADDED or \c B_TRANSLATOR_REMOVED
	(as defined in AppDefs.h) respectively.

	\retval B_OK \a target was successfully registered.
	\retval B_NO_MEMORY Unable to allocate more memory for the list of targets.
*/

/*!
	\fn status_t BTranslatorRoster::StopWatching(BMessenger target);
	\brief Unregister a messenger from the notification list.

	\param target The BMessenger to be removed.

	\retval B_OK \a target was successfully unsubscribed.
	\retval B_BAD_VALUE \a target could not be found on the notification list.

	\sa StartWatching(BMessenger target)
*/

//! @}