haiku/docs/user/locale/Catalog.dox

/*
 * Copyright 2011-2012 Haiku, Inc. All rights reserved.
 * Distributed under the terms of the MIT License.
 *
 * Authors:
 *		Axel Dörfler, axeld@pinc-software.de
 *		John Scipione, jscipione@gmail.com
 *		Oliver Tappe, zooey@hirschkaefer.de
 *
 * Corresponds to:
 *		headers/os/locale/Catalog.h	 hrev45083
 *		src/kits/locale/Catalog.cpp	 hrev45083
 */


/*!
	\file Catalog.h
	\ingroup locale
	\ingroup libbe
	\brief Provides the BCatalog class.
*/


/*!
	\class BCatalog
	\ingroup locale
	\ingroup libbe
	\brief String localization handling.

	BCatalog is the class that allows you to perform string localization. This
	means you give it a string in english, and it automatically returns the
	translation of this string in the user's specified language, if available.

	Most of the time, you don't have to deal with BCatalog directly. You use
	the translation macros instead. However, there are some cases where you
	will have to use catalogs directly. These include :
	- Tools for managing catalogs : if you want to add, remove or edit
	  entries in a catalog, you need to do it using the BCatalog class.
	- Accessing catalogs other than your own : the macros only grant you
	  access to the catalog linked with your application. To access
	  other catalogs (for example if you create a script interpreter and
	  want to localize the scripts), you will have to open a catalog
	  associated with your script.

	\section macros Using the macros
	You don't have to do much in your program to handle catalogs. You must
	first set the B_TRANSLATION_CONTEXT define to a string that identifies which
	part of the application the strings you will translate are in. This allows
	the translators to keep track of the strings in the catalog more easily,
	and find where they are visible in the application. then, all you have to
	do, is enclose any string you want to make translatable in the
	B_TRANSLATE() macro. This macro has two uses, it will allow your text to
	be replaced at run-time by the proper localized one, but it will also
	allow to build the base catalog, the one that you will send to the
	translator team, from your sourcecode.

	\section chaining Chaining of catalogs
	The catalogs you get from the locale kit are designed to use a fallback
	system so that the user get strings in the language he's the most fluent
	with, depending on what catalogs are available.

	For example, if the user sets his language preferences as french(France),
	spanish, english, when an application loads a catalog, the following rules
	are used:
	- Try to load a french(France) catalog. If it is found, this catalog
	  will automatically include strings from the generic french catalog.
	- Try to load a generic french catalog.
	- Try to load a generic spanish catalog.
	- Try to load a generic english catalog.
	- If all of them failed, use the strings that are in the source code.

	Note that french(France) will failback to french, but then directly to the
	language in the source code. This avoids mixing 3 or more languages in the
	same application if the catalogs are incomplete and avoids confusion.

	\since Haiku R1
*/


/*!
	\fn BCatalog::BCatalog()
	\brief Construct an empty BCatalog object.

	Should be followed by SetTo() method to set the catalog.

	\since Haiku R1
*/


/*!
	\fn BCatalog::BCatalog(const entry_ref& catalogOwner, const char* language,
		uint32 fingerprint)
	\brief Construct a BCatalog object for the given \a catalogOwner.

	If you don't specify a language, the system default list will be used.
	The language is passed here as a 2 letter ISO code.

	The fingerprint is a way to check that the catalog that will be loaded
	matches the current version of the application. A catalog made for a
	different version of the application can be loaded if you set the
	fingerprint to \c 0. This is usually not a problem, it only means that
	some strings may not be translated properly. But if you want to provide
	different versions of your application, it may be useful to separate their
	catalogs.

	\param catalogOwner entry_ref for which to load a catalog.
	\param language The language of the catalog to load. If \c NULL, the user
	       settings will be used.
	\param fingerprint The fingerprint version-info for the catalog to load.
	       If \c 0, the fingerprint will not be checked,and any version of the
	       catalog will be loaded.

	\since Haiku R1
*/


/*!
	\fn BCatalog::~BCatalog()
	\brief Destroys the BCatalog object freeing memory used by it.

	\since Haiku R1
*/


/*!
	\fn const char* BCatalog::GetString(const char* string,
		const char* context, const char* comment)
	\brief Get a string from the catalog.

	This method access the data of the catalog and returns you the translated
	version of the string. You must pass it the context where the string is, as
	the same string may appear somewhere else and need a different translation.
	The comment is optional. It is meant as an help to translators, when the
	string alone is not helpful enough or there are special things to note.
	The comment is also used as a way to uniquely identify a string, so if two
	identical strings share the same context, it is still possible to provide
	different translations.

	\param string The string to translate.
	\param context The context where the string is located.
	\param comment Supplementary comment for translators.

	\returns The translated string, or the one passed as a parameter if no
	         translation was found.

	\since Haiku R1
*/


/*!
	\fn const char* BCatalog::GetString(uint32 id)
	\brief Get a string by id from the catalog.

	The id based version of this method is slightly faster, as it doesn't
	have to compute the hash from the 3 parameters. However, it will fail
	if there is an hash collision, so you should still fallback to the first
	one in case of problems. Also note that the hash value may be different
	from one catalog to another, depending on the file format they are stored
	in, so you shouldn't rely on this method unless you are sure you can keep
	all the catalog files under control.

	\param id The identifier of the string.

	\returns The translated string if found, or an empty string.

	\since Haiku R1
*/


/*!
	\fn status_t BCatalog::GetData(const char* name, BMessage* msg)
	\brief Get custom data from the catalog.

	This method allows you to localize something else than raw text. This
	may include pictures, sounds, videos, or anything else. Note there is no
	support for generating a catalog with such data inside, and the current
	format may not support it. If you need to localize data that is not text,
	it is advised to handle it by yourself.

	\param name The name of the data to retrieve.
	\param msg The BMessage to fill in with the data.

	\returns A status code.
	\retval B_OK Everything went fine.
	\retval B_ERROR Unable to get an exclusive lock on data.
	\retval B_NO_INIT Catalog is \c NULL.
	\retval B_NAME_NOT_FOUND catalog with the specified \a name could not be
	        found.

	\since Haiku R1
*/


/*!
	\fn status_t BCatalog::GetData(uint32 id, BMessage* msg)
	\brief Get custom data from the catalog.

	As for GetString, the id-based version may be subject to hash-collisions,
	but is faster.

	Note the current catalog format doesn't allow storing custom data in
	catalogs, so the only way to use this method is providing your own
	catalog add-on for storing the data.

	\since Haiku R1
*/


/*!
	\fn status_t BCatalog::GetSignature(BString* sig)
	\brief Get the catalog mime-signature.

	This method fills the sig string with the mime-signature associated to the
	catalog.

	\param sig The string where to copy the signature.

	\returns An error code.

	\since Haiku R1
*/


/*!
	\fn status_t BCatalog::GetLanguage(BString* lang)
	\brief Get the catalog language.

	This method fills the lang string with the language name for the catalog.

	\param lang The string where to copy the language.

	\returns An error code.
	\retval B_OK Everything went as expected.
	\retval B_ERROR Could not get exclusive lock on catalog.
	\retval B_BAD_VALUE \a lang is \c NULL.
	\retval B_NO_INIT Catalog data is \c NULL.

	\since Haiku R1
*/


/*!
	\fn status_t BCatalog::GetFingerprint(uint32* fp)
	\brief Get the catalog fingerprint.

	This method setsfp to the fingerprint of the catalog. This allows you
	to check which version of the sourcecode this catalog was generated from.

	\param fp The integer to set to the fingerprint value.

	\returns An error code.
	\retval B_OK Everything went as expected.
	\retval B_ERROR Could not get exclusive lock on catalog.
	\retval B_BAD_VALUE \a fp is \c NULL.
	\retval B_NO_INIT Catalog data is \c NULL.

	\since Haiku R1
*/


/*!
	\fn status_t BCatalog::SetTo(const entry_ref& catalogOwner,
		const char* language, uint32 fingerprint)
	\brief Reload the string data.

	This method reloads the data for the given signature and fingerprint.

	\param catalogOwner The \c entry_ref of the catalog that you want to load.
	\param language The language of the catalog to load. If \c NULL, the user
	       settings will be used.
	\param fingerprint The fingerprint of the catalog you want to load.

	\returns A status code, \c B_OK on success, \c B_ERROR on error.

	\since Haiku R1
*/


/*!
	\fn status_t BCatalog::InitCheck() const
	\brief Check if the catalog is in a valid and usable state.

	\returns A status code.
	\retval B_OK The catalog is initialized properly.
	\retval B_ERROR Could not get exclusive lock on catalog.
	\retval B_NO_INIT Catalog data is \c NULL.

	\since Haiku R1
*/


/*!
	\fn int32 BCatalog::CountItems() const
	\brief Gets the number of items in the catalog.

	\returns the number of strings in the catalog or 0 on error.

	\since Haiku R1
*/