haiku/docs/user/locale/Catalog.dox

/*
 * Copyright 2011, 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:
 *		/trunk/headers/os/locale/Catalog.h	 rev 42274
 *		/trunk/src/kits/locale/Catalog.cpp	 rev 42274
 */


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


/*!
	\class BCatalog
	\ingroup locale
	\brief Class handling string localization.

	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 :
		\li 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.
		\li 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_TRANSLATE_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 :
		\li Try to load a french(France) catalog. If it is found, this catalog
			will automatically include strings from the generic french catalog.
		\li Try to load a generic french catalog.
		\li Try to load a generic spanish catalog.
		\li Try to load a generic english catalog.
		\li 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.
*/


/*!
	\fn BCatalog::BCatalog(const char* signature, const char* language = NULL,
		uint32 fingerprint = 0)
	\brief Construct a catalog for the given application.

	This constructor builds a catalog for the application with the given mime
	signature. In Haiku, the mime signature is used as a way to uniquely
	identify a catalog and match it with the corresponding application.

	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 signature Mime-signature of the application for which to load a
		catalog.
	\param language The language of the catalog to load. If 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.
*/


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

	This method access the data of the catalog and reeturns 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 differnet 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.
*/


/*!
	\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.
*/


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

	This function 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 An error code.
*/


/*!
	\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 function is providing your own
	catalog add-on for storing the data.
*/


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

	This function 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.
*/


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

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

	\param lang The string where to copy the language.

	\returns An error code.
*/


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

	This function 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.
*/


/*!
	\fn status_t BCatalog::SetCatalog(const char* signature, uint32 fingerprint)
	\brief Reload the string data.

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

	\param signature The signature of the catalog youwant to load
	\param fingerprint The fingerprint of the catalog you want to load.

	\returns An error code.
*/


/*!
	\fn status_t BCatalog::InitCheck() const
	\brief Check if the catalog is in an useable state.

	\returns \c B_OK if the catalog is initialized properly.
*/


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

	\returns the number of strings in the catalog.
*/


/*!
	\fn BCatalogaddOn* BCatalog::CatalogAddOn()
	\brief Returns the internal storage for this catalog.

	\returns the internal storage class used by this catalog. You should
	not have to use it.
*/