xref: /haiku/docs/user/locale/Catalog.dox (revision 991dadd6324f7b7a68e94743a39ebae789823228)
1/*
2 * Copyright 2011-2012 Haiku, Inc. All rights reserved.
3 * Distributed under the terms of the MIT License.
4 *
5 * Authors:
6 *		Axel Dörfler, axeld@pinc-software.de
7 *		John Scipione, jscipione@gmail.com
8 *		Oliver Tappe, zooey@hirschkaefer.de
9 *
10 * Corresponds to:
11 *		headers/os/locale/Catalog.h	 hrev45083
12 *		src/kits/locale/Catalog.cpp	 hrev45083
13 */
14
15
16/*!
17	\file Catalog.h
18	\ingroup locale
19	\ingroup libbe
20	\brief Provides the BCatalog class.
21*/
22
23
24/*!
25	\class BCatalog
26	\ingroup locale
27	\ingroup libbe
28	\brief String localization handling.
29
30	BCatalog is the class that allows you to perform string localization. This
31	means you give it a string in english, and it automatically returns the
32	translation of this string in the user's specified language, if available.
33
34	Most of the time, you don't have to deal with BCatalog directly. You use
35	the translation macros instead. However, there are some cases where you
36	will have to use catalogs directly. These include :
37	- Tools for managing catalogs : if you want to add, remove or edit
38	  entries in a catalog, you need to do it using the BCatalog class.
39	- Accessing catalogs other than your own : the macros only grant you
40	  access to the catalog linked with your application. To access
41	  other catalogs (for example if you create a script interpreter and
42	  want to localize the scripts), you will have to open a catalog
43	  associated with your script.
44
45	\section macros Using the macros
46	You don't have to do much in your program to handle catalogs. You must
47	first set the B_TRANSLATION_CONTEXT define to a string that identifies which
48	part of the application the strings you will translate are in. This allows
49	the translators to keep track of the strings in the catalog more easily,
50	and find where they are visible in the application. then, all you have to
51	do, is enclose any string you want to make translatable in the
52	B_TRANSLATE() macro. This macro has two uses, it will allow your text to
53	be replaced at run-time by the proper localized one, but it will also
54	allow to build the base catalog, the one that you will send to the
55	translator team, from your sourcecode.
56
57	\section chaining Chaining of catalogs
58	The catalogs you get from the locale kit are designed to use a fallback
59	system so that the user get strings in the language he's the most fluent
60	with, depending on what catalogs are available.
61
62	For example, if the user sets his language preferences as french(France),
63	spanish, english, when an application loads a catalog, the following rules
64	are used:
65	- Try to load a french(France) catalog. If it is found, this catalog
66	  will automatically include strings from the generic french catalog.
67	- Try to load a generic french catalog.
68	- Try to load a generic spanish catalog.
69	- Try to load a generic english catalog.
70	- If all of them failed, use the strings that are in the source code.
71
72	Note that french(France) will failback to french, but then directly to the
73	language in the source code. This avoids mixing 3 or more languages in the
74	same application if the catalogs are incomplete and avoids confusion.
75
76	\since Haiku R1
77*/
78
79
80/*!
81	\fn BCatalog::BCatalog()
82	\brief Construct an empty BCatalog object.
83
84	Should be followed by SetTo() method to set the catalog.
85
86	\since Haiku R1
87*/
88
89
90/*!
91	\fn BCatalog::BCatalog(const entry_ref& catalogOwner, const char* language,
92		uint32 fingerprint)
93	\brief Construct a BCatalog object for the given \a catalogOwner.
94
95	If you don't specify a language, the system default list will be used.
96	The language is passed here as a 2 letter ISO code.
97
98	The fingerprint is a way to check that the catalog that will be loaded
99	matches the current version of the application. A catalog made for a
100	different version of the application can be loaded if you set the
101	fingerprint to \c 0. This is usually not a problem, it only means that
102	some strings may not be translated properly. But if you want to provide
103	different versions of your application, it may be useful to separate their
104	catalogs.
105
106	\param catalogOwner entry_ref for which to load a catalog.
107	\param language The language of the catalog to load. If \c NULL, the user
108	       settings will be used.
109	\param fingerprint The fingerprint version-info for the catalog to load.
110	       If \c 0, the fingerprint will not be checked,and any version of the
111	       catalog will be loaded.
112
113	\since Haiku R1
114*/
115
116
117/*!
118	\fn BCatalog::~BCatalog()
119	\brief Destroys the BCatalog object freeing memory used by it.
120
121	\since Haiku R1
122*/
123
124
125/*!
126	\fn const char* BCatalog::GetString(const char* string,
127		const char* context, const char* comment)
128	\brief Get a string from the catalog.
129
130	This method access the data of the catalog and returns you the translated
131	version of the string. You must pass it the context where the string is, as
132	the same string may appear somewhere else and need a different translation.
133	The comment is optional. It is meant as an help to translators, when the
134	string alone is not helpful enough or there are special things to note.
135	The comment is also used as a way to uniquely identify a string, so if two
136	identical strings share the same context, it is still possible to provide
137	different translations.
138
139	\param string The string to translate.
140	\param context The context where the string is located.
141	\param comment Supplementary comment for translators.
142
143	\returns The translated string, or the one passed as a parameter if no
144	         translation was found.
145
146	\since Haiku R1
147*/
148
149
150/*!
151	\fn const char* BCatalog::GetString(uint32 id)
152	\brief Get a string by id from the catalog.
153
154	The id based version of this method is slightly faster, as it doesn't
155	have to compute the hash from the 3 parameters. However, it will fail
156	if there is an hash collision, so you should still fallback to the first
157	one in case of problems. Also note that the hash value may be different
158	from one catalog to another, depending on the file format they are stored
159	in, so you shouldn't rely on this method unless you are sure you can keep
160	all the catalog files under control.
161
162	\param id The identifier of the string.
163
164	\returns The translated string if found, or an empty string.
165
166	\since Haiku R1
167*/
168
169
170/*!
171	\fn status_t BCatalog::GetData(const char* name, BMessage* msg)
172	\brief Get custom data from the catalog.
173
174	This method allows you to localize something else than raw text. This
175	may include pictures, sounds, videos, or anything else. Note there is no
176	support for generating a catalog with such data inside, and the current
177	format may not support it. If you need to localize data that is not text,
178	it is advised to handle it by yourself.
179
180	\param name The name of the data to retrieve.
181	\param msg The BMessage to fill in with the data.
182
183	\returns A status code.
184	\retval B_OK Everything went fine.
185	\retval B_ERROR Unable to get an exclusive lock on data.
186	\retval B_NO_INIT Catalog is \c NULL.
187	\retval B_NAME_NOT_FOUND catalog with the specified \a name could not be
188	        found.
189
190	\since Haiku R1
191*/
192
193
194/*!
195	\fn status_t BCatalog::GetData(uint32 id, BMessage* msg)
196	\brief Get custom data from the catalog.
197
198	As for GetString, the id-based version may be subject to hash-collisions,
199	but is faster.
200
201	Note the current catalog format doesn't allow storing custom data in
202	catalogs, so the only way to use this method is providing your own
203	catalog add-on for storing the data.
204
205	\since Haiku R1
206*/
207
208
209/*!
210	\fn status_t BCatalog::GetSignature(BString* sig)
211	\brief Get the catalog mime-signature.
212
213	This method fills the sig string with the mime-signature associated to the
214	catalog.
215
216	\param sig The string where to copy the signature.
217
218	\returns An error code.
219
220	\since Haiku R1
221*/
222
223
224/*!
225	\fn status_t BCatalog::GetLanguage(BString* lang)
226	\brief Get the catalog language.
227
228	This method fills the lang string with the language name for the catalog.
229
230	\param lang The string where to copy the language.
231
232	\returns An error code.
233	\retval B_OK Everything went as expected.
234	\retval B_ERROR Could not get exclusive lock on catalog.
235	\retval B_BAD_VALUE \a lang is \c NULL.
236	\retval B_NO_INIT Catalog data is \c NULL.
237
238	\since Haiku R1
239*/
240
241
242/*!
243	\fn status_t BCatalog::GetFingerprint(uint32* fp)
244	\brief Get the catalog fingerprint.
245
246	This method setsfp to the fingerprint of the catalog. This allows you
247	to check which version of the sourcecode this catalog was generated from.
248
249	\param fp The integer to set to the fingerprint value.
250
251	\returns An error code.
252	\retval B_OK Everything went as expected.
253	\retval B_ERROR Could not get exclusive lock on catalog.
254	\retval B_BAD_VALUE \a fp is \c NULL.
255	\retval B_NO_INIT Catalog data is \c NULL.
256
257	\since Haiku R1
258*/
259
260
261/*!
262	\fn status_t BCatalog::SetTo(const entry_ref& catalogOwner,
263		const char* language, uint32 fingerprint)
264	\brief Reload the string data.
265
266	This method reloads the data for the given signature and fingerprint.
267
268	\param catalogOwner The \c entry_ref of the catalog that you want to load.
269	\param language The language of the catalog to load. If \c NULL, the user
270	       settings will be used.
271	\param fingerprint The fingerprint of the catalog you want to load.
272
273	\returns A status code, \c B_OK on success, \c B_ERROR on error.
274
275	\since Haiku R1
276*/
277
278
279/*!
280	\fn status_t BCatalog::InitCheck() const
281	\brief Check if the catalog is in a valid and usable state.
282
283	\returns A status code.
284	\retval B_OK The catalog is initialized properly.
285	\retval B_ERROR Could not get exclusive lock on catalog.
286	\retval B_NO_INIT Catalog data is \c NULL.
287
288	\since Haiku R1
289*/
290
291
292/*!
293	\fn int32 BCatalog::CountItems() const
294	\brief Gets the number of items in the catalog.
295
296	\returns the number of strings in the catalog or 0 on error.
297
298	\since Haiku R1
299*/
300