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1 /*
2  * Copyright © 2013 Ran Benita
3  *
4  * Permission is hereby granted, free of charge, to any person obtaining a
5  * copy of this software and associated documentation files (the "Software"),
6  * to deal in the Software without restriction, including without limitation
7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
8  * and/or sell copies of the Software, and to permit persons to whom the
9  * Software is furnished to do so, subject to the following conditions:
10  *
11  * The above copyright notice and this permission notice (including the next
12  * paragraph) shall be included in all copies or substantial portions of the
13  * Software.
14  *
15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
21  * DEALINGS IN THE SOFTWARE.
22  */
23 
24 #ifndef _XKBCOMMON_COMPOSE_H
25 #define _XKBCOMMON_COMPOSE_H
26 
27 #include <xkbcommon/xkbcommon.h>
28 
29 #ifdef __cplusplus
30 extern "C" {
31 #endif
32 
33 /**
34  * @file
35  * libxkbcommon Compose API - support for Compose and dead-keys.
36  */
37 
38 /**
39  * @defgroup compose Compose and dead-keys support
40  * Support for Compose and dead-keys.
41  * @since 0.5.0
42  *
43  * @{
44  */
45 
46 /**
47  * @page compose-overview Overview
48  * @parblock
49  *
50  * Compose and dead-keys are a common feature of many keyboard input
51  * systems.  They extend the range of the keysysm that can be produced
52  * directly from a keyboard by using a sequence of key strokes, instead
53  * of just one.
54  *
55  * Here are some example sequences, in the libX11 Compose file format:
56  *
57  *     <dead_acute> <a>         : "á"   aacute # LATIN SMALL LETTER A WITH ACUTE
58  *     <Multi_key> <A> <T>      : "@"   at # COMMERCIAL AT
59  *
60  * When the user presses a key which produces the \<dead_acute> keysym,
61  * nothing initially happens (thus the key is dubbed a "dead-key").  But
62  * when the user enters <a>, "á" is "composed", in place of "a".  If
63  * instead the user had entered a keysym which does not follow
64  * \<dead_acute\> in any compose sequence, the sequence is said to be
65  * "cancelled".
66  *
67  * Compose files define many such sequences.  For a description of the
68  * common file format for Compose files, see the Compose(5) man page.
69  *
70  * A successfuly-composed sequence has two results: a keysym and a UTF-8
71  * string.  At least one of the two is defined for each sequence.  If only
72  * a keysym is given, the keysym's string representation is used for the
73  * result string (using xkb_keysym_to_utf8()).
74  *
75  * This library provides low-level support for Compose file parsing and
76  * processing.  Higher-level APIs (such as libX11's Xutf8LookupString(3))
77  * may be built upon it, or it can be used directly.
78  *
79  * @endparblock
80  */
81 
82 /**
83  * @page compose-conflicting Conflicting Sequences
84  * @parblock
85  *
86  * To avoid ambiguity, a sequence is not allowed to be a prefix of another.
87  * In such a case, the conflict is resolved thus:
88  *
89  * 1. A longer sequence overrides a shorter one.
90  * 2. An equal sequence overrides an existing one.
91  * 3. A shorter sequence does not override a longer one.
92  *
93  * Sequences of length 1 are allowed, although they are not common.
94  *
95  * @endparblock
96  */
97 
98 /**
99  * @page compose-cancellation Cancellation Behavior
100  * @parblock
101  *
102  * What should happen when a sequence is cancelled?  For example, consider
103  * there are only the above sequences, and the input kesysms are
104  * \<dead_acute\> \<b\>.  There are a few approaches:
105  *
106  * 1. Swallow the cancelling keysym; that is, no keysym is produced.
107  *    This is the approach taken by libX11.
108  * 2. Let the cancelling keysym through; that is, \<b\> is produced.
109  * 3. Replay the entire sequence; that is, \<dead_acute\> \<b\> is produced.
110  *    This is the approach taken by Microsoft Windows (approximately;
111  *    instead of \<dead_acute\>, the underlying key is used.  This is
112  *    difficult to simulate with XKB keymaps).
113  *
114  * You can program whichever approach best fits users' expectations.
115  *
116  * @endparblock
117  */
118 
119 /**
120  * @struct xkb_compose_table
121  * Opaque Compose table object.
122  *
123  * The compose table holds the definitions of the Compose sequences, as
124  * gathered from Compose files.  It is immutable.
125  */
126 struct xkb_compose_table;
127 
128 /**
129  * @struct xkb_compose_state
130  * Opaque Compose state object.
131  *
132  * The compose state maintains state for compose sequence matching, such
133  * as which possible sequences are being matched, and the position within
134  * these sequences.  It acts as a simple state machine wherein keysyms are
135  * the input, and composed keysyms and strings are the output.
136  *
137  * The compose state is usually associated with a keyboard device.
138  */
139 struct xkb_compose_state;
140 
141 /** Flags affecting Compose file compilation. */
142 enum xkb_compose_compile_flags {
143     /** Do not apply any flags. */
144     XKB_COMPOSE_COMPILE_NO_FLAGS = 0
145 };
146 
147 /** The recognized Compose file formats. */
148 enum xkb_compose_format {
149     /** The classic libX11 Compose text format, described in Compose(5). */
150     XKB_COMPOSE_FORMAT_TEXT_V1 = 1
151 };
152 
153 /**
154  * @page compose-locale Compose Locale
155  * @parblock
156  *
157  * Compose files are locale dependent:
158  * - Compose files are written for a locale, and the locale is used when
159  *   searching for the appropriate file to use.
160  * - Compose files may reference the locale internally, with directives
161  *   such as %L.
162  * As such, functions like xkb_compose_table_new_from_locale() require
163  * a @p locale parameter.  This will usually be the current locale (see
164  * locale(7) for more details).  You may also want to allow the user to
165  * explicitly configure it, so he can use the Compose file of a given
166  * locale, but not use that locale for other things.
167  *
168  * You may query the current locale as follows:
169  * @code
170  *     const char *locale;
171  *     locale = setlocale(LC_CTYPE, NULL);
172  * @endcode
173  *
174  * This will only give useful results if the program had previously set
175  * the current locale using setlocale(3), with LC_CTYPE or LC_ALL and a
176  * non-NULL argument.
177  *
178  * If you prefer not to use the locale system of the C runtime library,
179  * you may nevertheless obtain the user's locale directly using
180  * environment variables, as described in locale(7).  For example,
181  * @code
182  *     locale = getenv("LC_ALL");
183  *     if (!locale)
184  *         locale = getenv("LC_CTYPE");
185  *     if (!locale)
186  *         locale = getenv("LANG");
187  *     if (!locale)
188  *         locale = "C";
189  * @endcode
190  *
191  * Note that some locales supported by the C standard library may not
192  * have a Compose file assigned.
193  *
194  * @endparblock
195  */
196 
197 /**
198  * Create a compose table for a given locale.
199  *
200  * The locale is used for searching the file-system for an appropriate
201  * Compose file.  The search order is described in Compose(5).  It is
202  * affected by the following environment variables:
203  * XCOMPOSEFILE, HOME, XLOCALEDIR.
204  *
205  * @param context
206  *     The library context in which to create the compose table.
207  * @param locale
208  *     The current locale.  See @ref compose-locale.
209  * @param flags
210  *     Optional flags for the compose table, or 0.
211  *
212  * @returns A compose table for the given locale, or NULL if the
213  * compilation failed or a Compose file was not found.
214  *
215  * @memberof xkb_compose_table
216  */
217 struct xkb_compose_table *
218 xkb_compose_table_new_from_locale(struct xkb_context *context,
219                                   const char *locale,
220                                   enum xkb_compose_compile_flags flags);
221 
222 /**
223  * Create a new compose table from a Compose file.
224  *
225  * @param context
226  *     The library context in which to create the compose table.
227  * @param file
228  *     The Compose file to compile.
229  * @param locale
230  *     The current locale.  See @ref compose-locale.
231  * @param format
232  *     The text format of the Compose file to compile.
233  * @param flags
234  *     Optional flags for the compose table, or 0.
235  *
236  * @returns A compose table compiled from the given file, or NULL if
237  * the compilation failed.
238  *
239  * @memberof xkb_compose_table
240  */
241 struct xkb_compose_table *
242 xkb_compose_table_new_from_file(struct xkb_context *context,
243                                 FILE *file,
244                                 const char *locale,
245                                 enum xkb_compose_format format,
246                                 enum xkb_compose_compile_flags flags);
247 
248 /**
249  * Create a new compose table from a memory buffer.
250  *
251  * This is just like xkb_compose_table_new_from_file(), but instead of
252  * a file, gets the table as one enormous string.
253  *
254  * @see xkb_compose_table_new_from_file()
255  * @memberof xkb_compose_table
256  */
257 struct xkb_compose_table *
258 xkb_compose_table_new_from_buffer(struct xkb_context *context,
259                                   const char *buffer, size_t length,
260                                   const char *locale,
261                                   enum xkb_compose_format format,
262                                   enum xkb_compose_compile_flags flags);
263 
264 /**
265  * Take a new reference on a compose table.
266  *
267  * @returns The passed in object.
268  *
269  * @memberof xkb_compose_table
270  */
271 struct xkb_compose_table *
272 xkb_compose_table_ref(struct xkb_compose_table *table);
273 
274 /**
275  * Release a reference on a compose table, and possibly free it.
276  *
277  * @param table The object.  If it is NULL, this function does nothing.
278  *
279  * @memberof xkb_compose_table
280  */
281 void
282 xkb_compose_table_unref(struct xkb_compose_table *table);
283 
284 /** Flags for compose state creation. */
285 enum xkb_compose_state_flags {
286     /** Do not apply any flags. */
287     XKB_COMPOSE_STATE_NO_FLAGS = 0
288 };
289 
290 /**
291  * Create a new compose state object.
292  *
293  * @param table
294  *     The compose table the state will use.
295  * @param flags
296  *     Optional flags for the compose state, or 0.
297  *
298  * @returns A new compose state, or NULL on failure.
299  *
300  * @memberof xkb_compose_state
301  */
302 struct xkb_compose_state *
303 xkb_compose_state_new(struct xkb_compose_table *table,
304                       enum xkb_compose_state_flags flags);
305 
306 /**
307  * Take a new reference on a compose state object.
308  *
309  * @returns The passed in object.
310  *
311  * @memberof xkb_compose_state
312  */
313 struct xkb_compose_state *
314 xkb_compose_state_ref(struct xkb_compose_state *state);
315 
316 /**
317  * Release a reference on a compose state object, and possibly free it.
318  *
319  * @param state The object.  If NULL, do nothing.
320  *
321  * @memberof xkb_compose_state
322  */
323 void
324 xkb_compose_state_unref(struct xkb_compose_state *state);
325 
326 /**
327  * Get the compose table which a compose state object is using.
328  *
329  * @returns The compose table which was passed to xkb_compose_state_new()
330  * when creating this state object.
331  *
332  * This function does not take a new reference on the compose table; you
333  * must explicitly reference it yourself if you plan to use it beyond the
334  * lifetime of the state.
335  *
336  * @memberof xkb_compose_state
337  */
338 struct xkb_compose_table *
339 xkb_compose_state_get_compose_table(struct xkb_compose_state *state);
340 
341 /** Status of the Compose sequence state machine. */
342 enum xkb_compose_status {
343     /** The initial state; no sequence has started yet. */
344     XKB_COMPOSE_NOTHING,
345     /** In the middle of a sequence. */
346     XKB_COMPOSE_COMPOSING,
347     /** A complete sequence has been matched. */
348     XKB_COMPOSE_COMPOSED,
349     /** The last sequence was cancelled due to an unmatched keysym. */
350     XKB_COMPOSE_CANCELLED
351 };
352 
353 /** The effect of a keysym fed to xkb_compose_state_feed(). */
354 enum xkb_compose_feed_result {
355     /** The keysym had no effect - it did not affect the status. */
356     XKB_COMPOSE_FEED_IGNORED,
357     /** The keysym started, advanced or cancelled a sequence. */
358     XKB_COMPOSE_FEED_ACCEPTED
359 };
360 
361 /**
362  * Feed one keysym to the Compose sequence state machine.
363  *
364  * This function can advance into a compose sequence, cancel a sequence,
365  * start a new sequence, or do nothing in particular .  The resulting
366  * status may be observed with xkb_compose_state_get_status().
367  *
368  * Some keysyms, such as keysysm for modifier keys, are ignored - they
369  * have no effect on the status or otherwise.
370  *
371  * The following is a description of the possible status transitions, in
372  * the format CURRENT STATUS => NEXT STATUS, given a non-ignored input
373  * keysym @p keysym:
374  *
375    @verbatim
376    NOTHING or CANCELLED or COMPOSED =>
377       NOTHING   if keysym does not start a sequence.
378       COMPOSING if keysym starts a sequence.
379       COMPOSED  if keysym starts and terminates a single-keysym sequence.
380 
381    COMPOSING =>
382       COMPOSING if keysym advances any of the currently possible
383                 sequences but does not terminate any of them.
384       COMPOSED  if keysym terminates one of the currently possible
385                 sequences.
386       CANCELLED if keysym does not advance any of the currently
387                 possible sequences.
388    @endverbatim
389  *
390  * The current Compose formats do not support multiple-keysyms.
391  * Therefore, if you are using a function such as xkb_state_key_get_syms()
392  * and it returns more than one keysym, consider feeding
393  * @p XKB_KEY_NoSymbol instead.
394  *
395  * @param state
396  *     The compose state object.
397  * @param keysym
398  *     A keysym, usually obtained after a key-press event, with a
399  *     function such as xkb_state_key_get_one_sym().
400  *
401  * @returns Whether the keysym was ignored.  This is useful, for example,
402  * if you want to keep a record of the sequence matched thus far.
403  *
404  * @memberof xkb_compose_state
405  */
406 enum xkb_compose_feed_result
407 xkb_compose_state_feed(struct xkb_compose_state *state,
408                        xkb_keysym_t keysym);
409 
410 /**
411  * Reset the Compose sequence state machine.
412  *
413  * The status is set to XKB_COMPOSE_NOTHING, and the current sequence
414  * is discarded.
415  *
416  * @memberof xkb_compose_state
417  */
418 void
419 xkb_compose_state_reset(struct xkb_compose_state *state);
420 
421 /**
422  * Get the current status of the compose state machine.
423  *
424  * @see xkb_compose_status
425  * @memberof xkb_compose_state
426  **/
427 enum xkb_compose_status
428 xkb_compose_state_get_status(struct xkb_compose_state *state);
429 
430 /**
431  * Get the result Unicode/UTF-8 string for a composed sequence.
432  *
433  * See @ref compose-overview for more details.  This function is only
434  * useful when the status is XKB_COMPOSE_COMPOSED.
435  *
436  * @param[in] state
437  *     The compose state.
438  * @param[out] buffer
439  *     A buffer to write the string into.
440  * @param[in] size
441  *     Size of the buffer.
442  *
443  * @warning If the buffer passed is too small, the string is truncated
444  * (though still NUL-terminated).
445  *
446  * @returns
447  *   The number of bytes required for the string, excluding the NUL byte.
448  *   If the sequence is not complete, or does not have a viable result
449  *   string, returns 0, and sets @p buffer to the empty string (if
450  *   possible).
451  * @returns
452  *   You may check if truncation has occurred by comparing the return value
453  *   with the size of @p buffer, similarly to the snprintf(3) function.
454  *   You may safely pass NULL and 0 to @p buffer and @p size to find the
455  *   required size (without the NUL-byte).
456  *
457  * @memberof xkb_compose_state
458  **/
459 int
460 xkb_compose_state_get_utf8(struct xkb_compose_state *state,
461                            char *buffer, size_t size);
462 
463 /**
464  * Get the result keysym for a composed sequence.
465  *
466  * See @ref compose-overview for more details.  This function is only
467  * useful when the status is XKB_COMPOSE_COMPOSED.
468  *
469  * @returns The result keysym.  If the sequence is not complete, or does
470  * not specify a result keysym, returns XKB_KEY_NoSymbol.
471  *
472  * @memberof xkb_compose_state
473  **/
474 xkb_keysym_t
475 xkb_compose_state_get_one_sym(struct xkb_compose_state *state);
476 
477 /** @} */
478 
479 #ifdef __cplusplus
480 } /* extern "C" */
481 #endif
482 
483 #endif /* _XKBCOMMON_COMPOSE_H */
484