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comparison: modules/freetype2/include/ftcache.h

modules/freetype2/include/ftcache.h

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1 /***************************************************************************/
2 /* */
3 /* ftcache.h */
4 /* */
5 /* FreeType Cache subsystem (specification). */
6 /* */
7 /* Copyright 1996-2008, 2010, 2013 by */
8 /* David Turner, Robert Wilhelm, and Werner Lemberg. */
9 /* */
10 /* This file is part of the FreeType project, and may only be used, */
11 /* modified, and distributed under the terms of the FreeType project */
12 /* license, LICENSE.TXT. By continuing to use, modify, or distribute */
13 /* this file you indicate that you have read the license and */
14 /* understand and accept it fully. */
15 /* */
16 /***************************************************************************/
17
18
19 #ifndef __FTCACHE_H__
20 #define __FTCACHE_H__
21
22
23 #include <ft2build.h>
24 #include FT_GLYPH_H
25
26
27 FT_BEGIN_HEADER
28
29
30 /*************************************************************************
31 *
32 * <Section>
33 * cache_subsystem
34 *
35 * <Title>
36 * Cache Sub-System
37 *
38 * <Abstract>
39 * How to cache face, size, and glyph data with FreeType~2.
40 *
41 * <Description>
42 * This section describes the FreeType~2 cache sub-system, which is used
43 * to limit the number of concurrently opened @FT_Face and @FT_Size
44 * objects, as well as caching information like character maps and glyph
45 * images while limiting their maximum memory usage.
46 *
47 * Note that all types and functions begin with the `FTC_' prefix.
48 *
49 * The cache is highly portable and thus doesn't know anything about the
50 * fonts installed on your system, or how to access them. This implies
51 * the following scheme:
52 *
53 * First, available or installed font faces are uniquely identified by
54 * @FTC_FaceID values, provided to the cache by the client. Note that
55 * the cache only stores and compares these values, and doesn't try to
56 * interpret them in any way.
57 *
58 * Second, the cache calls, only when needed, a client-provided function
59 * to convert an @FTC_FaceID into a new @FT_Face object. The latter is
60 * then completely managed by the cache, including its termination
61 * through @FT_Done_Face. To monitor termination of face objects, the
62 * finalizer callback in the `generic' field of the @FT_Face object can
63 * be used, which might also be used to store the @FTC_FaceID of the
64 * face.
65 *
66 * Clients are free to map face IDs to anything else. The most simple
67 * usage is to associate them to a (pathname,face_index) pair that is
68 * used to call @FT_New_Face. However, more complex schemes are also
69 * possible.
70 *
71 * Note that for the cache to work correctly, the face ID values must be
72 * *persistent*, which means that the contents they point to should not
73 * change at runtime, or that their value should not become invalid.
74 *
75 * If this is unavoidable (e.g., when a font is uninstalled at runtime),
76 * you should call @FTC_Manager_RemoveFaceID as soon as possible, to let
77 * the cache get rid of any references to the old @FTC_FaceID it may
78 * keep internally. Failure to do so will lead to incorrect behaviour
79 * or even crashes.
80 *
81 * To use the cache, start with calling @FTC_Manager_New to create a new
82 * @FTC_Manager object, which models a single cache instance. You can
83 * then look up @FT_Face and @FT_Size objects with
84 * @FTC_Manager_LookupFace and @FTC_Manager_LookupSize, respectively.
85 *
86 * If you want to use the charmap caching, call @FTC_CMapCache_New, then
87 * later use @FTC_CMapCache_Lookup to perform the equivalent of
88 * @FT_Get_Char_Index, only much faster.
89 *
90 * If you want to use the @FT_Glyph caching, call @FTC_ImageCache, then
91 * later use @FTC_ImageCache_Lookup to retrieve the corresponding
92 * @FT_Glyph objects from the cache.
93 *
94 * If you need lots of small bitmaps, it is much more memory efficient
95 * to call @FTC_SBitCache_New followed by @FTC_SBitCache_Lookup. This
96 * returns @FTC_SBitRec structures, which are used to store small
97 * bitmaps directly. (A small bitmap is one whose metrics and
98 * dimensions all fit into 8-bit integers).
99 *
100 * We hope to also provide a kerning cache in the near future.
101 *
102 *
103 * <Order>
104 * FTC_Manager
105 * FTC_FaceID
106 * FTC_Face_Requester
107 *
108 * FTC_Manager_New
109 * FTC_Manager_Reset
110 * FTC_Manager_Done
111 * FTC_Manager_LookupFace
112 * FTC_Manager_LookupSize
113 * FTC_Manager_RemoveFaceID
114 *
115 * FTC_Node
116 * FTC_Node_Unref
117 *
118 * FTC_ImageCache
119 * FTC_ImageCache_New
120 * FTC_ImageCache_Lookup
121 *
122 * FTC_SBit
123 * FTC_SBitCache
124 * FTC_SBitCache_New
125 * FTC_SBitCache_Lookup
126 *
127 * FTC_CMapCache
128 * FTC_CMapCache_New
129 * FTC_CMapCache_Lookup
130 *
131 *************************************************************************/
132
133
134 /*************************************************************************/
135 /*************************************************************************/
136 /*************************************************************************/
137 /***** *****/
138 /***** BASIC TYPE DEFINITIONS *****/
139 /***** *****/
140 /*************************************************************************/
141 /*************************************************************************/
142 /*************************************************************************/
143
144
145 /*************************************************************************
146 *
147 * @type: FTC_FaceID
148 *
149 * @description:
150 * An opaque pointer type that is used to identity face objects. The
151 * contents of such objects is application-dependent.
152 *
153 * These pointers are typically used to point to a user-defined
154 * structure containing a font file path, and face index.
155 *
156 * @note:
157 * Never use NULL as a valid @FTC_FaceID.
158 *
159 * Face IDs are passed by the client to the cache manager that calls,
160 * when needed, the @FTC_Face_Requester to translate them into new
161 * @FT_Face objects.
162 *
163 * If the content of a given face ID changes at runtime, or if the value
164 * becomes invalid (e.g., when uninstalling a font), you should
165 * immediately call @FTC_Manager_RemoveFaceID before any other cache
166 * function.
167 *
168 * Failure to do so will result in incorrect behaviour or even
169 * memory leaks and crashes.
170 */
171 typedef FT_Pointer FTC_FaceID;
172
173
174 /************************************************************************
175 *
176 * @functype:
177 * FTC_Face_Requester
178 *
179 * @description:
180 * A callback function provided by client applications. It is used by
181 * the cache manager to translate a given @FTC_FaceID into a new valid
182 * @FT_Face object, on demand.
183 *
184 * <Input>
185 * face_id ::
186 * The face ID to resolve.
187 *
188 * library ::
189 * A handle to a FreeType library object.
190 *
191 * req_data ::
192 * Application-provided request data (see note below).
193 *
194 * <Output>
195 * aface ::
196 * A new @FT_Face handle.
197 *
198 * <Return>
199 * FreeType error code. 0~means success.
200 *
201 * <Note>
202 * The third parameter `req_data' is the same as the one passed by the
203 * client when @FTC_Manager_New is called.
204 *
205 * The face requester should not perform funny things on the returned
206 * face object, like creating a new @FT_Size for it, or setting a
207 * transformation through @FT_Set_Transform!
208 */
209 typedef FT_Error
210 (*FTC_Face_Requester)( FTC_FaceID face_id,
211 FT_Library library,
212 FT_Pointer request_data,
213 FT_Face* aface );
214
215 /* */
216
217
218 /*************************************************************************/
219 /*************************************************************************/
220 /*************************************************************************/
221 /***** *****/
222 /***** CACHE MANAGER OBJECT *****/
223 /***** *****/
224 /*************************************************************************/
225 /*************************************************************************/
226 /*************************************************************************/
227
228
229 /*************************************************************************/
230 /* */
231 /* <Type> */
232 /* FTC_Manager */
233 /* */
234 /* <Description> */
235 /* This object corresponds to one instance of the cache-subsystem. */
236 /* It is used to cache one or more @FT_Face objects, along with */
237 /* corresponding @FT_Size objects. */
238 /* */
239 /* The manager intentionally limits the total number of opened */
240 /* @FT_Face and @FT_Size objects to control memory usage. See the */
241 /* `max_faces' and `max_sizes' parameters of @FTC_Manager_New. */
242 /* */
243 /* The manager is also used to cache `nodes' of various types while */
244 /* limiting their total memory usage. */
245 /* */
246 /* All limitations are enforced by keeping lists of managed objects */
247 /* in most-recently-used order, and flushing old nodes to make room */
248 /* for new ones. */
249 /* */
250 typedef struct FTC_ManagerRec_* FTC_Manager;
251
252
253 /*************************************************************************/
254 /* */
255 /* <Type> */
256 /* FTC_Node */
257 /* */
258 /* <Description> */
259 /* An opaque handle to a cache node object. Each cache node is */
260 /* reference-counted. A node with a count of~0 might be flushed */
261 /* out of a full cache whenever a lookup request is performed. */
262 /* */
263 /* If you look up nodes, you have the ability to `acquire' them, */
264 /* i.e., to increment their reference count. This will prevent the */
265 /* node from being flushed out of the cache until you explicitly */
266 /* `release' it (see @FTC_Node_Unref). */
267 /* */
268 /* See also @FTC_SBitCache_Lookup and @FTC_ImageCache_Lookup. */
269 /* */
270 typedef struct FTC_NodeRec_* FTC_Node;
271
272
273 /*************************************************************************/
274 /* */
275 /* <Function> */
276 /* FTC_Manager_New */
277 /* */
278 /* <Description> */
279 /* Create a new cache manager. */
280 /* */
281 /* <Input> */
282 /* library :: The parent FreeType library handle to use. */
283 /* */
284 /* max_faces :: Maximum number of opened @FT_Face objects managed by */
285 /* this cache instance. Use~0 for defaults. */
286 /* */
287 /* max_sizes :: Maximum number of opened @FT_Size objects managed by */
288 /* this cache instance. Use~0 for defaults. */
289 /* */
290 /* max_bytes :: Maximum number of bytes to use for cached data nodes. */
291 /* Use~0 for defaults. Note that this value does not */
292 /* account for managed @FT_Face and @FT_Size objects. */
293 /* */
294 /* requester :: An application-provided callback used to translate */
295 /* face IDs into real @FT_Face objects. */
296 /* */
297 /* req_data :: A generic pointer that is passed to the requester */
298 /* each time it is called (see @FTC_Face_Requester). */
299 /* */
300 /* <Output> */
301 /* amanager :: A handle to a new manager object. 0~in case of */
302 /* failure. */
303 /* */
304 /* <Return> */
305 /* FreeType error code. 0~means success. */
306 /* */
307 FT_EXPORT( FT_Error )
308 FTC_Manager_New( FT_Library library,
309 FT_UInt max_faces,
310 FT_UInt max_sizes,
311 FT_ULong max_bytes,
312 FTC_Face_Requester requester,
313 FT_Pointer req_data,
314 FTC_Manager *amanager );
315
316
317 /*************************************************************************/
318 /* */
319 /* <Function> */
320 /* FTC_Manager_Reset */
321 /* */
322 /* <Description> */
323 /* Empty a given cache manager. This simply gets rid of all the */
324 /* currently cached @FT_Face and @FT_Size objects within the manager. */
325 /* */
326 /* <InOut> */
327 /* manager :: A handle to the manager. */
328 /* */
329 FT_EXPORT( void )
330 FTC_Manager_Reset( FTC_Manager manager );
331
332
333 /*************************************************************************/
334 /* */
335 /* <Function> */
336 /* FTC_Manager_Done */
337 /* */
338 /* <Description> */
339 /* Destroy a given manager after emptying it. */
340 /* */
341 /* <Input> */
342 /* manager :: A handle to the target cache manager object. */
343 /* */
344 FT_EXPORT( void )
345 FTC_Manager_Done( FTC_Manager manager );
346
347
348 /*************************************************************************/
349 /* */
350 /* <Function> */
351 /* FTC_Manager_LookupFace */
352 /* */
353 /* <Description> */
354 /* Retrieve the @FT_Face object that corresponds to a given face ID */
355 /* through a cache manager. */
356 /* */
357 /* <Input> */
358 /* manager :: A handle to the cache manager. */
359 /* */
360 /* face_id :: The ID of the face object. */
361 /* */
362 /* <Output> */
363 /* aface :: A handle to the face object. */
364 /* */
365 /* <Return> */
366 /* FreeType error code. 0~means success. */
367 /* */
368 /* <Note> */
369 /* The returned @FT_Face object is always owned by the manager. You */
370 /* should never try to discard it yourself. */
371 /* */
372 /* The @FT_Face object doesn't necessarily have a current size object */
373 /* (i.e., face->size can be~0). If you need a specific `font size', */
374 /* use @FTC_Manager_LookupSize instead. */
375 /* */
376 /* Never change the face's transformation matrix (i.e., never call */
377 /* the @FT_Set_Transform function) on a returned face! If you need */
378 /* to transform glyphs, do it yourself after glyph loading. */
379 /* */
380 /* When you perform a lookup, out-of-memory errors are detected */
381 /* _within_ the lookup and force incremental flushes of the cache */
382 /* until enough memory is released for the lookup to succeed. */
383 /* */
384 /* If a lookup fails with `FT_Err_Out_Of_Memory' the cache has */
385 /* already been completely flushed, and still no memory was available */
386 /* for the operation. */
387 /* */
388 FT_EXPORT( FT_Error )
389 FTC_Manager_LookupFace( FTC_Manager manager,
390 FTC_FaceID face_id,
391 FT_Face *aface );
392
393
394 /*************************************************************************/
395 /* */
396 /* <Struct> */
397 /* FTC_ScalerRec */
398 /* */
399 /* <Description> */
400 /* A structure used to describe a given character size in either */
401 /* pixels or points to the cache manager. See */
402 /* @FTC_Manager_LookupSize. */
403 /* */
404 /* <Fields> */
405 /* face_id :: The source face ID. */
406 /* */
407 /* width :: The character width. */
408 /* */
409 /* height :: The character height. */
410 /* */
411 /* pixel :: A Boolean. If 1, the `width' and `height' fields are */
412 /* interpreted as integer pixel character sizes. */
413 /* Otherwise, they are expressed as 1/64th of points. */
414 /* */
415 /* x_res :: Only used when `pixel' is value~0 to indicate the */
416 /* horizontal resolution in dpi. */
417 /* */
418 /* y_res :: Only used when `pixel' is value~0 to indicate the */
419 /* vertical resolution in dpi. */
420 /* */
421 /* <Note> */
422 /* This type is mainly used to retrieve @FT_Size objects through the */
423 /* cache manager. */
424 /* */
425 typedef struct FTC_ScalerRec_
426 {
427 FTC_FaceID face_id;
428 FT_UInt width;
429 FT_UInt height;
430 FT_Int pixel;
431 FT_UInt x_res;
432 FT_UInt y_res;
433
434 } FTC_ScalerRec;
435
436
437 /*************************************************************************/
438 /* */
439 /* <Struct> */
440 /* FTC_Scaler */
441 /* */
442 /* <Description> */
443 /* A handle to an @FTC_ScalerRec structure. */
444 /* */
445 typedef struct FTC_ScalerRec_* FTC_Scaler;
446
447
448 /*************************************************************************/
449 /* */
450 /* <Function> */
451 /* FTC_Manager_LookupSize */
452 /* */
453 /* <Description> */
454 /* Retrieve the @FT_Size object that corresponds to a given */
455 /* @FTC_ScalerRec pointer through a cache manager. */
456 /* */
457 /* <Input> */
458 /* manager :: A handle to the cache manager. */
459 /* */
460 /* scaler :: A scaler handle. */
461 /* */
462 /* <Output> */
463 /* asize :: A handle to the size object. */
464 /* */
465 /* <Return> */
466 /* FreeType error code. 0~means success. */
467 /* */
468 /* <Note> */
469 /* The returned @FT_Size object is always owned by the manager. You */
470 /* should never try to discard it by yourself. */
471 /* */
472 /* You can access the parent @FT_Face object simply as `size->face' */
473 /* if you need it. Note that this object is also owned by the */
474 /* manager. */
475 /* */
476 /* <Note> */
477 /* When you perform a lookup, out-of-memory errors are detected */
478 /* _within_ the lookup and force incremental flushes of the cache */
479 /* until enough memory is released for the lookup to succeed. */
480 /* */
481 /* If a lookup fails with `FT_Err_Out_Of_Memory' the cache has */
482 /* already been completely flushed, and still no memory is available */
483 /* for the operation. */
484 /* */
485 FT_EXPORT( FT_Error )
486 FTC_Manager_LookupSize( FTC_Manager manager,
487 FTC_Scaler scaler,
488 FT_Size *asize );
489
490
491 /*************************************************************************/
492 /* */
493 /* <Function> */
494 /* FTC_Node_Unref */
495 /* */
496 /* <Description> */
497 /* Decrement a cache node's internal reference count. When the count */
498 /* reaches 0, it is not destroyed but becomes eligible for subsequent */
499 /* cache flushes. */
500 /* */
501 /* <Input> */
502 /* node :: The cache node handle. */
503 /* */
504 /* manager :: The cache manager handle. */
505 /* */
506 FT_EXPORT( void )
507 FTC_Node_Unref( FTC_Node node,
508 FTC_Manager manager );
509
510
511 /*************************************************************************
512 *
513 * @function:
514 * FTC_Manager_RemoveFaceID
515 *
516 * @description:
517 * A special function used to indicate to the cache manager that
518 * a given @FTC_FaceID is no longer valid, either because its
519 * content changed, or because it was deallocated or uninstalled.
520 *
521 * @input:
522 * manager ::
523 * The cache manager handle.
524 *
525 * face_id ::
526 * The @FTC_FaceID to be removed.
527 *
528 * @note:
529 * This function flushes all nodes from the cache corresponding to this
530 * `face_id', with the exception of nodes with a non-null reference
531 * count.
532 *
533 * Such nodes are however modified internally so as to never appear
534 * in later lookups with the same `face_id' value, and to be immediately
535 * destroyed when released by all their users.
536 *
537 */
538 FT_EXPORT( void )
539 FTC_Manager_RemoveFaceID( FTC_Manager manager,
540 FTC_FaceID face_id );
541
542
543 /*************************************************************************/
544 /* */
545 /* <Section> */
546 /* cache_subsystem */
547 /* */
548 /*************************************************************************/
549
550 /*************************************************************************
551 *
552 * @type:
553 * FTC_CMapCache
554 *
555 * @description:
556 * An opaque handle used to model a charmap cache. This cache is to
557 * hold character codes -> glyph indices mappings.
558 *
559 */
560 typedef struct FTC_CMapCacheRec_* FTC_CMapCache;
561
562
563 /*************************************************************************
564 *
565 * @function:
566 * FTC_CMapCache_New
567 *
568 * @description:
569 * Create a new charmap cache.
570 *
571 * @input:
572 * manager ::
573 * A handle to the cache manager.
574 *
575 * @output:
576 * acache ::
577 * A new cache handle. NULL in case of error.
578 *
579 * @return:
580 * FreeType error code. 0~means success.
581 *
582 * @note:
583 * Like all other caches, this one will be destroyed with the cache
584 * manager.
585 *
586 */
587 FT_EXPORT( FT_Error )
588 FTC_CMapCache_New( FTC_Manager manager,
589 FTC_CMapCache *acache );
590
591
592 /************************************************************************
593 *
594 * @function:
595 * FTC_CMapCache_Lookup
596 *
597 * @description:
598 * Translate a character code into a glyph index, using the charmap
599 * cache.
600 *
601 * @input:
602 * cache ::
603 * A charmap cache handle.
604 *
605 * face_id ::
606 * The source face ID.
607 *
608 * cmap_index ::
609 * The index of the charmap in the source face. Any negative value
610 * means to use the cache @FT_Face's default charmap.
611 *
612 * char_code ::
613 * The character code (in the corresponding charmap).
614 *
615 * @return:
616 * Glyph index. 0~means `no glyph'.
617 *
618 */
619 FT_EXPORT( FT_UInt )
620 FTC_CMapCache_Lookup( FTC_CMapCache cache,
621 FTC_FaceID face_id,
622 FT_Int cmap_index,
623 FT_UInt32 char_code );
624
625
626 /*************************************************************************/
627 /* */
628 /* <Section> */
629 /* cache_subsystem */
630 /* */
631 /*************************************************************************/
632
633
634 /*************************************************************************/
635 /*************************************************************************/
636 /*************************************************************************/
637 /***** *****/
638 /***** IMAGE CACHE OBJECT *****/
639 /***** *****/
640 /*************************************************************************/
641 /*************************************************************************/
642 /*************************************************************************/
643
644
645 /*************************************************************************
646 *
647 * @struct:
648 * FTC_ImageTypeRec
649 *
650 * @description:
651 * A structure used to model the type of images in a glyph cache.
652 *
653 * @fields:
654 * face_id ::
655 * The face ID.
656 *
657 * width ::
658 * The width in pixels.
659 *
660 * height ::
661 * The height in pixels.
662 *
663 * flags ::
664 * The load flags, as in @FT_Load_Glyph.
665 *
666 */
667 typedef struct FTC_ImageTypeRec_
668 {
669 FTC_FaceID face_id;
670 FT_Int width;
671 FT_Int height;
672 FT_Int32 flags;
673
674 } FTC_ImageTypeRec;
675
676
677 /*************************************************************************
678 *
679 * @type:
680 * FTC_ImageType
681 *
682 * @description:
683 * A handle to an @FTC_ImageTypeRec structure.
684 *
685 */
686 typedef struct FTC_ImageTypeRec_* FTC_ImageType;
687
688
689 /* */
690
691
692 #define FTC_IMAGE_TYPE_COMPARE( d1, d2 ) \
693 ( (d1)->face_id == (d2)->face_id && \
694 (d1)->width == (d2)->width && \
695 (d1)->flags == (d2)->flags )
696
697
698 /*************************************************************************/
699 /* */
700 /* <Type> */
701 /* FTC_ImageCache */
702 /* */
703 /* <Description> */
704 /* A handle to a glyph image cache object. They are designed to */
705 /* hold many distinct glyph images while not exceeding a certain */
706 /* memory threshold. */
707 /* */
708 typedef struct FTC_ImageCacheRec_* FTC_ImageCache;
709
710
711 /*************************************************************************/
712 /* */
713 /* <Function> */
714 /* FTC_ImageCache_New */
715 /* */
716 /* <Description> */
717 /* Create a new glyph image cache. */
718 /* */
719 /* <Input> */
720 /* manager :: The parent manager for the image cache. */
721 /* */
722 /* <Output> */
723 /* acache :: A handle to the new glyph image cache object. */
724 /* */
725 /* <Return> */
726 /* FreeType error code. 0~means success. */
727 /* */
728 FT_EXPORT( FT_Error )
729 FTC_ImageCache_New( FTC_Manager manager,
730 FTC_ImageCache *acache );
731
732
733 /*************************************************************************/
734 /* */
735 /* <Function> */
736 /* FTC_ImageCache_Lookup */
737 /* */
738 /* <Description> */
739 /* Retrieve a given glyph image from a glyph image cache. */
740 /* */
741 /* <Input> */
742 /* cache :: A handle to the source glyph image cache. */
743 /* */
744 /* type :: A pointer to a glyph image type descriptor. */
745 /* */
746 /* gindex :: The glyph index to retrieve. */
747 /* */
748 /* <Output> */
749 /* aglyph :: The corresponding @FT_Glyph object. 0~in case of */
750 /* failure. */
751 /* */
752 /* anode :: Used to return the address of of the corresponding cache */
753 /* node after incrementing its reference count (see note */
754 /* below). */
755 /* */
756 /* <Return> */
757 /* FreeType error code. 0~means success. */
758 /* */
759 /* <Note> */
760 /* The returned glyph is owned and managed by the glyph image cache. */
761 /* Never try to transform or discard it manually! You can however */
762 /* create a copy with @FT_Glyph_Copy and modify the new one. */
763 /* */
764 /* If `anode' is _not_ NULL, it receives the address of the cache */
765 /* node containing the glyph image, after increasing its reference */
766 /* count. This ensures that the node (as well as the @FT_Glyph) will */
767 /* always be kept in the cache until you call @FTC_Node_Unref to */
768 /* `release' it. */
769 /* */
770 /* If `anode' is NULL, the cache node is left unchanged, which means */
771 /* that the @FT_Glyph could be flushed out of the cache on the next */
772 /* call to one of the caching sub-system APIs. Don't assume that it */
773 /* is persistent! */
774 /* */
775 FT_EXPORT( FT_Error )
776 FTC_ImageCache_Lookup( FTC_ImageCache cache,
777 FTC_ImageType type,
778 FT_UInt gindex,
779 FT_Glyph *aglyph,
780 FTC_Node *anode );
781
782
783 /*************************************************************************/
784 /* */
785 /* <Function> */
786 /* FTC_ImageCache_LookupScaler */
787 /* */
788 /* <Description> */
789 /* A variant of @FTC_ImageCache_Lookup that uses an @FTC_ScalerRec */
790 /* to specify the face ID and its size. */
791 /* */
792 /* <Input> */
793 /* cache :: A handle to the source glyph image cache. */
794 /* */
795 /* scaler :: A pointer to a scaler descriptor. */
796 /* */
797 /* load_flags :: The corresponding load flags. */
798 /* */
799 /* gindex :: The glyph index to retrieve. */
800 /* */
801 /* <Output> */
802 /* aglyph :: The corresponding @FT_Glyph object. 0~in case of */
803 /* failure. */
804 /* */
805 /* anode :: Used to return the address of of the corresponding */
806 /* cache node after incrementing its reference count */
807 /* (see note below). */
808 /* */
809 /* <Return> */
810 /* FreeType error code. 0~means success. */
811 /* */
812 /* <Note> */
813 /* The returned glyph is owned and managed by the glyph image cache. */
814 /* Never try to transform or discard it manually! You can however */
815 /* create a copy with @FT_Glyph_Copy and modify the new one. */
816 /* */
817 /* If `anode' is _not_ NULL, it receives the address of the cache */
818 /* node containing the glyph image, after increasing its reference */
819 /* count. This ensures that the node (as well as the @FT_Glyph) will */
820 /* always be kept in the cache until you call @FTC_Node_Unref to */
821 /* `release' it. */
822 /* */
823 /* If `anode' is NULL, the cache node is left unchanged, which means */
824 /* that the @FT_Glyph could be flushed out of the cache on the next */
825 /* call to one of the caching sub-system APIs. Don't assume that it */
826 /* is persistent! */
827 /* */
828 /* Calls to @FT_Set_Char_Size and friends have no effect on cached */
829 /* glyphs; you should always use the FreeType cache API instead. */
830 /* */
831 FT_EXPORT( FT_Error )
832 FTC_ImageCache_LookupScaler( FTC_ImageCache cache,
833 FTC_Scaler scaler,
834 FT_ULong load_flags,
835 FT_UInt gindex,
836 FT_Glyph *aglyph,
837 FTC_Node *anode );
838
839
840 /*************************************************************************/
841 /* */
842 /* <Type> */
843 /* FTC_SBit */
844 /* */
845 /* <Description> */
846 /* A handle to a small bitmap descriptor. See the @FTC_SBitRec */
847 /* structure for details. */
848 /* */
849 typedef struct FTC_SBitRec_* FTC_SBit;
850
851
852 /*************************************************************************/
853 /* */
854 /* <Struct> */
855 /* FTC_SBitRec */
856 /* */
857 /* <Description> */
858 /* A very compact structure used to describe a small glyph bitmap. */
859 /* */
860 /* <Fields> */
861 /* width :: The bitmap width in pixels. */
862 /* */
863 /* height :: The bitmap height in pixels. */
864 /* */
865 /* left :: The horizontal distance from the pen position to the */
866 /* left bitmap border (a.k.a. `left side bearing', or */
867 /* `lsb'). */
868 /* */
869 /* top :: The vertical distance from the pen position (on the */
870 /* baseline) to the upper bitmap border (a.k.a. `top */
871 /* side bearing'). The distance is positive for upwards */
872 /* y~coordinates. */
873 /* */
874 /* format :: The format of the glyph bitmap (monochrome or gray). */
875 /* */
876 /* max_grays :: Maximum gray level value (in the range 1 to~255). */
877 /* */
878 /* pitch :: The number of bytes per bitmap line. May be positive */
879 /* or negative. */
880 /* */
881 /* xadvance :: The horizontal advance width in pixels. */
882 /* */
883 /* yadvance :: The vertical advance height in pixels. */
884 /* */
885 /* buffer :: A pointer to the bitmap pixels. */
886 /* */
887 typedef struct FTC_SBitRec_
888 {
889 FT_Byte width;
890 FT_Byte height;
891 FT_Char left;
892 FT_Char top;
893
894 FT_Byte format;
895 FT_Byte max_grays;
896 FT_Short pitch;
897 FT_Char xadvance;
898 FT_Char yadvance;
899
900 FT_Byte* buffer;
901
902 } FTC_SBitRec;
903
904
905 /*************************************************************************/
906 /* */
907 /* <Type> */
908 /* FTC_SBitCache */
909 /* */
910 /* <Description> */
911 /* A handle to a small bitmap cache. These are special cache objects */
912 /* used to store small glyph bitmaps (and anti-aliased pixmaps) in a */
913 /* much more efficient way than the traditional glyph image cache */
914 /* implemented by @FTC_ImageCache. */
915 /* */
916 typedef struct FTC_SBitCacheRec_* FTC_SBitCache;
917
918
919 /*************************************************************************/
920 /* */
921 /* <Function> */
922 /* FTC_SBitCache_New */
923 /* */
924 /* <Description> */
925 /* Create a new cache to store small glyph bitmaps. */
926 /* */
927 /* <Input> */
928 /* manager :: A handle to the source cache manager. */
929 /* */
930 /* <Output> */
931 /* acache :: A handle to the new sbit cache. NULL in case of error. */
932 /* */
933 /* <Return> */
934 /* FreeType error code. 0~means success. */
935 /* */
936 FT_EXPORT( FT_Error )
937 FTC_SBitCache_New( FTC_Manager manager,
938 FTC_SBitCache *acache );
939
940
941 /*************************************************************************/
942 /* */
943 /* <Function> */
944 /* FTC_SBitCache_Lookup */
945 /* */
946 /* <Description> */
947 /* Look up a given small glyph bitmap in a given sbit cache and */
948 /* `lock' it to prevent its flushing from the cache until needed. */
949 /* */
950 /* <Input> */
951 /* cache :: A handle to the source sbit cache. */
952 /* */
953 /* type :: A pointer to the glyph image type descriptor. */
954 /* */
955 /* gindex :: The glyph index. */
956 /* */
957 /* <Output> */
958 /* sbit :: A handle to a small bitmap descriptor. */
959 /* */
960 /* anode :: Used to return the address of of the corresponding cache */
961 /* node after incrementing its reference count (see note */
962 /* below). */
963 /* */
964 /* <Return> */
965 /* FreeType error code. 0~means success. */
966 /* */
967 /* <Note> */
968 /* The small bitmap descriptor and its bit buffer are owned by the */
969 /* cache and should never be freed by the application. They might */
970 /* as well disappear from memory on the next cache lookup, so don't */
971 /* treat them as persistent data. */
972 /* */
973 /* The descriptor's `buffer' field is set to~0 to indicate a missing */
974 /* glyph bitmap. */
975 /* */
976 /* If `anode' is _not_ NULL, it receives the address of the cache */
977 /* node containing the bitmap, after increasing its reference count. */
978 /* This ensures that the node (as well as the image) will always be */
979 /* kept in the cache until you call @FTC_Node_Unref to `release' it. */
980 /* */
981 /* If `anode' is NULL, the cache node is left unchanged, which means */
982 /* that the bitmap could be flushed out of the cache on the next */
983 /* call to one of the caching sub-system APIs. Don't assume that it */
984 /* is persistent! */
985 /* */
986 FT_EXPORT( FT_Error )
987 FTC_SBitCache_Lookup( FTC_SBitCache cache,
988 FTC_ImageType type,
989 FT_UInt gindex,
990 FTC_SBit *sbit,
991 FTC_Node *anode );
992
993
994 /*************************************************************************/
995 /* */
996 /* <Function> */
997 /* FTC_SBitCache_LookupScaler */
998 /* */
999 /* <Description> */
1000 /* A variant of @FTC_SBitCache_Lookup that uses an @FTC_ScalerRec */
1001 /* to specify the face ID and its size. */
1002 /* */
1003 /* <Input> */
1004 /* cache :: A handle to the source sbit cache. */
1005 /* */
1006 /* scaler :: A pointer to the scaler descriptor. */
1007 /* */
1008 /* load_flags :: The corresponding load flags. */
1009 /* */
1010 /* gindex :: The glyph index. */
1011 /* */
1012 /* <Output> */
1013 /* sbit :: A handle to a small bitmap descriptor. */
1014 /* */
1015 /* anode :: Used to return the address of of the corresponding */
1016 /* cache node after incrementing its reference count */
1017 /* (see note below). */
1018 /* */
1019 /* <Return> */
1020 /* FreeType error code. 0~means success. */
1021 /* */
1022 /* <Note> */
1023 /* The small bitmap descriptor and its bit buffer are owned by the */
1024 /* cache and should never be freed by the application. They might */
1025 /* as well disappear from memory on the next cache lookup, so don't */
1026 /* treat them as persistent data. */
1027 /* */
1028 /* The descriptor's `buffer' field is set to~0 to indicate a missing */
1029 /* glyph bitmap. */
1030 /* */
1031 /* If `anode' is _not_ NULL, it receives the address of the cache */
1032 /* node containing the bitmap, after increasing its reference count. */
1033 /* This ensures that the node (as well as the image) will always be */
1034 /* kept in the cache until you call @FTC_Node_Unref to `release' it. */
1035 /* */
1036 /* If `anode' is NULL, the cache node is left unchanged, which means */
1037 /* that the bitmap could be flushed out of the cache on the next */
1038 /* call to one of the caching sub-system APIs. Don't assume that it */
1039 /* is persistent! */
1040 /* */
1041 FT_EXPORT( FT_Error )
1042 FTC_SBitCache_LookupScaler( FTC_SBitCache cache,
1043 FTC_Scaler scaler,
1044 FT_ULong load_flags,
1045 FT_UInt gindex,
1046 FTC_SBit *sbit,
1047 FTC_Node *anode );
1048
1049
1050 /* */
1051
1052 FT_END_HEADER
1053
1054 #endif /* __FTCACHE_H__ */
1055
1056
1057 /* END */

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