1 /*
2 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
3 *
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9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
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25
26
27 /*
28 *
29 * (C) Copyright IBM Corp. 1998-2007 - All Rights Reserved
30 *
31 */
32
33 #ifndef __LEFONTINSTANCE_H
34 #define __LEFONTINSTANCE_H
35
36 #include "LETypes.h"
37 /**
38 * \file
39 * \brief C++ API: Layout Engine Font Instance object
40 */
41
42 U_NAMESPACE_BEGIN
43
44 /**
45 * Instances of this class are used by <code>LEFontInstance::mapCharsToGlyphs</code> and
46 * <code>LEFontInstance::mapCharToGlyph</code> to adjust character codes before the character
47 * to glyph mapping process. Examples of this are filtering out control characters
48 * and character mirroring - replacing a character which has both a left and a right
49 * hand form with the opposite form.
50 *
51 * @stable ICU 3.2
52 */
53 class LECharMapper /* not : public UObject because this is an interface/mixin class */
54 {
55 public:
56 /**
57 * Destructor.
58 * @stable ICU 3.2
59 */
60 virtual ~LECharMapper();
61
62 /**
63 * This method does the adjustments.
64 *
65 * @param ch - the input character
66 *
67 * @return the adjusted character
68 *
69 * @stable ICU 2.8
70 */
71 virtual LEUnicode32 mapChar(LEUnicode32 ch) const = 0;
72 };
73
74 /**
75 * This is a forward reference to the class which holds the per-glyph
76 * storage.
77 *
78 * @stable ICU 3.0
79 */
80 class LEGlyphStorage;
81
82 /**
83 * This is a virtual base class that serves as the interface between a LayoutEngine
84 * and the platform font environment. It allows a LayoutEngine to access font tables, do
85 * character to glyph mapping, and obtain metrics information without knowing any platform
86 * specific details. There are also a few utility methods for converting between points,
87 * pixels and funits. (font design units)
88 *
89 * An instance of an <code>LEFontInstance</code> represents a font at a particular point
90 * size. Each instance can represent either a single physical font, or a composite font.
91 * A composite font is a collection of physical fonts, each of which contains a subset of
92 * the characters contained in the composite font.
93 *
94 * Note: with the exception of <code>getSubFont</code>, the methods in this class only
95 * make sense for a physical font. If you have an <code>LEFontInstance</code> which
96 * represents a composite font you should only call the methods below which have
97 * an <code>LEGlyphID</code>, an <code>LEUnicode</code> or an <code>LEUnicode32</code>
98 * as one of the arguments because these can be used to select a particular subfont.
99 *
100 * Subclasses which implement composite fonts should supply an implementation of these
101 * methods with some default behavior such as returning constant values, or using the
102 * values from the first subfont.
103 *
104 * @stable ICU 3.0
105 */
106 class U_LAYOUT_API LEFontInstance : public UObject
107 {
108 public:
109
110 /**
111 * This virtual destructor is here so that the subclass
112 * destructors can be invoked through the base class.
113 *
114 * @stable ICU 2.8
115 */
116 virtual ~LEFontInstance();
117
118 /**
119 * Get a physical font which can render the given text. For composite fonts,
120 * if there is no single physical font which can render all of the text,
121 * return a physical font which can render an initial substring of the text,
122 * and set the <code>offset</code> parameter to the end of that substring.
123 *
124 * Internally, the LayoutEngine works with runs of text all in the same
125 * font and script, so it is best to call this method with text which is
126 * in a single script, passing the script code in as a hint. If you don't
127 * know the script of the text, you can use zero, which is the script code
128 * for characters used in more than one script.
129 *
130 * The default implementation of this method is intended for instances of
131 * <code>LEFontInstance</code> which represent a physical font. It returns
132 * <code>this</code> and indicates that the entire string can be rendered.
133 *
134 * This method will return a valid <code>LEFontInstance</code> unless you
135 * have passed illegal parameters, or an internal error has been encountered.
136 * For composite fonts, it may return the warning <code>LE_NO_SUBFONT_WARNING</code>
137 * to indicate that the returned font may not be able to render all of
138 * the text. Whenever a valid font is returned, the <code>offset</code> parameter
139 * will be advanced by at least one.
140 *
141 * Subclasses which implement composite fonts must override this method.
142 * Where it makes sense, they should use the script code as a hint to render
143 * characters from the COMMON script in the font which is used for the given
144 * script. For example, if the input text is a series of Arabic words separated
145 * by spaces, and the script code passed in is <code>arabScriptCode</code> you
146 * should return the font used for Arabic characters for all of the input text,
147 * including the spaces. If, on the other hand, the input text contains characters
148 * which cannot be rendered by the font used for Arabic characters, but which can
149 * be rendered by another font, you should return that font for those characters.
150 *
151 * @param chars - the array of Unicode characters.
152 * @param offset - a pointer to the starting offset in the text. On exit this
153 * will be set the the limit offset of the text which can be
154 * rendered using the returned font.
155 * @param limit - the limit offset for the input text.
156 * @param script - the script hint.
157 * @param success - set to an error code if the arguments are illegal, or no font
158 * can be returned for some reason. May also be set to
159 * <code>LE_NO_SUBFONT_WARNING</code> if the subfont which
160 * was returned cannot render all of the text.
161 *
162 * @return an <code>LEFontInstance</code> for the sub font which can render the characters, or
163 * <code>NULL</code> if there is an error.
164 *
165 * @see LEScripts.h
166 *
167 * @stable ICU 3.2
168 */
169 virtual const LEFontInstance *getSubFont(const LEUnicode chars[], le_int32 *offset, le_int32 limit, le_int32 script, LEErrorCode &success) const;
170
171 //
172 // Font file access
173 //
174
175 /**
176 * This method reads a table from the font. Note that in general,
177 * it only makes sense to call this method on an <code>LEFontInstance</code>
178 * which represents a physical font - i.e. one which has been returned by
179 * <code>getSubFont()</code>. This is because each subfont in a composite font
180 * will have different tables, and there's no way to know which subfont to access.
181 *
182 * Subclasses which represent composite fonts should always return <code>NULL</code>.
183 *
184 * Note that implementing this function does not allow for range checking.
185 * Subclasses that desire the safety of range checking must implement the
186 * variation which has a length parameter.
187 *
188 * @param tableTag - the four byte table tag. (e.g. 'cmap')
189 *
190 * @return the address of the table in memory, or <code>NULL</code>
191 * if the table doesn't exist.
192 *
193 * @stable ICU 2.8
194 */
195 virtual const void *getFontTable(LETag tableTag) const = 0;
196
197 /**
198 * This method reads a table from the font. Note that in general,
199 * it only makes sense to call this method on an <code>LEFontInstance</code>
200 * which represents a physical font - i.e. one which has been returned by
201 * <code>getSubFont()</code>. This is because each subfont in a composite font
202 * will have different tables, and there's no way to know which subfont to access.
203 *
204 * Subclasses which represent composite fonts should always return <code>NULL</code>.
205 *
206 * This version sets a length, for range checking.
207 * Note that range checking can only be accomplished if this function is
208 * implemented in subclasses.
209 *
210 * @param tableTag - the four byte table tag. (e.g. 'cmap')
211 * @param length - ignored on entry, on exit will be the length of the table if known, or -1 if unknown.
212 * @return the address of the table in memory, or <code>NULL</code>
213 * if the table doesn't exist.
214 * @internal
215 */
216 virtual const void* getFontTable(LETag tableTag, size_t &length) const { length=-1; return getFontTable(tableTag); } /* -1 = unknown length */
217
218 virtual void *getKernPairs() const = 0;
219 virtual void setKernPairs(void *pairs) const = 0;
220
221 /**
222 * This method is used to determine if the font can
223 * render the given character. This can usually be done
224 * by looking the character up in the font's character
225 * to glyph mapping.
226 *
227 * The default implementation of this method will return
228 * <code>TRUE</code> if <code>mapCharToGlyph(ch)</code>
229 * returns a non-zero value.
230 *
231 * @param ch - the character to be tested
232 *
233 * @return <code>TRUE</code> if the font can render ch.
234 *
235 * @stable ICU 3.2
236 */
237 virtual le_bool canDisplay(LEUnicode32 ch) const;
238
239 /**
240 * This method returns the number of design units in
241 * the font's EM square.
242 *
243 * @return the number of design units pre EM.
244 *
245 * @stable ICU 2.8
246 */
247 virtual le_int32 getUnitsPerEM() const = 0;
248
249 /**
250 * This method maps an array of character codes to an array of glyph
251 * indices, using the font's character to glyph map.
252 *
253 * The default implementation iterates over all of the characters and calls
254 * <code>mapCharToGlyph(ch, mapper)</code> on each one. It also handles surrogate
255 * characters, storing the glyph ID for the high surrogate, and a deleted glyph (0xFFFF)
256 * for the low surrogate.
257 *
258 * Most sublcasses will not need to implement this method.
259 *
260 * @param chars - the character array
261 * @param offset - the index of the first character
262 * @param count - the number of characters
263 * @param reverse - if <code>TRUE</code>, store the glyph indices in reverse order.
264 * @param mapper - the character mapper.
265 * @param filterZeroWidth - <code>TRUE</code> if ZWJ / ZWNJ characters should map to a glyph w/ no contours.
266 * @param glyphStorage - the object which contains the output glyph array
267 *
268 * @see LECharMapper
269 *
270 * @stable ICU 3.6
271 */
272 virtual void mapCharsToGlyphs(const LEUnicode chars[], le_int32 offset, le_int32 count, le_bool reverse, const LECharMapper *mapper, le_bool filterZeroWidth, LEGlyphStorage &glyphStorage) const;
273
274 /**
275 * This method maps a single character to a glyph index, using the
276 * font's character to glyph map. The default implementation of this
277 * method calls the mapper, and then calls <code>mapCharToGlyph(mappedCh)</code>.
278 *
279 * @param ch - the character
280 * @param mapper - the character mapper
281 * @param filterZeroWidth - <code>TRUE</code> if ZWJ / ZWNJ characters should map to a glyph w/ no contours.
282 *
283 * @return the glyph index
284 *
285 * @see LECharMapper
286 *
287 * @stable ICU 3.6
288 */
289 virtual LEGlyphID mapCharToGlyph(LEUnicode32 ch, const LECharMapper *mapper, le_bool filterZeroWidth) const;
290
291 /**
292 * This method maps a single character to a glyph index, using the
293 * font's character to glyph map. The default implementation of this
294 * method calls the mapper, and then calls <code>mapCharToGlyph(mappedCh)</code>.
295 *
296 * @param ch - the character
297 * @param mapper - the character mapper
298 *
299 * @return the glyph index
300 *
301 * @see LECharMapper
302 *
303 * @stable ICU 3.2
304 */
305 virtual LEGlyphID mapCharToGlyph(LEUnicode32 ch, const LECharMapper *mapper) const;
306
307 /**
308 * This method maps a single character to a glyph index, using the
309 * font's character to glyph map. There is no default implementation
310 * of this method because it requires information about the platform
311 * font implementation.
312 *
313 * @param ch - the character
314 *
315 * @return the glyph index
316 *
317 * @stable ICU 3.2
318 */
319 virtual LEGlyphID mapCharToGlyph(LEUnicode32 ch) const = 0;
320
321 //
322 // Metrics
323 //
324
325 /**
326 * This method gets the X and Y advance of a particular glyph, in pixels.
327 *
328 * @param glyph - the glyph index
329 * @param advance - the X and Y pixel values will be stored here
330 *
331 * @stable ICU 3.2
332 */
333 virtual void getGlyphAdvance(LEGlyphID glyph, LEPoint &advance) const = 0;
334
335 virtual void getKerningAdjustment(LEPoint &adjustment) const = 0;
336
337 /**
338 * This method gets the hinted X and Y pixel coordinates of a particular
339 * point in the outline of the given glyph.
340 *
341 * @param glyph - the glyph index
342 * @param pointNumber - the number of the point
343 * @param point - the point's X and Y pixel values will be stored here
344 *
345 * @return <code>TRUE</code> if the point coordinates could be stored.
346 *
347 * @stable ICU 2.8
348 */
349 virtual le_bool getGlyphPoint(LEGlyphID glyph, le_int32 pointNumber, LEPoint &point) const = 0;
350
351 /**
352 * This method returns the width of the font's EM square
353 * in pixels.
354 *
355 * @return the pixel width of the EM square
356 *
357 * @stable ICU 2.8
358 */
359 virtual float getXPixelsPerEm() const = 0;
360
361 /**
362 * This method returns the height of the font's EM square
363 * in pixels.
364 *
365 * @return the pixel height of the EM square
366 *
367 * @stable ICU 2.8
368 */
369 virtual float getYPixelsPerEm() const = 0;
370
371 /**
372 * This method converts font design units in the
373 * X direction to points.
374 *
375 * @param xUnits - design units in the X direction
376 *
377 * @return points in the X direction
378 *
379 * @stable ICU 3.2
380 */
381 virtual float xUnitsToPoints(float xUnits) const;
382
383 /**
384 * This method converts font design units in the
385 * Y direction to points.
386 *
387 * @param yUnits - design units in the Y direction
388 *
389 * @return points in the Y direction
390 *
391 * @stable ICU 3.2
392 */
393 virtual float yUnitsToPoints(float yUnits) const;
394
395 /**
396 * This method converts font design units to points.
397 *
398 * @param units - X and Y design units
399 * @param points - set to X and Y points
400 *
401 * @stable ICU 3.2
402 */
403 virtual void unitsToPoints(LEPoint &units, LEPoint &points) const;
404
405 /**
406 * This method converts pixels in the
407 * X direction to font design units.
408 *
409 * @param xPixels - pixels in the X direction
410 *
411 * @return font design units in the X direction
412 *
413 * @stable ICU 3.2
414 */
415 virtual float xPixelsToUnits(float xPixels) const;
416
417 /**
418 * This method converts pixels in the
419 * Y direction to font design units.
420 *
421 * @param yPixels - pixels in the Y direction
422 *
423 * @return font design units in the Y direction
424 *
425 * @stable ICU 3.2
426 */
427 virtual float yPixelsToUnits(float yPixels) const;
428
429 /**
430 * This method converts pixels to font design units.
431 *
432 * @param pixels - X and Y pixel
433 * @param units - set to X and Y font design units
434 *
435 * @stable ICU 3.2
436 */
437 virtual void pixelsToUnits(LEPoint &pixels, LEPoint &units) const;
438
439 /**
440 * Get the X scale factor from the font's transform. The default
441 * implementation of <code>transformFunits()</code> will call this method.
442 *
443 * @return the X scale factor.
444 *
445 *
446 * @see transformFunits
447 *
448 * @stable ICU 3.2
449 */
450 virtual float getScaleFactorX() const = 0;
451
452 /**
453 * Get the Y scale factor from the font's transform. The default
454 * implementation of <code>transformFunits()</code> will call this method.
455 *
456 * @return the Yscale factor.
457 *
458 * @see transformFunits
459 *
460 * @stable ICU 3.2
461 */
462 virtual float getScaleFactorY() const = 0;
463
464 /**
465 * This method transforms an X, Y point in font design units to a
466 * pixel coordinate, applying the font's transform. The default
467 * implementation of this method calls <code>getScaleFactorX()</code>
468 * and <code>getScaleFactorY()</code>.
469 *
470 * @param xFunits - the X coordinate in font design units
471 * @param yFunits - the Y coordinate in font design units
472 * @param pixels - the tranformed co-ordinate in pixels
473 *
474 * @see getScaleFactorX
475 * @see getScaleFactorY
476 *
477 * @stable ICU 3.2
478 */
479 virtual void transformFunits(float xFunits, float yFunits, LEPoint &pixels) const;
480
481 /**
482 * This is a convenience method used to convert
483 * values in a 16.16 fixed point format to floating point.
484 *
485 * @param fixed - the fixed point value
486 *
487 * @return the floating point value
488 *
489 * @stable ICU 2.8
490 */
491 static inline float fixedToFloat(le_int32 fixed);
492
493 /**
494 * This is a convenience method used to convert
495 * floating point values to 16.16 fixed point format.
496 *
497 * @param theFloat - the floating point value
498 *
499 * @return the fixed point value
500 *
501 * @stable ICU 2.8
502 */
503 static inline le_int32 floatToFixed(float theFloat);
504
505 //
506 // These methods won't ever be called by the LayoutEngine,
507 // but are useful for clients of <code>LEFontInstance</code> who
508 // need to render text.
509 //
510
511 /**
512 * Get the font's ascent.
513 *
514 * @return the font's ascent, in points. This value
515 * will always be positive.
516 *
517 * @stable ICU 3.2
518 */
519 virtual le_int32 getAscent() const = 0;
520
521 /**
522 * Get the font's descent.
523 *
524 * @return the font's descent, in points. This value
525 * will always be positive.
526 *
527 * @stable ICU 3.2
528 */
529 virtual le_int32 getDescent() const = 0;
530
531 /**
532 * Get the font's leading.
533 *
534 * @return the font's leading, in points. This value
535 * will always be positive.
536 *
537 * @stable ICU 3.2
538 */
539 virtual le_int32 getLeading() const = 0;
540
541 /**
542 * Get the line height required to display text in
543 * this font. The default implementation of this method
544 * returns the sum of the ascent, descent, and leading.
545 *
546 * @return the line height, in points. This vaule will
547 * always be positive.
548 *
549 * @stable ICU 3.2
550 */
551 virtual le_int32 getLineHeight() const;
552
553 /**
554 * ICU "poor man's RTTI", returns a UClassID for the actual class.
555 *
556 * @stable ICU 3.2
557 */
558 virtual UClassID getDynamicClassID() const;
559
560 /**
561 * ICU "poor man's RTTI", returns a UClassID for this class.
562 *
563 * @stable ICU 3.2
564 */
565 static UClassID getStaticClassID();
566
567 };
568
569 inline float LEFontInstance::fixedToFloat(le_int32 fixed)
570 {
571 return (float) (fixed / 65536.0);
572 }
573
574 inline le_int32 LEFontInstance::floatToFixed(float theFloat)
575 {
576 return (le_int32) (theFloat * 65536.0);
577 }
578
579 U_NAMESPACE_END
580 #endif