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 * This version sets a length, for range checking.
185 * Note that range checking can only be accomplished if this function is
186 * implemented in subclasses.
187 *
188 * @param tableTag - the four byte table tag. (e.g. 'cmap')
189 * @param length - ignored on entry, on exit will be the length of the table if known, or -1 if unknown.
190 * @return the address of the table in memory, or <code>NULL</code>
191 * if the table doesn't exist.
192 * @internal
193 */
194 virtual const void* getFontTable(LETag tableTag, size_t &length) const = 0;
195
196 virtual void *getKernPairs() const = 0;
197 virtual void setKernPairs(void *pairs) const = 0;
198
199 /**
200 * This method is used to determine if the font can
201 * render the given character. This can usually be done
202 * by looking the character up in the font's character
203 * to glyph mapping.
204 *
205 * The default implementation of this method will return
206 * <code>TRUE</code> if <code>mapCharToGlyph(ch)</code>
207 * returns a non-zero value.
208 *
209 * @param ch - the character to be tested
210 *
211 * @return <code>TRUE</code> if the font can render ch.
212 *
213 * @stable ICU 3.2
214 */
215 virtual le_bool canDisplay(LEUnicode32 ch) const;
216
217 /**
218 * This method returns the number of design units in
219 * the font's EM square.
220 *
221 * @return the number of design units pre EM.
222 *
223 * @stable ICU 2.8
224 */
225 virtual le_int32 getUnitsPerEM() const = 0;
226
227 /**
228 * This method maps an array of character codes to an array of glyph
229 * indices, using the font's character to glyph map.
230 *
231 * The default implementation iterates over all of the characters and calls
232 * <code>mapCharToGlyph(ch, mapper)</code> on each one. It also handles surrogate
233 * characters, storing the glyph ID for the high surrogate, and a deleted glyph (0xFFFF)
234 * for the low surrogate.
235 *
236 * Most sublcasses will not need to implement this method.
237 *
238 * @param chars - the character array
239 * @param offset - the index of the first character
240 * @param count - the number of characters
241 * @param reverse - if <code>TRUE</code>, store the glyph indices in reverse order.
242 * @param mapper - the character mapper.
243 * @param filterZeroWidth - <code>TRUE</code> if ZWJ / ZWNJ characters should map to a glyph w/ no contours.
244 * @param glyphStorage - the object which contains the output glyph array
245 *
246 * @see LECharMapper
247 *
248 * @stable ICU 3.6
249 */
250 virtual void mapCharsToGlyphs(const LEUnicode chars[], le_int32 offset, le_int32 count, le_bool reverse, const LECharMapper *mapper, le_bool filterZeroWidth, LEGlyphStorage &glyphStorage) const;
251
252 /**
253 * This method maps a single character to a glyph index, using the
254 * font's character to glyph map. The default implementation of this
255 * method calls the mapper, and then calls <code>mapCharToGlyph(mappedCh)</code>.
256 *
257 * @param ch - the character
258 * @param mapper - the character mapper
259 * @param filterZeroWidth - <code>TRUE</code> if ZWJ / ZWNJ characters should map to a glyph w/ no contours.
260 *
261 * @return the glyph index
262 *
263 * @see LECharMapper
264 *
265 * @stable ICU 3.6
266 */
267 virtual LEGlyphID mapCharToGlyph(LEUnicode32 ch, const LECharMapper *mapper, le_bool filterZeroWidth) const;
268
269 /**
270 * This method maps a single character to a glyph index, using the
271 * font's character to glyph map. The default implementation of this
272 * method calls the mapper, and then calls <code>mapCharToGlyph(mappedCh)</code>.
273 *
274 * @param ch - the character
275 * @param mapper - the character mapper
276 *
277 * @return the glyph index
278 *
279 * @see LECharMapper
280 *
281 * @stable ICU 3.2
282 */
283 virtual LEGlyphID mapCharToGlyph(LEUnicode32 ch, const LECharMapper *mapper) const;
284
285 /**
286 * This method maps a single character to a glyph index, using the
287 * font's character to glyph map. There is no default implementation
288 * of this method because it requires information about the platform
289 * font implementation.
290 *
291 * @param ch - the character
292 *
293 * @return the glyph index
294 *
295 * @stable ICU 3.2
296 */
297 virtual LEGlyphID mapCharToGlyph(LEUnicode32 ch) const = 0;
298
299 //
300 // Metrics
301 //
302
303 /**
304 * This method gets the X and Y advance of a particular glyph, in pixels.
305 *
306 * @param glyph - the glyph index
307 * @param advance - the X and Y pixel values will be stored here
308 *
309 * @stable ICU 3.2
310 */
311 virtual void getGlyphAdvance(LEGlyphID glyph, LEPoint &advance) const = 0;
312
313 virtual void getKerningAdjustment(LEPoint &adjustment) const = 0;
314
315 /**
316 * This method gets the hinted X and Y pixel coordinates of a particular
317 * point in the outline of the given glyph.
318 *
319 * @param glyph - the glyph index
320 * @param pointNumber - the number of the point
321 * @param point - the point's X and Y pixel values will be stored here
322 *
323 * @return <code>TRUE</code> if the point coordinates could be stored.
324 *
325 * @stable ICU 2.8
326 */
327 virtual le_bool getGlyphPoint(LEGlyphID glyph, le_int32 pointNumber, LEPoint &point) const = 0;
328
329 /**
330 * This method returns the width of the font's EM square
331 * in pixels.
332 *
333 * @return the pixel width of the EM square
334 *
335 * @stable ICU 2.8
336 */
337 virtual float getXPixelsPerEm() const = 0;
338
339 /**
340 * This method returns the height of the font's EM square
341 * in pixels.
342 *
343 * @return the pixel height of the EM square
344 *
345 * @stable ICU 2.8
346 */
347 virtual float getYPixelsPerEm() const = 0;
348
349 /**
350 * This method converts font design units in the
351 * X direction to points.
352 *
353 * @param xUnits - design units in the X direction
354 *
355 * @return points in the X direction
356 *
357 * @stable ICU 3.2
358 */
359 virtual float xUnitsToPoints(float xUnits) const;
360
361 /**
362 * This method converts font design units in the
363 * Y direction to points.
364 *
365 * @param yUnits - design units in the Y direction
366 *
367 * @return points in the Y direction
368 *
369 * @stable ICU 3.2
370 */
371 virtual float yUnitsToPoints(float yUnits) const;
372
373 /**
374 * This method converts font design units to points.
375 *
376 * @param units - X and Y design units
377 * @param points - set to X and Y points
378 *
379 * @stable ICU 3.2
380 */
381 virtual void unitsToPoints(LEPoint &units, LEPoint &points) const;
382
383 /**
384 * This method converts pixels in the
385 * X direction to font design units.
386 *
387 * @param xPixels - pixels in the X direction
388 *
389 * @return font design units in the X direction
390 *
391 * @stable ICU 3.2
392 */
393 virtual float xPixelsToUnits(float xPixels) const;
394
395 /**
396 * This method converts pixels in the
397 * Y direction to font design units.
398 *
399 * @param yPixels - pixels in the Y direction
400 *
401 * @return font design units in the Y direction
402 *
403 * @stable ICU 3.2
404 */
405 virtual float yPixelsToUnits(float yPixels) const;
406
407 /**
408 * This method converts pixels to font design units.
409 *
410 * @param pixels - X and Y pixel
411 * @param units - set to X and Y font design units
412 *
413 * @stable ICU 3.2
414 */
415 virtual void pixelsToUnits(LEPoint &pixels, LEPoint &units) const;
416
417 /**
418 * Get the X scale factor from the font's transform. The default
419 * implementation of <code>transformFunits()</code> will call this method.
420 *
421 * @return the X scale factor.
422 *
423 *
424 * @see transformFunits
425 *
426 * @stable ICU 3.2
427 */
428 virtual float getScaleFactorX() const = 0;
429
430 /**
431 * Get the Y scale factor from the font's transform. The default
432 * implementation of <code>transformFunits()</code> will call this method.
433 *
434 * @return the Yscale factor.
435 *
436 * @see transformFunits
437 *
438 * @stable ICU 3.2
439 */
440 virtual float getScaleFactorY() const = 0;
441
442 /**
443 * This method transforms an X, Y point in font design units to a
444 * pixel coordinate, applying the font's transform. The default
445 * implementation of this method calls <code>getScaleFactorX()</code>
446 * and <code>getScaleFactorY()</code>.
447 *
448 * @param xFunits - the X coordinate in font design units
449 * @param yFunits - the Y coordinate in font design units
450 * @param pixels - the tranformed co-ordinate in pixels
451 *
452 * @see getScaleFactorX
453 * @see getScaleFactorY
454 *
455 * @stable ICU 3.2
456 */
457 virtual void transformFunits(float xFunits, float yFunits, LEPoint &pixels) const;
458
459 /**
460 * This is a convenience method used to convert
461 * values in a 16.16 fixed point format to floating point.
462 *
463 * @param fixed - the fixed point value
464 *
465 * @return the floating point value
466 *
467 * @stable ICU 2.8
468 */
469 static inline float fixedToFloat(le_int32 fixed);
470
471 /**
472 * This is a convenience method used to convert
473 * floating point values to 16.16 fixed point format.
474 *
475 * @param theFloat - the floating point value
476 *
477 * @return the fixed point value
478 *
479 * @stable ICU 2.8
480 */
481 static inline le_int32 floatToFixed(float theFloat);
482
483 //
484 // These methods won't ever be called by the LayoutEngine,
485 // but are useful for clients of <code>LEFontInstance</code> who
486 // need to render text.
487 //
488
489 /**
490 * Get the font's ascent.
491 *
492 * @return the font's ascent, in points. This value
493 * will always be positive.
494 *
495 * @stable ICU 3.2
496 */
497 virtual le_int32 getAscent() const = 0;
498
499 /**
500 * Get the font's descent.
501 *
502 * @return the font's descent, in points. This value
503 * will always be positive.
504 *
505 * @stable ICU 3.2
506 */
507 virtual le_int32 getDescent() const = 0;
508
509 /**
510 * Get the font's leading.
511 *
512 * @return the font's leading, in points. This value
513 * will always be positive.
514 *
515 * @stable ICU 3.2
516 */
517 virtual le_int32 getLeading() const = 0;
518
519 /**
520 * Get the line height required to display text in
521 * this font. The default implementation of this method
522 * returns the sum of the ascent, descent, and leading.
523 *
524 * @return the line height, in points. This vaule will
525 * always be positive.
526 *
527 * @stable ICU 3.2
528 */
529 virtual le_int32 getLineHeight() const;
530
531 /**
532 * ICU "poor man's RTTI", returns a UClassID for the actual class.
533 *
534 * @stable ICU 3.2
535 */
536 virtual UClassID getDynamicClassID() const;
537
538 /**
539 * ICU "poor man's RTTI", returns a UClassID for this class.
540 *
541 * @stable ICU 3.2
542 */
543 static UClassID getStaticClassID();
544
545 };
546
547 inline float LEFontInstance::fixedToFloat(le_int32 fixed)
548 {
549 return (float) (fixed / 65536.0);
550 }
551
552 inline le_int32 LEFontInstance::floatToFixed(float theFloat)
553 {
554 return (le_int32) (theFloat * 65536.0);
555 }
556
557 U_NAMESPACE_END
558 #endif