1
2 /*
3 *
4 * (C) Copyright IBM Corp. 1998-2013 - All Rights Reserved
5 *
6 */
7
8 #ifndef __LEFONTINSTANCE_H
9 #define __LEFONTINSTANCE_H
10
11 #include "LETypes.h"
12 /**
13 * \file
14 * \brief C++ API: Layout Engine Font Instance object
15 */
16
17 U_NAMESPACE_BEGIN
18
19 /**
20 * Instances of this class are used by <code>LEFontInstance::mapCharsToGlyphs</code> and
21 * <code>LEFontInstance::mapCharToGlyph</code> to adjust character codes before the character
22 * to glyph mapping process. Examples of this are filtering out control characters
23 * and character mirroring - replacing a character which has both a left and a right
24 * hand form with the opposite form.
25 *
26 * @stable ICU 3.2
27 */
28 class LECharMapper /* not : public UObject because this is an interface/mixin class */
29 {
30 public:
31 /**
32 * Destructor.
33 * @stable ICU 3.2
34 */
35 virtual ~LECharMapper();
36
37 /**
38 * This method does the adjustments.
39 *
40 * @param ch - the input character
41 *
42 * @return the adjusted character
43 *
44 * @stable ICU 2.8
45 */
46 virtual LEUnicode32 mapChar(LEUnicode32 ch) const = 0;
47 };
48
49 /**
50 * This is a forward reference to the class which holds the per-glyph
51 * storage.
52 *
53 * @stable ICU 3.0
54 */
55 class LEGlyphStorage;
56
57 /**
58 * This is a virtual base class that serves as the interface between a LayoutEngine
59 * and the platform font environment. It allows a LayoutEngine to access font tables, do
60 * character to glyph mapping, and obtain metrics information without knowing any platform
61 * specific details. There are also a few utility methods for converting between points,
62 * pixels and funits. (font design units)
63 *
64 * An instance of an <code>LEFontInstance</code> represents a font at a particular point
65 * size. Each instance can represent either a single physical font, or a composite font.
66 * A composite font is a collection of physical fonts, each of which contains a subset of
67 * the characters contained in the composite font.
68 *
69 * Note: with the exception of <code>getSubFont</code>, the methods in this class only
70 * make sense for a physical font. If you have an <code>LEFontInstance</code> which
71 * represents a composite font you should only call the methods below which have
72 * an <code>LEGlyphID</code>, an <code>LEUnicode</code> or an <code>LEUnicode32</code>
73 * as one of the arguments because these can be used to select a particular subfont.
74 *
75 * Subclasses which implement composite fonts should supply an implementation of these
76 * methods with some default behavior such as returning constant values, or using the
77 * values from the first subfont.
78 *
79 * @stable ICU 3.0
80 */
81 class U_LAYOUT_API LEFontInstance : public UObject
82 {
83 public:
84
85 /**
86 * This virtual destructor is here so that the subclass
87 * destructors can be invoked through the base class.
88 *
89 * @stable ICU 2.8
90 */
91 virtual ~LEFontInstance();
92
93 /**
94 * Get a physical font which can render the given text. For composite fonts,
95 * if there is no single physical font which can render all of the text,
96 * return a physical font which can render an initial substring of the text,
97 * and set the <code>offset</code> parameter to the end of that substring.
98 *
99 * Internally, the LayoutEngine works with runs of text all in the same
100 * font and script, so it is best to call this method with text which is
101 * in a single script, passing the script code in as a hint. If you don't
102 * know the script of the text, you can use zero, which is the script code
103 * for characters used in more than one script.
104 *
105 * The default implementation of this method is intended for instances of
106 * <code>LEFontInstance</code> which represent a physical font. It returns
107 * <code>this</code> and indicates that the entire string can be rendered.
108 *
109 * This method will return a valid <code>LEFontInstance</code> unless you
110 * have passed illegal parameters, or an internal error has been encountered.
111 * For composite fonts, it may return the warning <code>LE_NO_SUBFONT_WARNING</code>
112 * to indicate that the returned font may not be able to render all of
113 * the text. Whenever a valid font is returned, the <code>offset</code> parameter
114 * will be advanced by at least one.
115 *
116 * Subclasses which implement composite fonts must override this method.
117 * Where it makes sense, they should use the script code as a hint to render
118 * characters from the COMMON script in the font which is used for the given
119 * script. For example, if the input text is a series of Arabic words separated
120 * by spaces, and the script code passed in is <code>arabScriptCode</code> you
121 * should return the font used for Arabic characters for all of the input text,
122 * including the spaces. If, on the other hand, the input text contains characters
123 * which cannot be rendered by the font used for Arabic characters, but which can
124 * be rendered by another font, you should return that font for those characters.
125 *
126 * @param chars - the array of Unicode characters.
127 * @param offset - a pointer to the starting offset in the text. On exit this
128 * will be set the the limit offset of the text which can be
129 * rendered using the returned font.
130 * @param limit - the limit offset for the input text.
131 * @param script - the script hint.
132 * @param success - set to an error code if the arguments are illegal, or no font
133 * can be returned for some reason. May also be set to
134 * <code>LE_NO_SUBFONT_WARNING</code> if the subfont which
135 * was returned cannot render all of the text.
136 *
137 * @return an <code>LEFontInstance</code> for the sub font which can render the characters, or
138 * <code>NULL</code> if there is an error.
139 *
140 * @see LEScripts.h
141 *
142 * @stable ICU 3.2
143 */
144 virtual const LEFontInstance *getSubFont(const LEUnicode chars[], le_int32 *offset, le_int32 limit, le_int32 script, LEErrorCode &success) const;
145
146 //
147 // Font file access
148 //
149
150 /**
151 * This method reads a table from the font. Note that in general,
152 * it only makes sense to call this method on an <code>LEFontInstance</code>
153 * which represents a physical font - i.e. one which has been returned by
154 * <code>getSubFont()</code>. This is because each subfont in a composite font
155 * will have different tables, and there's no way to know which subfont to access.
156 *
157 * Subclasses which represent composite fonts should always return <code>NULL</code>.
158 *
159 * Note that implementing this function does not allow for range checking.
160 * Subclasses that desire the safety of range checking must implement the
161 * variation which has a length parameter.
162 *
163 * @param tableTag - the four byte table tag. (e.g. 'cmap')
164 *
165 * @return the address of the table in memory, or <code>NULL</code>
166 * if the table doesn't exist.
167 *
168 * @stable ICU 2.8
169 */
170 virtual const void *getFontTable(LETag tableTag) const = 0;
171
172 /**
173 * This method reads a table from the font. Note that in general,
174 * it only makes sense to call this method on an <code>LEFontInstance</code>
175 * which represents a physical font - i.e. one which has been returned by
176 * <code>getSubFont()</code>. This is because each subfont in a composite font
177 * will have different tables, and there's no way to know which subfont to access.
178 *
179 * Subclasses which represent composite fonts should always return <code>NULL</code>.
180 *
181 * This version sets a length, for range checking.
182 * Note that range checking can only be accomplished if this function is
183 * implemented in subclasses.
184 *
185 * @param tableTag - the four byte table tag. (e.g. 'cmap')
186 * @param length - ignored on entry, on exit will be the length of the table if known, or -1 if unknown.
187 * @return the address of the table in memory, or <code>NULL</code>
188 * if the table doesn't exist.
189 * @draft ICU 52
190 */
getFontTable(LETag tableTag,size_t & length)191 virtual const void* getFontTable(LETag tableTag, size_t &length) const { length=-1; return getFontTable(tableTag); } /* -1 = unknown length */
192
193 /**
194 * This method is used to determine if the font can
195 * render the given character. This can usually be done
196 * by looking the character up in the font's character
197 * to glyph mapping.
198 *
199 * The default implementation of this method will return
200 * <code>TRUE</code> if <code>mapCharToGlyph(ch)</code>
201 * returns a non-zero value.
202 *
203 * @param ch - the character to be tested
204 *
205 * @return <code>TRUE</code> if the font can render ch.
206 *
207 * @stable ICU 3.2
208 */
209 virtual le_bool canDisplay(LEUnicode32 ch) const;
210
211 /**
212 * This method returns the number of design units in
213 * the font's EM square.
214 *
215 * @return the number of design units pre EM.
216 *
217 * @stable ICU 2.8
218 */
219 virtual le_int32 getUnitsPerEM() const = 0;
220
221 /**
222 * This method maps an array of character codes to an array of glyph
223 * indices, using the font's character to glyph map.
224 *
225 * The default implementation iterates over all of the characters and calls
226 * <code>mapCharToGlyph(ch, mapper)</code> on each one. It also handles surrogate
227 * characters, storing the glyph ID for the high surrogate, and a deleted glyph (0xFFFF)
228 * for the low surrogate.
229 *
230 * Most sublcasses will not need to implement this method.
231 *
232 * @param chars - the character array
233 * @param offset - the index of the first character
234 * @param count - the number of characters
235 * @param reverse - if <code>TRUE</code>, store the glyph indices in reverse order.
236 * @param mapper - the character mapper.
237 * @param filterZeroWidth - <code>TRUE</code> if ZWJ / ZWNJ characters should map to a glyph w/ no contours.
238 * @param glyphStorage - the object which contains the output glyph array
239 *
240 * @see LECharMapper
241 *
242 * @stable ICU 3.6
243 */
244 virtual void mapCharsToGlyphs(const LEUnicode chars[], le_int32 offset, le_int32 count, le_bool reverse, const LECharMapper *mapper, le_bool filterZeroWidth, LEGlyphStorage &glyphStorage) const;
245
246 /**
247 * This method maps a single character to a glyph index, using the
248 * font's character to glyph map. The default implementation of this
249 * method calls the mapper, and then calls <code>mapCharToGlyph(mappedCh)</code>.
250 *
251 * @param ch - the character
252 * @param mapper - the character mapper
253 * @param filterZeroWidth - <code>TRUE</code> if ZWJ / ZWNJ characters should map to a glyph w/ no contours.
254 *
255 * @return the glyph index
256 *
257 * @see LECharMapper
258 *
259 * @stable ICU 3.6
260 */
261 virtual LEGlyphID mapCharToGlyph(LEUnicode32 ch, const LECharMapper *mapper, le_bool filterZeroWidth) const;
262
263 /**
264 * This method maps a single character to a glyph index, using the
265 * font's character to glyph map. The default implementation of this
266 * method calls the mapper, and then calls <code>mapCharToGlyph(mappedCh)</code>.
267 *
268 * @param ch - the character
269 * @param mapper - the character mapper
270 *
271 * @return the glyph index
272 *
273 * @see LECharMapper
274 *
275 * @stable ICU 3.2
276 */
277 virtual LEGlyphID mapCharToGlyph(LEUnicode32 ch, const LECharMapper *mapper) const;
278
279 /**
280 * This method maps a single character to a glyph index, using the
281 * font's character to glyph map. There is no default implementation
282 * of this method because it requires information about the platform
283 * font implementation.
284 *
285 * @param ch - the character
286 *
287 * @return the glyph index
288 *
289 * @stable ICU 3.2
290 */
291 virtual LEGlyphID mapCharToGlyph(LEUnicode32 ch) const = 0;
292
293 //
294 // Metrics
295 //
296
297 /**
298 * This method gets the X and Y advance of a particular glyph, in pixels.
299 *
300 * @param glyph - the glyph index
301 * @param advance - the X and Y pixel values will be stored here
302 *
303 * @stable ICU 3.2
304 */
305 virtual void getGlyphAdvance(LEGlyphID glyph, LEPoint &advance) const = 0;
306
307 /**
308 * This method gets the hinted X and Y pixel coordinates of a particular
309 * point in the outline of the given glyph.
310 *
311 * @param glyph - the glyph index
312 * @param pointNumber - the number of the point
313 * @param point - the point's X and Y pixel values will be stored here
314 *
315 * @return <code>TRUE</code> if the point coordinates could be stored.
316 *
317 * @stable ICU 2.8
318 */
319 virtual le_bool getGlyphPoint(LEGlyphID glyph, le_int32 pointNumber, LEPoint &point) const = 0;
320
321 /**
322 * This method returns the width of the font's EM square
323 * in pixels.
324 *
325 * @return the pixel width of the EM square
326 *
327 * @stable ICU 2.8
328 */
329 virtual float getXPixelsPerEm() const = 0;
330
331 /**
332 * This method returns the height of the font's EM square
333 * in pixels.
334 *
335 * @return the pixel height of the EM square
336 *
337 * @stable ICU 2.8
338 */
339 virtual float getYPixelsPerEm() const = 0;
340
341 /**
342 * This method converts font design units in the
343 * X direction to points.
344 *
345 * @param xUnits - design units in the X direction
346 *
347 * @return points in the X direction
348 *
349 * @stable ICU 3.2
350 */
351 virtual float xUnitsToPoints(float xUnits) const;
352
353 /**
354 * This method converts font design units in the
355 * Y direction to points.
356 *
357 * @param yUnits - design units in the Y direction
358 *
359 * @return points in the Y direction
360 *
361 * @stable ICU 3.2
362 */
363 virtual float yUnitsToPoints(float yUnits) const;
364
365 /**
366 * This method converts font design units to points.
367 *
368 * @param units - X and Y design units
369 * @param points - set to X and Y points
370 *
371 * @stable ICU 3.2
372 */
373 virtual void unitsToPoints(LEPoint &units, LEPoint &points) const;
374
375 /**
376 * This method converts pixels in the
377 * X direction to font design units.
378 *
379 * @param xPixels - pixels in the X direction
380 *
381 * @return font design units in the X direction
382 *
383 * @stable ICU 3.2
384 */
385 virtual float xPixelsToUnits(float xPixels) const;
386
387 /**
388 * This method converts pixels in the
389 * Y direction to font design units.
390 *
391 * @param yPixels - pixels in the Y direction
392 *
393 * @return font design units in the Y direction
394 *
395 * @stable ICU 3.2
396 */
397 virtual float yPixelsToUnits(float yPixels) const;
398
399 /**
400 * This method converts pixels to font design units.
401 *
402 * @param pixels - X and Y pixel
403 * @param units - set to X and Y font design units
404 *
405 * @stable ICU 3.2
406 */
407 virtual void pixelsToUnits(LEPoint &pixels, LEPoint &units) const;
408
409 /**
410 * Get the X scale factor from the font's transform. The default
411 * implementation of <code>transformFunits()</code> will call this method.
412 *
413 * @return the X scale factor.
414 *
415 *
416 * @see transformFunits
417 *
418 * @stable ICU 3.2
419 */
420 virtual float getScaleFactorX() const = 0;
421
422 /**
423 * Get the Y scale factor from the font's transform. The default
424 * implementation of <code>transformFunits()</code> will call this method.
425 *
426 * @return the Yscale factor.
427 *
428 * @see transformFunits
429 *
430 * @stable ICU 3.2
431 */
432 virtual float getScaleFactorY() const = 0;
433
434 /**
435 * This method transforms an X, Y point in font design units to a
436 * pixel coordinate, applying the font's transform. The default
437 * implementation of this method calls <code>getScaleFactorX()</code>
438 * and <code>getScaleFactorY()</code>.
439 *
440 * @param xFunits - the X coordinate in font design units
441 * @param yFunits - the Y coordinate in font design units
442 * @param pixels - the tranformed co-ordinate in pixels
443 *
444 * @see getScaleFactorX
445 * @see getScaleFactorY
446 *
447 * @stable ICU 3.2
448 */
449 virtual void transformFunits(float xFunits, float yFunits, LEPoint &pixels) const;
450
451 /**
452 * This is a convenience method used to convert
453 * values in a 16.16 fixed point format to floating point.
454 *
455 * @param fixed - the fixed point value
456 *
457 * @return the floating point value
458 *
459 * @stable ICU 2.8
460 */
461 static inline float fixedToFloat(le_int32 fixed);
462
463 /**
464 * This is a convenience method used to convert
465 * floating point values to 16.16 fixed point format.
466 *
467 * @param theFloat - the floating point value
468 *
469 * @return the fixed point value
470 *
471 * @stable ICU 2.8
472 */
473 static inline le_int32 floatToFixed(float theFloat);
474
475 //
476 // These methods won't ever be called by the LayoutEngine,
477 // but are useful for clients of <code>LEFontInstance</code> who
478 // need to render text.
479 //
480
481 /**
482 * Get the font's ascent.
483 *
484 * @return the font's ascent, in points. This value
485 * will always be positive.
486 *
487 * @stable ICU 3.2
488 */
489 virtual le_int32 getAscent() const = 0;
490
491 /**
492 * Get the font's descent.
493 *
494 * @return the font's descent, in points. This value
495 * will always be positive.
496 *
497 * @stable ICU 3.2
498 */
499 virtual le_int32 getDescent() const = 0;
500
501 /**
502 * Get the font's leading.
503 *
504 * @return the font's leading, in points. This value
505 * will always be positive.
506 *
507 * @stable ICU 3.2
508 */
509 virtual le_int32 getLeading() const = 0;
510
511 /**
512 * Get the line height required to display text in
513 * this font. The default implementation of this method
514 * returns the sum of the ascent, descent, and leading.
515 *
516 * @return the line height, in points. This vaule will
517 * always be positive.
518 *
519 * @stable ICU 3.2
520 */
521 virtual le_int32 getLineHeight() const;
522
523 /**
524 * ICU "poor man's RTTI", returns a UClassID for the actual class.
525 *
526 * @stable ICU 3.2
527 */
528 virtual UClassID getDynamicClassID() const;
529
530 /**
531 * ICU "poor man's RTTI", returns a UClassID for this class.
532 *
533 * @stable ICU 3.2
534 */
535 static UClassID getStaticClassID();
536
537 };
538
fixedToFloat(le_int32 fixed)539 inline float LEFontInstance::fixedToFloat(le_int32 fixed)
540 {
541 return (float) (fixed / 65536.0);
542 }
543
floatToFixed(float theFloat)544 inline le_int32 LEFontInstance::floatToFixed(float theFloat)
545 {
546 return (le_int32) (theFloat * 65536.0);
547 }
548
549 U_NAMESPACE_END
550 #endif
551