1
2 /*
3 *
4 * (C) Copyright IBM Corp. 1998-2007 - 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 * @param tableTag - the four byte table tag. (e.g. 'cmap')
160 *
161 * @return the address of the table in memory, or <code>NULL</code>
162 * if the table doesn't exist.
163 *
164 * @stable ICU 2.8
165 */
166 virtual const void *getFontTable(LETag tableTag) const = 0;
167
168 /**
169 * This method is used to determine if the font can
170 * render the given character. This can usually be done
171 * by looking the character up in the font's character
172 * to glyph mapping.
173 *
174 * The default implementation of this method will return
175 * <code>TRUE</code> if <code>mapCharToGlyph(ch)</code>
176 * returns a non-zero value.
177 *
178 * @param ch - the character to be tested
179 *
180 * @return <code>TRUE</code> if the font can render ch.
181 *
182 * @stable ICU 3.2
183 */
184 virtual le_bool canDisplay(LEUnicode32 ch) const;
185
186 /**
187 * This method returns the number of design units in
188 * the font's EM square.
189 *
190 * @return the number of design units pre EM.
191 *
192 * @stable ICU 2.8
193 */
194 virtual le_int32 getUnitsPerEM() const = 0;
195
196 /**
197 * This method maps an array of character codes to an array of glyph
198 * indices, using the font's character to glyph map.
199 *
200 * The default implementation iterates over all of the characters and calls
201 * <code>mapCharToGlyph(ch, mapper)</code> on each one. It also handles surrogate
202 * characters, storing the glyph ID for the high surrogate, and a deleted glyph (0xFFFF)
203 * for the low surrogate.
204 *
205 * Most sublcasses will not need to implement this method.
206 *
207 * @param chars - the character array
208 * @param offset - the index of the first character
209 * @param count - the number of characters
210 * @param reverse - if <code>TRUE</code>, store the glyph indices in reverse order.
211 * @param mapper - the character mapper.
212 * @param filterZeroWidth - <code>TRUE</code> if ZWJ / ZWNJ characters should map to a glyph w/ no contours.
213 * @param glyphStorage - the object which contains the output glyph array
214 *
215 * @see LECharMapper
216 *
217 * @stable ICU 3.6
218 */
219 virtual void mapCharsToGlyphs(const LEUnicode chars[], le_int32 offset, le_int32 count, le_bool reverse, const LECharMapper *mapper, le_bool filterZeroWidth, LEGlyphStorage &glyphStorage) const;
220
221 /**
222 * This method maps a single character to a glyph index, using the
223 * font's character to glyph map. The default implementation of this
224 * method calls the mapper, and then calls <code>mapCharToGlyph(mappedCh)</code>.
225 *
226 * @param ch - the character
227 * @param mapper - the character mapper
228 * @param filterZeroWidth - <code>TRUE</code> if ZWJ / ZWNJ characters should map to a glyph w/ no contours.
229 *
230 * @return the glyph index
231 *
232 * @see LECharMapper
233 *
234 * @stable ICU 3.6
235 */
236 virtual LEGlyphID mapCharToGlyph(LEUnicode32 ch, const LECharMapper *mapper, le_bool filterZeroWidth) const;
237
238 /**
239 * This method maps a single character to a glyph index, using the
240 * font's character to glyph map. The default implementation of this
241 * method calls the mapper, and then calls <code>mapCharToGlyph(mappedCh)</code>.
242 *
243 * @param ch - the character
244 * @param mapper - the character mapper
245 *
246 * @return the glyph index
247 *
248 * @see LECharMapper
249 *
250 * @stable ICU 3.2
251 */
252 virtual LEGlyphID mapCharToGlyph(LEUnicode32 ch, const LECharMapper *mapper) const;
253
254 /**
255 * This method maps a single character to a glyph index, using the
256 * font's character to glyph map. There is no default implementation
257 * of this method because it requires information about the platform
258 * font implementation.
259 *
260 * @param ch - the character
261 *
262 * @return the glyph index
263 *
264 * @stable ICU 3.2
265 */
266 virtual LEGlyphID mapCharToGlyph(LEUnicode32 ch) const = 0;
267
268 //
269 // Metrics
270 //
271
272 /**
273 * This method gets the X and Y advance of a particular glyph, in pixels.
274 *
275 * @param glyph - the glyph index
276 * @param advance - the X and Y pixel values will be stored here
277 *
278 * @stable ICU 3.2
279 */
280 virtual void getGlyphAdvance(LEGlyphID glyph, LEPoint &advance) const = 0;
281
282 /**
283 * This method gets the hinted X and Y pixel coordinates of a particular
284 * point in the outline of the given glyph.
285 *
286 * @param glyph - the glyph index
287 * @param pointNumber - the number of the point
288 * @param point - the point's X and Y pixel values will be stored here
289 *
290 * @return <code>TRUE</code> if the point coordinates could be stored.
291 *
292 * @stable ICU 2.8
293 */
294 virtual le_bool getGlyphPoint(LEGlyphID glyph, le_int32 pointNumber, LEPoint &point) const = 0;
295
296 /**
297 * This method returns the width of the font's EM square
298 * in pixels.
299 *
300 * @return the pixel width of the EM square
301 *
302 * @stable ICU 2.8
303 */
304 virtual float getXPixelsPerEm() const = 0;
305
306 /**
307 * This method returns the height of the font's EM square
308 * in pixels.
309 *
310 * @return the pixel height of the EM square
311 *
312 * @stable ICU 2.8
313 */
314 virtual float getYPixelsPerEm() const = 0;
315
316 /**
317 * This method converts font design units in the
318 * X direction to points.
319 *
320 * @param xUnits - design units in the X direction
321 *
322 * @return points in the X direction
323 *
324 * @stable ICU 3.2
325 */
326 virtual float xUnitsToPoints(float xUnits) const;
327
328 /**
329 * This method converts font design units in the
330 * Y direction to points.
331 *
332 * @param yUnits - design units in the Y direction
333 *
334 * @return points in the Y direction
335 *
336 * @stable ICU 3.2
337 */
338 virtual float yUnitsToPoints(float yUnits) const;
339
340 /**
341 * This method converts font design units to points.
342 *
343 * @param units - X and Y design units
344 * @param points - set to X and Y points
345 *
346 * @stable ICU 3.2
347 */
348 virtual void unitsToPoints(LEPoint &units, LEPoint &points) const;
349
350 /**
351 * This method converts pixels in the
352 * X direction to font design units.
353 *
354 * @param xPixels - pixels in the X direction
355 *
356 * @return font design units in the X direction
357 *
358 * @stable ICU 3.2
359 */
360 virtual float xPixelsToUnits(float xPixels) const;
361
362 /**
363 * This method converts pixels in the
364 * Y direction to font design units.
365 *
366 * @param yPixels - pixels in the Y direction
367 *
368 * @return font design units in the Y direction
369 *
370 * @stable ICU 3.2
371 */
372 virtual float yPixelsToUnits(float yPixels) const;
373
374 /**
375 * This method converts pixels to font design units.
376 *
377 * @param pixels - X and Y pixel
378 * @param units - set to X and Y font design units
379 *
380 * @stable ICU 3.2
381 */
382 virtual void pixelsToUnits(LEPoint &pixels, LEPoint &units) const;
383
384 /**
385 * Get the X scale factor from the font's transform. The default
386 * implementation of <code>transformFunits()</code> will call this method.
387 *
388 * @return the X scale factor.
389 *
390 *
391 * @see transformFunits
392 *
393 * @stable ICU 3.2
394 */
395 virtual float getScaleFactorX() const = 0;
396
397 /**
398 * Get the Y scale factor from the font's transform. The default
399 * implementation of <code>transformFunits()</code> will call this method.
400 *
401 * @return the Yscale factor.
402 *
403 * @see transformFunits
404 *
405 * @stable ICU 3.2
406 */
407 virtual float getScaleFactorY() const = 0;
408
409 /**
410 * This method transforms an X, Y point in font design units to a
411 * pixel coordinate, applying the font's transform. The default
412 * implementation of this method calls <code>getScaleFactorX()</code>
413 * and <code>getScaleFactorY()</code>.
414 *
415 * @param xFunits - the X coordinate in font design units
416 * @param yFunits - the Y coordinate in font design units
417 * @param pixels - the tranformed co-ordinate in pixels
418 *
419 * @see getScaleFactorX
420 * @see getScaleFactorY
421 *
422 * @stable ICU 3.2
423 */
424 virtual void transformFunits(float xFunits, float yFunits, LEPoint &pixels) const;
425
426 /**
427 * This is a convenience method used to convert
428 * values in a 16.16 fixed point format to floating point.
429 *
430 * @param fixed - the fixed point value
431 *
432 * @return the floating point value
433 *
434 * @stable ICU 2.8
435 */
436 static inline float fixedToFloat(le_int32 fixed);
437
438 /**
439 * This is a convenience method used to convert
440 * floating point values to 16.16 fixed point format.
441 *
442 * @param theFloat - the floating point value
443 *
444 * @return the fixed point value
445 *
446 * @stable ICU 2.8
447 */
448 static inline le_int32 floatToFixed(float theFloat);
449
450 //
451 // These methods won't ever be called by the LayoutEngine,
452 // but are useful for clients of <code>LEFontInstance</code> who
453 // need to render text.
454 //
455
456 /**
457 * Get the font's ascent.
458 *
459 * @return the font's ascent, in points. This value
460 * will always be positive.
461 *
462 * @stable ICU 3.2
463 */
464 virtual le_int32 getAscent() const = 0;
465
466 /**
467 * Get the font's descent.
468 *
469 * @return the font's descent, in points. This value
470 * will always be positive.
471 *
472 * @stable ICU 3.2
473 */
474 virtual le_int32 getDescent() const = 0;
475
476 /**
477 * Get the font's leading.
478 *
479 * @return the font's leading, in points. This value
480 * will always be positive.
481 *
482 * @stable ICU 3.2
483 */
484 virtual le_int32 getLeading() const = 0;
485
486 /**
487 * Get the line height required to display text in
488 * this font. The default implementation of this method
489 * returns the sum of the ascent, descent, and leading.
490 *
491 * @return the line height, in points. This vaule will
492 * always be positive.
493 *
494 * @stable ICU 3.2
495 */
496 virtual le_int32 getLineHeight() const;
497
498 /**
499 * ICU "poor man's RTTI", returns a UClassID for the actual class.
500 *
501 * @stable ICU 3.2
502 */
503 virtual UClassID getDynamicClassID() const;
504
505 /**
506 * ICU "poor man's RTTI", returns a UClassID for this class.
507 *
508 * @stable ICU 3.2
509 */
510 static UClassID getStaticClassID();
511
512 };
513
fixedToFloat(le_int32 fixed)514 inline float LEFontInstance::fixedToFloat(le_int32 fixed)
515 {
516 return (float) (fixed / 65536.0);
517 }
518
floatToFixed(float theFloat)519 inline le_int32 LEFontInstance::floatToFixed(float theFloat)
520 {
521 return (le_int32) (theFloat * 65536.0);
522 }
523
524 U_NAMESPACE_END
525 #endif
526
527
528