1 2 /* 3 * 4 * (C) Copyright IBM Corp. 1998-2012 - 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 #if 0 /* Google Patch: withdraw this function. https://b.corp.google.com/issue?id=8593098 */ 169 /** 170 * This method reads a table from the font. Note that in general, 171 * it only makes sense to call this method on an <code>LEFontInstance</code> 172 * which represents a physical font - i.e. one which has been returned by 173 * <code>getSubFont()</code>. This is because each subfont in a composite font 174 * will have different tables, and there's no way to know which subfont to access. 175 * 176 * Subclasses which represent composite fonts should always return <code>NULL</code>. 177 * 178 * This version sets a length, for range checking. 179 * 180 * @param tableTag - the four byte table tag. (e.g. 'cmap') 181 * @param length - ignored on entry, on exit will be the length of the table if known, or -1 if unknown. 182 * @return the address of the table in memory, or <code>NULL</code> 183 * if the table doesn't exist. 184 * @internal 185 */ 186 virtual const void* getFontTable(LETag tableTag, size_t &length) const { length=-1; return getFontTable(tableTag); } /* -1 = unknown length */ 187 #endif /* End Google Patch */ 188 189 /** 190 * This method is used to determine if the font can 191 * render the given character. This can usually be done 192 * by looking the character up in the font's character 193 * to glyph mapping. 194 * 195 * The default implementation of this method will return 196 * <code>TRUE</code> if <code>mapCharToGlyph(ch)</code> 197 * returns a non-zero value. 198 * 199 * @param ch - the character to be tested 200 * 201 * @return <code>TRUE</code> if the font can render ch. 202 * 203 * @stable ICU 3.2 204 */ 205 virtual le_bool canDisplay(LEUnicode32 ch) const; 206 207 /** 208 * This method returns the number of design units in 209 * the font's EM square. 210 * 211 * @return the number of design units pre EM. 212 * 213 * @stable ICU 2.8 214 */ 215 virtual le_int32 getUnitsPerEM() const = 0; 216 217 /** 218 * This method maps an array of character codes to an array of glyph 219 * indices, using the font's character to glyph map. 220 * 221 * The default implementation iterates over all of the characters and calls 222 * <code>mapCharToGlyph(ch, mapper)</code> on each one. It also handles surrogate 223 * characters, storing the glyph ID for the high surrogate, and a deleted glyph (0xFFFF) 224 * for the low surrogate. 225 * 226 * Most sublcasses will not need to implement this method. 227 * 228 * @param chars - the character array 229 * @param offset - the index of the first character 230 * @param count - the number of characters 231 * @param reverse - if <code>TRUE</code>, store the glyph indices in reverse order. 232 * @param mapper - the character mapper. 233 * @param filterZeroWidth - <code>TRUE</code> if ZWJ / ZWNJ characters should map to a glyph w/ no contours. 234 * @param glyphStorage - the object which contains the output glyph array 235 * 236 * @see LECharMapper 237 * 238 * @stable ICU 3.6 239 */ 240 virtual void mapCharsToGlyphs(const LEUnicode chars[], le_int32 offset, le_int32 count, le_bool reverse, const LECharMapper *mapper, le_bool filterZeroWidth, LEGlyphStorage &glyphStorage) const; 241 242 /** 243 * This method maps a single character to a glyph index, using the 244 * font's character to glyph map. The default implementation of this 245 * method calls the mapper, and then calls <code>mapCharToGlyph(mappedCh)</code>. 246 * 247 * @param ch - the character 248 * @param mapper - the character mapper 249 * @param filterZeroWidth - <code>TRUE</code> if ZWJ / ZWNJ characters should map to a glyph w/ no contours. 250 * 251 * @return the glyph index 252 * 253 * @see LECharMapper 254 * 255 * @stable ICU 3.6 256 */ 257 virtual LEGlyphID mapCharToGlyph(LEUnicode32 ch, const LECharMapper *mapper, le_bool filterZeroWidth) const; 258 259 /** 260 * This method maps a single character to a glyph index, using the 261 * font's character to glyph map. The default implementation of this 262 * method calls the mapper, and then calls <code>mapCharToGlyph(mappedCh)</code>. 263 * 264 * @param ch - the character 265 * @param mapper - the character mapper 266 * 267 * @return the glyph index 268 * 269 * @see LECharMapper 270 * 271 * @stable ICU 3.2 272 */ 273 virtual LEGlyphID mapCharToGlyph(LEUnicode32 ch, const LECharMapper *mapper) const; 274 275 /** 276 * This method maps a single character to a glyph index, using the 277 * font's character to glyph map. There is no default implementation 278 * of this method because it requires information about the platform 279 * font implementation. 280 * 281 * @param ch - the character 282 * 283 * @return the glyph index 284 * 285 * @stable ICU 3.2 286 */ 287 virtual LEGlyphID mapCharToGlyph(LEUnicode32 ch) const = 0; 288 289 // 290 // Metrics 291 // 292 293 /** 294 * This method gets the X and Y advance of a particular glyph, in pixels. 295 * 296 * @param glyph - the glyph index 297 * @param advance - the X and Y pixel values will be stored here 298 * 299 * @stable ICU 3.2 300 */ 301 virtual void getGlyphAdvance(LEGlyphID glyph, LEPoint &advance) const = 0; 302 303 /** 304 * This method gets the hinted X and Y pixel coordinates of a particular 305 * point in the outline of the given glyph. 306 * 307 * @param glyph - the glyph index 308 * @param pointNumber - the number of the point 309 * @param point - the point's X and Y pixel values will be stored here 310 * 311 * @return <code>TRUE</code> if the point coordinates could be stored. 312 * 313 * @stable ICU 2.8 314 */ 315 virtual le_bool getGlyphPoint(LEGlyphID glyph, le_int32 pointNumber, LEPoint &point) const = 0; 316 317 /** 318 * This method returns the width of the font's EM square 319 * in pixels. 320 * 321 * @return the pixel width of the EM square 322 * 323 * @stable ICU 2.8 324 */ 325 virtual float getXPixelsPerEm() const = 0; 326 327 /** 328 * This method returns the height of the font's EM square 329 * in pixels. 330 * 331 * @return the pixel height of the EM square 332 * 333 * @stable ICU 2.8 334 */ 335 virtual float getYPixelsPerEm() const = 0; 336 337 /** 338 * This method converts font design units in the 339 * X direction to points. 340 * 341 * @param xUnits - design units in the X direction 342 * 343 * @return points in the X direction 344 * 345 * @stable ICU 3.2 346 */ 347 virtual float xUnitsToPoints(float xUnits) const; 348 349 /** 350 * This method converts font design units in the 351 * Y direction to points. 352 * 353 * @param yUnits - design units in the Y direction 354 * 355 * @return points in the Y direction 356 * 357 * @stable ICU 3.2 358 */ 359 virtual float yUnitsToPoints(float yUnits) const; 360 361 /** 362 * This method converts font design units to points. 363 * 364 * @param units - X and Y design units 365 * @param points - set to X and Y points 366 * 367 * @stable ICU 3.2 368 */ 369 virtual void unitsToPoints(LEPoint &units, LEPoint &points) const; 370 371 /** 372 * This method converts pixels in the 373 * X direction to font design units. 374 * 375 * @param xPixels - pixels in the X direction 376 * 377 * @return font design units in the X direction 378 * 379 * @stable ICU 3.2 380 */ 381 virtual float xPixelsToUnits(float xPixels) const; 382 383 /** 384 * This method converts pixels in the 385 * Y direction to font design units. 386 * 387 * @param yPixels - pixels in the Y direction 388 * 389 * @return font design units in the Y direction 390 * 391 * @stable ICU 3.2 392 */ 393 virtual float yPixelsToUnits(float yPixels) const; 394 395 /** 396 * This method converts pixels to font design units. 397 * 398 * @param pixels - X and Y pixel 399 * @param units - set to X and Y font design units 400 * 401 * @stable ICU 3.2 402 */ 403 virtual void pixelsToUnits(LEPoint &pixels, LEPoint &units) const; 404 405 /** 406 * Get the X scale factor from the font's transform. The default 407 * implementation of <code>transformFunits()</code> will call this method. 408 * 409 * @return the X scale factor. 410 * 411 * 412 * @see transformFunits 413 * 414 * @stable ICU 3.2 415 */ 416 virtual float getScaleFactorX() const = 0; 417 418 /** 419 * Get the Y scale factor from the font's transform. The default 420 * implementation of <code>transformFunits()</code> will call this method. 421 * 422 * @return the Yscale factor. 423 * 424 * @see transformFunits 425 * 426 * @stable ICU 3.2 427 */ 428 virtual float getScaleFactorY() const = 0; 429 430 /** 431 * This method transforms an X, Y point in font design units to a 432 * pixel coordinate, applying the font's transform. The default 433 * implementation of this method calls <code>getScaleFactorX()</code> 434 * and <code>getScaleFactorY()</code>. 435 * 436 * @param xFunits - the X coordinate in font design units 437 * @param yFunits - the Y coordinate in font design units 438 * @param pixels - the tranformed co-ordinate in pixels 439 * 440 * @see getScaleFactorX 441 * @see getScaleFactorY 442 * 443 * @stable ICU 3.2 444 */ 445 virtual void transformFunits(float xFunits, float yFunits, LEPoint &pixels) const; 446 447 /** 448 * This is a convenience method used to convert 449 * values in a 16.16 fixed point format to floating point. 450 * 451 * @param fixed - the fixed point value 452 * 453 * @return the floating point value 454 * 455 * @stable ICU 2.8 456 */ 457 static inline float fixedToFloat(le_int32 fixed); 458 459 /** 460 * This is a convenience method used to convert 461 * floating point values to 16.16 fixed point format. 462 * 463 * @param theFloat - the floating point value 464 * 465 * @return the fixed point value 466 * 467 * @stable ICU 2.8 468 */ 469 static inline le_int32 floatToFixed(float theFloat); 470 471 // 472 // These methods won't ever be called by the LayoutEngine, 473 // but are useful for clients of <code>LEFontInstance</code> who 474 // need to render text. 475 // 476 477 /** 478 * Get the font's ascent. 479 * 480 * @return the font's ascent, in points. This value 481 * will always be positive. 482 * 483 * @stable ICU 3.2 484 */ 485 virtual le_int32 getAscent() const = 0; 486 487 /** 488 * Get the font's descent. 489 * 490 * @return the font's descent, in points. This value 491 * will always be positive. 492 * 493 * @stable ICU 3.2 494 */ 495 virtual le_int32 getDescent() const = 0; 496 497 /** 498 * Get the font's leading. 499 * 500 * @return the font's leading, in points. This value 501 * will always be positive. 502 * 503 * @stable ICU 3.2 504 */ 505 virtual le_int32 getLeading() const = 0; 506 507 /** 508 * Get the line height required to display text in 509 * this font. The default implementation of this method 510 * returns the sum of the ascent, descent, and leading. 511 * 512 * @return the line height, in points. This vaule will 513 * always be positive. 514 * 515 * @stable ICU 3.2 516 */ 517 virtual le_int32 getLineHeight() const; 518 519 /** 520 * ICU "poor man's RTTI", returns a UClassID for the actual class. 521 * 522 * @stable ICU 3.2 523 */ 524 virtual UClassID getDynamicClassID() const; 525 526 /** 527 * ICU "poor man's RTTI", returns a UClassID for this class. 528 * 529 * @stable ICU 3.2 530 */ 531 static UClassID getStaticClassID(); 532 533 }; 534 535 inline float LEFontInstance::fixedToFloat(le_int32 fixed) 536 { 537 return (float) (fixed / 65536.0); 538 } 539 540 inline le_int32 LEFontInstance::floatToFixed(float theFloat) 541 { 542 return (le_int32) (theFloat * 65536.0); 543 } 544 545 U_NAMESPACE_END 546 #endif 547 548 549
