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 17U_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 */ 28class LECharMapper /* not : public UObject because this is an interface/mixin class */ 29{ 30public: 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 */ 55class 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 */ 81class U_LAYOUT_API LEFontInstance : public UObject 82{ 83public: 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 514inline float LEFontInstance::fixedToFloat(le_int32 fixed) 515{ 516 return (float) (fixed / 65536.0); 517} 518 519inline le_int32 LEFontInstance::floatToFixed(float theFloat) 520{ 521 return (le_int32) (theFloat * 65536.0); 522} 523 524U_NAMESPACE_END 525#endif 526 527 528