icuSources/layout/LEFontInstance.h

   1
   2 /*
   3  *
   4  * (C) Copyright IBM Corp. 1998-2004 - All Rights Reserved
   5  *
   6  */
   7
   8 #ifndef __LEFONTINSTANCE_H
   9 #define __LEFONTINSTANCE_H
  10
  11 #include "LETypes.h"
  12
  13 U_NAMESPACE_BEGIN
  14
  15 /**
  16  * Instances of this class are used by <code>LEFontInstance::mapCharsToGlyphs</code> and
  17  * <code>LEFontInstance::mapCharToGlyph</code> to adjust character codes before the character
  18  * to glyph mapping process. Examples of this are filtering out control characters
  19  * and character mirroring - replacing a character which has both a left and a right
  20  * hand form with the opposite form.
  21  *
  22  * @draft ICU 2.2
  23  */
  24 class LECharMapper /* not : public UObject because this is an interface/mixin class */
  25 {
  26 public:
  27     /**
  28      * Destructor.
  29      * @draft ICU 2.4
  30      */
  31     virtual inline ~LECharMapper() {};
  32
  33     /**
  34      * This method does the adjustments.
  35      *
  36      * @param ch - the input character
  37      *
  38      * @return the adjusted character
  39      *
  40      * @stable ICU 2.8
  41      */
  42     virtual LEUnicode32 mapChar(LEUnicode32 ch) const = 0;
  43 };
  44
  45 /**
  46  * This is a forward reference to the class which holds the per-glyph
  47  * storage.
  48  *
  49  * @draft ICU 3.0
  50  */
  51 class LEGlyphStorage;
  52
  53 /**
  54  * This is a virtual base class that serves as the interface between a LayoutEngine
  55  * and the platform font environment. It allows a LayoutEngine to access font tables, do
  56  * character to glyph mapping, and obtain metrics information without knowing any platform
  57  * specific details. There are also a few utility methods for converting between points,
  58  * pixels and funits. (font design units)
  59  *
  60  * An instance of an <code>LEFontInstance</code> represents a font at a particular point
  61  * size. Each instance can represent either a single physical font, or a composite font.
  62  * A composite font is a collection of physical fonts, each of which contains a subset of
  63  * the characters contained in the composite font.
  64  *
  65  * Note: with the exception of <code>getSubFont</code>, the methods in this class only
  66  * make sense for a physical font. If you have an <code>LEFontInstance</code> which
  67  * represents a composite font you should only call the methods below which have
  68  * an <code>LEGlyphID</code>, an <code>LEUnicode</code> or an <code>LEUnicode32</code>
  69  * as one of the arguments because these can be used to select a particular subfont.
  70  *
  71  * Subclasses which implement composite fonts should supply an implementation of these
  72  * methods with some default behavior such as returning constant values, or using the
  73  * values from the first subfont.
  74  *
  75  * @draft ICU 3.0
  76  */
  77 class U_LAYOUT_API LEFontInstance : public UObject
  78 {
  79 public:
  80
  81     /**
  82      * This virtual destructor is here so that the subclass
  83      * destructors can be invoked through the base class.
  84      *
  85      * @stable ICU 2.8
  86      */
  87     virtual inline ~LEFontInstance() {};
  88
  89     /**
  90      * Get a physical font which can render the given text. For composite fonts,
  91      * if there is no single physical font which can render all of the text,
  92      * return a physical font which can render an initial substring of the text,
  93      * and set the <code>offset</code> parameter to the end of that substring.
  94      *
  95      * Internally, the LayoutEngine works with runs of text all in the same
  96      * font and script, so it is best to call this method with text which is
  97      * in a single script, passing the script code in as a hint. If you don't
  98      * know the script of the text, you can use zero, which is the script code
  99      * for characters used in more than one script.
 100      *
 101      * The default implementation of this method is intended for instances of
 102      * <code>LEFontInstance</code> which represent a physical font. It returns
 103      * <code>this</code> and indicates that the entire string can be rendered.
 104      *
 105      * This method will return a valid <code>LEFontInstance</code> unless you
 106      * have passed illegal parameters, or an internal error has been encountered.
 107      * For composite fonts, it may return the warning <code>LE_NO_SUBFONT_WARNING</code>
 108      * to indicate that the returned font may not be able to render all of
 109      * the text. Whenever a valid font is returned, the <code>offset</code> parameter
 110      * will be advanced by at least one.
 111      *
 112      * Subclasses which implement composite fonts must override this method.
 113      * Where it makes sense, they should use the script code as a hint to render
 114      * characters from the COMMON script in the font which is used for the given
 115      * script. For example, if the input text is a series of Arabic words separated
 116      * by spaces, and the script code passed in is <code>arabScriptCode</code> you
 117      * should return the font used for Arabic characters for all of the input text,
 118      * including the spaces. If, on the other hand, the input text contains characters
 119      * which cannot be rendered by the font used for Arabic characters, but which can
 120      * be rendered by another font, you should return that font for those characters.
 121      *
 122      * @param chars   - the array of Unicode characters.
 123      * @param offset  - a pointer to the starting offset in the text. On exit this
 124      *                  will be set the the limit offset of the text which can be
 125      *                  rendered using the returned font.
 126      * @param limit   - the limit offset for the input text.
 127      * @param script  - the script hint.
 128      * @param success - set to an error code if the arguments are illegal, or no font
 129      *                  can be returned for some reason. May also be set to
 130      *                  <code>LE_NO_SUBFONT_WARNING</code> if the subfont which
 131      *                  was returned cannot render all of the text.
 132      *
 133      * @return an <code>LEFontInstance</code> for the sub font which can render the characters, or
 134      *         <code>NULL</code> if there is an error.
 135      *
 136      * @see LEScripts.h
 137      *
 138      * @draft ICU 2.6
 139      */
 140     virtual const LEFontInstance *getSubFont(const LEUnicode chars[], le_int32 *offset, le_int32 limit, le_int32 script, LEErrorCode &success) const;
 141
 142     //
 143     // Font file access
 144     //
 145
 146     /**
 147      * This method reads a table from the font. Note that in general,
 148      * it only makes sense to call this method on an <code>LEFontInstance</code>
 149      * which represents a physical font - i.e. one which has been returned by
 150      * <code>getSubFont()</code>. This is because each subfont in a composite font
 151      * will have different tables, and there's no way to know which subfont to access.
 152      *
 153      * Subclasses which represent composite fonts should always return <code>NULL</code>.
 154      *
 155      * @param tableTag - the four byte table tag. (e.g. 'cmap')
 156      *
 157      * @return the address of the table in memory, or <code>NULL</code>
 158      *         if the table doesn't exist.
 159      *
 160      * @stable ICU 2.8
 161      */
 162     virtual const void *getFontTable(LETag tableTag) const = 0;
 163
 164     /**
 165      * This method is used to determine if the font can
 166      * render the given character. This can usually be done
 167      * by looking the character up in the font's character
 168      * to glyph mapping.
 169      *
 170      * The default implementation of this method will return
 171      * <code>TRUE</code> if <code>mapCharToGlyph(ch)</code>
 172      * returns a non-zero value.
 173      *
 174      * @param ch - the character to be tested
 175      *
 176      * @return <code>TRUE</code> if the font can render ch.
 177      *
 178      * @draft ICU 2.6
 179      */
 180     virtual le_bool canDisplay(LEUnicode32 ch) const;
 181
 182     /**
 183      * This method returns the number of design units in
 184      * the font's EM square.
 185      *
 186      * @return the number of design units pre EM.
 187      *
 188      * @stable ICU 2.8
 189      */
 190     virtual le_int32 getUnitsPerEM() const = 0;
 191
 192     /**
 193      * This method maps an array of character codes to an array of glyph
 194      * indices, using the font's character to glyph map.
 195      *
 196      * The default implementation iterates over all of the characters and calls
 197      * <code>mapCharToGlyph(ch, mapper)</code> on each one. It also handles surrogate
 198      * characters, storing the glyph ID for the high surrogate, and a deleted glyph (0xFFFF)
 199      * for the low surrogate.
 200      *
 201      * Most sublcasses will not need to implement this method.
 202      *
 203      * @param chars - the character array
 204      * @param offset - the index of the first character
 205      * @param count - the number of characters
 206      * @param reverse - if <code>TRUE</code>, store the glyph indices in reverse order.
 207      * @param mapper - the character mapper.
 208      * @param glyphStorage - the object which contains the output glyph array
 209      *
 210      * @see LECharMapper
 211      *
 212      * @draft ICU 3.0
 213      */
 214     virtual void mapCharsToGlyphs(const LEUnicode chars[], le_int32 offset, le_int32 count, le_bool reverse, const LECharMapper *mapper, LEGlyphStorage &glyphStorage) const;
 215
 216     /**
 217      * This method maps a single character to a glyph index, using the
 218      * font's character to glyph map. The default implementation of this
 219      * method calls the mapper, and then calls <code>mapCharToGlyph(mappedCh)</code>.
 220      *
 221      * @param ch - the character
 222      * @param mapper - the character mapper
 223      *
 224      * @return the glyph index
 225      *
 226      * @see LECharMapper
 227      *
 228      * @draft ICU 2.6
 229      */
 230     virtual LEGlyphID mapCharToGlyph(LEUnicode32 ch, const LECharMapper *mapper) const;
 231
 232     /**
 233      * This method maps a single character to a glyph index, using the
 234      * font's character to glyph map. There is no default implementation
 235      * of this method because it requires information about the platform
 236      * font implementation.
 237      *
 238      * @param ch - the character
 239      *
 240      * @return the glyph index
 241      *
 242      * @draft ICU 2.6
 243      */
 244     virtual LEGlyphID mapCharToGlyph(LEUnicode32 ch) const = 0;
 245
 246     //
 247     // Metrics
 248     //
 249
 250     /**
 251      * This method gets the X and Y advance of a particular glyph, in pixels.
 252      *
 253      * @param glyph - the glyph index
 254      * @param advance - the X and Y pixel values will be stored here
 255      *
 256      * @draft ICU 2.2
 257      */
 258     virtual void getGlyphAdvance(LEGlyphID glyph, LEPoint &advance) const = 0;
 259
 260     /**
 261      * This method gets the hinted X and Y pixel coordinates of a particular
 262      * point in the outline of the given glyph.
 263      *
 264      * @param glyph - the glyph index
 265      * @param pointNumber - the number of the point
 266      * @param point - the point's X and Y pixel values will be stored here
 267      *
 268      * @return <code>TRUE</code> if the point coordinates could be stored.
 269      *
 270      * @stable ICU 2.8
 271      */
 272     virtual le_bool getGlyphPoint(LEGlyphID glyph, le_int32 pointNumber, LEPoint &point) const = 0;
 273
 274     /**
 275      * This method returns the width of the font's EM square
 276      * in pixels.
 277      *
 278      * @return the pixel width of the EM square
 279      *
 280      * @stable ICU 2.8
 281      */
 282     virtual float getXPixelsPerEm() const = 0;
 283
 284     /**
 285      * This method returns the height of the font's EM square
 286      * in pixels.
 287      *
 288      * @return the pixel height of the EM square
 289      *
 290      * @stable ICU 2.8
 291      */
 292     virtual float getYPixelsPerEm() const = 0;
 293
 294     /**
 295      * This method converts font design units in the
 296      * X direction to points.
 297      *
 298      * @param xUnits - design units in the X direction
 299      *
 300      * @return points in the X direction
 301      *
 302      * @draft ICU 2.6
 303      */
 304     virtual float xUnitsToPoints(float xUnits) const;
 305
 306     /**
 307      * This method converts font design units in the
 308      * Y direction to points.
 309      *
 310      * @param yUnits - design units in the Y direction
 311      *
 312      * @return points in the Y direction
 313      *
 314      * @draft ICU 2.6
 315      */
 316     virtual float yUnitsToPoints(float yUnits) const;
 317
 318     /**
 319      * This method converts font design units to points.
 320      *
 321      * @param units - X and Y design units
 322      * @param points - set to X and Y points
 323      *
 324      * @draft ICU 2.6
 325      */
 326     virtual void unitsToPoints(LEPoint &units, LEPoint &points) const;
 327
 328     /**
 329      * This method converts pixels in the
 330      * X direction to font design units.
 331      *
 332      * @param xPixels - pixels in the X direction
 333      *
 334      * @return font design units in the X direction
 335      *
 336      * @draft ICU 2.6
 337      */
 338     virtual float xPixelsToUnits(float xPixels) const;
 339
 340     /**
 341      * This method converts pixels in the
 342      * Y direction to font design units.
 343      *
 344      * @param yPixels - pixels in the Y direction
 345      *
 346      * @return font design units in the Y direction
 347      *
 348      * @draft ICU 2.6
 349      */
 350     virtual float yPixelsToUnits(float yPixels) const;
 351
 352     /**
 353      * This method converts pixels to font design units.
 354      *
 355      * @param pixels - X and Y pixel
 356      * @param units - set to X and Y font design units
 357      *
 358      * @draft ICU 2.6
 359      */
 360     virtual void pixelsToUnits(LEPoint &pixels, LEPoint &units) const;
 361
 362     /**
 363      * Get the X scale factor from the font's transform. The default
 364      * implementation of <code>transformFunits()</code> will call this method.
 365      *
 366      * @return the X scale factor.
 367      *
 368      *
 369      * @see transformFunits
 370      *
 371      * @draft ICU 2.6
 372      */
 373     virtual float getScaleFactorX() const = 0;
 374
 375     /**
 376      * Get the Y scale factor from the font's transform. The default
 377      * implementation of <code>transformFunits()</code> will call this method.
 378      *
 379      * @return the Yscale factor.
 380      *
 381      * @see transformFunits
 382      *
 383      * @draft ICU 2.6
 384      */
 385     virtual float getScaleFactorY() const = 0;
 386
 387     /**
 388      * This method transforms an X, Y point in font design units to a
 389      * pixel coordinate, applying the font's transform. The default
 390      * implementation of this method calls <code>getScaleFactorX()</code>
 391      * and <code>getScaleFactorY()</code>.
 392      *
 393      * @param xFunits - the X coordinate in font design units
 394      * @param yFunits - the Y coordinate in font design units
 395      * @param pixels - the tranformed co-ordinate in pixels
 396      *
 397      * @see getScaleFactorX
 398      * @see getScaleFactorY
 399      *
 400      * @draft ICU 2.6
 401      */
 402     virtual void transformFunits(float xFunits, float yFunits, LEPoint &pixels) const;
 403
 404     /**
 405      * This is a convenience method used to convert
 406      * values in a 16.16 fixed point format to floating point.
 407      *
 408      * @param fixed - the fixed point value
 409      *
 410      * @return the floating point value
 411      *
 412      * @stable ICU 2.8
 413      */
 414     static float fixedToFloat(le_int32 fixed);
 415
 416     /**
 417      * This is a convenience method used to convert
 418      * floating point values to 16.16 fixed point format.
 419      *
 420      * @param theFloat - the floating point value
 421      *
 422      * @return the fixed point value
 423      *
 424      * @stable ICU 2.8
 425      */
 426     static le_int32 floatToFixed(float theFloat);
 427
 428     //
 429     // These methods won't ever be called by the LayoutEngine,
 430     // but are useful for clients of <code>LEFontInstance</code> who
 431     // need to render text.
 432     //
 433
 434     /**
 435      * Get the font's ascent.
 436      *
 437      * @return the font's ascent, in points. This value
 438      * will always be positive.
 439      *
 440      * @draft ICU 2.6
 441      */
 442     virtual le_int32 getAscent() const = 0;
 443
 444     /**
 445      * Get the font's descent.
 446      *
 447      * @return the font's descent, in points. This value
 448      * will always be positive.
 449      *
 450      * @draft ICU 2.6
 451      */
 452     virtual le_int32 getDescent() const = 0;
 453
 454     /**
 455      * Get the font's leading.
 456      *
 457      * @return the font's leading, in points. This value
 458      * will always be positive.
 459      *
 460      * @draft ICU 2.6
 461      */
 462     virtual le_int32 getLeading() const = 0;
 463
 464     /**
 465      * Get the line height required to display text in
 466      * this font. The default implementation of this method
 467      * returns the sum of the ascent, descent, and leading.
 468      *
 469      * @return the line height, in points. This vaule will
 470      * always be positive.
 471      *
 472      * @draft ICU 2.6
 473      */
 474     virtual le_int32 getLineHeight() const;
 475
 476     /**
 477      * ICU "poor man's RTTI", returns a UClassID for the actual class.
 478      *
 479      * @draft ICU 2.6
 480      */
 481     virtual UClassID getDynamicClassID() const;
 482
 483     /**
 484      * ICU "poor man's RTTI", returns a UClassID for this class.
 485      *
 486      * @draft ICU 2.6
 487      */
 488     static UClassID getStaticClassID();
 489
 490 };
 491
 492 inline le_bool LEFontInstance::canDisplay(LEUnicode32 ch) const
 493 {
 494     return LE_GET_GLYPH(mapCharToGlyph(ch)) != 0;
 495 }
 496
 497 inline float LEFontInstance::xUnitsToPoints(float xUnits) const
 498 {
 499     return (xUnits * getXPixelsPerEm()) / (float) getUnitsPerEM();
 500 }
 501
 502 inline float LEFontInstance::yUnitsToPoints(float yUnits) const
 503 {
 504     return (yUnits * getYPixelsPerEm()) / (float) getUnitsPerEM();
 505 }
 506
 507 inline void LEFontInstance::unitsToPoints(LEPoint &units, LEPoint &points) const
 508 {
 509     points.fX = xUnitsToPoints(units.fX);
 510     points.fY = yUnitsToPoints(units.fY);
 511 }
 512
 513 inline float LEFontInstance::xPixelsToUnits(float xPixels) const
 514 {
 515     return (xPixels * getUnitsPerEM()) / (float) getXPixelsPerEm();
 516 }
 517
 518 inline float LEFontInstance::yPixelsToUnits(float yPixels) const
 519 {
 520     return (yPixels * getUnitsPerEM()) / (float) getYPixelsPerEm();
 521 }
 522
 523 inline void LEFontInstance::pixelsToUnits(LEPoint &pixels, LEPoint &units) const
 524 {
 525     units.fX = xPixelsToUnits(pixels.fX);
 526     units.fY = yPixelsToUnits(pixels.fY);
 527 }
 528
 529 inline void LEFontInstance::transformFunits(float xFunits, float yFunits, LEPoint &pixels) const
 530 {
 531     pixels.fX = xUnitsToPoints(xFunits) * getScaleFactorX();
 532     pixels.fY = yUnitsToPoints(yFunits) * getScaleFactorY();
 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 inline le_int32 LEFontInstance::getLineHeight() const
 546 {
 547     return getAscent() + getDescent() + getLeading();
 548 }
 549
 550 U_NAMESPACE_END
 551 #endif
 552
 553