icuSources/layout/LEFontInstance.h

   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
 514 inline float LEFontInstance::fixedToFloat(le_int32 fixed)
 515 {
 516     return (float) (fixed / 65536.0);
 517 }
 518
 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