icuSources/layout/LEFontInstance.h

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