icuSources/layout/LayoutEngine.h

   1 /*
   2  * (C) Copyright IBM Corp. and others 1998-2014 - All Rights Reserved
   3  */
   4
   5 #ifndef __LAYOUTENGINE_H
   6 #define __LAYOUTENGINE_H
   7
   8 #include "LETypes.h"
   9
  10 /**
  11  * \file
  12  * \brief C++ API: DEPRECATED: Virtual base class for complex text layout.
  13  */
  14
  15 U_NAMESPACE_BEGIN
  16
  17 class LEFontInstance;
  18 class LEGlyphFilter;
  19 class LEGlyphStorage;
  20
  21 /**
  22  * NOTE: This class is deprecated, please instead use HarfBuzz.
  23  * See: http://www.freedesktop.org/wiki/Software/HarfBuzz/
  24  * and http://userguide.icu-project.org/layoutengine
  25  *
  26  * This is a virtual base class used to do complex text layout. The text must all
  27  * be in a single font, script, and language. An instance of a LayoutEngine can be
  28  * created by calling the layoutEngineFactory method. Fonts are identified by
  29  * instances of the LEFontInstance class. Script and language codes are identified
  30  * by integer codes, which are defined in ScriptAndLanuageTags.h.
  31  *
  32  * Note that this class is not public API. It is declared public so that it can be
  33  * exported from the library that it is a part of.
  34  *
  35  * The input to the layout process is an array of characters in logical order,
  36  * and a starting X, Y position for the text. The output is an array of glyph indices,
  37  * an array of character indices for the glyphs, and an array of glyph positions.
  38  * These arrays are protected members of LayoutEngine which can be retreived by a
  39  * public method. The reset method can be called to free these arrays so that the
  40  * LayoutEngine can be reused.
  41  *
  42  * The layout process is done in three steps. There is a protected virtual method
  43  * for each step. These methods have a default implementation which only does
  44  * character to glyph mapping and default positioning using the glyph's advance
  45  * widths. Subclasses can override these methods for more advanced layout.
  46  * There is a public method which invokes the steps in the correct order.
  47  *
  48  * The steps are:
  49  *
  50  * 1) Glyph processing - character to glyph mapping and any other glyph processing
  51  *    such as ligature substitution and contextual forms.
  52  *
  53  * 2) Glyph positioning - position the glyphs based on their advance widths.
  54  *
  55  * 3) Glyph position adjustments - adjustment of glyph positions for kerning,
  56  *    accent placement, etc.
  57  *
  58  * NOTE: in all methods below, output parameters are references to pointers so
  59  * the method can allocate and free the storage as needed. All storage allocated
  60  * in this way is owned by the object which created it, and will be freed when it
  61  * is no longer needed, or when the object's destructor is invoked.
  62  *
  63  * @see LEFontInstance
  64  * @see ScriptAndLanguageTags.h
  65  *
  66  * @deprecated ICU 54. See {@link icu::LayoutEngine}
  67  *  Instead, please use HarfBuzz.
  68  *         see http://www.freedesktop.org/wiki/Software/HarfBuzz/
  69  *         and http://userguide.icu-project.org/layoutengine
  70  */
  71 class U_LAYOUT_API LayoutEngine : public UObject {
  72 public:
  73 #ifndef U_HIDE_INTERNAL_API
  74     /** @internal Flag to request kerning. Use LE_Kerning_FEATURE_FLAG instead. */
  75     static const le_int32 kTypoFlagKern;
  76     /** @internal Flag to request ligatures. Use LE_Ligatures_FEATURE_FLAG instead. */
  77     static const le_int32 kTypoFlagLiga;
  78 #endif  /* U_HIDE_INTERNAL_API */
  79
  80 protected:
  81     /**
  82      * The object which holds the glyph storage
  83      *
  84      * @internal
  85      */
  86     LEGlyphStorage *fGlyphStorage;
  87
  88     /**
  89      * The font instance for the text font.
  90      *
  91      * @see LEFontInstance
  92      *
  93      * @internal
  94      */
  95     const LEFontInstance *fFontInstance;
  96
  97     /**
  98      * The script code for the text
  99      *
 100      * @see ScriptAndLanguageTags.h for script codes.
 101      *
 102      * @internal
 103      */
 104     le_int32 fScriptCode;
 105
 106     /**
 107      * The langauge code for the text
 108      *
 109      * @see ScriptAndLanguageTags.h for language codes.
 110      *
 111      * @internal
 112      */
 113     le_int32 fLanguageCode;
 114
 115     /**
 116      * The typographic control flags
 117      *
 118      * @internal
 119      */
 120     le_int32 fTypoFlags;
 121
 122     /**
 123      * <code>TRUE</code> if <code>mapCharsToGlyphs</code> should replace ZWJ / ZWNJ with a glyph
 124      * with no contours.
 125      *
 126      * @internal
 127      */
 128     le_bool fFilterZeroWidth;
 129
 130 #ifndef U_HIDE_INTERNAL_API
 131     /**
 132      * This constructs an instance for a given font, script and language. Subclass constructors
 133      * must call this constructor.
 134      *
 135      * @param fontInstance - the font for the text
 136      * @param scriptCode - the script for the text
 137      * @param languageCode - the language for the text
 138      * @param typoFlags - the typographic control flags for the text (a bitfield).  Use kTypoFlagKern
 139      * if kerning is desired, kTypoFlagLiga if ligature formation is desired.  Others are reserved.
 140      * @param success - set to an error code if the operation fails
 141      *
 142      * @see LEFontInstance
 143      * @see ScriptAndLanguageTags.h
 144      *
 145      * @internal
 146      */
 147     LayoutEngine(const LEFontInstance *fontInstance,
 148                  le_int32 scriptCode,
 149                  le_int32 languageCode,
 150                  le_int32 typoFlags,
 151                  LEErrorCode &success);
 152 #endif  /* U_HIDE_INTERNAL_API */
 153
 154     // Do not enclose the protected default constructor with #ifndef U_HIDE_INTERNAL_API
 155     // or else the compiler will create a public default constructor.
 156     /**
 157      * This overrides the default no argument constructor to make it
 158      * difficult for clients to call it. Clients are expected to call
 159      * layoutEngineFactory.
 160      *
 161      * @internal
 162      */
 163     LayoutEngine();
 164
 165     /**
 166      * This method does any required pre-processing to the input characters. It
 167      * may generate output characters that differ from the input charcters due to
 168      * insertions, deletions, or reorderings. In such cases, it will also generate an
 169      * output character index array reflecting these changes.
 170      *
 171      * Subclasses must override this method.
 172      *
 173      * Input parameters:
 174      * @param chars - the input character context
 175      * @param offset - the index of the first character to process
 176      * @param count - the number of characters to process
 177      * @param max - the number of characters in the input context
 178      * @param rightToLeft - TRUE if the characters are in a right to left directional run
 179      * @param outChars - the output character array, if different from the input
 180      * @param glyphStorage - the object that holds the per-glyph storage. The character index array may be set.
 181      * @param success - set to an error code if the operation fails
 182      *
 183      * @return the output character count (input character count if no change)
 184      *
 185      * @internal
 186      */
 187     virtual le_int32 characterProcessing(const LEUnicode chars[], le_int32 offset, le_int32 count, le_int32 max, le_bool rightToLeft,
 188             LEUnicode *&outChars, LEGlyphStorage &glyphStorage, LEErrorCode &success);
 189
 190     /**
 191      * This method does the glyph processing. It converts an array of characters
 192      * into an array of glyph indices and character indices. The characters to be
 193      * processed are passed in a surrounding context. The context is specified as
 194      * a starting address and a maximum character count. An offset and a count are
 195      * used to specify the characters to be processed.
 196      *
 197      * The default implementation of this method only does character to glyph mapping.
 198      * Subclasses needing more elaborate glyph processing must override this method.
 199      *
 200      * Input parameters:
 201      * @param chars - the character context
 202      * @param offset - the offset of the first character to process
 203      * @param count - the number of characters to process
 204      * @param max - the number of characters in the context.
 205      * @param rightToLeft - TRUE if the text is in a right to left directional run
 206      * @param glyphStorage - the object which holds the per-glyph storage. The glyph and char indices arrays
 207      *                       will be set.
 208      *
 209      * Output parameters:
 210      * @param success - set to an error code if the operation fails
 211      *
 212      * @return the number of glyphs in the glyph index array
 213      *
 214      * @internal
 215      */
 216     virtual le_int32 computeGlyphs(const LEUnicode chars[], le_int32 offset, le_int32 count, le_int32 max, le_bool rightToLeft, LEGlyphStorage &glyphStorage, LEErrorCode &success);
 217
 218     /**
 219      * This method does basic glyph positioning. The default implementation positions
 220      * the glyphs based on their advance widths. This is sufficient for most uses. It
 221      * is not expected that many subclasses will override this method.
 222      *
 223      * Input parameters:
 224      * @param glyphStorage - the object which holds the per-glyph storage. The glyph position array will be set.
 225      * @param x - the starting X position
 226      * @param y - the starting Y position
 227      * @param success - set to an error code if the operation fails
 228      *
 229      * @internal
 230      */
 231     virtual void positionGlyphs(LEGlyphStorage &glyphStorage, float x, float y, LEErrorCode &success);
 232
 233     /**
 234      * This method does positioning adjustments like accent positioning and
 235      * kerning. The default implementation does nothing. Subclasses needing
 236      * position adjustments must override this method.
 237      *
 238      * Note that this method has both characters and glyphs as input so that
 239      * it can use the character codes to determine glyph types if that information
 240      * isn't directly available. (e.g. Some Arabic OpenType fonts don't have a GDEF
 241      * table)
 242      *
 243      * @param chars - the input character context
 244      * @param offset - the offset of the first character to process
 245      * @param count - the number of characters to process
 246      * @param reverse - <code>TRUE</code> if the glyphs in the glyph array have been reordered
 247      * @param glyphStorage - the object which holds the per-glyph storage. The glyph positions will be
 248      *                       adjusted as needed.
 249      * @param success - output parameter set to an error code if the operation fails
 250      *
 251      * @internal
 252      */
 253     virtual void adjustGlyphPositions(const LEUnicode chars[], le_int32 offset, le_int32 count, le_bool reverse, LEGlyphStorage &glyphStorage, LEErrorCode &success);
 254
 255     /**
 256      * This method gets a table from the font associated with
 257      * the text. The default implementation gets the table from
 258      * the font instance. Subclasses which need to get the tables
 259      * some other way must override this method.
 260      *
 261      * @param tableTag - the four byte table tag.
 262      * @param length - length to use
 263      *
 264      * @return the address of the table.
 265      *
 266      * @internal
 267      */
 268     virtual const void *getFontTable(LETag tableTag, size_t &length) const;
 269
 270     /**
 271      * @deprecated ICU 54. See {@link icu::LayoutEngine}
 272      */
 273     virtual const void *getFontTable(LETag tableTag) const { size_t ignored; return getFontTable(tableTag, ignored); }
 274
 275     /**
 276      * This method does character to glyph mapping. The default implementation
 277      * uses the font instance to do the mapping. It will allocate the glyph and
 278      * character index arrays if they're not already allocated. If it allocates the
 279      * character index array, it will fill it it.
 280      *
 281      * This method supports right to left
 282      * text with the ability to store the glyphs in reverse order, and by supporting
 283      * character mirroring, which will replace a character which has a left and right
 284      * form, such as parens, with the opposite form before mapping it to a glyph index.
 285      *
 286      * Input parameters:
 287      * @param chars - the input character context
 288      * @param offset - the offset of the first character to be mapped
 289      * @param count - the number of characters to be mapped
 290      * @param reverse - if <code>TRUE</code>, the output will be in reverse order
 291      * @param mirror - if <code>TRUE</code>, do character mirroring
 292      * @param glyphStorage - the object which holds the per-glyph storage. The glyph and char
 293      *                       indices arrays will be filled in.
 294      * @param success - set to an error code if the operation fails
 295      *
 296      * @see LEFontInstance
 297      *
 298      * @internal
 299      */
 300     virtual void mapCharsToGlyphs(const LEUnicode chars[], le_int32 offset, le_int32 count, le_bool reverse, le_bool mirror, LEGlyphStorage &glyphStorage, LEErrorCode &success);
 301
 302 #ifndef U_HIDE_INTERNAL_API
 303     /**
 304      * This is a convenience method that forces the advance width of mark
 305      * glyphs to be zero, which is required for proper selection and highlighting.
 306      *
 307      * @param glyphStorage - the object containing the per-glyph storage. The positions array will be modified.
 308      * @param markFilter - used to identify mark glyphs
 309      * @param success - output parameter set to an error code if the operation fails
 310      *
 311      * @see LEGlyphFilter
 312      *
 313      * @internal
 314      */
 315     static void adjustMarkGlyphs(LEGlyphStorage &glyphStorage, LEGlyphFilter *markFilter, LEErrorCode &success);
 316
 317
 318     /**
 319      * This is a convenience method that forces the advance width of mark
 320      * glyphs to be zero, which is required for proper selection and highlighting.
 321      * This method uses the input characters to identify marks. This is required in
 322      * cases where the font does not contain enough information to identify them based
 323      * on the glyph IDs.
 324      *
 325      * @param chars - the array of input characters
 326      * @param charCount - the number of input characers
 327      * @param glyphStorage - the object containing the per-glyph storage. The positions array will be modified.
 328      * @param reverse - <code>TRUE</code> if the glyph array has been reordered
 329      * @param markFilter - used to identify mark glyphs
 330      * @param success - output parameter set to an error code if the operation fails
 331      *
 332      * @see LEGlyphFilter
 333      *
 334      * @internal
 335      */
 336     static void adjustMarkGlyphs(const LEUnicode chars[], le_int32 charCount, le_bool reverse, LEGlyphStorage &glyphStorage, LEGlyphFilter *markFilter, LEErrorCode &success);
 337 #endif  /* U_HIDE_INTERNAL_API */
 338
 339 public:
 340     /**
 341      * The destructor. It will free any storage allocated for the
 342      * glyph, character index and position arrays by calling the reset
 343      * method. It is declared virtual so that it will be invoked by the
 344      * subclass destructors.
 345      *
 346      * @deprecated ICU 54. See {@link icu::LayoutEngine}
 347      */
 348     virtual ~LayoutEngine();
 349
 350     /**
 351      * This method will invoke the layout steps in their correct order by calling
 352      * the computeGlyphs, positionGlyphs and adjustGlyphPosition methods. It will
 353      * compute the glyph, character index and position arrays.
 354      *
 355      * @param chars - the input character context
 356      * @param offset - the offset of the first character to process
 357      * @param count - the number of characters to process
 358      * @param max - the number of characters in the input context
 359      * @param rightToLeft - TRUE if the characers are in a right to left directional run
 360      * @param x - the initial X position
 361      * @param y - the initial Y position
 362      * @param success - output parameter set to an error code if the operation fails
 363      *
 364      * @return the number of glyphs in the glyph array
 365      *
 366      * Note: The glyph, character index and position array can be accessed
 367      * using the getter methods below.
 368      *
 369      * Note: If you call this method more than once, you must call the reset()
 370      * method first to free the glyph, character index and position arrays
 371      * allocated by the previous call.
 372      *
 373      * @deprecated ICU 54. See {@link icu::LayoutEngine}
 374      */
 375     virtual le_int32 layoutChars(const LEUnicode chars[], le_int32 offset, le_int32 count, le_int32 max, le_bool rightToLeft, float x, float y, LEErrorCode &success);
 376
 377     /**
 378      * This method returns the number of glyphs in the glyph array. Note
 379      * that the number of glyphs will be greater than or equal to the number
 380      * of characters used to create the LayoutEngine.
 381      *
 382      * @return the number of glyphs in the glyph array
 383      *
 384      * @deprecated ICU 54. See {@link icu::LayoutEngine}
 385      */
 386     le_int32 getGlyphCount() const;
 387
 388     /**
 389      * This method copies the glyph array into a caller supplied array.
 390      * The caller must ensure that the array is large enough to hold all
 391      * the glyphs.
 392      *
 393      * @param glyphs - the destiniation glyph array
 394      * @param success - set to an error code if the operation fails
 395      *
 396      * @deprecated ICU 54. See {@link icu::LayoutEngine}
 397      */
 398     void getGlyphs(LEGlyphID glyphs[], LEErrorCode &success) const;
 399
 400     /**
 401      * This method copies the glyph array into a caller supplied array,
 402      * ORing in extra bits. (This functionality is needed by the JDK,
 403      * which uses 32 bits pre glyph idex, with the high 16 bits encoding
 404      * the composite font slot number)
 405      *
 406      * @param glyphs - the destination (32 bit) glyph array
 407      * @param extraBits - this value will be ORed with each glyph index
 408      * @param success - set to an error code if the operation fails
 409      *
 410      * @deprecated ICU 54. See {@link icu::LayoutEngine}
 411      */
 412     virtual void getGlyphs(le_uint32 glyphs[], le_uint32 extraBits, LEErrorCode &success) const;
 413
 414     /**
 415      * This method copies the character index array into a caller supplied array.
 416      * The caller must ensure that the array is large enough to hold a
 417      * character index for each glyph.
 418      *
 419      * @param charIndices - the destiniation character index array
 420      * @param success - set to an error code if the operation fails
 421      *
 422      * @deprecated ICU 54. See {@link icu::LayoutEngine}
 423      */
 424     void getCharIndices(le_int32 charIndices[], LEErrorCode &success) const;
 425
 426     /**
 427      * This method copies the character index array into a caller supplied array.
 428      * The caller must ensure that the array is large enough to hold a
 429      * character index for each glyph.
 430      *
 431      * @param charIndices - the destiniation character index array
 432      * @param indexBase - an offset which will be added to each index
 433      * @param success - set to an error code if the operation fails
 434      *
 435      * @deprecated ICU 54. See {@link icu::LayoutEngine}
 436      */
 437     void getCharIndices(le_int32 charIndices[], le_int32 indexBase, LEErrorCode &success) const;
 438
 439     /**
 440      * This method copies the position array into a caller supplied array.
 441      * The caller must ensure that the array is large enough to hold an
 442      * X and Y position for each glyph, plus an extra X and Y for the
 443      * advance of the last glyph.
 444      *
 445      * @param positions - the destiniation position array
 446      * @param success - set to an error code if the operation fails
 447      *
 448      * @deprecated ICU 54. See {@link icu::LayoutEngine}
 449      */
 450     void getGlyphPositions(float positions[], LEErrorCode &success) const;
 451
 452     /**
 453      * This method returns the X and Y position of the glyph at
 454      * the given index.
 455      *
 456      * Input parameters:
 457      * @param glyphIndex - the index of the glyph
 458      *
 459      * Output parameters:
 460      * @param x - the glyph's X position
 461      * @param y - the glyph's Y position
 462      * @param success - set to an error code if the operation fails
 463      *
 464      * @deprecated ICU 54. See {@link icu::LayoutEngine}
 465      */
 466     void getGlyphPosition(le_int32 glyphIndex, float &x, float &y, LEErrorCode &success) const;
 467
 468     /**
 469      * This method frees the glyph, character index and position arrays
 470      * so that the LayoutEngine can be reused to layout a different
 471      * characer array. (This method is also called by the destructor)
 472      *
 473      * @deprecated ICU 54. See {@link icu::LayoutEngine}
 474      */
 475     virtual void reset();
 476
 477     /**
 478      * This method returns a LayoutEngine capable of laying out text
 479      * in the given font, script and langauge. Note that the LayoutEngine
 480      * returned may be a subclass of LayoutEngine.
 481      *
 482      * @param fontInstance - the font of the text
 483      * @param scriptCode - the script of the text
 484      * @param languageCode - the language of the text
 485      * @param success - output parameter set to an error code if the operation fails
 486      *
 487      * @return a LayoutEngine which can layout text in the given font.
 488      *
 489      * @see LEFontInstance
 490      *
 491      * @deprecated ICU 54. See {@link icu::LayoutEngine}
 492      */
 493     static LayoutEngine *layoutEngineFactory(const LEFontInstance *fontInstance, le_int32 scriptCode, le_int32 languageCode, LEErrorCode &success);
 494
 495     /**
 496      * Override of existing call that provides flags to control typography.
 497      * @deprecated ICU 54. See {@link icu::LayoutEngine}
 498      */
 499     static LayoutEngine *layoutEngineFactory(const LEFontInstance *fontInstance, le_int32 scriptCode, le_int32 languageCode, le_int32 typo_flags, LEErrorCode &success);
 500
 501     /**
 502      * ICU "poor man's RTTI", returns a UClassID for the actual class.
 503      *
 504      * @deprecated ICU 54. See {@link icu::LayoutEngine}
 505      */
 506     virtual UClassID getDynamicClassID() const;
 507
 508     /**
 509      * ICU "poor man's RTTI", returns a UClassID for this class.
 510      *
 511      * @deprecated ICU 54. See {@link icu::LayoutEngine}
 512      */
 513     static UClassID getStaticClassID();
 514
 515 };
 516
 517 U_NAMESPACE_END
 518 #endif