text: /*
   * (C) Copyright IBM Corp. 1998-2011 - All Rights Reserved
   */
  
  #ifndef __LAYOUTENGINE_H
  #define __LAYOUTENGINE_H
  
  #include "LETypes.h"
  
  /**
   * \file 
   * \brief C++ API: Virtual base class for complex text layout.
   */
  
  U_NAMESPACE_BEGIN
  
  class LEFontInstance;
  class LEGlyphFilter;
  class LEGlyphStorage;
  
  /**
   * This is a virtual base class used to do complex text layout. The text must all
   * be in a single font, script, and language. An instance of a LayoutEngine can be
   * created by calling the layoutEngineFactory method. Fonts are identified by
   * instances of the LEFontInstance class. Script and language codes are identified
   * by integer codes, which are defined in ScriptAndLanuageTags.h.
   *
   * Note that this class is not public API. It is declared public so that it can be
   * exported from the library that it is a part of.
   *
   * The input to the layout process is an array of characters in logical order,
   * and a starting X, Y position for the text. The output is an array of glyph indices,
   * an array of character indices for the glyphs, and an array of glyph positions.
   * These arrays are protected members of LayoutEngine which can be retreived by a
   * public method. The reset method can be called to free these arrays so that the
   * LayoutEngine can be reused.
   *
   * The layout process is done in three steps. There is a protected virtual method
   * for each step. These methods have a default implementation which only does
   * character to glyph mapping and default positioning using the glyph's advance
   * widths. Subclasses can override these methods for more advanced layout.
   * There is a public method which invokes the steps in the correct order.
   * 
   * The steps are:
   *
   * 1) Glyph processing - character to glyph mapping and any other glyph processing
   *    such as ligature substitution and contextual forms.
   *
   * 2) Glyph positioning - position the glyphs based on their advance widths.
   *
   * 3) Glyph position adjustments - adjustment of glyph positions for kerning,
   *    accent placement, etc.
   *
   * NOTE: in all methods below, output parameters are references to pointers so
   * the method can allocate and free the storage as needed. All storage allocated
   * in this way is owned by the object which created it, and will be freed when it
   * is no longer needed, or when the object's destructor is invoked.
   *
   * @see LEFontInstance
   * @see ScriptAndLanguageTags.h
   *
   * @stable ICU 2.8
   */
  class U_LAYOUT_API LayoutEngine : public UObject {
  public:
  #ifndef U_HIDE_INTERNAL_API
      /** @internal Flag to request kerning. */
      static const le_int32 kTypoFlagKern;
      /** @internal Flag to request ligatures. */
      static const le_int32 kTypoFlagLiga;
  #endif  /* U_HIDE_INTERNAL_API */
  
  protected:
      /**
       * The object which holds the glyph storage
       *
       * @internal
       */
      LEGlyphStorage *fGlyphStorage;
  
      /**
       * The font instance for the text font.
       *
       * @see LEFontInstance
       *
       * @internal
       */
      const LEFontInstance *fFontInstance;
  
      /**
       * The script code for the text
       *
       * @see ScriptAndLanguageTags.h for script codes.
       *
       * @internal
       */
      le_int32 fScriptCode;
  
      /**
       * The langauge code for the text
       *
       * @see ScriptAndLanguageTags.h for language codes.
       *
       * @internal
       */
      le_int32 fLanguageCode;
  
      /**
       * The typographic control flags
       *
       * @internal
       */
      le_int32 fTypoFlags;
  
      /**
       * <code>TRUE</code> if <code>mapCharsToGlyphs</code> should replace ZWJ / ZWNJ with a glyph
       * with no contours.
       *
       * @internal
       */
      le_bool fFilterZeroWidth;
  
  #ifndef U_HIDE_INTERNAL_API
      /**
       * This constructs an instance for a given font, script and language. Subclass constructors
       * must call this constructor.
       *
       * @param fontInstance - the font for the text
       * @param scriptCode - the script for the text
       * @param languageCode - the language for the text
       * @param typoFlags - the typographic control flags for the text (a bitfield).  Use kTypoFlagKern
       * if kerning is desired, kTypoFlagLiga if ligature formation is desired.  Others are reserved.
       * @param success - set to an error code if the operation fails
       *
       * @see LEFontInstance
       * @see ScriptAndLanguageTags.h
       *
       * @internal
       */
      LayoutEngine(const LEFontInstance *fontInstance,
                   le_int32 scriptCode,
                   le_int32 languageCode,
                   le_int32 typoFlags,
                   LEErrorCode &success);
  #endif  /* U_HIDE_INTERNAL_API */
  
      // Do not enclose the protected default constructor with #ifndef U_HIDE_INTERNAL_API
      // or else the compiler will create a public default constructor.
      /**
       * This overrides the default no argument constructor to make it
       * difficult for clients to call it. Clients are expected to call
       * layoutEngineFactory.
       *
       * @internal
       */
      LayoutEngine();
  
      /**
       * This method does any required pre-processing to the input characters. It
       * may generate output characters that differ from the input charcters due to
       * insertions, deletions, or reorderings. In such cases, it will also generate an
       * output character index array reflecting these changes.
       *
       * Subclasses must override this method.
       *
       * Input parameters:
       * @param chars - the input character context
       * @param offset - the index of the first character to process
       * @param count - the number of characters to process
       * @param max - the number of characters in the input context
       * @param rightToLeft - TRUE if the characters are in a right to left directional run
       * @param outChars - the output character array, if different from the input
       * @param glyphStorage - the object that holds the per-glyph storage. The character index array may be set.
       * @param success - set to an error code if the operation fails
       *
       * @return the output character count (input character count if no change)
       *
       * @internal
       */
      virtual le_int32 characterProcessing(const LEUnicode chars[], le_int32 offset, le_int32 count, le_int32 max, le_bool rightToLeft,
              LEUnicode *&outChars, LEGlyphStorage &glyphStorage, LEErrorCode &success);
  
      /**
       * This method does the glyph processing. It converts an array of characters
       * into an array of glyph indices and character indices. The characters to be
       * processed are passed in a surrounding context. The context is specified as
       * a starting address and a maximum character count. An offset and a count are
       * used to specify the characters to be processed.
       *
       * The default implementation of this method only does character to glyph mapping.
       * Subclasses needing more elaborate glyph processing must override this method.
       *
       * Input parameters:
       * @param chars - the character context
       * @param offset - the offset of the first character to process
       * @param count - the number of characters to process
       * @param max - the number of characters in the context.
       * @param rightToLeft - TRUE if the text is in a right to left directional run
       * @param glyphStorage - the object which holds the per-glyph storage. The glyph and char indices arrays
       *                       will be set.
       *
       * Output parameters:
       * @param success - set to an error code if the operation fails
       *
       * @return the number of glyphs in the glyph index array
       *
       * @internal
       */
      virtual le_int32 computeGlyphs(const LEUnicode chars[], le_int32 offset, le_int32 count, le_int32 max, le_bool rightToLeft, LEGlyphStorage &glyphStorage, LEErrorCode &success);
  
      /**
       * This method does basic glyph positioning. The default implementation positions
       * the glyphs based on their advance widths. This is sufficient for most uses. It
       * is not expected that many subclasses will override this method.
       *
       * Input parameters:
       * @param glyphStorage - the object which holds the per-glyph storage. The glyph position array will be set.
       * @param x - the starting X position
       * @param y - the starting Y position
       * @param success - set to an error code if the operation fails
       *
       * @internal
       */
      virtual void positionGlyphs(LEGlyphStorage &glyphStorage, float x, float y, LEErrorCode &success);
  
      /**
       * This method does positioning adjustments like accent positioning and
       * kerning. The default implementation does nothing. Subclasses needing
       * position adjustments must override this method.
       *
       * Note that this method has both characters and glyphs as input so that
       * it can use the character codes to determine glyph types if that information
       * isn't directly available. (e.g. Some Arabic OpenType fonts don't have a GDEF
       * table)
       *
       * @param chars - the input character context
       * @param offset - the offset of the first character to process
       * @param count - the number of characters to process
       * @param reverse - <code>TRUE</code> if the glyphs in the glyph array have been reordered
       * @param glyphStorage - the object which holds the per-glyph storage. The glyph positions will be
       *                       adjusted as needed.
       * @param success - output parameter set to an error code if the operation fails
       *
       * @internal
       */
      virtual void adjustGlyphPositions(const LEUnicode chars[], le_int32 offset, le_int32 count, le_bool reverse, LEGlyphStorage &glyphStorage, LEErrorCode &success);
  
      /**
       * This method gets a table from the font associated with
       * the text. The default implementation gets the table from
       * the font instance. Subclasses which need to get the tables
       * some other way must override this method.
       * 
       * @param tableTag - the four byte table tag.
       *
       * @return the address of the table.
       *
       * @internal
       */
      virtual const void *getFontTable(LETag tableTag) const;
  
      /**
       * This method does character to glyph mapping. The default implementation
       * uses the font instance to do the mapping. It will allocate the glyph and
       * character index arrays if they're not already allocated. If it allocates the
       * character index array, it will fill it it.
       *
       * This method supports right to left
       * text with the ability to store the glyphs in reverse order, and by supporting
       * character mirroring, which will replace a character which has a left and right
       * form, such as parens, with the opposite form before mapping it to a glyph index.
       *
       * Input parameters:
       * @param chars - the input character context
       * @param offset - the offset of the first character to be mapped
       * @param count - the number of characters to be mapped
       * @param reverse - if <code>TRUE</code>, the output will be in reverse order
       * @param mirror - if <code>TRUE</code>, do character mirroring
       * @param glyphStorage - the object which holds the per-glyph storage. The glyph and char
       *                       indices arrays will be filled in.
       * @param success - set to an error code if the operation fails
       *
       * @see LEFontInstance
       *
       * @internal
       */
      virtual void mapCharsToGlyphs(const LEUnicode chars[], le_int32 offset, le_int32 count, le_bool reverse, le_bool mirror, LEGlyphStorage &glyphStorage, LEErrorCode &success);
  
  #ifndef U_HIDE_INTERNAL_API
      /**
       * This is a convenience method that forces the advance width of mark
       * glyphs to be zero, which is required for proper selection and highlighting.
       * 
       * @param glyphStorage - the object containing the per-glyph storage. The positions array will be modified.
       * @param markFilter - used to identify mark glyphs
       * @param success - output parameter set to an error code if the operation fails
       *
       * @see LEGlyphFilter
       *
       * @internal
       */
      static void adjustMarkGlyphs(LEGlyphStorage &glyphStorage, LEGlyphFilter *markFilter, LEErrorCode &success);
  
  
      /**
       * This is a convenience method that forces the advance width of mark
       * glyphs to be zero, which is required for proper selection and highlighting.
       * This method uses the input characters to identify marks. This is required in
       * cases where the font does not contain enough information to identify them based
       * on the glyph IDs.
       * 
       * @param chars - the array of input characters
       * @param charCount - the number of input characers
       * @param glyphStorage - the object containing the per-glyph storage. The positions array will be modified.
       * @param reverse - <code>TRUE</code> if the glyph array has been reordered
       * @param markFilter - used to identify mark glyphs
       * @param success - output parameter set to an error code if the operation fails
       *
       * @see LEGlyphFilter
       *
       * @internal
       */
      static void adjustMarkGlyphs(const LEUnicode chars[], le_int32 charCount, le_bool reverse, LEGlyphStorage &glyphStorage, LEGlyphFilter *markFilter, LEErrorCode &success);
  #endif  /* U_HIDE_INTERNAL_API */
  
  public:
      /**
       * The destructor. It will free any storage allocated for the
       * glyph, character index and position arrays by calling the reset
       * method. It is declared virtual so that it will be invoked by the
       * subclass destructors.
       *
       * @stable ICU 2.8
       */
      virtual ~LayoutEngine();
  
      /**
       * This method will invoke the layout steps in their correct order by calling
       * the computeGlyphs, positionGlyphs and adjustGlyphPosition methods. It will
       * compute the glyph, character index and position arrays.
       *
       * @param chars - the input character context
       * @param offset - the offset of the first character to process
       * @param count - the number of characters to process
       * @param max - the number of characters in the input context
       * @param rightToLeft - TRUE if the characers are in a right to left directional run
       * @param x - the initial X position
       * @param y - the initial Y position
       * @param success - output parameter set to an error code if the operation fails
       *
       * @return the number of glyphs in the glyph array
       *
       * Note: The glyph, character index and position array can be accessed
       * using the getter methods below.
       *
       * Note: If you call this method more than once, you must call the reset()
       * method first to free the glyph, character index and position arrays
       * allocated by the previous call.
       *
       * @stable ICU 2.8
       */
      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);
  
      /**
       * This method returns the number of glyphs in the glyph array. Note
       * that the number of glyphs will be greater than or equal to the number
       * of characters used to create the LayoutEngine.
       *
       * @return the number of glyphs in the glyph array
       *
       * @stable ICU 2.8
       */
      le_int32 getGlyphCount() const;
  
      /**
       * This method copies the glyph array into a caller supplied array.
       * The caller must ensure that the array is large enough to hold all
       * the glyphs.
       *
       * @param glyphs - the destiniation glyph array
       * @param success - set to an error code if the operation fails
       *
       * @stable ICU 2.8
       */
      void getGlyphs(LEGlyphID glyphs[], LEErrorCode &success) const;
  
      /**
       * This method copies the glyph array into a caller supplied array,
       * ORing in extra bits. (This functionality is needed by the JDK,
       * which uses 32 bits pre glyph idex, with the high 16 bits encoding
       * the composite font slot number)
       *
       * @param glyphs - the destination (32 bit) glyph array
       * @param extraBits - this value will be ORed with each glyph index
       * @param success - set to an error code if the operation fails
       *
       * @stable ICU 2.8
       */
      virtual void getGlyphs(le_uint32 glyphs[], le_uint32 extraBits, LEErrorCode &success) const;
  
      /**
       * This method copies the character index array into a caller supplied array.
       * The caller must ensure that the array is large enough to hold a
       * character index for each glyph.
       *
       * @param charIndices - the destiniation character index array
       * @param success - set to an error code if the operation fails
       *
       * @stable ICU 2.8
       */
      void getCharIndices(le_int32 charIndices[], LEErrorCode &success) const;
  
      /**
       * This method copies the character index array into a caller supplied array.
       * The caller must ensure that the array is large enough to hold a
       * character index for each glyph.
       *
       * @param charIndices - the destiniation character index array
       * @param indexBase - an offset which will be added to each index
       * @param success - set to an error code if the operation fails
       *
       * @stable ICU 2.8
       */
      void getCharIndices(le_int32 charIndices[], le_int32 indexBase, LEErrorCode &success) const;
  
      /**
       * This method copies the position array into a caller supplied array.
       * The caller must ensure that the array is large enough to hold an
       * X and Y position for each glyph, plus an extra X and Y for the
       * advance of the last glyph.
       *
       * @param positions - the destiniation position array
       * @param success - set to an error code if the operation fails
       *
       * @stable ICU 2.8
       */
      void getGlyphPositions(float positions[], LEErrorCode &success) const;
  
      /**
       * This method returns the X and Y position of the glyph at
       * the given index.
       *
       * Input parameters:
       * @param glyphIndex - the index of the glyph
       *
       * Output parameters:
       * @param x - the glyph's X position
       * @param y - the glyph's Y position
       * @param success - set to an error code if the operation fails
       *
       * @stable ICU 2.8
       */
      void getGlyphPosition(le_int32 glyphIndex, float &x, float &y, LEErrorCode &success) const;
  
      /**
       * This method frees the glyph, character index and position arrays
       * so that the LayoutEngine can be reused to layout a different
       * characer array. (This method is also called by the destructor)
       *
       * @stable ICU 2.8
       */
      virtual void reset();
  
      /**
       * This method returns a LayoutEngine capable of laying out text
       * in the given font, script and langauge. Note that the LayoutEngine
       * returned may be a subclass of LayoutEngine.
       *
       * @param fontInstance - the font of the text
       * @param scriptCode - the script of the text
       * @param languageCode - the language of the text
       * @param success - output parameter set to an error code if the operation fails
       *
       * @return a LayoutEngine which can layout text in the given font.
       *
       * @see LEFontInstance
       *
       * @stable ICU 2.8
       */
      static LayoutEngine *layoutEngineFactory(const LEFontInstance *fontInstance, le_int32 scriptCode, le_int32 languageCode, LEErrorCode &success);
  
      /**
       * Override of existing call that provides flags to control typography.
       * @stable ICU 3.4
       */
      static LayoutEngine *layoutEngineFactory(const LEFontInstance *fontInstance, le_int32 scriptCode, le_int32 languageCode, le_int32 typo_flags, LEErrorCode &success);
  
      /**
       * ICU "poor man's RTTI", returns a UClassID for the actual class.
       *
       * @stable ICU 2.8
       */
      virtual UClassID getDynamicClassID() const;
  
      /**
       * ICU "poor man's RTTI", returns a UClassID for this class.
       *
       * @stable ICU 2.8
       */
      static UClassID getStaticClassID();
  
  };
  
  U_NAMESPACE_END
  #endif
  