layout/LayoutEngine.h - platform/external/icu4c.git - Git at Google

 /*
  * (C) Copyright IBM Corp. and others 1998-2013 - 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. Use LE_Kerning_FEATURE_FLAG instead. */
     static const le_int32 kTypoFlagKern;
     /** @internal Flag to request ligatures. Use LE_Ligatures_FEATURE_FLAG instead. */
     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.
      * @param length - length to use
      *
      * @return the address of the table.
      *
      * @internal
      */
     virtual const void *getFontTable(LETag tableTag, size_t &length) const;

     /**
      * @deprecated
      */
     virtual const void *getFontTable(LETag tableTag) const { size_t ignored; return getFontTable(tableTag, ignored); }

     /**
      * 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
	/*
	* (C) Copyright IBM Corp. and others 1998-2013 - 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. Use LE_Kerning_FEATURE_FLAG instead. */
	static const le_int32 kTypoFlagKern;
	/** @internal Flag to request ligatures. Use LE_Ligatures_FEATURE_FLAG instead. */
	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.
	* @param length - length to use
	*
	* @return the address of the table.
	*
	* @internal
	*/
	virtual const void *getFontTable(LETag tableTag, size_t &length) const;

	/**
	* @deprecated
	*/
	virtual const void *getFontTable(LETag tableTag) const { size_t ignored; return getFontTable(tableTag, ignored); }

	/**
	* 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