source/layout/LayoutEngine.h - external/github.com/unicode-org/icu - Git at Google


 /*
  * %W% %W%
  *
  * (C) Copyright IBM Corp. 1998, 1999, 2000, 2001 - All Rights Reserved
  *
  */

 #ifndef __LAYOUTENGINE_H
 #define __LAYOUTENGINE_H

 #ifndef __LETYPES_H
 #include "LETypes.h"
 #endif

 #include <string.h>

 U_NAMESPACE_BEGIN

 class LEFontInstance;
 class LEGlyphFilter;

 /**
  * 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
  */
 class U_LAYOUT_API LayoutEngine
 {
 protected:
 	/**
 	 * The number of glyphs in the output
 	 */
     le_int32 fGlyphCount;

 	/**
 	 * The output glyph array
 	 */
     LEGlyphID *fGlyphs;

 	/**
 	 * The character index array. One entry for each output glyph, giving the index
 	 * in the input character array of the character which corresponds to this glyph.
 	 */
     le_int32 *fCharIndices;

 	/**
 	 * The glyph position array. There are two entries for each glyph giving the
 	 * X and Y positions of the glyph. Thus, for glyph i, the X position is at index
 	 * 2i, and the Y position is at index 2i + 1. There are also two entries for the
 	 * X and Y position of the advance of the last glyph.
 	 */
     float *fPositions;

 	/**
 	 * The font instance for the text font.
 	 *
 	 * @see LEFontInstance
 	 */
     const LEFontInstance *fFontInstance;

 	/**
 	 * The script code for the text
 	 *
 	 * @see ScriptAndLanguageTags.h for script codes.
 	 */
     le_int32 fScriptCode;

 	/**
 	 * The langauge code for the text
 	 *
 	 * @see ScriptAndLanguageTags.h for language codes.
 	 */
     le_int32 fLanguageCode;

 	/**
 	 * 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 langaugeCode - the language for the text
 	 *
 	 * @see LEFontInstance
 	 * @see ScriptAndLanguageTags.h
 	 */
     LayoutEngine(const LEFontInstance *fontInstance, le_int32 scriptCode, le_int32 languageCode);

     /**
 	 * This overrides the default no argument constructor to make it
 	 * difficult for clients to call it. Clients are expected to call
 	 * layoutEngineFactory.
 	 */
     LayoutEngine();

 	/**
 	 * 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
 	 *
 	 * Output parameters:
 	 * @param glyphs - the glyph index array
 	 * @param charIndices - the character index array
 	 * @param success - set to an error code if the operation fails
 	 *
 	 * @return the number of glyphs in the glyph index array
 	 */
     virtual le_int32 computeGlyphs(const LEUnicode chars[], le_int32 offset, le_int32 count, le_int32 max, le_bool rightToLeft, LEGlyphID *&glyphs, le_int32 *&charIndices, 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 glyphs - the input glyph array
 	 * @param glyphCount - the number of glyphs in the glyph array
 	 * @param x - the starting X position
 	 * @param y - the starting Y position
 	 *
 	 * Output parameters:
 	 * @param positions - the output X and Y positions (two entries per glyph)
 	 */
     virtual void positionGlyphs(const LEGlyphID glyphs[], le_int32 glyphCount, float x, float y, float *&positions, 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 - true if the glyphs in the glyph array have been reordered
 	 * @param glyphs - the input glyph array
 	 * @param glyphCount - the number of glyphs
 	 * @param positions - the position array, will be updated as needed
 	 * @param success - output parameter set to an error code if the operation fails
 	 *
 	 * Note: the positions are passed as a plain array because this method should
 	 * not need to reallocate them.
 	 */
     virtual void adjustGlyphPositions(const LEUnicode chars[], le_int32 offset, le_int32 count, le_bool reverse, LEGlyphID glyphs[], le_int32 glyphCount, float positions[], LEErrorCode &success)
     {
 		if (LE_FAILURE(success)) {
 			return;
 		}

 		if (chars == NULL || glyphs == NULL || positions == NULL || offset < 0 || count < 0) {
 			success = LE_ILLEGAL_ARGUMENT_ERROR;
 			return;
 		}

         // default is no adjustments
 		return;
     };

 	/**
 	 * 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.
 	 */
     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 true, the output will be in reverse order
 	 * @param mirror - if true, do character mirroring
 	 *
 	 * Output parameters:
 	 * @param glyphs - the glyph array
 	 * @param charIndices - the character index array
 	 * @param success - set to an error code if the operation fails
 	 *
 	 * @see LEFontInstance
 	 */
     virtual void mapCharsToGlyphs(const LEUnicode chars[], le_int32 offset, le_int32 count, le_bool reverse, le_bool mirror, LEGlyphID *&glyphs, le_int32 *&charIndices, 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.
 	 *
 	 * @param glyphs - the glyph array
 	 * @param glyphCount - the number of glyphs
 	 * @param reverse - true if the glyph array has been reordered
 	 * @param markFilter - used to identify mark glyphs
 	 * @param positions - the glyph position array - updated as required
 	 * @param success - output parameter set to an error code if the operation fails
 	 *
 	 * @see LEGlyphFilter
 	 */
     static void adjustMarkGlyphs(const LEGlyphID glyphs[], le_int32 glyphCount, le_bool reverse, LEGlyphFilter *markFilter, float positions[], LEErrorCode &success);

 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.
 	 */
     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 method below.
 	 */
     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
 	 */
 	le_int32 getGlyphCount() const
 	{
 		return fGlyphCount;
 	};

 	/**
 	 * 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
 	 */
     void getGlyphs(LEGlyphID glyphs[], LEErrorCode &success) const
     {
 		if (LE_FAILURE(success)) {
 			return;
 		}

 		if (glyphs == NULL) {
 			success = LE_ILLEGAL_ARGUMENT_ERROR;
 			return;
 		}

 		if (fGlyphs == NULL) {
 			success = LE_NO_LAYOUT_ERROR;
 		}

         LE_ARRAY_COPY(glyphs, fGlyphs, fGlyphCount);
     };

 	/**
 	 * 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
 	 */
     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
 	 */
     void getCharIndices(le_int32 charIndices[], LEErrorCode &success) const
     {
 		if LE_FAILURE(success) {
 			return;
 		}

 		if (charIndices == NULL) {
 			success = LE_ILLEGAL_ARGUMENT_ERROR;
 			return;
 		}

 		if (fCharIndices == NULL) {
 			success = LE_NO_LAYOUT_ERROR;
 			return;
 		}

         LE_ARRAY_COPY(charIndices, fCharIndices, fGlyphCount);
     };

 	/**
 	 * 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
 	 */
     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 glyphs - the destiniation position array
 	 * @param success - set to an error code if the operation fails
 	 */
     void getGlyphPositions(float positions[], LEErrorCode &success) const
     {
 		if LE_FAILURE(success) {
 			return;
 		}

 		if (positions == NULL) {
 			success = LE_ILLEGAL_ARGUMENT_ERROR;
 			return;
 		}

 		if (fPositions == NULL) {
 			success = LE_NO_LAYOUT_ERROR;
 			return;
 		}

         LE_ARRAY_COPY(positions, fPositions, fGlyphCount * 2 + 2);
     };

 	/**
 	 * 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
 	 *
 	 */
     void getGlyphPosition(le_int32 glyphIndex, float &x, float &y, LEErrorCode &success) const
     {
 		if (LE_FAILURE(success)) {
 			return;
 		}

 		if (glyphIndex > fGlyphCount) {
 			success = LE_INDEX_OUT_OF_BOUNDS_ERROR;
 			return;
 		}

 		if (fPositions == NULL) {
 			success = LE_NO_LAYOUT_ERROR;
 			return;
 		}

         x = fPositions[glyphIndex * 2];
 		y = fPositions[glyphIndex * 2 + 1];
     };

 	/**
 	 * 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)
 	 */
     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 langaugeCode - 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
 	 */
     static LayoutEngine *layoutEngineFactory(const LEFontInstance *fontInstance, le_int32 scriptCode, le_int32 languageCode, LEErrorCode &success);

 };

 U_NAMESPACE_END
 #endif

	/*
	* %W% %W%
	*
	* (C) Copyright IBM Corp. 1998, 1999, 2000, 2001 - All Rights Reserved
	*
	*/

	#ifndef __LAYOUTENGINE_H
	#define __LAYOUTENGINE_H

	#ifndef __LETYPES_H
	#include "LETypes.h"
	#endif

	#include <string.h>

	U_NAMESPACE_BEGIN

	class LEFontInstance;
	class LEGlyphFilter;

	/**
	* 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
	*/
	class U_LAYOUT_API LayoutEngine
	{
	protected:
	/**
	* The number of glyphs in the output
	*/
	le_int32 fGlyphCount;

	/**
	* The output glyph array
	*/
	LEGlyphID *fGlyphs;

	/**
	* The character index array. One entry for each output glyph, giving the index
	* in the input character array of the character which corresponds to this glyph.
	*/
	le_int32 *fCharIndices;

	/**
	* The glyph position array. There are two entries for each glyph giving the
	* X and Y positions of the glyph. Thus, for glyph i, the X position is at index
	* 2i, and the Y position is at index 2i + 1. There are also two entries for the
	* X and Y position of the advance of the last glyph.
	*/
	float *fPositions;

	/**
	* The font instance for the text font.
	*
	* @see LEFontInstance
	*/
	const LEFontInstance *fFontInstance;

	/**
	* The script code for the text
	*
	* @see ScriptAndLanguageTags.h for script codes.
	*/
	le_int32 fScriptCode;

	/**
	* The langauge code for the text
	*
	* @see ScriptAndLanguageTags.h for language codes.
	*/
	le_int32 fLanguageCode;

	/**
	* 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 langaugeCode - the language for the text
	*
	* @see LEFontInstance
	* @see ScriptAndLanguageTags.h
	*/
	LayoutEngine(const LEFontInstance *fontInstance, le_int32 scriptCode, le_int32 languageCode);

	/**
	* This overrides the default no argument constructor to make it
	* difficult for clients to call it. Clients are expected to call
	* layoutEngineFactory.
	*/
	LayoutEngine();

	/**
	* 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
	*
	* Output parameters:
	* @param glyphs - the glyph index array
	* @param charIndices - the character index array
	* @param success - set to an error code if the operation fails
	*
	* @return the number of glyphs in the glyph index array
	*/
	virtual le_int32 computeGlyphs(const LEUnicode chars[], le_int32 offset, le_int32 count, le_int32 max, le_bool rightToLeft, LEGlyphID &glyphs, le_int32 &charIndices, 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 glyphs - the input glyph array
	* @param glyphCount - the number of glyphs in the glyph array
	* @param x - the starting X position
	* @param y - the starting Y position
	*
	* Output parameters:
	* @param positions - the output X and Y positions (two entries per glyph)
	*/
	virtual void positionGlyphs(const LEGlyphID glyphs[], le_int32 glyphCount, float x, float y, float *&positions, 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 - true if the glyphs in the glyph array have been reordered
	* @param glyphs - the input glyph array
	* @param glyphCount - the number of glyphs
	* @param positions - the position array, will be updated as needed
	* @param success - output parameter set to an error code if the operation fails
	*
	* Note: the positions are passed as a plain array because this method should
	* not need to reallocate them.
	*/
	virtual void adjustGlyphPositions(const LEUnicode chars[], le_int32 offset, le_int32 count, le_bool reverse, LEGlyphID glyphs[], le_int32 glyphCount, float positions[], LEErrorCode &success)
	{
	if (LE_FAILURE(success)) {
	return;
	}

	if (chars == NULL \|\| glyphs == NULL \|\| positions == NULL \|\| offset < 0 \|\| count < 0) {
	success = LE_ILLEGAL_ARGUMENT_ERROR;
	return;
	}

	// default is no adjustments
	return;
	};

	/**
	* 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.
	*/
	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 true, the output will be in reverse order
	* @param mirror - if true, do character mirroring
	*
	* Output parameters:
	* @param glyphs - the glyph array
	* @param charIndices - the character index array
	* @param success - set to an error code if the operation fails
	*
	* @see LEFontInstance
	*/
	virtual void mapCharsToGlyphs(const LEUnicode chars[], le_int32 offset, le_int32 count, le_bool reverse, le_bool mirror, LEGlyphID &glyphs, le_int32 &charIndices, 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.
	*
	* @param glyphs - the glyph array
	* @param glyphCount - the number of glyphs
	* @param reverse - true if the glyph array has been reordered
	* @param markFilter - used to identify mark glyphs
	* @param positions - the glyph position array - updated as required
	* @param success - output parameter set to an error code if the operation fails
	*
	* @see LEGlyphFilter
	*/
	static void adjustMarkGlyphs(const LEGlyphID glyphs[], le_int32 glyphCount, le_bool reverse, LEGlyphFilter *markFilter, float positions[], LEErrorCode &success);

	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.
	*/
	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 method below.
	*/
	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
	*/
	le_int32 getGlyphCount() const
	{
	return fGlyphCount;
	};

	/**
	* 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
	*/
	void getGlyphs(LEGlyphID glyphs[], LEErrorCode &success) const
	{
	if (LE_FAILURE(success)) {
	return;
	}

	if (glyphs == NULL) {
	success = LE_ILLEGAL_ARGUMENT_ERROR;
	return;
	}

	if (fGlyphs == NULL) {
	success = LE_NO_LAYOUT_ERROR;
	}

	LE_ARRAY_COPY(glyphs, fGlyphs, fGlyphCount);
	};

	/**
	* 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
	*/
	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
	*/
	void getCharIndices(le_int32 charIndices[], LEErrorCode &success) const
	{
	if LE_FAILURE(success) {
	return;
	}

	if (charIndices == NULL) {
	success = LE_ILLEGAL_ARGUMENT_ERROR;
	return;
	}

	if (fCharIndices == NULL) {
	success = LE_NO_LAYOUT_ERROR;
	return;
	}

	LE_ARRAY_COPY(charIndices, fCharIndices, fGlyphCount);
	};

	/**
	* 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
	*/
	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 glyphs - the destiniation position array
	* @param success - set to an error code if the operation fails
	*/
	void getGlyphPositions(float positions[], LEErrorCode &success) const
	{
	if LE_FAILURE(success) {
	return;
	}

	if (positions == NULL) {
	success = LE_ILLEGAL_ARGUMENT_ERROR;
	return;
	}

	if (fPositions == NULL) {
	success = LE_NO_LAYOUT_ERROR;
	return;
	}

	LE_ARRAY_COPY(positions, fPositions, fGlyphCount * 2 + 2);
	};

	/**
	* 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
	*
	*/
	void getGlyphPosition(le_int32 glyphIndex, float &x, float &y, LEErrorCode &success) const
	{
	if (LE_FAILURE(success)) {
	return;
	}

	if (glyphIndex > fGlyphCount) {
	success = LE_INDEX_OUT_OF_BOUNDS_ERROR;
	return;
	}

	if (fPositions == NULL) {
	success = LE_NO_LAYOUT_ERROR;
	return;
	}

	x = fPositions[glyphIndex * 2];
	y = fPositions[glyphIndex * 2 + 1];
	};

	/**
	* 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)
	*/
	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 langaugeCode - 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
	*/
	static LayoutEngine layoutEngineFactory(const LEFontInstance fontInstance, le_int32 scriptCode, le_int32 languageCode, LEErrorCode &success);

	};

	U_NAMESPACE_END
	#endif