source/layout/IndicLayoutEngine.h

/*
 * @(#)IndicLayoutEngine.h	1.4 00/03/15
 *
 * (C) Copyright IBM Corp. 1998, 1999, 2000, 2001 - All Rights Reserved
 *
 */

#ifndef __INDICLAYOUTENGINE_H
#define __INDICLAYOUTENGINE_H

#include "LETypes.h"
#include "LEFontInstance.h"
#include "LEGlyphFilter.h"
#include "LayoutEngine.h"
#include "OpenTypeLayoutEngine.h"

#include "GlyphSubstitutionTables.h"
#include "GlyphDefinitionTables.h"
#include "GlyphPositioningTables.h"

#include <string.h>

U_NAMESPACE_BEGIN

/**
 * This class implements OpenType layout for Indic OpenType fonts, as
 * specified by Microsoft in "Creating and Supporting OpenType Fonts for
 * Indic Scripts" (http://www.microsoft.com/typography/otspec/indicot/default.htm)
 *
 * This class overrides the characterProcessing method to do Indic character processing
 * and reordering, and the glyphProcessing method to implement post-GSUB processing for
 * left matras. (See the MS spec. for more details)
 */
class IndicOpenTypeLayoutEngine : public OpenTypeLayoutEngine
{
public:
	/**
	 * This is the main constructor. It constructs an instance of IndicOpenTypeLayoutEngine for
	 * a particular font, script and language. It takes the GSUB table as a parameter since
	 * LayoutEngine::layoutEngineFactory has to read the GSUB table to know that it has an
	 * Indic OpenType font.
	 *
	 * @param fontInstance - the font
	 * @param scriptCode - the script
	 * @param langaugeCode - the language
	 * @param gsubTable - the GSUB table
	 *
	 * @see LayoutEngine::layoutEngineFactory
	 * @see OpenTypeLayoutEngine
	 * @see ScriptAndLangaugeTags.h for script and language codes
	 */
    IndicOpenTypeLayoutEngine(const LEFontInstance *fontInstance, le_int32 scriptCode, le_int32 languageCode,
                            const GlyphSubstitutionTableHeader *gsubTable);

	/**
	 * This constructor is used when the font requires a "canned" GSUB table which can't be known
	 * until after this constructor has been invoked.
	 *
	 * @param fontInstance - the font
	 * @param scriptCode - the script
	 * @param langaugeCode - the language
	 *
	 * @see OpenTypeLayoutEngine
	 * @see ScriptAndLangaugeTags.h for script and language codes
	 */
    IndicOpenTypeLayoutEngine(const LEFontInstance *fontInstance, le_int32 scriptCode, le_int32 languageCode);

 	/**
	 * The destructor, virtual for correct polymorphic invocation.
	 */
   virtual ~IndicOpenTypeLayoutEngine();

protected:

	/**
	 * This method does Indic OpenType character processing. It assigns the OpenType feature
	 * tags to the characters, and may generate output characters which have been reordered. For
	 * some Indic scripts, it may also split some vowels, resulting in more output characters
	 * than input characters.
	 *
	 * 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
	 *
	 * Output parameters:
	 * @param outChars - the output character arrayt
	 * @param charIndices - the output character index array
	 * @param featureTags - the output feature tag array
	 * @param success - set to an error code if the operation fails
	 *
	 * @return the output character count
	 */
    virtual le_int32 characterProcessing(const LEUnicode chars[], le_int32 offset, le_int32 count, le_int32 max, le_bool rightToLeft,
            LEUnicode *&outChars, le_int32 *&charIndices, const LETag **&featureTags, LEErrorCode &success);

	/**
	 * This method does character to glyph mapping, applies the GSUB table and applies
	 * any post GSUB fixups for left matras. It calls OpenTypeLayoutEngine::glyphProcessing
	 * to do the character to glyph mapping, and apply the GSUB table.
	 *
	 * Note that in the case of "canned" GSUB tables, the output glyph indices may be
	 * "fake" glyph indices that need to be converted to "real" glyph indices by the
	 * glyphPostProcessing 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 featureTags - the feature tag array
	 *
	 * Output parameters:
	 * @param glyphs - the output glyph index array
	 * @param charIndices - the output character index array
	 * @param success - set to an error code if the operation fails
	 *
	 * @return the number of glyphs in the output glyph index array
	 *
	 * Note: if the character index array was already set by the characterProcessing
	 * method, this method won't change it.
	 */
    // Input: characters, tags
    // Output: glyphs, char indices
    virtual le_int32 glyphProcessing(const LEUnicode chars[], le_int32 offset, le_int32 count, le_int32 max, le_bool rightToLeft,
            const LETag **featureTags, LEGlyphID *&glyphs, le_int32 *&charIndices, LEErrorCode &success);
};

U_NAMESPACE_END
#endif