icuSources/layout/IndicLayoutEngine.h

   1
   2 /*
   3  *
   4  * (C) Copyright IBM Corp. 1998-2009 - All Rights Reserved
   5  *
   6  */
   7
   8 #ifndef __INDICLAYOUTENGINE_H
   9 #define __INDICLAYOUTENGINE_H
  10
  11 #include "LETypes.h"
  12 #include "LEFontInstance.h"
  13 #include "LEGlyphFilter.h"
  14 #include "LayoutEngine.h"
  15 #include "OpenTypeLayoutEngine.h"
  16
  17 #include "GlyphSubstitutionTables.h"
  18 #include "GlyphDefinitionTables.h"
  19 #include "GlyphPositioningTables.h"
  20
  21 U_NAMESPACE_BEGIN
  22
  23 class MPreFixups;
  24 class LEGlyphStorage;
  25
  26 /**
  27  * This class implements OpenType layout for Indic OpenType fonts, as
  28  * specified by Microsoft in "Creating and Supporting OpenType Fonts for
  29  * Indic Scripts" (http://www.microsoft.com/typography/otspec/indicot/default.htm)
  30  *
  31  * This class overrides the characterProcessing method to do Indic character processing
  32  * and reordering, and the glyphProcessing method to implement post-GSUB processing for
  33  * left matras. (See the MS spec. for more details)
  34  *
  35  * @internal
  36  */
  37 class IndicOpenTypeLayoutEngine : public OpenTypeLayoutEngine
  38 {
  39 public:
  40     /**
  41      * This is the main constructor. It constructs an instance of IndicOpenTypeLayoutEngine for
  42      * a particular font, script and language. It takes the GSUB table as a parameter since
  43      * LayoutEngine::layoutEngineFactory has to read the GSUB table to know that it has an
  44      * Indic OpenType font.
  45      *
  46      * @param fontInstance - the font
  47      * @param scriptCode - the script
  48      * @param langaugeCode - the language
  49      * @param gsubTable - the GSUB table
  50      * @param success - set to an error code if the operation fails
  51      *
  52      * @see LayoutEngine::layoutEngineFactory
  53      * @see OpenTypeLayoutEngine
  54      * @see ScriptAndLangaugeTags.h for script and language codes
  55      *
  56      * @internal
  57      */
  58     IndicOpenTypeLayoutEngine(const LEFontInstance *fontInstance, le_int32 scriptCode, le_int32 languageCode,
  59                             le_int32 typoFlags, le_bool version2, const GlyphSubstitutionTableHeader *gsubTable, LEErrorCode &success);
  60
  61     /**
  62      * This constructor is used when the font requires a "canned" GSUB table which can't be known
  63      * until after this constructor has been invoked.
  64      *
  65      * @param fontInstance - the font
  66      * @param scriptCode - the script
  67      * @param langaugeCode - the language
  68      * @param success - set to an error code if the operation fails
  69      *
  70      * @see OpenTypeLayoutEngine
  71      * @see ScriptAndLangaugeTags.h for script and language codes
  72      *
  73      * @internal
  74      */
  75     IndicOpenTypeLayoutEngine(const LEFontInstance *fontInstance, le_int32 scriptCode, le_int32 languageCode,
  76                               le_int32 typoFlags, LEErrorCode &success);
  77
  78     /**
  79      * The destructor, virtual for correct polymorphic invocation.
  80      *
  81      * @internal
  82      */
  83    virtual ~IndicOpenTypeLayoutEngine();
  84
  85     /**
  86      * ICU "poor man's RTTI", returns a UClassID for the actual class.
  87      *
  88      * @stable ICU 2.8
  89      */
  90     virtual UClassID getDynamicClassID() const;
  91
  92     /**
  93      * ICU "poor man's RTTI", returns a UClassID for this class.
  94      *
  95      * @stable ICU 2.8
  96      */
  97     static UClassID getStaticClassID();
  98
  99 protected:
 100
 101     /**
 102      * This method does Indic OpenType character processing. It assigns the OpenType feature
 103      * tags to the characters, and may generate output characters which have been reordered. For
 104      * some Indic scripts, it may also split some vowels, resulting in more output characters
 105      * than input characters.
 106      *
 107      * Input parameters:
 108      * @param chars - the input character context
 109      * @param offset - the index of the first character to process
 110      * @param count - the number of characters to process
 111      * @param max - the number of characters in the input context
 112      * @param rightToLeft - <code>TRUE</code> if the characters are in a right to left directional run
 113      * @param glyphStorage - the glyph storage object. The glyph and character index arrays will be set.
 114      *                       the auxillary data array will be set to the feature tags.
 115      *
 116      * Output parameters:
 117      * @param success - set to an error code if the operation fails
 118      *
 119      * @return the output character count
 120      *
 121      * @internal
 122      */
 123     virtual le_int32 characterProcessing(const LEUnicode chars[], le_int32 offset, le_int32 count, le_int32 max, le_bool rightToLeft,
 124             LEUnicode *&outChars, LEGlyphStorage &glyphStorage, LEErrorCode &success);
 125
 126     /**
 127      * This method does character to glyph mapping, applies the GSUB table and applies
 128      * any post GSUB fixups for left matras. It calls OpenTypeLayoutEngine::glyphProcessing
 129      * to do the character to glyph mapping, and apply the GSUB table.
 130      *
 131      * Note that in the case of "canned" GSUB tables, the output glyph indices may be
 132      * "fake" glyph indices that need to be converted to "real" glyph indices by the
 133      * glyphPostProcessing method.
 134      *
 135      * Input parameters:
 136      * @param chars - the input character context
 137      * @param offset - the index of the first character to process
 138      * @param count - the number of characters to process
 139      * @param max - the number of characters in the input context
 140      * @param rightToLeft - <code>TRUE</code> if the characters are in a right to left directional run
 141      * @param featureTags - the feature tag array
 142      * @param glyphStorage - the glyph storage object. The glyph and char index arrays will be set.
 143      *
 144      * Output parameters:
 145      * @param success - set to an error code if the operation fails
 146      *
 147      * @return the number of glyphs in the output glyph index array
 148      *
 149      * Note: if the character index array was already set by the characterProcessing
 150      * method, this method won't change it.
 151      *
 152      * @internal
 153      */
 154     virtual le_int32 glyphProcessing(const LEUnicode chars[], le_int32 offset, le_int32 count, le_int32 max, le_bool rightToLeft,
 155             LEGlyphStorage &glyphStorage, LEErrorCode &success);
 156
 157     le_bool fVersion2;
 158
 159 private:
 160
 161     MPreFixups *fMPreFixups;
 162
 163 };
 164
 165 U_NAMESPACE_END
 166 #endif
 167