icuSources/layout/IndicLayoutEngine.h

   1
   2 /*
   3  *
   4  * (C) Copyright IBM Corp. 1998-2004 - 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      *
  51      * @see LayoutEngine::layoutEngineFactory
  52      * @see OpenTypeLayoutEngine
  53      * @see ScriptAndLangaugeTags.h for script and language codes
  54      *
  55      * @internal
  56      */
  57     IndicOpenTypeLayoutEngine(const LEFontInstance *fontInstance, le_int32 scriptCode, le_int32 languageCode,
  58                             const GlyphSubstitutionTableHeader *gsubTable);
  59
  60     /**
  61      * This constructor is used when the font requires a "canned" GSUB table which can't be known
  62      * until after this constructor has been invoked.
  63      *
  64      * @param fontInstance - the font
  65      * @param scriptCode - the script
  66      * @param langaugeCode - the language
  67      *
  68      * @see OpenTypeLayoutEngine
  69      * @see ScriptAndLangaugeTags.h for script and language codes
  70      *
  71      * @internal
  72      */
  73     IndicOpenTypeLayoutEngine(const LEFontInstance *fontInstance, le_int32 scriptCode, le_int32 languageCode);
  74
  75     /**
  76      * The destructor, virtual for correct polymorphic invocation.
  77      *
  78      * @internal
  79      */
  80    virtual ~IndicOpenTypeLayoutEngine();
  81
  82     /**
  83      * ICU "poor man's RTTI", returns a UClassID for the actual class.
  84      *
  85      * @stable ICU 2.8
  86      */
  87     virtual UClassID getDynamicClassID() const;
  88
  89     /**
  90      * ICU "poor man's RTTI", returns a UClassID for this class.
  91      *
  92      * @stable ICU 2.8
  93      */
  94     static UClassID getStaticClassID();
  95
  96 protected:
  97
  98     /**
  99      * This method does Indic OpenType character processing. It assigns the OpenType feature
 100      * tags to the characters, and may generate output characters which have been reordered. For
 101      * some Indic scripts, it may also split some vowels, resulting in more output characters
 102      * than input characters.
 103      *
 104      * Input parameters:
 105      * @param chars - the input character context
 106      * @param offset - the index of the first character to process
 107      * @param count - the number of characters to process
 108      * @param max - the number of characters in the input context
 109      * @param rightToLeft - <code>TRUE</code> if the characters are in a right to left directional run
 110      * @param glyphStorage - the glyph storage object. The glyph and character index arrays will be set.
 111      *                       the auxillary data array will be set to the feature tags.
 112      *
 113      * Output parameters:
 114      * @param success - set to an error code if the operation fails
 115      *
 116      * @return the output character count
 117      *
 118      * @internal
 119      */
 120     virtual le_int32 characterProcessing(const LEUnicode chars[], le_int32 offset, le_int32 count, le_int32 max, le_bool rightToLeft,
 121             LEUnicode *&outChars, LEGlyphStorage &glyphStorage, LEErrorCode &success);
 122
 123     /**
 124      * This method does character to glyph mapping, applies the GSUB table and applies
 125      * any post GSUB fixups for left matras. It calls OpenTypeLayoutEngine::glyphProcessing
 126      * to do the character to glyph mapping, and apply the GSUB table.
 127      *
 128      * Note that in the case of "canned" GSUB tables, the output glyph indices may be
 129      * "fake" glyph indices that need to be converted to "real" glyph indices by the
 130      * glyphPostProcessing method.
 131      *
 132      * Input parameters:
 133      * @param chars - the input character context
 134      * @param offset - the index of the first character to process
 135      * @param count - the number of characters to process
 136      * @param max - the number of characters in the input context
 137      * @param rightToLeft - <code>TRUE</code> if the characters are in a right to left directional run
 138      * @param featureTags - the feature tag array
 139      * @param glyphStorage - the glyph storage object. The glyph and char index arrays will be set.
 140      *
 141      * Output parameters:
 142      * @param success - set to an error code if the operation fails
 143      *
 144      * @return the number of glyphs in the output glyph index array
 145      *
 146      * Note: if the character index array was already set by the characterProcessing
 147      * method, this method won't change it.
 148      *
 149      * @internal
 150      */
 151     virtual le_int32 glyphProcessing(const LEUnicode chars[], le_int32 offset, le_int32 count, le_int32 max, le_bool rightToLeft,
 152             LEGlyphStorage &glyphStorage, LEErrorCode &success);
 153
 154 private:
 155
 156     MPreFixups *fMPreFixups;
 157 };
 158
 159 U_NAMESPACE_END
 160 #endif
 161