/*

  *

  * (C) Copyright IBM Corp. 1998-2005 - 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 {

 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;

     /**

      * The glyph ID of Malayalam RA for RAKAR

      *

      * @internal

      */

     LEGlyphID fGidOfRA;

     /**

      * 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.  Set bit 1 if kerning

      * is desired, set bit 2 if ligature formation is desired.  Others are reserved.

      *

      * @see LEFontInstance

      * @see ScriptAndLanguageTags.h

      *

      * @internal

      */

     LayoutEngine(const LEFontInstance *fontInstance, le_int32 scriptCode, le_int32 languageCode, le_int32 typoFlags);

     /**

      * Returns true if the constructor failed, leaving the object in an

      * inconsistent state.

      *

      * @internal

      */

     le_bool isBogus();

     /**

      * 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.

      *

      * @return the address of the table.

      *

      * @internal

      */

     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 <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);

     /**

      * 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);

 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 method below.

      *

      * @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.

      * @draft 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